THE CNC PROJECT

 

Part 4

THE DUST BOOT

The milling spindle of the CNC spins at thousands of RPM’s and it spits out dust that goes everywhere if you don’t have some way of collecting it: this is the job of the Dust Boot.

The standard one that you can buy for the OneFinity has a socket for the suction hose in front of the spindle. This is not workable for me because it not only blocks vision of what the mill is doing, it also sticks forward and that won’t fit in my cabinet – there just isn’t room.

In my trials assembling the bench to mount the CNC on top of, I made the benchtop 1220 deep as that was the width of plywood available.

I thought about patching another bit of ply on the end but that would have been very hard to clamp on straight while the glue dried and even then I had doubts about the strength and flatness of such a patched panel - so 1220 it is.

I needed something that sucked up the dust from the back where there is a lot more room due to the design of the 1F.

 

I looked around and PWN CNC made one that looked pretty good. It wasn’t cheap and it is mostly 3D printed parts but that’s okay – the variety of parts make it flexible and it can be set up to fit behind the drag chain, something I really needed.

The Suction Hose

The back end of it runs up through a clear tube and then joins the first hose piece through a magnetic clip which is pretty neat. You can pull off the hose and use it to clean up any overspill inside the enclosure.

 

This then runs through the flexible hose to the back right corner of the bench and down underneath to connect to the shop vac.

This is still in the trial and error phase of things – the middle of the hose hangs from an arm that is supposed to stop it fouling the head as it moves around but in manual testing it is not yet working properly yet: it jams or the magnetic fitting pops off.

Fixing the shoe mounting

The back end of the shoe is dragging on the deck. This partly the mounting arms and partly the load on it from all of the hoses and fittings.

At “A” you can see the bolt head where the two parts of the mounting arms are fixed together: this join is loose which contributes to the back of the shoe dragging on the deck. “B” is the slots where the shoe slides fit in and they are loose too.

You can see the sag at “C” and the duct tape. That’s temporary.

I bought a pair of mini drawer rails to mount the arms to the carriage.

This is still not ideal but it is better than it was.

I want dust shielding for the mini rails. Not sure exactly how but I will work something out.

 

mini rails test fitted to the carriage.

They don’t need to be perfect since the rails will not be moving when the machine is operating but it is still important.

Here is a diagram of my idea for mounting the dust shoe on the rails.

The arms need some sort of locking mechanism that allows adjustment.

I would like to have springs in there too – or some sort of friction brake so that when it hits something it will move up and not break. Well, that’s the theory.

This is all good but there is also a serious space limitation that it needs to fit in since adding to the width of the carriage will cut down on the working area of the machine.

 

I might 3D model the whole carriage so that I can design the rail covers and other bits since it is a narrow area and there is a lot of bits to fit in.

Thought some more about shoe drag and came up with this: the arm that holds up the hose should be sprung so that there is almost no weight on the back of the shoe: then the shoe will be just fine and the adjustment problem disappears. This hose arm also needs to provide pivoting for the hose but I think both those things can be achieved in one device.

I still need to finish the shoe mount and add a position setting widget but this will solve a lot of the problems.

The hose is nearly touching the back wall at most rear position so the hose will need to curve forward before it goes back: moving directly back with the carriage at the far right will cause maximum curving of the hose.

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A change of plans

I changed my plans for the dust shoe mounting as they were just too complex and as soon as things get dirty those drawer slides would have gummed up.

As this part of the project had stalled I dropped all of the fancy stuff - and since I now have a really good 3D printer (Plug here for the BAMBU LAB X1 Carbon!) I designed a new mounting arm and got it right on the second iteration ( I’m getting better at it now, the first couple of 3D printed parts I designed took five or six tries )

Printed and test fitted them, yup, all looking good. YAY!!!! Finally.

Also printed new knobs for the Dust Shoe mount and fitted them to the new mount arms. All is good so far, next up is making a new part to extend the tube running back from the shoe to the vertical tube.

This is the CAD pic of the new shoe mount in Blender. This is the inside face, the outside is flat.

 

I have no idea how the old ones were supposed to work - with the 80mm spindle mount installed they won’t fit. Mine has a cutout to allow the spindle mount to get past, the bolt holes are correctly aligned and the knobs on the bolts are shaped to avoid hitting too. The are designed to fit on Hex head M4 SS bolts. I used the same magnetic locking system as both Onefinity and PWN – 6mm dia x 4mm magnets. I used four bolts rather than two to make things stronger since the big issue here is the load on the the back of the dust shoe.

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Here is the new setup. I used the clamping plates ( metal plates that run in the back of the vertical slots) from both the original and the PWN CNC mountings so that there are four bolts holding it on.

The shoe slides bolted to the PWN shoe itself that slot into the arms were too narrow and slopped around so I glued some ABS sheet on and filed it down until it was tight in the shoe mounts.

Below is the pic of the shoe installed showing the mounting arms and knobs.

You can also see in the second pic below my 3D printed side screen mounts with 3mm clear plex screens, the Estop button fitted and the white box under the bench is the power meter so I can see what sort of current the whole thing will pull.

There is also a small LCD above the Estop that gives a temperature reading for the cooling water tank.

 

 

 . . . . . . and this is where I got to just about the same time Onefinity announced the Elite Series upgrade kit. 

 The control panel is finished, the lights work, most of the fabrication is done but there are still a few things to finish such as getting all of the limit sensors mounted - I was making my own because I really wanted them and they didn't come in the box. . .

 . . . but I was still having problems - mounting the limit switches on the Z axis was one, but the software was a much bigger one: I do not want to get into coding.  The whole point of this machine is to be able to use it to make parts for other projects.  It was not supposed to be a major project itself. Yeah, I know. 

So I'm getting the Elite upgrade kit. It solves a lot of my concerns with the original unit namely the lack of limit switches and step counting - and perhaps more importantly, software improvements. . . . . .

I hope to use a lot of my exisitng parts but we'll see about that. The dust collecting bits should not change and if you want the STL for the better mounting arms just email me. 

The biggest problem I can see with installing the Elite kit in my setup is that the X servo will stick out past the wall of my cabinet : I will need to make a new right side wall with a bulge in it for that.  I have already figured out a way to fit the Y servos by adding a "bump" but they are not going to move. That bulge is not so easy.

 I originally made a plywood cabinet to put the control boxes in but then learned from the Onefinity forums of troubles other folks were having due to RF interference, particularly with VFDs and unsheilded cables so I dropped that and bought a PC cabinet which I shored up with some sheetmetal to make a well shielded box.

So there it is, looks like it will be early next year before I get it running but I am not in a big rush.  Better to do things right even if it takes longer.

I was going to do a Part 5 with all of the wiring but that wil need to be redone with the new system and cables.  

 

ABOUT THAT SO-CALLED "ARTIFICIAL INTELLIGENCE":

 

The Management Problem

 A long time ago I saw how there seemed to be people in positions of power who really should never be in power.  I called it "The Management Problem" because I think it is the biggest problem for humans ever.

This video talks about it in detail and offers suggestions for how we can solve a lot of it.  It is long but very worth watching.  Thankyou Brian Klaas, I wish that more people can learn from your work.

 

THE CNC PROJECT

Part 3

DRAG CHAINS

What are drag chains? 

 They are a sort of hollow chain that is used to carry the cables from the fixed part of a machine to the moving part while protecting the cables and stopping them from getting tangled up.

The OneFinity I bought did not come with any and I wanted to add a milling spindle with water cooling so I bought some and made my own mountings to fit them to the 1F. 

I first looked at what other people had made on the 1F forums and one person was selling 3D printed drag chain fittings - but when I looked at them I was not happy.

There are three parts to such a set: the Top Mount, the X End Bracket and the X Bend Mount that curves all of the cables 90 degrees and then runs them into the second drag chain which goes to the benchtop.

This is his Top Mount:

I may not be a qualified engineer but I am pretty sure bending cables back 180 degrees is not a good idea.

Here is his X End Bracket and X Bend Mount:

Not bad but I think I can do a lot better. I also want to make sure that my cooling pipes from the spindle are smoothly routed as any sharp bend will restrict the flow.

I started with cardboard and sticky tape: I stuck the bits onto the machine with masking tape and marked where things went and fiddled with things until it all worked right, then drew the shapes carefully with compass and rulers.

Here is my pattern for the most important part, the X Bend Mount:

The idea is that the fluid pipes will go round the outside of the curve with the wires on the inside. The side walls are to be built up in two layers of 5mm thick ABS sheet while the bottom is 2mm ABS sheet.

The mountings use “L” shaped bits of the same 2mm sheet and three are used – two for the Bend mount and one for the end mount that is only there to support the aluminium rails that the drag chain rests in.

Here you can see the patterns and the parts ready to be cut from the sheet:

On the left are the side wall patterns and below them the bracket pattern.

The parts were first roughed out and then the sidewalls were glued together to final thickness before lots and lots of cutting, filing and sanding.

Note that the glue faces must be sanded first and cleaned to get a good gluing. I used “superglue” - I have some experience with it.

Note also the use of masking tape to allow drawing on black plastic sheet, an otherwise impossible task.

The mounting brackets needed two bolt holes in them so I drilled these and used the holes to bolt all three together for easier shaping.

During the production some details of the design chainged but that is normal and the main parts were checked repeatedly to make sure they would fit as planned.

This took some time but I think it all came together quite well.

Here are the finished parts: On the left, the X End Bracket, right is the X Bend Mount and below is the Top bracket.

My brackets have a step for the drag chains to mount on so that the cables run smoothly on and off the chains.

The Top bracket has a magnetic fitting under it where a clip for the dust boot pipe fixes on – you can see the magnet in the picture.

Here is how they look fitted to the machine: you can see the rails that the drag chain rests in on the X axis. Yes, I know it’s not all polished but I don’t care: it’s not worth the trouble for a piece of industrial machinery.

When the pic was taken I was getting the rails for the Y chain ready to be fitted. They are “L” profile alu extrusion screwed to the benchtop.

You can also see back end of the dust shoe I bought to run the suction back and behind the drag chain rails. More about that in part 4.

Here is another view of it, this time with the cooling pipes fitted and . .

a rope.

How do you get the cables and pipes into the drag chains?

This is my answer.

Get a rope and a driver bit. I used a phillips bit as it was less likely to catch on anything. It had a narrow collar near the back and I used a small bit of thin iron wire to fix it to the end of the rope and then covered it all with duct tape to make a smooth outside.

The last part is a good strong magnet.

I threaded the end into the drag chain and then use the magnet to pull the driver bit along inside the chain from outside. When I got to the bend I went right up to it, then moved the carriage so the bend went past the driver bit then carried on pulling it with the magnet to the end. 

 Now the rope is all the way through and you can fix your cable to end of the rope and pull it gently through. Note that this really only works well with bare ended wires – you need to add the plugs etc. after threading.

Here is the same X Bend Mount in a more finished state with the cable cover plates fitted. The X motor cable runs over top and through the small white clip.

Finally, here is where the cables and pipes run through the benchtop:

I bought a lot of grommets and plugs for this project and here you can see some of them.

 See you in part 4

 

THE CNC PROJECT

Part 2

DUST AND MORE DUST

All milling machines make dust – or swarf, or shavings or whatever you want to call it, but the faster they work and the better they cut, the more dust they make and you better have a way to clear that away for your milling head or it will clog up, overheat and maybe even break a tip.

So you need a dust collection system.

Yes, you could just get a shopvac but that won’t cut it: once the vac bag gets about half full its suction drops off and you are forever going to be buying new dust bags, and this thing is going to be sucking a lot of dust over long periods.

What works so much better is a cyclone filter. This is a specially shaped chamber that causes a “cyclone” in the air that gets the particles in the air to drop out. This goes in front of the vac so that the air being sucked into the vac is almost clean while all of the dust is easily collected out the bottom of the cyclone.

At first I thought of putting the whole thing under the CNC but this is a very useful thing to have: almost every workshop power tool makes dust and they have a collection port that you can hook up the vac to, so why not have it on a mobile trolley for general use?

The cyclone cost $32. The Shop Vac was $100. Other than that there were some bits of 50mm PVC plumbing and a metal 20L drum I found for free at my work. I had a trolley that I got for some other use that just happened to be exactly big enough to fit the shop vac on the bottom shelf. I estimate the total cost at $180.

Just have a look at how much the fancy shop vacs go for and note that these do not usually have cyclones on them: you will be buying a lot of dust bags if you want to use them for a CNC mill.

The big pipe has a threaded joiner in the middle that acts as a swivel so that the top can be removed from the cyclone (the black bit) and the drum has a clamp on it that can be undone to get the dust emptied. The fitting on the bottom that locks onto the vac has a swivel that is airtight and has slots that lock on the pins on the vac body so you can remove the bits above it easily to empty the vac itself (although this won’t be often).

There are other neat details but the main thing is that it all works well. See the picture below.

As a project this worked out really well. It made me think and it was good practice putting various parts together to make something that works properly.

It also kept me going while I waited for parts of the CNC to arrive.  There was a lot of waiting involved.

 

THE CNC PROJECT

Part 1

Overview

What I really want is to make nice clean things that work because the parts all fit together neatly. I want to make some spinning motors and such in future and that needs high quality accurate machining. It will take time to develop, yes, but the results will be usable as opposed to rough-as-guts hand manufacture. I know that only too well.

The best way to do this is with a CNC Mill. That’s Computer Numerical Control. When I worked in a machine shop as a teenager the CNCs were big and expensive. We cut stainless steel like it was cheese.

Nowadays there are small, cheap and low power models that you can run from your garage. This is defined as subtractive machining – you take a lump of material and subtract the bits you don’t want from it. The opposite is additive machining, or 3D printing. I have one of those too – they are good but the parts it makes cannot equal the strength of a machined aluminium part. Having both in your workshop is the best option.

I looked around the net and after careful thought I decided on the OneFinity Woodworker X-50 32 x 32 inch. It cost about $5K AUD including delivery from Canada.

Why did I choose the OneFinity?

1. Ball screws. It has Ball screws which are solid unlike a lot of other machines which have belts. Belts are fine for machinery that does not take a lot of force such as 3D printers, but for milling they are just too weak imo.

2. Solid construction with linear bearings. This is the only home CNC that has decent rails and lead screws.

3. Flexibility with the choice of machine head and software.

The maker does not recommend using it for cutting steel and that is fine. They also don’t supply a milling head or drag chains and that’s fine, I will get my own. They supply the three motion axes, the controller box for them and the control panel. There are a few extras that are worth getting from OneFinity such as the touch probe but everything else you get for yourself and assemble yourself.

So now there is a whole lot of work to get all of the parts together and assemble them into a working machine - metalwork, woodwork, electronics, plastic work, painting, design . . . . there’s all of them needed and a few other things too. Then once it is all working I need to work out the software to make it all go.

I actually started the whole thing in august last year. There has been a lot of time spent waiting for parts to arrive and a lot of frustrations when things did not go according to plan, but now it's looking pretty good.

The Bench

The machine needs a solid bench and I bought one, twice.

The frame of the bench needs to be solid and it looks like the best one is made by a company called Kreg. It comes in parts that bolt together and it is thick steel – but for some reason they are very hard to get here in Oz. The first time I ordered it they refunded me a week or two later because they could not get one.

I ended up having to buy a smaller one just for the vertical legs and a set of long horizontal bars direct from the US. It was worth it though, I did not see any other item that was as solid.

I tried out other options -  (getting cheap chinese metal benches and widening them) - but they were so flimsy and wonky that the bench would never have been stiff enough to use. They are okay for what they are – I have three in the garage, but no good for mounting the CNC on.

Then there was the bench top.

I could not get plywood thick or wide enough for my initial plans so I ended up getting thinner 12mm sheets, redesigning things so the bench was only 1220 deep (max plywood width) and then gluing two sheets of the ply together to make one solid plate 24mm thick to mount the CNC on.

I don’t recommend this to anyone: with no proper tools or even a bench 1220 x 1300 to sit them on it while gluing it’s surprising that they turned out okay. Even then the whole thing is not quite flat: it has a slight bulge in the centre.

I had hoped that gluing them together would flatten it but nope.

Now that the machine is bolted to it I will use the machine itself to mill the middle of the bench flat before I put the spoil board on.

Other bits

I added a lower level shelf from some bits of a cheap metal bench and another piece of the same plywood to stabilise the bench a bit and give me somewhere to put other parts of the machinery out of the way – the electronics, the water cooling system for the milling head and the suction hoses and so on.

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The plan

I didn’t just throw all of this together, I made plans from the start – and I designed, re-designed and re-re-designed things in 3D using Blender, my preferred design tool.

This is version twentyfour of the Blender model, and for reference below is a photo of the real thing : Not too far off. The cover frame is only a test fit here.

I am missing out a lot of the details here, trying to give a short report on a very long and drawn out project. This is where I spend my weekends.

More soon in Part Two. Thanks for reading.