5 Common Rapid CNC Machining Questions

Posted On April 14, 2017 By Tony Holtz
machine operator places solid plastic in cnc machine
CNC machining is a subtractive manufacturing process that mills away at a block of solid plastic or metal.

Most are familiar with machining, but what makes it unique at Proto Labs? These are a few of the most common questions we receive about our rapid CNC machining service. These answers will help you optimize your design for CNC machining and determine how it can improve your product development efforts.

1. What is unique about Proto Labs’ CNC machining process?
In order to efficiently machine low quantities as fast as possible, we do things a bit differently compared to a traditional machine shop. When you upload a 3D CAD file to protolabs.com, our proprietary software analyzes the design, creates a quote, and generates the CNC toolpaths. By automating the front-end of the manufacturing process, we can machine a part in as fast as one day.

2. How does the quoting process work?
Once you upload your 3D CAD model to our website, the software calculates the price—not a budgetary estimate—to machine your design. Within a few hours, you’ll receive an email with an interactive quote. Here, you can select different materials and quantities and receive real-time price updates. The quote even contains a 3D-view of your machined part, which will highlight any differences between the machined part and the original 3D CAD model. See a ProtoQuote preview here.

cylindrical turning part
Turning with live tooling creates cylindrical parts with high-quality surface finishes.

3. What is the typical cost of a machined part at Proto Labs?
Prices start around $65 for milled and turned parts. From that starting point, price is determined by part geometry, materials, quantities, and lead time. Due to our proprietary software and automated fixturing processes, there are no up-front non-recurring engineering (NRE) costs–making it a cost-effective way to purchase quantities that range from 1 to 200 parts.

4. What are Proto Labs’ machining capabilities?
For milling we can support part sizes as small as 0.25 in. by 0.25 in. by 0.25 in. and our standard maximum sizes are 10 in. by 7 in. by 3.75 in for most materials. Note that minimum and maximum dimensions can slightly differ between materials. If you’re machining ABS, acetal, or aluminum, we can support larger sizes.

CNC turning with live tooling has a maximum diameter of 2.95 in. by 9.0 in. in length and a minimum diameter of 0.16 in. and a minimum part length of 0.050 in., but no diameter should be less than 0.030 in.

View our machining design guidelines for more details.

5. How do CNC machining and 3D printing compare? What applications are best-suited for machining?
A machined part will have the true properties of the commercial-grade material you select, which makes it well-suited for injection molded prototyping. But it’s also appropriate for end-use parts due to high-quality surface finishes that are free from the layer lines you often find on 3D-printed parts. And, if you have a short lead-time, our quick-turn process allows you to get parts CNC machined from commercial-grade plastics and metals in the same time frame, if not faster, than 3D-printed parts.

We stock a variety of metals and plastic resins that are available in the sheet and rod stock. To see a full list of more than 40 stocked materials, visit our CNC Machining Materials pages on our website.

To learn more about CNC machining at Proto Labs, watch our presentation, “How to Design Efficient Parts for Rapid CNC Machining.” You can also contact us by emailing customerservice@protolabs.com or by calling 877.479.7541 and ask to speak to one of our knowledgeable application engineers.