The urethane casting build process involves first creating a master pattern — essentially a replica (often 3D printed) of the final part. The pattern is then fully encased in liquid silicone and allowed to cure. The mold is cut into halves and the pattern removed. From there, the process can be repeated using the proper urethane casting resin.

Polyurethane casting materials are capable of providing performance characteristics comparable — if not superior — to the thermoplastics used in injection molding. However, as with other production methods, the process of casting high-quality parts that meet all performance requirements also requires that product teams follow design for manufacturability (DFM) best practices. Here are some of the most important guidelines for product teams to keep in mind:

Tolerances

Some degree of variation is inevitable in manufacturing (though teams should endeavor to account for as many of the variables as possible), and tolerances are the acceptable amount of dimensional variation between individual units. Cast urethane tolerances are typically around  ± 0.015” or ± 0.003 per inch, whichever is greater. Tighter tolerances may be offered on a case-by-case basis.

In general, a shrinkage rate of +0.15% is typical. This is caused by the thermal expansion of the urethane casting material and how the flexible silicone mold warms in response.

Additionally, it’s important to note that while urethane cast parts take well to post-processing (though additional processes, such as polishing or custom finishing, can quickly drive up production costs), some design features like sharp corners or lettering may experience slight rounding in the cooling process, impacting the definition of finer details. That said, it is possible to add a finish to the master pattern that mimics an SPI finish or texture. You can also paint urethane cast parts to match Pantone colors, and certain color and pigments can be added directly to the casting materials, as well.

Wall Thickness

Parts produced with urethane casting should have a minimum wall thickness of 0.040” (1mm), though walls as thin as 0.020” (0.5mm) can be achieved for some small components. Larger parts generally require thicker walls in order to ensure the piece’s structural integrity.

Urethane casting does allow for parts with varying wall thicknesses or irregular geometries, but designing parts as such should be done only when strictly necessary. Maintaining a consistent thickness helps to minimize the potential for improper shrinkage and deformation during the curing process.

Undercuts and Draft

While undercuts can quickly complicate injection molding design, the flexible nature of the silicone molds used in urethane casting typically allows for parts to be removed easily and without damage.

The same is true for draft angles: they are a necessity for ejecting pieces from metal molds, but less essential for urethane-cast parts. That said, incorporating 3-5 degrees of draft into part design can significantly reduce strain on your mold and extend its life cycle.

Ribs

Ribs add stability and strength, but it’s important to ensure that they are oriented so as to maximize the bending stiffness of the walls they support. As a general rule of thumb, the rib’s height should be no more than three times its width, and the width of the rib where it meets the part wall should be between 40-60% of the wall thickness. Lastly, to maximize the strength of the rib, all interior corners should have a fillet radius of at least 25% of the part’s wall thickness.

Bosses

Bosses allow secure mating parts to be attached through the use of screws, pins, and other fasteners. As with ribs, the base radius should be about 25% of the part’s wall thickness, which has the added benefit in this case of helping to prevent the fastener from burning when it’s set into the boss.

Interior boss corners should use a 0.060” (1.5mm) fillet radius to minimize thickness and reduce the likelihood of sinks developing. Ensuring that bosses are no more than 60% of the nominal wall thickness also helps to minimize shrinkage.

Leverage the Benefits of Urethane Casting Today

The advantages of urethane casting — short lead times, low cost, and design and material flexibility, to name a few — only truly pay off if you adhere to design and manufacturing best practices. This means paying attention to variables like urethane casting material properties, general tolerances for rubber parts, and everything in between — which quickly becomes complicated without the assistance of an experienced manufacturing partner.

With our agile approach, we’re able to significantly shorten lead times and increase operational efficiency for product teams of all shapes and sizes. And at SyBridge, our business isn’t just based on manufacturing superior parts — we also work tirelessly to make sure that our production processes are as efficient as possible, even if that means using a combination of techniques to get the job done. Contact us today to learn more.

The post Critical Design Guidelines for Urethane Casting appeared first on SyBridge Technologies.

Design for manufacturability (DFM) involves optimizing part design so manufacturers can fabricate high-quality parts with the lowest possible cost-per-unit. By taking the manufacturing method and its restrictions into account, designers can reduce production time, cut costs, and prevent extensive redesigns.

DFM best practices vary depending on the product you’re making and your chosen manufacturing method. While injection molding and urethane casting are both molding technologies that can create molded plastic parts, they have different DFM guidelines. Here’s everything you need to know.

Urethane Casting vs. Injection Molding

Before starting to injection mold parts, the appropriate tooling needs to be designed and manufactured via CNC machining. Your part’s geometry will directly impact your tooling, so if you have a complex component, you’ll need complex tooling. Complex parts may need to incorporate slide actions, lifters, or removable cores into the mold’s design. During the injection molding process, the core and cavity will come together. Molten plastic will then be injected into the tooling, cooled, hardened, and ejected to create a usable part.

Urethane casting begins with a master pattern that is created via CNC machining or 3D printing. The operator places the master pattern in a mold box, fills the box with liquid silicone, and then cures it. After the curing process is complete, the mold is cut in half to remove the master pattern. What’s left behind is a cavity in the shape of the part that will be molded. Then, the cavity is filled with urethane casting resin and placed in a heated vacuum chamber for curing.

While both processes involve filling a mold’s cavity with a plastic material, there are some key differences between urethane casting and injection molding.

• Molds for injection molding are often made of steel or aluminum, making them far more durable than the silicone molds used in urethane casting.
• Creating a urethane casting mold is less expensive than creating one for injection molding. Complex injection molds can easily cost tens of thousands of dollars, but fabricating a urethane casting mold typically costs hundreds or thousands of dollars.
• While it may take several months for an injection mold to enter the production stage, urethane casting molds can be tooled in under two weeks.
• Urethane casting is more forgiving with regard to wall thickness and undercuts than injection molding.

If you’re planning a high-volume production run or have tight tolerances, consider injection molding. Metal molds are more durable and rigid than silicone molds, and metal will continually deliver consistent part quality. Plus, you’ll have far more control when injection molding compared to urethane casting. Not only can the manufacturer control material flow and cooling rates, but also injection temperature and location when injection molding. While the cost of creating a mold for injection molding may seem high initially, it becomes cost-effective when divided among thousands of parts.

On the other hand, urethane casting is ideal when developing prototypes or executing low-volume production runs, as soft tooling offers speed, flexibility, and affordability. If you have a high demand for your product but your permanent tooling isn’t ready yet, you can start production with urethane casting.

Top DFM Concerns for Urethane Casting and Injection Molding

When it comes to DFM for urethane casting or injection molding, you’ll want to keep tolerances, wall thickness, and undercuts in mind.

Tolerances

No manufacturing process is perfect, so designers and engineers allow for these variations by establishing acceptable tolerances. Parts are compared to these acceptable measurement variations from base measurements, so those whose dimensions adhere to these constraints will be considered acceptable. Those with dimensional variations over the amount defined in the tolerance won’t work as intended. These tolerances are established during the design process, and they dictate which manufacturing processes can be used.

Achieving tight tolerances with cast urethane is very difficult — if not impossible — because the molds are made of flexible silicone that can be moved by the vacuum load. You shouldn’t use cast urethane to manufacture your parts if you need incredibly accurate components.

On the other hand, metal injection molds offer less variation in final measured dimensions, as they can’t move around as much. However, molten plastic contracts as it cools, which causes minor variations in the part’s final measured dimensions. You’ll need to establish injection mold tolerances that reflect this.

Under-tolerancing can be more affordable, but it can affect usability, and over-tolerancing is more expensive and time-consuming. By taking the time to find the perfect balance between the two, you can make sure your parts are reliable, functional, and fit with other parts as intended. Consider your part’s function, tolerance stacking, and the manufacturing and assembly processes. If your chosen manufacturing method can’t meet your tolerance requirements, you may need to use a different manufacturing technology. You can also redesign your part so it functions with loose tolerances.

Wall Thickness

Maintaining a uniform wall thickness is important because it increases part-to-part consistency, improves stress distribution, and reduces costs. Inconsistent or non-uniform wall thickness can result in warpage, sink marks, shrinkage, short shots, or voids in injection molded parts.

A part’s ideal wall thickness depends on its size, geometry, and structural and aesthetic requirements. For best results, we recommended that wall thicknesses for injection molded parts be between 1-4 mm. It’s possible to have walls of varying thicknesses when creating parts with urethane casting, though you may experience some shrinkage or deformation during curing. For both processes, it’s best to keep wall thickness below 5mm.

Undercuts

Any protrusions or indentations that prevent you from ejecting your part from a one-piece mold without damage are considered undercuts. In some cases, recessed surfaces, grooves, and overhang features can make the demolding process difficult and damage your part. Other times, these features won’t cause any harm. It depends on how you designed and oriented these features and your component.

The impact of undercuts also depends on your manufacturing method. Thanks to the flexibility urethane casting silicone offers, you can simply bend and stretch the tooling out of the way to release your part if you happen to have an undercut. The same cannot be said for the metal tooling used in injection molding, which is far less flexible. Your manufacturer may need to add actions, create a hole or slot in your mold, or redesign your mold with features parallel to the axis where the mold separates in order to ensure your part can be ejected. This results in more complex and more expensive tooling.

Design for Manufacturing With SyBridge

Whether you choose urethane casting or injection molding, integrating DFM into the design process will lower your cost-per-part and save time. By taking your manufacturing method, tolerances, wall thicknesses, and undercuts into account while designing, you can minimize part misalignments and optimize the production process.

No matter which manufacturing process you choose, SyBridge can help you design for manufacturability to ensure you’re satisfied with the final product’s quality and cost. Our team of experts can advise you on appropriate tolerances and wall thicknesses or help you determine which undercut workaround is best suited for your design. Contact us today to get started.

The post Urethane Casting vs. Injection Molding — A DFM Guide appeared first on SyBridge Technologies.

If you look closely at the innovations coming out of the top industries today — automotive, medical, aerospace — odds are you’ll find some form of robotics technology. Recent advancements in computing and sensory technology have inspired explosive growth in advanced robotics manufacturing, and the applications are wide-ranging. Within the last few years, we’ve seen surgical robots perform intricate procedures, robot dogs assist military and law enforcement officials, and much more.

Even though the robotics industry changes rapidly and capitalizes on the most cutting-edge technologies available, the processes used for manufacturing robotics parts also include tried-and-true traditional processes like CNC machining and urethane casting.

Urethane casting is typically associated with prototyping and low-volume production runs of consumer goods like ergonomic grips and skateboard wheels, but this process plays a surprisingly important role in advanced robotics manufacturing. Here’s what you need to know:

An overview of urethane casting

Urethane casting is a versatile manufacturing process that allows you to create high-quality flexible and rigid plastic parts without the expenses associated with injection molding or the costs of laborious hard tooling.

During the urethane casting process, a master pattern — created using 3D printing or CNC machining — is placed in a mold box and then filled with liquid silicone. Once the silicone has cured overnight, the silicone block is cut into two pieces, revealing the mold that will be used to create additional copies of the part. Each piece of silicone is reassembled, filled with urethane casting resin, and placed in a heated vacuum chamber to cure. Once cured, you’ll have a 1:1 scale replica of your master pattern that requires little if any post-processing.

Ideal for low- to medium-volume production runs, urethane casting is easy to use and boasts faster turnaround times than injection molding. However, the cost per part can be high, and strict thickness requirements can limit design flexibility. These pain points notwithstanding, product teams can still manufacture many different kinds of high-quality parts with urethane casting. Common applications include logos, molded bearings, mechanical joints with overlapping features, as well as robot parts.

Common urethane casting applications in the robotics industry

In general, the mechanical and chemical properties of urethane casting resins render them excellent materials for advanced robotics manufacturing. Urethane casting materials are known for their wear, abrasion, corrosion, and chemical resistance. Plus, urethane casting parts are excellent for minimizing unnecessary vibration.

These characteristics are advantageous to industrial robot manufacturers, designers, and engineers who need parts for robots that will be operating in extreme weather conditions or on rough terrain and uneven surfaces. Common applications include wheel systems for robotic forklifts, bomb disposal robots, and other robotic applications in the military and law enforcement sectors.

Urethane casting is also showing a lot of promise in soft robotics, a specific subgenre of robotics engineering that deals with constructing robots from highly compliant materials to mimic the way living organisms move and adapt to their environments.

In the early days of advanced robotics manufacturing, robots were primarily relegated to test laboratory settings. Today’s robots see a high degree of field use and are more frequently used for applications that come into close contact with humans. For example, industrial robot manufacturers in Tokyo have developed a wearable robot exosuit that contours to the wearer’s body to improve their strength, balance, and endurance. Industrial robot manufacturers are also developing robots that can safely and comfortably support the elderly or injured and help healthcare practitioners mobilize them.

Soft robotics use-cases like these wouldn’t be possible without soft gripping elements, for which urethane casting is ideal. The polyurethanes used in urethane casting are tough enough to grip hard-to-handle objects without slipping, but gentle enough to handle delicate objects like an arm in a cast. Urethane casting plays a major role in robotics used in a wide variety of real-world applications.

The future of advanced robotics manufacturing with urethane casting

It’s challenging to predict exactly how the robotics sector will evolve because the possibilities are so vast and technology is advancing at an unprecedented rate. However, if industrial robot manufacturers continue to pursue soft robotics innovations designed to work alongside humans, we can expect to see more urethane casting in the robotics sector very soon. Product teams can break into this dynamic industry as soon as possible with the help of an experienced manufacturing partner.

When you partner with SyBridge to manufacture urethane casting parts, you can expect quick turnaround times, low-upfront costs, and unmatched material flexibility. All of the polyurethane materials we offer come in a variety of colors, durometers, and textures that are sure to fit your unique project requirements. If you’re looking to push the envelope and venture into advanced robotics manufacturing, we can also help you reach those goals. Contact us today to learn more about how we can turn your robotics designs into reality.

The post Urethane Casting in the Robotics Industry appeared first on SyBridge Technologies.

Urethane casting is a rapid and cost-effective method for producing end-use plastic parts in low to medium volumes. The process involves creating silicone casting molds from a part’s master pattern, then cutting the molds in half so that they can be brought to production. Able to support a wide range of viable part designs, urethane casting is commonly used for parts prototyping, bridge tooling, and fabricating parts with fine details, varying wall thicknesses, and complex geometries.

Among the process’ notable advantages, urethane casting can accelerate time-to-market, as most parts can be cast in less than two weeks. Further, casted parts tend to experience lower shrinkage rates than those produced through processes like injection molding.

Considering that urethane casting is a highly versatile manufacturing process, material selection can involve a variety of factors. It’s important that product teams do their due diligence to ensure they select the best-fit material for their given project.

Urethane Casting Material Selection Factors

Urethane casting is compatible with a wide range of both rigid and flexible materials — so cast urethane parts can be produced in a variety of colors, textures, and finishes. However, with so many options available, it’s important that you adhere to design for manufacturability (DFM) best practices when selecting a material. You’ll be weighing a complex set of factors, including:

• Application requirements: Does the part need to store or dissipate energy? Does it require tear resistance, load-bearing, or sound-dampening? Each of these factors necessitates different physical and chemical properties, which should help refine the pool of viable material options.
• Environmental considerations: If the application requirements will expose the part to extreme temperatures, humidity, UV radiation, or chemicals, these environmental considerations should also inform your material selection.
• Expectations: Other factors like cosmetic considerations and managing the customer’s expectations when it comes to part life, durability, and cost may play a significant role in determining the final choice.

Ultimately, determining the best-fit material for a given application is vital to ensuring the entire production cycle is positioned for success. Urethane casting materials including silicones, foams, and urethane casting resins can be categorized by their hardness according to durometer scale. Here’s a quick look at durometer, the Shore scale, and some of the most common urethane casting materials.

A Note on Durometer and the Shore Scale

Rubbers, plastics, and metals can vary widely in terms of their physical properties and characteristics, which has a direct impact on the applications for which each material is suited — a soft, bendable plastic obviously won’t do when hardened steel is required, and vice versa.

Durometer is the standardized metric for measuring the hardness of a given material, which is to say how resistant it is to local deformation. The durometer of most of these materials will fall into one of three categories: Shore 00, Shore A, or Shore D, each of which represent a range of hardness, with Shore 00 being the softest and Shore D being the hardest. Urethanes typically range in hardness from 25 shore 00 (something like a gel bicycle seat) to 75 shore D (something like a bowling ball).

Rigid Urethane (Shore D Resins)

The Shore D spectrum spans from rigid polyurethane resins to highly rigid ones. Most materials harder than 65 Shore D will feel completely rigid to the human hand and will not have the surface flex or bendability provided by softer Shore A materials. At the upper end of the Shore D spectrum comes the Rockwell scale, which is used to measure metals and extremely hard resins like acetals and nylons.

Common shore D materials include:

AFP3100 (85 shore D)

Extremely durable and resistant to both heat and impact, this rigid resin is often used to create covers and housings for consumer electronics and medical equipment. It is comparable to ABS and PC/ABS plastics.

AFP3200 (80 Shore D)

Similar to HDPE, this urethane offers high tensile and impact strength, rigidity, and stiffness, and is used extensively in consumer packaged goods, industrial piping and tanks, and auto body components like fenders, hoods, and wheel wells.

AFP3320 (80 Shore D)

This urethane is often used for high-heat applications due to its excellent heat and impact resistance. It is an excellent option for HVAC and underhood applications.

AFP3400 (70 Shore D)

Comparable in many ways to polypropylene, this material offers flexibility while still maintaining a low flexural modulus and good impact resistance. This resin is well-suited for applications like living hinges where superior elongation is essential.

AFP3600 (~82 Shore D)

This clear material can be easily pigmented, provides good heat resistance, and provides enough flexibility for small parts like clips and snap fits. Lenses, housings, backlight applications, and both clear and frosted components are often made with this urethane.

PT8958 (85 Shore D)

This material is most often used to create medium or large medical components that must be both MRI-transparent and flame-retardant.

RC 79D (85 Shore D ±5)

Also MRI-transparent and flame-retardant, this tough, impact-resistant material is often a good fit for smaller medical devices and assemblies.

Urethane Elastomers (Shore A Resins)

Shore A materials are softer than the rigid shore D materials, providing greater flex and, often, good tear strength. At one end of the material spectrum, 0 Shore A refers to soft, gel-like materials, while semi-rigid plastics measure 90 or 95 Shore A.

Common shore A materials include:

E1005AL (5 Shore A)

This extra soft elastomer is an excellent all-around soft rubber that’s easy to dye and offers good tensile and tear strength. For this reason, it’s commonly used to create medical training models, special effects, and props.

E1015AL (15 Shore A)

Similar to E1005AL, but with slightly increased rigidity, this elastomer is excellent for creating soft rubber grips and stretchable linings.

E1040AL (40 Shore A)

This medium-soft resin is similar in hardness to a standard pencil eraser, making it well suited for overmolding and keypads.

E1060AL (60 Shore A)

This medium-hard material is a good general purpose elastomer often used to create bellows, boots, and overmolded components.

E1070 AB (70 Shore A)

Comparable to the hardness of automotive tires, this material’s blend of durability and wear resistance is also ideal for cable connectors.

E1095AB (95 Shore A)

This material offers good abrasion and tear resistance, and is often used to manufacture shopping cart wheels, rollers, and bumpers.

Each of these thermoplastic elastomer resins are compliant with the European Union’s Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) and the Restriction of Hazardous Substances (RoHS) standards.

Silicones

Silicones are softer than shore A materials and are used to create a select few kinds of parts; however, they are commonly used to create the molds by which end-use parts are cast. This is especially true when using the cast urethane molding process for bridge tooling, an interim step that allows production to begin while the injection molds and other hard tooling is machined and finalized. Castings for bridge tooling can also be done in urethane, foam, or metal.

Common silicones include:

AFS15 (15 Shore A)

A soft rubber, this silicone is often used in applications like ink stamp pads and pressure pads that require good flexibility.

AFS30 (30 Shore A)

A little firmer than AFS15, this casting silicone can be used in mold-making and to encapsulate other components.

AFS40 (40 Shore A)

This medium-soft silicone makes excellent buttons and keypads, while also providing good water resistance.

AFS60 (60 Shore A)

This medium-hard rubber works well for mold-making and applications that require encapsulating.

Each of these silicones can also be used to create viable components like gaskets and seals in varying hardnesses.

Leverage the Benefits of These Common Urethane Casting Materials Today

Urethane casting is a useful method of manufacturing for a number of reasons. One, it’s fast and generally quite cost-effective. Two, it produces high-quality, end-use parts. Three, you have a huge variety of polyurethane elastomer resins at your fingertips with which to work. However, having so many options available can sometimes be overwhelming — how can you determine how subtle differences between materials will affect the longevity and performance of your part down the line?

The good news is that partnering with a skilled, on-demand manufacturer SyBridge takes the hassle out of material selection, design, and production. In fact, our approach has been shown to cut urethane casting costs by up to 60%. If you’re interested in learning more about how our flexible production methods can bring your plans to life — on time and on budget — contact us today.

The post A Breakdown of Common Urethane Casting Materials: Silicones, Elastomers, and Rigid Urethanes appeared first on SyBridge Technologies.

Urethane casting is a versatile traditional manufacturing process that uses a 3D-printed master pattern and a silicone mold to create end-use plastic parts. During the urethane casting process, the master pattern is placed inside a sealed box, covered with liquid silicone, and then cured. After the silicone has set, a manufacturer cuts it in half to release the master pattern — at this point, the cast urethane mold is ready for use.

To create custom cast urethane parts, engineers pour urethane casting resin — typically a polyurethane material that can mimic the physical properties of the plastic used in injection molding — into the mold and cure it in an oven. The final part generally requires little, if any, post-processing.

Less expensive and less time-consuming than hard tooling, urethane casting is ideal for rapid prototyping and low- to medium-volume production runs of complex builds. To get the most out of this manufacturing process, product teams must design for manufacturability and optimize mold design early on to streamline the production process and keep costs low. Here are five essential design tips for creating clean and functional custom cast urethane parts:

5 Top Design Tips for Urethane Casting

1. Give even wall thickness

Many engineers prefer urethane casting over injection molding because the former process affords greater variation in wall thicknesses, but it’s still important to ensure that a given urethane mold design features uniform walls. Uniform walls reduce the risk of deformation during curing, ensure the mold will be filled completely and accurately, and mitigate other design issues.

A minimum wall thickness of .040” (1mm) is recommended, but there are cases in which walls may be as thin as .020”(.5mm) in small parts. For larger parts, wall thickness should always increase in proportion to the size of the part to guarantee that the walls can provide adequate support.

2. Account for shrinkage

When two walls with different thicknesses intersect in a urethane mold design, shrinkage can occur. Since thicker walls solidify slower than thinner walls, the area to which they are attached at the nominal wall will shrink as the projection — a rib or a boss —  shrinks. This causes a sunken area in the nominal wall. To minimize shrinkage and prevent sunken areas, engineers should ensure rib thickness falls between 50% and 60% of the walls to which they’re attached.

Still, sometimes urethane casted parts shrink for reasons other than a urethane mold design flaw. The final dimensions of a urethane casted part depends on the accuracy of the master pattern and mold, part geometry, as well as urethane casting materials. A shrinkage rate of 0.15% is considered acceptable, but engineers should revisit their urethane mold design if the shrink rate surpasses this threshold.

3. Employ ribs

Adding ribs to a urethane mold design can increase the end part’s strength and rigidity without adding thickness. To use ribs properly, engineers should adhere to the following guidelines:

Height

Longer ribs provide greater reinforcement, but casting a long rib can make the part difficult to mold. For this reason, a rib shouldn’t exceed a height that’s three times its thickness. To avoid the height issue altogether, engineers can use multiple short ribs instead of one long rib to increase the stiffness of the part.

Width

The width of the rib at the intersection of the part should be 40% to 60% of the thickness of the part. If a fillet radius is included in the design, it should be at least 25% of the thickness of the part. These parameters help make the rib as strong as possible.

Draft Angle

Engineers must draft a rib designed to reduce the possibility of sinking. Draft angles for each side should be between 0.25 and 0.5 degrees and the draft angle of each side should be equal. For textured surfaces, add an additional 1.0 degree draft for every 0.025 (0.001 inch) depth of texture.

Spacing

Engineers should set consecutive ribs at least two times the thickness away from each other to evenly distribute the part’s weight across all ribs.

Orientation

Rib orientation determines how and where the part experiences stress, so engineers should be careful to arrange ribs in a way that maximizes the bending stiffness of the part. If the ribs are placed in the wrong position, they won’t have any positive impact on the part’s strength.

Product teams should also be mindful of intersections and sinking when working with ribs. At the point where a rib intersects with the part, a heavy rib can cause the part to dip. To avoid sinking at the rib intersection, engineers can use fillets to ease the stress on the part’s surface and reduce sink on the opposite side of the part. The radii of the fillets should be at least a quarter of the thickness of the part. Further, coring or lightweighting the part reduces the amount of material used and helps maintain a uniform wall thickness throughout the part.

Ribs can dramatically improve an end-part’s performance, but engineers and product teams shouldn’t get carried away. Ribs are only useful when the part requires extra reinforcement. In situations where this isn’t the case, ribs are often placed improperly and do little to improve the strength or rigidity of the part. Also, unnecessary ribs increase the weight and price of the part, cause molding problems, and contribute to material waste. Engineers and product teams should keep these considerations in mind when deciding whether or not their urethane mold design requires a rib.

4. Consider drafts and undercuts

Drafts and undercuts are not a concern with urethane casting because liquid silicone can take the shape of any mold. However, if an engineer is using urethane casting to build a prototype that will eventually be manufactured using a different process, like injection molding, they should create the design as intended for end-use production. This might include incorporating drafts and undercuts. Long zero-draft features come with a slight risk of part breakage when extracting the part from the mold, so a slight angle may be useful, especially for larger production runs.

5. Include enough spacing between letters and logos

With urethane casting, it’s easy for designers to mold high-quality raised or recessed letters and logos into custom cast urethane parts. To make sure letters are as beautiful and readable as possible, designers should keep height or feature depth, feature width, radii on the feature, and the space between features in mind.

Product teams should leave at least 0.050” between features, though this can vary depending on the particulars of the design. All radii should be at least equal to half the feature height, but larger radii are even better. Finally, the width of all logos or letters should be twice their height.

Optimize Your Urethane Casted Parts

With urethane casting and designing for manufacturability, a few small design alterations go a long way. Engineers and designers should seek to maintain uniform wall thicknesses, account for shrinkage, and ensure they’re using ribs effectively. Product teams can further optimize manufacturability by creating designs as they are intended for end-use production and making sure they leave enough space in between letters and logos to boost aesthetics.

An experienced manufacturing partner like SyBridge can help product teams simplify designing for manufacturability. We’re passionate about developing products that were once thought impossible to make, and we make it a point to keep up with the latest digital design technologies.

Product teams looking to develop a breakthrough application or optimize an existing urethane mold design can benefit from our design team’s years of experience across manufacturing processes. Contact us today to get started on your custom cast urethane parts.

The post Five Design Tips for Urethane Casting appeared first on SyBridge Technologies.

Urethane casting is a useful manufacturing method that involves creating a silicone mold from a master pattern, which is essentially a replica of the final part. The mold is then filled with a shot of urethane casting resin and allowed to cure. Once the part has cooled, it can be ejected and the mold refilled. This allows for high-quality parts to be created quickly and cost-effectively, especially when used to produce parts in relatively low volumes.

It’s unfortunate that many product teams are not familiar with the process or aware that it can be a viable manufacturing method — in fact, many who are familiar with urethane casting only see the process as a bridge tooling method on the path to producing end-use parts via injection molding. In any case, teams often overlook the breadth of advantages and value propositions that urethane casting offers as an end-use manufacturing method. Here are five benefits of urethane casting:

1. Reduced Tooling and Part Costs

Urethane-cast parts are typically more cost-effective to produce on a per-unit basis than those made through additive manufacturing methods, as order volume increases.

During prototyping, additive processes may require multiple build cycles to create a higher number of parts, which adds to the overall cost of production. Urethane casting, on the other hand, can be used to rapidly fabricate prototypes, avoiding the need for additional — and costly — build cycles.

The cast urethane molding process also uses silicone, which makes it far more affordable than the hard tooling needed to create the durable metal molds used in injection molding. Silicone molds can be fabricated in as little as 24 hours for hundreds or thousands of dollars (depending on the size and design of the given  mold), whereas aluminum and steel mold tooling may require weeks and tens of thousands of dollars to finish.

2. Increased Design Flexibility

Urethane casting is highly flexible with regard to part material; product development teams have hundreds of different materials in all sorts of colors and durometers to choose from. And in contrast to the many rigid thermoplastics and thermosets used in manufacturing, silicone urethane casting resins are softer and more flexible, which makes the molds more forgiving.

For instance, draft angles (which must be incorporated into mold design to allow parts to be ejected without damage) are no longer necessary with molds made from elastomeric materials like silicone. This allows designers to incorporate features into parts that would otherwise be impossible to achieve without expensive slides and actions, including undercuts and overmolds.

Furthermore, design changes can be easily incorporated into mold designs based on the results of prototype testing or consumer feedback without the expense of hard tooling. Because silicone molds have a lifetime of 25-30 shots, modifications can be easily integrated between molds at a minimal expense. This does create the need for additional molds as production volume increases, but, as mentioned, silicone molds can be produced at a fraction of the cost of hard molds.

3. Impressive Speed of Production

Silicone molds are much faster to produce than hard tools, with some molds being ready to use within 24 hours of being poured. Thanks to this speed, urethane casting is ideal for producing parts in lower volumes that would not justify the significant investment of a metal injection mold.

The process can also be used as a bridge to production if parts are needed immediately, enabling product teams to begin fabricating first-run parts while the hard tools are finalized. The majority of cast urethane parts can be shipped to market within two to four weeks, giving savvy manufacturers a valuable competitive edge.

4. High Precision and Quality

Urethane casting enables manufacturers to create high quality parts in a variety of shapes, sizes, and materials — all with good tolerances. Typical tolerances are +/- .020″ per inch for cast urethane parts, though tolerances are still dependent on part geometry and other factors.

Deviances to normal tolerances may be caused by the thermal interaction between the liquid shot and the silicone mold. In general, teams should anticipate a material shrinkage rate of +0.15%, meaning the volume of the part will increase.

Further, it’s worth noting that many polyurethane casting resins are capable of providing chemical and physical properties comparable or superior to production-grade plastics. In contrast to additive technologies, which are limited in some material and structural ways, urethane casting allows for the rapid production of strong, high-quality end-use parts made of a wide variety of materials.

5. Excellent Surface Finish

Much like injection-molded parts, cast urethane parts offer excellent surface finish, and can be customized to include colors, surface textures, or post-production processes like painting. These options guarantee that parts will remain aesthetically pleasing even if they should be damaged or scratched during use. Urethane can be used to create parts featuring mechanical properties comparable to materials ranging from rigid plastic to rubber-like elastomer. Many materials are available in a breadth of translucencies, as well.

Discover Efficient, Affordable Part Production

When it comes down to urethane casting vs. injection molding, additive manufacturing, or any other process, there are a few key factors to consider. If a large number of prototypes is needed quickly, urethane casting’s speed and design flexibility make it a very compelling option. At the same time, if order volumes are huge, then urethane casting is an excellent way to beat competitors to the market until production tooling is ready.

The speed and affordability of urethane casting make it an exceptionally useful means of production that offers a range of benefits to product teams of all kinds. Partnering with an experienced manufacturing team is the best way to ensure you’re taking advantage of all the value-adds of urethane casting and optimizing your product development process.

SyBridge is a cutting-edge on-demand digital manufacturing platform reimagining what’s possible in modern manufacturing. Our design and production capabilities are backed by decades of experience, and we specialize in doing the previously undoable — usually faster and more efficiently than our customers expect. Contact us today to get started.

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Cast urethane is a manufacturing method that allows designers and engineers to consistently create production-quality plastic parts with a range of material properties. The process begins by placing a master pattern — which is essentially a replica of the desired final part — in a mold box and covering it with liquid silicone. Once the silicone has cured, the block is cut in half to extract the master from the silicone mold. As a final series of steps, the master pattern is replicated by filling the mold with casting resin and curing the part in a heated vacuum chamber.

The process combines the strength of injection-molded parts with high-quality surface finishes and chemical and abrasion resistance. The short lead times and low cost of soft tooling make the process especially useful for prototyping and for low- to medium-volume production that doesn’t warrant the expense or time required for hard tooling.

Cast urethane is compatible with a wide range of materials, and its versatility is a benefit for designers and engineers. However, it’s critical that product teams select an appropriate material based on their specific project requirements — which can include cost, functionality, aesthetics, and other factors — in order to maximize the quality and performance of the final part. Here’s what teams need to know.

Key Considerations for Cast Urethane Material Selection

As with most manufacturing projects, the desired qualities and characteristics of the final part application should inform the material selection process. For example, gaskets, overmolds, and skateboard wheels — while all commonly manufactured via cast urethane  — have widely differing performance requirements. In order to provide better sealant and fit, gaskets and overmolds should be made from softer, rubber-like materials, while skateboard wheels need to offer a combination of durability and noise- and shock-absorption.

The urethane resin family is highly versatile and can provide material and performance characteristics comparable to many engineering-grade plastics. Resins can often be augmented with additives, such milled glass fibers and other particulates, to improve the part’s strength, anti-static qualities, flame resistance, or other desirable properties. The material and additive offerings of individual suppliers will vary, but urethane resins are often broadly categorized according to the Shore durometer hardness scale (in which an “A” rating indicates softer, elastomeric materials, and a “D” rating refers to highly rigid materials).

Rigid Polyurethanes

ABS-like polyurethanes are low-cost, general purpose resins that provide comparable — if not better — strength and impact resistance to acrylonitrile butadiene styrene (ABS), a thermoplastic polymer commonly used in vehicle exteriors.

With typical durometers of 80-85 Shore D, these resins make excellent product enclosures and components that will stand up to frequent handling (such as game console controllers). Urethanes are susceptible to UV radiation and will therefore require stabilizers or coatings if used in exterior applications.

Acrylic-like polyurethanes are another common casting material. These resins are stiff and transparent, offering similar properties to polymethylmethacrylate (PMMA), a lightweight acrylic commonly used as a glass substitute. Offering durometers around 87 Shore D, these materials are excellent for creating durable, transparent parts such as light tubing.

Softer rigid resins (such as those that fall between 60 and 75 Shore D on the durometer scale) can also be used to create firm parts with a degree of flexibility, such as car tires or hard hats. These resins have low viscosity and are therefore excellent for filling complex mold designs.

Elastomeric Polyurethanes

Elastomeric polyurethanes offer similar properties to flexible materials like TPE, TPU, and silicone rubber, making them ideal for manufacturing products such as wearable components and bumper pads.

Much like rigid resins, elastomeric polyurethanes come with a number of mechanical advantages. Those with durometers of 50 Shore A and below provide high tensile strength, toughness, and flexibility, while those between 60 and 80 Shore A are well-suited for producing abrasion-resistant parts and fixtures with a degree of flex. Shore A resins can also be used to create urethane casting molds that are more durable than their silicone counterparts.

Hard elastomeric urethane materials include durometers ranging from 90 Shore A to 60 Shore D, and are ideal for demanding industrial applications like forming dies and gears. In some cases, these resins are able to outlast metal patterns.

Getting Started With Cast Urethane

Urethane casting is an efficient and effective process for many manufacturers, as it enables short production timelines, flexible material choice, and inexpensive tooling costs. In addition, polyurethane materials can endow a part with a range of desirable properties — from malleability and heat resistance to high tensile strength and rigidity.

However, a trusted manufacturing partner like SyBridge can ease some of that burden. Our talented team of designers and engineers work closely with every customer, providing expert advice and assistance from ideation through to post-processing and fulfillment. Contact us today to discover how we can optimize the product life cycle for maximum efficiency.

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Permanent production tooling needs to stand up to repeated use, which is typically why tools like molds are made from hardened steel. These molds yield highly accurate and precise parts with extreme consistency, but they can take weeks and tens of thousands of dollars to manufacture.

For some production orders, the additional lead time may not be a significant factor, but it becomes a cause for concern when supply is low or demand rises above expected rates. Manufacturers can turn to methods such as urethane casting, which enables them to begin production to meet immediate demand until the permanent tooling becomes available.

How urethane casting can streamline the production process

Injection molding is extremely economical for mass production, but prohibitively expensive for small runs or highly customized parts. Urethane casting and other soft tooling processes bridge this gap, enabling the production of lower volumes of parts at high speed and cost-efficiency. What’s more, many silicone molds take less than a day to set, while hard-tooled molds can take weeks to manufacture and prepare for production.

Urethane casting, also called silicone tooling, works by using silicone molds to create identical copies of parts. Urethane casting is a form of soft tooling, meaning that the molds are less durable than their metal counterparts. In general, these kinds of molds are good for 25 to 50 shots. This allows manufacturers to essentially start producing small volume runs while the permanent tooling is finalized.

Parts made by urethane casting often have mechanical properties comparable to those of parts made through hard tooling processes like injection molding. This makes silicone tooling a useful method for creating everything from various consumer products to medical devices. Engineers can also test different materials with the same cast urethane mold without needing to modify the CAD file.

Considerations for cast urethane tooling

There are a few factors that can help manufacturers determine whether urethane casting might be an effective choice for bridge tooling.

The first is the geometry of the part. Silicone molds entirely encase master patterns that have been 3D printed or CNC machined, resulting in exact replicas of the desired part. Simple production runs, or the production of parts with simple geometries requiring no additional components, can usually be fulfilled effectively through injection molding. However, urethane casting can create more complex geometries and offers more flexibility for changes in part design.

Time is another key consideration. It can take months to ramp up to production with hard tooling. Changes made to hard-tooled designs cause cost-intensive setbacks, which — considering the recent rise in on-demand manufacturing — may present a business liability. On the other hand, cast urethane parts can be completed in as little as a week, allowing manufacturers to meet critical deadlines and prevent downtime.

The durability of the tool is another important factor. While hard tools take longer to create, they can last for thousands of shots, as opposed to the 25 to 50 that can be expected of soft tools.

Urethane casting allows for more versatile forms of production

In the right circumstances, using urethane casting for bridge tooling offers serious benefits to manufacturers. Technological innovations have made it possible to produce customized parts and parts in small volumes economically. Today, bridge tooling via urethane casting enables manufacturers not only to meet demand more quickly and efficiently, but also to more easily move into niche or specialized markets.

SyBridge is your one-stop shop for manufacturing innovation. Our full-service team of engineers and designers is committed to providing end-to-end support to every customers. As collaborative partners, we streamline everything from design optimization to order fulfillment. Contact us today to get started on your next project.

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While it may seem like common sense, it’s important that parts are designed in a way that streamlines production. This principle — known as Design for Manufacturability or Design for Manufacturing (DFM) — not only helps to reduce the overall cost of production, but the time and energy required to make the parts, as well.

There are a range of opportunities within the design phase to optimize efficiency downstream. That’s why DFM is often discussed in tandem with the concept of Design for Assembly (DFA). DFA is the practice of designing parts in such a way that they are easy to assemble.

This piece will touch on how modular design and finite element analysis (FEA) can help optimize the design process and boost overall ROI by saving costs, energy, and time.

Design for Manufacturing and Assembly to Increase Efficiency

A key strategy for optimizing efficiency and cost savings in the manufacturing process is limiting the number of part components from the get-go. Doing so creates a ripple effect on the rest of the production pipeline, resulting in the need for less inventory and ultimately streamlining operations.

Considering the advantages of using additive manufacturing methods can help reduce overall part count. This is because additive manufacturing often enables engineers to combine numerous parts — generally made one-by-one via traditional manufacturing methods — into a single part.

Additionally, assessing the range of materials required for various components may aid in increasing efficiency. Certain components demand materials of specific physical or chemical properties to prepare the part for its end-use. However, if possible, cutting down on the number of unique materials goes a long way toward reducing manufacturing costs and production times.

Modular design is another way to reduce production costs. By using a similar set of sub-assembly components within a given design, engineers can reduce the time needed for multiple design iterations.

Prioritizing modular design also allows for the creation of multi-use sub-assembly components that can be used across different part orders, removing the potentially expensive and time-consuming need to design new components for each new production run. By identifying the sub-assembly components that do not require customization between parts, redundancies can be avoided.

Double Check Your Work With Finite Element Analysis Software

After streamlining the design and manufacturing processes through the preliminary measures outlined above, the next step is employing finite element analysis (FEA), which is a software-driven method of testing product designs before they go into production.

In the development and design phases, the ability to iterate and test parts quickly is crucial to optimizing the overall production process, and FEA is one of the fastest ways of troubleshooting potential issues before a part goes into physical prototyping. The software allows engineers and designers to predict how parts will respond when exposed to common real-world stressors — solely using design files.

These stressors include vibration, heat, mechanical stress, fatigue, fluid flow, and other forces. FEA is also a highly cost-effective option for mission critical components or high value assemblies, though it may come at a higher price tag for other kinds of parts.

While FEA is not a complete substitute for testing actual physical prototypes, it’s an excellent way to test for part failure, as it determines, with precision, how individual regions of the part are likely to respond when put under stress, which can inform key engineering and design decisions.

FEA software performs complex mathematical calculations far faster than engineers can do by hand, meaning that, should a part need to be redesigned, new models can be tested virtually in a matter of hours or days, rather than the weeks or months that might be needed to test a physical prototype. In many cases, FEA software even allows designers to change the features within the design file to achieve certain desired properties.

Manufacturing On Demand: The SyBridge Difference

The ability to produce parts on demand is the final point consideration when looking to maximize ROI. The manufacturing-on-demand model is flexible, enabling rapid production and delivery in response to changes in demand. This ability mitigates excess supply and lost sales opportunities. Whether it’s for a massive production run of uniform parts or for a small run of parts with complex and varied geometries, it’s critical that engineers, designers, and manufacturers choose the right on-demand manufacturing partner.

SyBridge is a one-stop, on demand manufacturing partner. Our team of experts work closely with customers at every stage of the manufacturing cycle, from ideation and prototyping to manufacturing and fulfillment, ensuring that you receive superior quality parts quickly and at a good price to ensure you get the best return on investment.

Contact us today if you’re ready to get started on an order, or if you have any questions or concerns about the production process.

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Urethane casting is a versatile manufacturing process that consistently yields flexible or rigid plastic parts at production-level quality, but without the expenses associated with injection molding. For this reason, urethane casting tends to have two primary uses: prototyping and low-volume production runs that do not justify the costs of time-consuming hard tooling.

The cast urethane process begins with a master pattern, which can be made using 3D printing, CNC machining, or may be customer-supplied. The pattern is placed in a mold box, which is filled with liquid silicone and allowed to cure overnight. The silicone block is then surgically cut into two pieces, freeing the master pattern and creating the mold that will be used to make additional copies of the part. The two pieces of silicone are reassembled, the cavity is filled with urethane casting resin, and the mold is placed in a heated vacuum chamber to cure. The end result is a 1:1 scale replica of the master pattern that requires little — if any — post-production finishing.

Advantages of urethane casting

Because urethane casting creates incredibly precise replicas of the master pattern, the process serves a range of applications, including parts with joints or features that overlap, or pieces with raised or inset letters or designs. The process also enables the addition of ribs, which can increase the strength and rigidity of casted parts (which already tend to be as strong or stronger than injection molded or 3D printed parts).

What’s more, urethane casting can be completed with a variety of materials — running the gamut from soft and flexible to rigid and impact-resistant. Materials can also be blended to create a unique color.

Additionally, the turnaround time is faster for urethane casting than it is for injection molding. The molds for cast urethane parts can be tooled and ready for use in two weeks (sometimes even faster), whereas the production of injection molds is more labor-intensive and can therefore take several months before entering the production stage.

Common uses of urethane casting

Prototyping

Cast urethane is often used as a bridge between SLA prototyping and mass production. Cost-effective and versatile, the process can be used to manufacture parts in a variety of sizes, durometers, materials, and colors, while still providing production-level material performance.

The ability to rapidly generate multiple prototypes means that changes can be incorporated and retested quickly, making urethane casting an ideal method for consumer testing or end-user evaluation of parts.

Bridge tooling

Also called rapid tooling, bridge tooling is the process between product development and production. Since the process of retooling molds is expensive and sometimes impossible, it’s important to make sure a tool works correctly before moving into volume production. The flexibility of cast urethane allows the simple evolution of prototypes in response to user testing, while also ensuring that each part remains accurate in accordance with the master pattern — even down to detailed internal features.

Low volume production

Urethane casting is a consistent, flexible, and precise manufacturing process — factors that are ideal for low-volume runs of production-grade parts. With the development of cast urethane soft tooling, low-volume production has become increasingly cost-effective and efficient for a wide range of consumer products and medical devices.

Fine details

Because urethane casting supports a high degree of complexity and intricacy in the initial build. This allows for the speedy production of parts with small details, involved geometries, and varying wall thicknesses — eliminating the need for additional passes or manufacturing phases that can become expensive when executed across an entire production run.

Urethane casting: A versatile manufacturing process

Ultimately, urethane casting is an effective way to manufacture low- to mid-volume production runs for detailed prototypes and plastic parts. It’s a flexible and scalable process that works with a wide range of materials, and costs far less that the aluminum or steel tooling required for injection molding. At the same time, cast urethane parts offer comparable strength to injection molded parts, as well as production-quality wear and performance properties.

At SyBridge, we take pride in providing excellent service and delivering superior parts — enabling our customers to push the boundaries of what’s possible. If you’d like to learn more about the differences between urethane casting and injection molding, or if you’re ready to get started on a project, contact us today.

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