Long Vacuum Extraction Dust Skirt/Brush

I think I will have to use a thin, soft (probably silicone) rubber sealing strip and fashion it into a makeshift skirt by scoring it with a craft knife every 2 mm or so along the length.

Doug

I have had another think about this and I think these 75 mm door brush seals from Screwfix will just screw on to the side of a rectangular (100 x 75 x 12 mm thick) acrylic sheet if I put some threaded inserts around the edge:

http://www.screwfix.com/p/stormguard-industrial-door-brush-seal-aluminium-effect-1-25m-2-pack/95547

The filaments appear to be fairly soft polypropylene which is good. If I use a coach bolt to mount it through the 15 mm locating rod with a wing nut or nyloc nut on the bottom face of the orange mounting plate, then it will be very easy to remove to change cutters.

I will report back when I get this made.

Doug

Doug, I've been using the standard tool length sensor for Z-axis and I like it a lot. I have used the paper method before but the sensor was a very welcome addition. Besides, I don't smoke.

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As promised - an almost complete kit of parts for the super mousetrap!!

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Hi Peter, how's this going? I've been working with the 4th axis a lot and accurate zeroing alignment of the y-axis is crucial. I have been employing an optical method I brought in from an entirely different context, for now with Eyeball Mk.1 I get a <0.5mm error which for me is too much. I can improve on this with time and proper instruments but it will always be terribly time consuming. So if you have a better solution you'd like to share I'd be interested :cheer:

Hi,

The "super mousetrap" works exceedingly well. I don't have the tools available to accurately measure the sensitivity, but using the UCCNC DRO the trip point is repeatable to better than .01mm (0.0004") both vertically and horizontally.

PCB was milled on my SC420/2 and uses polished phosphor bronze balls ans gold plated connector pins for the electrical "clever bits". Centre carrier is black delrin with a Renishaw ruby stylus. Metalwork made on my mini lathe and mini mill with the help of a precision rotary table for accurate drilling of critical holes.

Peter

I'm still working on this design, hopefully I'll cut the 12 mm acrylic sheet this weekend.

I realised just yesterday that since I won't be using the Stepcraft HF spindle exhaust system ever again (the StoneyCNC small industrial HF spindle fully obscures the exhaust port), I can just attach my VonHaus ash vacuum's hose (38 mm i. d. on the plastic coupling) directly to my DIY dust shoe, rather than keep on using the length of 24 mm i.d. hose from the Stepcraft kit).

Therefore I'm now on my second revision! I assemble the GCode manually by decrementing successive 0.5 mm depths per pass using the output from MeshCAM's "pencil cleanup" toolpaths. I ordered a length of 38 mm o.d. acrylic tube for the exhaust flue yesterday.

Incidentally, if anybody wants the Stepcraft HF spindle exhaust kit, I am happy to sell it. The new price is now £72.00 including VAT from StoneyCNC. I have drilled and retapped a mouting bolt hole right through the mounting bush but other than that, it has been little used. I could probably do it for £40 + shipping.

Doug

Here's what progress I've managed to make on this DIY/custom dust skirt:

Speeded up video (parameters on the YouTube listing)

http://www.youtube.com/watch?v=T0iGVesYtxw

https://www.youtube.com/watch?v=T0iGVesYtxw

I don't know whether it will work well until I've assembled then tested it. I ordered some M4 brass press-in threaded inserts for plastic to try instead of the M3 ones.

Doug

O.k., my DIY dust skirt is essentially finished. I need to think about adding a locating pin that engages into the gap in the orange plate where the securing bolt for the spindle is and my idea of using a wing nut to allow easy removal didn't work because the wings foul on the aluminium brush carrier.

I will test it eventually and post up a YouTube video.

If anybody wants any further info, let me know. I have attached the STL file and my G Code toolpath for the base plate.

The aluminium brush carrier sections are secured into M4 brass press-in threaded inserts using M4 x 8 mm stainless steel dome head allen key machine screws. I have already posted where I obtained the brush filament and aluminium carrier - this will be very easy to obtain in many countries. The base plate is 12 mm thick acrylic and the exhaust flue a 38 mm o.d., 3 mm i.d. acrylic tube. This is just sanded and interference fitted into the rebate. It is an extremely tight mechanical fit proving that plastic cement is unnecessary.

Obviously if you go for the 75 mm long brush filaments, you can trim them to your desired shorter length.

The total mass of the assembly as shown (less the M6 mounting bolt and washers) is 238 grams on reasonably accurate digital kitchen scales.

Doug

Here is a short video of my DIY dust skirt in action which thicknessing an ebony fretboard to 7 mm in 1 mm passes with a 6 mm 2 flute solid carbide slot drill.

http://www.youtube.com/watch?v=ZTAu_hyw22Q

https://www.youtube.com/watch?v=ZTAu_hyw22Q

The vonHaus ash vacuum is very noisy so nothing much else can be heard.

Commissioning it threw up two issues:

1. It's slightly too wide to allow the X axis to home so I had to home the machine first then attach the dust skirt later.

2. It built up static electricity which caused a discharge (not visible or audible on this video) which caused the toolpath to stop on one occasion and lose Y steps only on the other.

I seem to recall from high school physics lessons that rubbing Perspex/acrylic or ebony rod caused a build up of static electricity so maybe ebony is the problem here?

I detached it and continued with the toolpaths for the fretboard which turned out rather well. Less than an hour's work to get it cut and the mother of pearl marker dots in. It was 'rough' cut to 6.6-6.7 mm thick at the crown ready for final radius sanding with a StewMac aluminium radiusing beam to 1/4" (6.35 mm).

Doug

Apparently static build up from vacuum systems is well known (just not to me): :blush:

http://www.talkshopbot.com/forum/archive/index.php/t-15249.html

I will need to attach an earthing lead via one of the M4 mounting bolts to the machine bed, or better, to the earthing wire from the machine itself.

This is clearly a very important consideration guys. I presume that this doesn't afflict the Stepcraft vacuum extraction system because the dust shoe is made of metal? Therefore, nobody else will have likely experienced this problem?

Doug

I now believe that the reason this has just become a problem is because my previous setup included the section of anti static 24 mm i.d. hose supplied with the Stepcraft exhaust adapter inserted into the end of the vonHaus ash vacuum. The hose on the ash vacuum is exposed METAL inside with a plastic outer. The body of the ash vacuum is stainless steel. In the new set up, the metal hose was attached directly to the machine via the DIY dust skirt. So I think that the smaller diameter hose was acting to insulate the machine from any static build up in the larger diameter hose.

The many thousands of wood particles blasting over the metal hose obviously leads to a rapid build up of static electricity.

This being the case, I believe that the solution should be simple: buy a length of anti static 38 mm i.d. ribbed vacuum hose, remove the two end cuffs from the hose on my vonHaus ash vacuum, attach them to new hose and crack on.

Doug