Saturday, August 26, 2017

A Dusty Boot For A 4030 CNC

I've been trying to figure out the hang of CNC machining for a while now. I quickly decided that I would need a dust boot to contain all the wooden particulates of various sizes that the machine kicks up. However, the few models that looked like they would work with my Chinese 4030 CNC machine did not impress me. So I decided to make my own.

My first design used a two-piece boot that would be magnetised. A plate would be attached to the gantry using an existing hole and some screws to clamp to the outside (so no new holes would need to be cut). A wooden beam would connect the two. A screw would press a tensioning piece against the beam to tighten it up. The design looked like this:

I ordered some strips of nylon bristles and cut two pieces of the appropriate length, trimming the bristles to the desired height.

I then glued and screwed the two strips to the outsides of the two halves of the boot.

Once it was dried the magnets held them together well enough.

Finally it all went together.

Meanwhile I was sorting out a dust collector. I bought a vortex dust separator and screwed it onto the top of a bucket, after cutting a hole out of course.

Unfortunately that didn't work out as well as I'd hoped. It turned out the bucket wasn't strong enough; it compressed somewhat under the pressure, eventually cracking.

So off I went to buy a stronger bucket. Fortunately this one stood up to the force of suction just fine.

I soon found out that wasn't the only problem; it turned out the dust boot wasn't rigid enough. As the gantry moved the hose started to apply pressure in different directions, torquing the whole assembly and causing the boot to simply fall apart.

Clearly the magnets weren't strong enough and the assembly wasn't rigid enough. So it was back to the drawing board. After stumbling across an interesting design from someone called "Pointy", I started working on a new design that would be simpler, smaller, and more rigid.

You've heard the old adage "measure twice, cut once"? Well, let's just say I had to carve the boot several times as I kept making mistakes with my measurements or numbers. And in the middle of that, my Y-axis suddenly stopped working.

I was very dispirited at this point and had to distance myself from the whole endeavor. Eventually though I came back and tracked the problem down to the actual cable connecting the controller to the stepper motor. Fortunately I was able to fashion a crude replacement.

At last I was able to cut the design and start to assemble it. The plan was to use a plastic pipe to connect the boot to the plate; this would mean a smaller boot with less force being applied directly to it. The tube would be clamped in place, and the clamps would be bulked up with additional layers of wood for rigidity. The boot itself would be one piece, with a channel along one side that would allow it to pivot with the bit in place.

In it's brief trial run the large size of the first boot prototype caused me some issues, so one of my goals with this new one was to reduce the size of the boot itself. To that end I decided to cut a groove in the underside of boot for the bristles, rather than gluing them to the outside. While working on this, I ended up putting together a jig that would help me cut the bristles to even lengths.

Fortunately that did the job, and I was able to get a fairly even skirt of bristles. When finally assembled and put to the test, I'm happy to say that the new boot worked quite well. It's not perfect, but it does do the job.

It took a lot more time and effort than I would have liked, but it does make the machine much easier to use. I wrote the gcode using a custom python script. All the parameters such as the connecting tube size and screw diameters are variables that are easily changed, so I can cut new boots to fit different parts should anything need to be replaced. If anyone would like to get the gcode so they can cut a boot for their own 4030 CNC machine, you can leave a comment and I'll contact you.

I'm thinking about trying to cut a clear acrylic boot to replace the wooden one someday, but I reckon it will be a good long while before I can be bothered. My next plans include an improved spoil board, a sort of bed extension/clamp, and a new controller box to house the upgraded components I'm using. I really hope they don't take as long to make, or give me as much trouble, as this dust boot did.

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