Rapid-prototyping firm First Cut Prototype, Maple Plain, Minn., (firstcut.com) says if you send in a solid model of a needed part, it will machine up to 10 of them from any one of the most commonly used thermoplastic resins and have them in the mail within 1 to 3 business days. Of course delivery depends on part complexity and quantity, but currently most orders, they say, are being shipped within this timeframe. There is also no surcharge at this time for this fast delivery. Stocked materials include most common thermoplastics, including some materials that are not on the injection molding list at the sister division, Protomold.

“We call the process ‘subtractive rapid prototyping’ because it uses CNC milling,” says VP of operations Mark Kubicek. “Prototypes ship as quickly as those from additive RP processes. Parts are machined from blocks of plastic, not ‘plastic-like’ materials used in additive rapid prototyping,” he adds. CNC machining eliminates stair stepping inherent in additive processes.

Typical applications for parts made this way involve functional testing before committing to injection-mold tooling or high-volume machining, and custom “one off” projects such as jigs and fixtures that require only a few parts.

Machining is limited to three-axis milling from two sides. Parts are milled from the one side, turned 180°, and milled from the other. Undercuts or secondary operations are not supported. Kubicek says expect tolerances of ±0.005 in. And the estimated lead time is the best estimate available at the time of quote for the part.