Most CNC Router users don’t need to go down the rabbit hole of ultra-precise adjustments. The factory setup is usually good enough. But if you’re after that last bit of perfection—the kind of accuracy that makes your work stand out—you’ll eventually need to shim your gantry.
We’ve already confirmed that the machine is square and parallel. But I wanted to squeeze out just a little more accuracy. On our CNC Router, we’ve got two mounting plates: one at the back, and another at the front. By adjusting these, we can correct any forward or backwards lean in the gantry.
How I Do It
First, I loosen the bolts just enough to give the gantry a tiny bit of movement. Then I slip in shims—thin pieces of stainless steel that come in different thicknesses, like 0.05 mm. Stainless steel is great because it won’t compress over time like aluminium can.
Next, I put the machine under a little preload (a gentle bounce or two), set my dial gauge to zero, and check the readings as I rotate it around.
- If the gauge goes positive at the back, the gantry is leaning backward.
- If it goes negative, it’s leaning forward.
This gauge is super sensitive—one full rotation is just 1 mm. Given where we’re measuring, even being half a millimetre off is already pretty good. For woodworking, that’s more than fine. But if you’re doing precision mould work, you might want to get it down even tighter.
The Secret to Tightening
When it comes time to lock everything in, don’t just crank the bolts down. Tighten slowly, in small stages, checking your gauge as you go. Go too fast, and you can undo all the careful work you just did.
I work from point A to point B, making sure both ends stay as close to zero as possible. Once it’s dialled in, that’s it—you’ve got a gantry that’s as square as it can get.
Final Thoughts
It doesn’t matter if you’ve got a CNC Machine that cost a couple of hundred rand or a machine worth millions—the process is the same if you want top-tier precision.
If you’re into machines and want to learn more about setting up and tuning CNCs, stick around. In the next session, we’ll walk through an AM.CO.ZA CNC machine and how to get the best out of it.
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