Not the Ultimate Dust Shoe / Two-Part Acrylic CNC Extraction Boot

In this video I am going to make a dust shoe for the CNC machine. I’m going to base mine on a two part design which uses magnets to attach the brush section to an upper part which is clamped onto the spindle. You can see this Parametric Dust Shoe by and a similar one by KentCNC – which I’m using as inspiration. Theirs sells for quite a lot but the material cost shouldn’t be too high. The main different I will make, is splitting the bottom section with the brush into two so I can more easily remove them to change bits.

I am cutting out a practice piece from 9mm MDF to check the design before I use more expensive acrylic for the final version. I made this design from scratch, using an older version of ArtCAM. However, this version isn’t available any more and their subscription software is really expensive, but you could create a vector file in software like Inkscape, for free.

So this this came out really well. I am really impressed. The finish is not too bad considering I used a 1/8 of an inch bit which was probably about 30mm long. So that’s quite a long bit. If I used a smaller bit that’s held up in the collet a bit higher I probably reduced some of these lines at the bottom, which to be honest are barely visible. That’s a really good finish. And the thing I suspect and will double check this now. Look at that, barely went through to the wasteboard. This measured as 9.12mm and I set that in the software, and it didn’t cut into the waste-board at all. It’s so accurate. I can’t believe I’ve built a machine with birch-ply plates and it cuts better than the bloody xcarve.

It is difficult to clamp stuff down on such a small bed, I feel like I’m really wasting material because I’m trying to hold everything flat. That really should have been all the way over there but I was nervous about putting a metal mending bracket so close to edge. Of course if  I clamp something like this I wouldn’t have any room.

Because of the fixed deign of top section, I will have to make different bottom section with various length of brushes to cover the different bit and material depth combinations.

So I’ve bought a couple strips of this brushed draft excluder. Each one cost about 2 quid from my local Wilko. And  I’ve done the sensible thing of actually cutting my template and test dust shoe out before I had the chance to measure the metal along here. It’s a little bit bent because I’ve already tried to bed it. This all comes out. It’s a pretty decent price for two quid, and I’ve obviously spent four for this. What I’m going to try do is check whether I can cut it, how it’s assembled, whether the brushes fall out, if I can bend it and so no.

I did look for flexible brushed draft excluder but couldn’t find anything here in the UK. The rigid stuff in contrast was really cheap.

By the looks of it I think the way this is made, there is a wire that goes in the centre of the brush which is laied out like that, and it is folded over with this piece of aluminium to keep it in position. And that sorta crimps over the central rod or whatever’s in there.

In retrospect it would have been easier if I had design the grooves for the brushes as a collection of straight lines –  but that might have impacted the feng shui of the machine.

Alternatively I could have used Ethylene-Vinyl Acetate or EVA craft foam sheets. You can get these in various thicknesses and they can be glued and are easily cut.

I decided to make a template to clamp the brush-strip against, and create the shape I needed. The machine might seem a bit slow, but that’s because the acceleration is still left at 10mm/sec2 – but as I’m still getting to know how this machine operates I’ll play around with that when I feel a bit more confident.

The channel is a little tight for the brush, so I will adjust the vector file to compensate.

I am now drilling some holes into the acrylic to work out the offset needed to get as tight a fit as possible for the magnets I will be using.

Ok I’ve just spent an hour trying to cut different holes out doing area clears just to see if I get the setting right. The feed-rate and step-over so this 7mm magnet can actually fit inside and I’ve managed to get it to the point where I’ve had to hammer it in, and I can’t get it out now. But that’s not a bad thing because I essentially want this to be stuck in there, and if I can avoid using any glue that’s even better.

It took a while to get the setting right but in the end I used an RPM of 15000, a feed rate of 620 mm/min and a plunge rate of 200mm/min, and the thing no one ever tells you – a step over of 25% of the bit width. I am using 1/8 of an inch bits which is 3.175mm, so 25% of that is roughly 0.79mm.

Knowing the step-over is important because I’ll be doing an area clear for the magnets and the brushes. The bits are quite long, and this can effect the speed and step-over. Shorter bits are more rigid and therefore you can go faster, a longer bits can more easily flex and should be ran slower.

The chips look amazing on this. I mean nothing melted. It looks like snow.

So I made a few mistakes in the end, cracking the acrylic where I would pass the clamping bolt through and realising I wanted to change the design after I had cut parts out.

Ahh you f**k.

The size of the machine screw heads was also too large and left a gap between the top and bottom pieces of acrylic.

I’m not sure how that will effect the extraction if I’ll be pulling air from here as well as from the bottom.

I eventually cut a few different versions as I went along, and even improved my drilling technique. This is how drilled the hole for the clamping screw, learning from the mistakes from the first attempt. I used a centre drill bit to first mark where I would drill through and also placed a piece of mdf between the gap to prevent the pieces flexing.

I added small 1/8 inch through holes where the magnets would fit so I could push the magnets out if I ever needed too… and I did.

I also noticed that magnets become weaker if they are struck – so  here’s some advice, don’t use a hammer.

I eventually changed to machine screws with smaller diameter heads because one magnet was moved out of alignment when acrylic was clamped to the spindle. But these were also thinner could use that 1/8 inch through holes to push the magnets back so they made a positive contact… and I simply push.

The last thing I did was use larger garage door draft brushing, to make a second dust shoe attachment. I had to cut each section in half so it could shape and push them into position. This was arduous work and my hands were aching afterwards.

That was hard.

So you probably want to see this in action, and here it is. I’m cutting a piece of MDF. I’m actually cutting a test plate for the second version of this CNC machine. I designed this on Fusion 360 with parameters to help develop the design and solve some of the problems with the first version. The joke it I have redesign the CNC machine to the point now that if I make a new one, I will also have to redesign the dust shoe. So this is not the ultimate dust shoe. Anyway if you want to see see the walk-through video where I explain what I have done on Fusion360 I’ll link to that at the end of this video. Thanks again for watching.


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