If you’ve ever used a CNC router or mill, you’ll know how many little things need to go right before you get anything resembling acceptable results. We could (and probably should?) run a whole series of posts on selecting the correct bit for the job at hand and figuring out the appropriate feeds and speeds. But before you even get to that point, there’s something even more critical you need to do: hold the workpiece down so it doesn’t blast off into orbit when the tool touches it.
Now that might sound like an easy enough job, and for basic flat stock, it often is. But if you’ve got an oddly shaped piece of material, you’ll quickly realize how inadequate those trusty c-clamps really are. When you get to that point, it might time to check out these OpenSCAD hold down clamps from [ostat]. Thanks to its parametric nature, you can plug whatever dimensions you need into the script, and in a few seconds it will spit out an STL file for a bespoke clamp that you can print out and put to work.
As currently implemented, you can easily change the height, overhang, and angle of the front of the clamp. It’s also possible to adjust the parameters of the rear of the clamp, but you’ve got fewer options there. You can also dial in the parameters for the bolt that will attach the clamp to the bed, such as the diameter and cutout length.
If you have OpenSCAD installed you can do it all locally, but [ostat] also has the script working with MakerWorld’s online customizer if you’d rather go the web route.
Now, we know what some of you might be thinking — do I really want to hold down my work piece with a printed clamp? Having experienced first-hand the havoc that can be caused by a work piece coming loose during a milling operation, it’s a valid enough concern. But the beauty of being able to run these clamps off on your desktop 3D printer for a few pennies worth of plastic each is that you don’t have to limit yourself to just one or two. You know the saying: many printed clamps make light the work…or something like that.
Not even a washer under those screw heads with that small grip on plastic? It will get chewed up after a few times which I assume is what these custom made hold-downs are for. A square washer filling the width would be better yet, could be plastic with a round washer on top.
Great comment: Aliexpress has heaps of square washers and rectangular nuts too.
“… hold the workpiece down so it doesn’t blast off into orbit when the tool touches it”
Hey, you figured out how to solve single stage to orbit! ;)
Every tool is an earth-to-orbit cannon if you operate it wrong enough?
I’ve been using these instead: https://www.thingiverse.com/thing:1071010
Their geometry lets a single clamp work for stock of thicknesses ranging from zero to about 1.5 inches (though at 1.5 inches they don’t hold quite so well). They feel solid and I’ve never had one fail. The only thing I added was 3D printed triwing knobs with captive nuts ( https://www.thingiverse.com/thing:3419779 ) for tool-free use.
Though much of the time when cutting with a 1/8″ bit, I just use double sided tape.
+ those can be printed laying on their side which makes them almost immune to breaking via layer separation.
The ones in the article have the clamping force ripping the layers apart. I wouldn’t trust those…
Good idea. Though, they have to sized stout enough to do the job they are asked to do.