Extensive Insight into Urethane Vacuum Casting
Creatingway is on the leading edge of urethane vacuum casting technology. We first produce silicone rubber molds. This then allows us to create urethane cast components easily and accurately. Urethane vacuum casting ideally enables us to test functionality and design verification.
Quick Short-Run Production for Small Batch Plastic Prototypes
Creatingway’s urethane vacuum casting technology avails a variety of materials. This enables us to create cast urethane components. It also allows us to carry out low volume production, functional evaluation, and pre-production tests. Some clients prefer cast urethane parts, as they are quick and inexpensive to produce. Additionally, there is no need to invest in metal tooling when quantities are a few dozen short runs. In some instances, we can make deliveries in a matter of weeks.
We sometimes refer to urethane vacuum casting as polyurethane casting. We occasionally use this technique to simulate finished products or final injection molded parts. Normally, we create molds from silicone rubber. We then use SLA or CNC part as a master pattern. These molds help duplicate textures and fixtures. Moreover, they give consistent finishes from one component to the next.
How to Make Master Patterns from Urethane Vacuum Casting
We determine the quality of the casting parts from the quality of the master pattern. We first machine most master patterns by CNC machining. It allows us to hold tight tolerances of up to +/- 0.05mm. However, we opt to make the master pattern by SLA for complicated structures. When comparing the two, CNC is more costly and takes longer than SLA.
Secondly, we determine the quantity of the masters from the total quantity of the casting parts. For instance, if the casting quantity is a few pieces, then one master pattern is enough. In the case of over 30 pieces, we first must factor in the delivery time. After this, we find out that two masters will be enough. This allows us to make more silicone molds to do the casting faster.
Some clients want parts with high tolerance, glossy finish, and optical clarity. In this instance, we manufacture the master pattern through CNC machining. It makes urethane vacuum casting with high specification precision machining. Therefore, the casting part comes out the same as without needing extra surface finishes.
How Do You Make Silicon Rubber Molds?
We create silicone rubber molds or RTV molds from a master patter. Firstly, silicone rubber offers excellent flexibility, self-releasing properties, and chemical stability. Secondly, it offers minimal shrinkage and effectively carries fine details.
We commence the silicone rubber mold making process by sticking thin films into the master. This makes the mold easier to cut. Additionally, it acts as a seam for the final mold. We then proceed to suspend the master model in a box that has attached gates and vents. It has risers at the top allowing air to escape from the final mold. Afterward, we pour silicone around the master then utilize a vacuum to remove all the air. Our casters proceed to cure it in an oven at 40 degrees. This takes between 8-16 hours depending on the volume of the mold. Upon completion of curing, we remove the box and risers. The silicon rubber mold forms after the removal of the silicone.
The Polyurethane Vacuum Casting Process
Creatingway’s standardized operational techniques assure accurate and consistent part replication. The operational parameters our casting technicians control are:
Steps to the Urethane Vacuum Process
The first phase is the preparation. It involves placing the silicone mold in an oven and heating to 60 – 70 degrees. We normally assemble the mold before vacuum casting urethane. We then select an appropriate release agent. This is vital to avoiding surface defects and stickiness. Afterward, we proceed to prepare the polyurethane resins by preheating it to 40 degrees. We mix two-component resins in exact amounts. We then proceed to fully stir and degas for 50-60 seconds under vacuum.
Under computer control, we pour the resin into the mold in the vacuum chamber and cure it again. Small parts cure for an average of 1-3 hours while big parts take up 3-6 hours. We finally remove the part from the silicone mold after curing and leave an exact copy of the original. We can now proceed to prepare to repeat the cycle.
Applications of Polyurethane Vacuum Casting
Short Production Runs/ Low Volume Manufacturing
Vacuum casting is ideal for top-notch plastic prototypes. Some volumes do not justify investment in injection molding and short-run manufacturing. Vacuum casting allows faster creation of these parts than traditional molding.
Functional Testing/ Engineering Verification
Urethane Vacuum casting is a relatively inexpensive tooling process. It thus allows for economical design changes and engineering verification. Moreover, we can then perform functional tests before the mass production of a component.
Color and Texture Studies/ Aesthetic Models
The urethane vacuum casting part can be a complete set aesthetic model. This is since it possesses different colors, finishes, and textures under the same idea. We can help undecided clients on the ideal color for their product, and achieve this by first making a silicone mold to produce 10-15 castings. We then paint each with your design texture and color, and also can then proceed to discuss internally with the design departments.
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