3D Printed CNC Machine – Compact Dust Shoe, Surfacing Wasteboard and Mistakes.

 

In the previous videos I assembled and setup my 3D printed CNC machine. I designed the machine to include several features which address issues I had with earlier versions, or similar hobbyist CNC machines I have used (like the dreaded X carve).

I think the machine is pretty good for a hobbyist machine but none would be complete without a dust shoe. One of the first things you should do with your CNC machine is level your wasteboard. But that can be a very messy process, so I’m going make a dust shoe to dramatically minimise the particles that can be emitted while CNC’ing.

It’s not bad at all really. I think I put the radius on this a lot larger than the other three. That’s a bit stupid.

I began by cutting one out with the machine itself using some scrap ply. You can see how simple it could be to make. I’m using scrap bits of flexible PVC curtain, which I’m stapling onto the ply frame. After which I snip using a garden secateurs to create the flaps so air can pass through to help with extraction.

Eventually however, I realised the dust shoe was a little too wide for the wasteboard and would push against the y axis c beams on either side of the machine. Also the bit I wanted to use to use to surface the wasteboard couldn’t reach the furthest ends.

It then occurred to me having my wasteboard that low was an odd design feature. It meant I was restricting the maximum width along the x axis between the c beam and not the plates. There’s not much I can do about that now but maybe I can reconsider this in future designs.

I then thought to myself, if I’ve 3D printed all the plates so far why don’t I also 3D print the dust shoe as well. I took some measurement off my model for the machine which I had design. This included the offset of the centre extraction hose to the centre of the spindle, and the spindle to the z axis c beam; and once I had those measurements it was pretty easy to draw something new.

This is what I drew. It will be a stationary shoe which the spindle passes through. As I’ll be mainly machining 2D profiles I can adjust the bottom of the shoe to run along or just above my material, keeping the distance to a minimum and ensuring the maximum amount of dust is extracted.

Ok I’ve made a 3D printed dust shoe that fits, on my CNC machine like this. It’s a fixed position one so the so the spindle actually moves through the opening, and this hose here eventually clips into place here when the bit is a little further down.

I printed two versions. The first having a few things I overlooked. I tried to bevel the top spindle opening and make it more aerodynamic, but somehow made this narrower than the spindle diameter which was a silly mistake. And secondly the mounts for the arms being a little to short. The print time was about 10 hours in total.

I’m preparing the machine to surface the wasteboard. Probing the bit, homing the machine, and moving to the origin position. While doing this I noticed something I had to address with my dust shoe assembly.

So the machine screw is actually in the channel along here. Essentially this bit here can’t move, so that’s not going to be a problem. I just need to make sure that when I set my shape to area-clear that I don’t exceed the outside of the bit, so I take the bit into account when creating that rectangle.

I spoke too soon, and my first attempt to level the wasteboard resulted in a crash. Ok so that went straight into the side of the machine. I over shot my wasteboard dimension and bumped the dust shoe into the c beam on the left hand side of the machine. I think after I homing the machine, I didn’t compensate for the origin, being further in. I also didn’t realise but the machine screw on the dust shoe had bottomed out in the channel of the c-beam, so I couldn’t move right to the edge.

So what I’m going to do is take the bottom machine screws out and replace them with smaller ones which will hold this in line with the slots, but I’ll only tighten the top.

The bottom machine screws will act like studs, and help keep the shoe square, and I only have to tighten two screws instead of four.

I decided to use my brain, and after homing, I moved the gantry over to the opposite corner manually, reading the measurements off the software I was using – bCNC. Ok I’ve moved my spindle across to the other corner and taken a count of the position – writing that down. And then what I’ve done is offset another rectangle the diameter of the bit I am using which is about 25mm, and that’s centred. I’m going to create two gcode files now. One that goes along this perimeter and an area clear within it.

With all the machines I’ve made, I’ve always had a clicking noise while moving along the x axis, and I can’t quite tell where that is coming from.

I did a perimeter area clear but ran into another problem. Some where my own mistakes or oversights while others were accidental. This one was accidental, I think. I’m sure I tightened the motor coupler for the x axis. Anyway this had become loose and meant the leadscrew was slipping. I fixed that by tightening the grub screws.

Ok the coupler on this side here has come loose, so I’m going to have to tighten that up as it’s slipping.

The next thing that went wrong, was the bit I had used to surface began to scorch the wasteboard. It was sold as a surfacing bit but I can never get the feeds and speeds right for these smaller, three toothed ones. I tried changing the cuttings method from conventional to climb – this is simply clockwise or counter clockwise, or visa versa. The blade travelling into the cut or away from it, but that didn’t help so I decided to use a different bit.

I am now doing a raster surfacing attempt. I went from side to side along my x axis. I decided to avoid doing front to back as that would have hidden the effects of the spindle nod, which my pivot plates would help eliminate or dramatically reduce. I also checked the temperature of the spindle using my laser temp measurer. What I notice is under straign – using the three tooth surfacing bit built up more heat in the tool and the spindle. As long as you don’t over strain the tool and try not to cut too much off in one go, the spindle shouldn’t heat up too much. I got reading of a max of 30 celsius.

That’s the bit I used in the end.

So that took me a couple goes to do. The cutting job by itself was about 40 minutes. I was running the tool at 1200mm/min and there is a bit of dust around, especially when the shoe got to the edge but that’s a lot less than when I’ve had to do this or have done this without a dust shoe on the previous machines.

The other thing that happened to go wrong, was managing to plunge straight into the corner of the waste board, twice. I was lucky I didn’t reach the aluminium profile the second time. The first time was because I didn’t probe the bit and set the depth correctly after changing to the new tool. But the second time was a bit more confusing. It seems that I have to home my machine, import the dxf file and then probe. I didn’t do it in that order and something went wrong.

The last thing I did was check how square the freshly surfaces waste-board was to the spindle bit, and to make final adjustments. I found the longest parallel bit I had, using an engineers square to hold my bevel box to the bit. I slackened the machine screws on the pivot plates and made my final adjustments.

While this isn’t the most rigid CNC machine you could build for the cost and method, it’s easy to do and the features I’ve desinged into the machine help reduce the errors that are often present with hobbyist machines.

I’m now going to use the machine to cut some test pieces out of another design I’ve been working on which will use 12mm linear guides, and I’ll be showing that in the next video.

Thanks again for watching and to all my patreons for their support.

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