Skill Builder: 10 Questions to Ask Before Renting Time on a CNC Mill

If you’re like most of us, you probably don’t own an expensive CNC mill in your garage. In many parts of the country, one isn’t that far away. To use one, you’re likely going to have to rent time on it. Make every minute of time in front of the machine count by preparing in advance with these steps.

• Consider the capabilities of the machine.
  • How big is the machine? Does it move 48″×96″, or does it cut that size? If the latter, the movement of the machine is likely larger than 48″×96″, which means you can use all of a full sheet of ply.
  • What bits are available to use? Do they match your material?
  • Does the machine have a hold down like a vacuum, or do you need to bring your own hold downs?
  • Can you familiarize yourself with the machine before hand? See if you can get an owner’s manual for the machine you’ll be using ahead of time. Even if it’s being operated by someone else it’s valuable to understand the machine.

• Software
  • Do you have your file in the right format? Find out what kinds of files the machine you’re using takes. It’s likely DXF but check to be sure.
  • Are you going to find quirks in the control software used by the machine? See if you can get a trial version of the machine control (CAM) software. Often times this is available as a trial for you to download. The more you can learn about the machine control software the less time you’ll spend fooling with it when you get there.
  • Can you run a simulation to find possible problems? See if you can find control software that offers toolpath simulation. Vectric products have an excellent tool path simulator that can help you work the bugs out of your toolpath file long before you sit down at the machine. Even if the control software on the machine is different, this can teach you a lot about how CNC machines cut.
• Materials, safety, and cleanup
  • Do you need to bring any tools? If you’re using someone else’s machine, ask them what wear items you might need to bring. For example:
    • Screws, scrap wood, bits.
  • Do you need to supply your own safety equipment such as hearing protection?
  • Are you prepared to clean up afterwards? My grandfather always said you should return something in better shape than it was when you borrowed it. Bring along a broom or small ShopVac to clean up after yourself. You certainly want to be asked back to use the machine again, don’t you?

Now that you have an idea of how you’re going to mill your next thing, you’re going to need to find a machine. CNC machines are actually in more places than you think. Here are some suggestions for finding one:

• 100kGarages is a great database of available machines. You can see what machines are around, their capabilities and contact info for their owners.
• Your local Maker Space, like Techshop, houses a variety of machines.
• Local woodshops are also great resources. Medium and large size shops often have CNC machines and they see a fair bit of down time. Shops like this usually don’t advertise CNC services, but you may have luck if you pick up the phone and call.
• Call a CNC manufacturer like ShopBot and ask them if they know anyone near you who would be willing to rent you time or help you mill your project.