I’ve never had issues with designing parts, but I’ve never really delved too much into the realm of CNC. Being a gaming hobbyist (and having access to a large industrial CNC Router), I thought I’d rectify that. Finding myself in dire need of a way to store things in between games, I designed up a simple box for cards and dice, and began experimenting with Fusion 360’s CAM functionality…and I have to say, I’m rather impressed.
Here’s a list of some of the most important things I’ve learned along the way:
Know what drill bits you have and how they work.
This is actually pretty important on the CAM side of things. A fluted drill bit will have to ramped down into a pocket cut as opposed to a spiral bit, which can make a plunge cut, which (depending on how many pockets you have) can drastically speed up production.
The 2d Pocket operation allows for Helix cuts (essentially a circular cut that ramps down into a specified depth).
This is drastically slower than a Plunge straight into the wood – spiral bits are designed much like a drill bit,
allowing for a longer cutting edge.
Here is the actual helix path operation.
For precision and quality, always perform a roughing pass on edges before a finishing pass.
After the first time of attempting the manufacturing process on the CNC Machine, I definitely did not consider a finishing pass and wound up ripping up any corners that faced the cutting edge of the router bit. I was not pleased. Adding your initial cut with a roughing pass allows you to chew through a bulk of the material quicker, while leaving the finer more important locations (such as the edges) to be finished with a slower passing and smaller bit for getting into and around tight locations. You can set up a roughing pass by simply setting the amount of “Stock to Leave” in the Passes section of your tooling feature:
Radial Stock controls the amount of material to leave around the sides of the router bit, whereas
Axial Stock controls the amount of material to leave in Z-axis direction (ideally going straight down).
If you’re unsure on the operation, pay attention to the Tooltips!
Typically this can be said of pretty much any tool or feature in an Autodesk Program, however they really went to the next level with the CAM operations. Beyond the actual CAM Feature Tooltips, they actually provide a tooltip for nearly every option within their features.
Great googly moogly these Tooltips are awesome!
Know the machine that you will be working with and how it operates.
This probably should have been higher up in the list of things I’ve learned, but definitely deserves an important spot. This will translate into how to not only setup your part prior to creating your cutting paths, but also creating the necessary G-Code. When setting up your part, it’s important to know how your CNC Router (or laser) handles X, Y, and Z coordinates. The Z-direction should always be perpendicular to your top face that you’ll be cutting from.
Notice that the Z-Axis is set to point away from my cutting face. For large parts it may be quite important
to specify the location of your X-axis as well.
I found that it was prudent to note this operation. If your parts Coordinate system doesn’t match up correctly to the CNC router, it can cause you a bit of a headache trying to figure out why the router bit is refusing to face the correct direction.
Know how your CNC machine handles tool changes and design for that accordingly.
Ask anyone who has ever used a CNC router, and they’ll tell you that one of the most depressing things is incorrectly cutting your part (i.e. not taking into account how the machine handles the code). If your machine will automatically perform tool changes, you could probably skip this step. If your design requires a manual tool change, then it might be prudent to consider designing two separate G-Code Outputs. Some Router Machines will pause operations or offer a few seconds of time between a tool change to stop the Router and perform the bit change. Other machines (like the one I was using) will simply just ignore that pause and continue detailing out fine details with a giant ½” router bit – yeah, it destroyed the part and wasted about 10 minutes of Routing time.
You can easily create G-Code for individual router bits by manually selecting the operations using
one sized bit, right-clicking, and then selecting “Post Process.” Make sure to save it as something
easily recognizable and acceptable by the router.
Behold the full summation of all of my tool paths:
It was manually cut out on a band saw and finished on a sander.
…and the produced product with only a few minor changes:
If you have any additional tips or good stories on your CNC blunders, feel free to share them in the comments!