Urethane Casting at China Machining Services
Urethane Casting
Urethane casting delivers high quality parts by using a 3D printed (or machined) single master part to create silicone molds. The molds are then filled with a prepolymer resin and cured by heat or radiation. The end product is a highly resilient plastic or rubber piece that can be suited for many applications.
As a general rule of thumb: 3D printing is best suited for low quantities (1-20), cast urethane for medium quantities (20-300) and injection molding for high quantities (300+). Cast urethane is one of the most versatile processes to fabricate plastic and rubber parts and can be used in a variety of industries and applications.
Cost and Time Savings
Cast urethane parts can be more cost effective in price per part than 3D printing. When larger amounts of prototypes are needed, 3D printing may require multiple machines. Each machine could potentially be running, and consuming energy, for 20+ hours to get 1 part. Whereas, the cast urethane process can continuously mold parts with minimal energy consumption.
Silicone molds are created from the master part and used to cast the urethane pieces. The cost for creating the silicone mold is far less expensive than aluminum or steel tools used in injection molding and also far less than the cost of purchasing multiple 3D printers.
The lack of tooling and accessories needed for the cast urethane process translates to a much shorter lead time than injection molding. The lead time for an injection mold tool can range from 4-8 weeks, but silicone molds used in cast urethane can be ready in 1-2 weeks or shorter.
Materials Offered
Urethane casting is conducive to many different types of polyurethane resins that can range from flexible like a rubberband, to rigid like a hard hat. The hardness of these resins are commonly measured using the Shore Hardness scale. Within the Shore Hardness scale there are 3 different levels of the Shore scale to measure hardness (or lack of).
Shore 00
Ranges from extra soft to medium hard.
- Shore 00 10 is extremely soft (like a gummy bear)
- Shore 00 30 is soft rubber (like a gel insert)
- Shore 00 60 is soft rubber (like a rubberband)
Shore A
Ranges from flexible rubbers to hard plastics.
- Shore A 20 is very soft (like a mouse pad)
- Shore A 40 is soft and rubbery (like a bottle nipple)
- Shore A 90 is hard rubber (like a cart wheel)
Shore D
Ranges from flexible rubbers to hard plastics.
- Shore D 10 is hard rubber (like a tire tread)
- Shore D 50 is harder rubber (like a shoe heal)
- Shore D 80 is hard plastic (like a hard hat)
Please note that for simplicity, China Machining Services offers 4 main resins for casting: soft rubber, hard rubber, flexible plastic and hard plastic. If you have a specific hardness that you need please let us know and we will accommodate it.
Part Finish
When compared to injection molded parts, cast urethane parts show very similar properties of strength and surface finish. Depending on the complexity of the part and the accuracy of the mold there may be a need for post casting work to be done (deburr, polishing, etc) If color is needed you can choose to cast in a specific color to the part or paint it.
General Tolerances
- ±0.010 in. or ±0.003 in. per inch, whichever is larger, is typical. Irregular or overly thick geometries may cause a deviance or deflection due to shrinkage.
- A shrinkage rate of +0.15% can be expected due to thermal expansion of the liquid, and the response of the flexible mold.
- Surface finish is externally smoothed to a satin or matte surface. Grow lines may be present on internal or difficult-to-access features. Polishing or custom finishes must be clearly defined and agreed upon at the point of order.
- We recommend a minimum wall thickness of 0.040 in. (1 mm). However, there are cases where thinner walls down to 0.020 in. (0.5 mm) are possible on small parts. The larger the part, the larger the wall should be to ensure proper support.
Submit your RFQ for Cast Urethane parts below!
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Information
At China Machining Services, not all of the services we offer relate to a order. We know there is a lot of information out there and a lot of it is helpful. It is part of our mission to make sure the most helpful information is available to our customers. This is why we have compiled the key information about the CNC process, materials, and finishes.
Not sure what material you need? Or maybe you’re not sure what part category your project would fall into? We want to offer the information that will make your project right. So if you do run in to a issue or a question feel free to contact us.
Precision, Quality and Affordability at any volume
In addition to Urethane Casting, our Modern CNC machines can handle small radius cuts and maintain a high quality level whether you want one piece or one hundred. Chamfered edges, multi radius curves, and tapped holes are a few things that make machining a part more workable for any projects. We take pride in making quality, custom, low cost, cast and machined parts.
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