CNC machining and urethane casting are widely used in the plastic parts manufacturing and rapid prototyping industry. They work differently to create parts and have their advantages. Sometimes, engineers need to choose between these processes. today, in this article, Kusla will explore the difference between CNC machining and Urethance casting to help you make the final decision for your project.
How does CNC machining work?
CNC machining is a subtractive manufacturing process that removes part of a material block with instructions from a CAD model. The programmed computer software controls the movement of cutting tools and machinery. It is widely used in both plastic and metal prototypes and parts manufacturing.
Advantages of CNC machining
- High precision: Because of Computer control, CNC machining can create high-precision parts with Complex geometries. The minimum part dimension tolerance CNC machining can make is 0.02mm.
- Material Versatility: CNC machining can work on a wide range of plastic and metal materials, covering almost all rigid materials. So whatever materials you need, CNC machining can make it.
Disadvantages of CNC machining
- Poor Consistency: CNC machining often requires manual post-finishing such as bonding, polishing, and painting, which can not accurately control the final quality of the product. the manual operations lead to poor consistency when CNC machining a small batch of parts.
- Not good for High-volume production: In terms of cost and speed, CNC machining is not good for high-volume production, because of the long per-part cycle time needed to make each part.
How does Urethane casting work?
Urethane casting, also called vacuum casting, is a process that uses the master pattern to make a silicone mold in a vacuum state, and then casts the parts using PU, silicone, nylon, ABS, and other materials in a vacuum state, cloning a replica that is the same as the master pattern.
Read more about our article: Guide to Urethane Casting Process
Advantages of Urethane casting
- Cost-effective: the cost of the Urethane casting process is lower than CNC machining and 3D printing due to urethane material cost is low.
- Perfect for small-batch production: After creating a master pattern, Urethane casting can create many copies of the master pattern in a short time.
- Easy to operate: After curing, the soft silicone molds are transparent or translucent, have good tensile strength, and are easy to cut and separate.
- Good Consistency: The silicone used for mold has good fluidity before curing, and when combined with vacuum deaeration, the detailed structure and decoration of the model can be accurately maintained.
Disadvantages of Urethane casting
- Easy to deform: The silicone material is easy to shrink and deform when heated at a high temperature and then cooled, which results in deformation. The general tolerance of urethane casting prototypes is 0.2mm.
Difference of CNC Machining vs Urethane Casting
Materials
CNC machining materials are extensive and include plastic and metal materials such as ABS, acrylic, PP, PC, POM, nylon and aluminum alloys, copper, steel, iron, and so on. however, only the plastic can be used for urethane casting such as ABS-like, and polycarbonate-like resins.
Precision
The precision of CNC machining is much higher than that of urethane casting. The accuracy of CNC machining is generally between 0.1-0.02mm. In comparison, the precision of urethane casting is generally 0.2mm, this is because of the influence of thermal expansion and cold contraction of silicone mold. So the precision requirements of cast urethane prototypes are usually not so strict.
Volume
CNC machining is commonly used to create one or two prototypes. If it is over three pieces, urethane casting will be perfect. One silicone mold can create 25 copies of parts.
Lead time
Generally, CNC machining takes more time than urethane casting for the same quantities. CNC machining process requires making parts one by one and repeating all the processes. Urethane casting only needs to cast the materials in the silicone mold and cure.
Cost
CNC machining cost is generally higher than urethane casting to make the same part. Usually, a CNC machined prototype costs $50 while a urethane casting prototype costs only $10. check more details about Rapid Prototyping Cost.
Alternatives of CNC machining and Urethane Casting
3D printing
3D printing can make more complex geometry parts than CNC machining, with a faster lead time and lower cost, however, the part strength is not as good as CNC machining and injection molding because it uses a layer-by-layer method to create the plastic part. Anyway, 3D printing prototyping is worth to be considered when you need to make plastic prototypes.
Injection molding prototyping
Injection molding prototyping is the process of creating small batches of plastic parts in a short time with rapid injection mold tooling. it is perfect for the production volume range from 100 to 10000 Pieces.
Conclusion
After you know the difference between CNC machining and the Urethane casting process, before you start a parts manufacturing project, you will need a professional supplier to help you make the final choice. KUSLA, covering all rapid prototyping and most of parts manufacturing capabilities, will help up get your parts quickly and cost-effectively.
You may also interested in other plastic parts manufacturing process comparisons
- Urethane casting vs injection molding
- CNC machining vs 3D Printing
- CNC Machining vs Injection Molding
- Urethane Casting vs 3D Printing
FAQ
Is CNC machining better than Urethane casting?
The answer depends on the requirements of the project. for high-precision parts, CNC machining is better, For small-volume parts, Urethane casting is better in terms of cost.
What is the lead time of CNC machining and urethane casting?
Generally, the lead time of CNC Machining takes 5 to 7 days for one part. Urethane casting takes around 5 to 7 days for ten parts.
