CNC miller instead of laser cutter?

Martin Wynne

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You might find that you can get rid of the Unix returns in the post processor of Carbide Create. I don't know the software but I suspect that its post-processor is intended to deal with the a large amount of the machine controllers around, some of which might be looking for Unix returns.
@Jim Gu7thrie

Hi Jim,

Thanks. I've already tried changing the gcode post-processor to GRBL, but it still outputs Unix LF instead of CRLF. The files open fine in the GRBL/Candle onscreen USB controller, but not on the machine from the SD card.

It's not a problem now I know, and I can include a one-click file conversion utility in Templot if necessary.

The free 2.5D version of Carbide Create is a clunky thing to use, its main purpose seems to be as a sales aid for Carbide3D's (expensive) milling cutters. But it will do what we want, if the idea of CNC milled timbers comes to anything.

cheers,

Martin.
 
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Hi Martin,
Looking good with your new toy :) How do you think it would be for milling PCB 'timbers' ? For my US layouts that will use FB rail and spiked baseplates it crossed my mind that milling them from PCB may work nicely - the idea would be to mill about 0.2mm off the material leaving copper to act as the baseplates which would be drilled to suit either cosmetic or functional spikes. The rail would be soldered to the baseplate pads. This is similar to a DCC Concepts idea for sleepers except I think they etch the sleepers rather than mill.

A while back I set about milling some PCB material to a custom depth on the milling machine and that seemed to work well but I didn't do enough of them to get an idea of how long the milling bits would last. Do you have a view on this ?

Rob
 
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Martin Wynne

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First trial cut off the miller. 3mm MDF, 4mm/ft scale:

cnc_first_cut2.jpg


cnc_first_cut1.jpg


I think this is going to be doable. :)

I used 3mm MDF for stability on the miller. It would mean packing flexi-track to match the height. I might try 2mm MDF to compare.

Cut wth a 3mm dia. 2-flute slot-drill, gently cleaned up with a Stanley-bladed window scraper, and a light rub with 120 grit sanding block. As usual the camera is cruel, but in the flesh the timbers are a good match for plywood strip. No grain in MDF of course, but some natural texture to the surface, which might take stain rather than paint.

Cutting time was 12 minutes, but still the sockets to do. Plenty of scope in the settings for speeding things up.

The cut depth varies between 0.40 - 0.55 mm (I was aiming for 0.5mm) -- I was warned on the forums that the Z-precision is not too good on these machines (relying on the motor bearings). Which might be a worry for precision machining, but doesn't matter in the least for what we are doing here. The cutter didn't seem to be struggling, so I might go a bit deeper next time, 0.4mm might be difficult to ballast cleanly. A 1.5" mesh ballast stone is 0.5mm at 4mm/ft.

But the timber outline size is good, 4.05 - 4.10 mm wide. The left-most timber above was the final cut, and there is no obvious degradation in the cutter. With my toolmaker hat on I might go for a finishing cut with a sharp 4-flute end mill kept for the purpose, but it all adds time to the job.

I'm not intending to mill the sockets right through, a depth of around 2mm should be enough, and easier on the cutter. But it's helpful not to have a fully blind sealed socket, for adding adhesive from below or pushing out the chairs if necessary. So my plan is to drill a hole through the centres of the sockets. Either manually afterwards, or using the miller as a jig borer first.

Having proved the machine works, there is now a lot of trial and error to find the optimum sizes and materials, including trying plywood and the iron-on hardwood veneer idea.

cheers,

Martin.
 
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Martin Wynne

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How did your dust extraction system work out?

@Steve_Cornford

Thanks Steve.

Worked very well. I treated Henry to a new bag before I started. :)

There were little piles of swarf left on the surface of the MDF, but all airborne dust was being captured -- there is no film of dust on the machine afterwards. It should be even better when I have FDMed a proper nozzle reaching closer to the cutter.

I could also try Henry on full power, but that makes him noisier, and his entire cable length has to be pulled out for me to trip over.

So far I'm very pleased with progress. Lots still to do.

cheers,

Martin.
 
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Thanks. I've already tried changing the gcode post-processor to GRBL, but it still outputs Unix LF instead of CRLF. The files open fine in the GRBL/Candle onscreen USB controller, but not on the machine from the SD card.

Since I last posted, I've downloaded Carbide Create and had a look at it. It only seems to give four options in its post processor and has no facility to edit the post processor. So if none of the options suit your machine then you are stumped. :( I also had a look at the CAM program I use - Cut2D from Vectric. It has about 450 options in its post processor output (so much for a standard GCode :):) ) and there is also the option to edit a post processor to suit a particular machine controller.

To get over your problem are you intending that Templot outputs GCode direct to the mill? If so you might have to provide up to 450 options for all the other machine controllers. :):):)

Jim.
 
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Martin Wynne

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To get over your problem are you intending that Templot outputs GCode direct to the mill? If so you might have to provide up to 450 options for all the other machine controllers. :):):)
@Jim Gu7thrie

Hi Jim,

No, just a one-click utility to select a gcode file (.nc) from Carbide Create, and modify it to suit the GRBL firmware on the CNC machine, before saving it to the SD card.

The firmware is more picky than the Candle/GRBL onscreen computer control, so if folks are happy to have a computer close to the machine rather than using the SD card, the file from Carbide Create is fine as it stands, Unix line endings and all. Candle/GRBL is free and supplied with the machine. The supplied screened USB cable is 1.5m long.

Had a look at Cut2D -- very good, but not free. The main (or only?) attraction of Carbide Create is that it's free. Also Easel, but that won't import Templot's DXF files.

I'm not going to attempt the other 449 options :) -- if folks are using some other CNC miller it's likely they already have suitable CAM software.

cheers,

Martin.
 
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No, just a one-click utility to select a gcode file (.nc) from Carbide Create, and modify it to suit the GRBL firmware on the CNC machine, before saving it to the SD card.

Martin,

I had to do something similar years ago where some of the files I got had the LF only instead of CR/LF - I think I remember that PC based applications used CR/LF and Mac based applications used LF and I was working in Film post production where there was a big mix of PC and Mac.

Jim.
 
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Derek

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UK, Midlands
Martin,

Why "Henry". Is he your eighth vacuum cleaner?

BTW, my air compressor is called Edward. Edward the Compressor.

Andy
Ah, the compressor vanquished by a horse chestnut. To his friends, he was William of Normandy, but colloquially he was known as William the Conker.

OK. I'll stick to my day job.
 
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Martin Wynne

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Idea #1 for how to connect the milled timbering panels -- "Plugs on a plate":

plug_plate.png


Resin-printed at the same time as the chairs. To link a timber at one end of a panel to the first timber on the next panel, while the panels are being fixed in place on the baseboard.

For linking where there are no timbers, dummy sockets could be cut in the milled-out areas.

It's not necessary for the panels to have neat joins, they could be sawn by hand after milling, just outside the end timbers. Or a milled slot could be provided, for easy sawing or snapping off.

( The panels can't be fully cut to size on the miller, otherwise there would be no means to hold them onto the machine bed. They are held by corner screws into the wasteboard.)

The FDM brick connector clips are probably too small to replicate in MDF or plywood. The above idea could also be used with the FDM bricks if preferred. In which case the "plugs on a plate" could be FDM-printed.

p.s. for use with the milled sockets, the plugs will actually have semicircular ends.

Martin.
 
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Martin Wynne

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We have sockets. :)

EM gauge in MDF:

mdf_sockets3.jpg


MDF is almost impossible to photograph. I dry-brushed some water-based wood stain over it to help, but I think I made it worse to photograph. They do look good in the flesh, and the wood stain retains the surface texture better than paint.

The sockets look good for size, but I can't try any chairs in them until I have coded some radiused corners on the plugs.

Feeds and speeds on the machine were a complete guess, but the machine looked happy doing it, and the 1.5mm cutter emerged unscathed. The final socket is as clean cut as the first one. I made them 1.75mm deep. No through holes yet.

Total time on the machine for 8 long timbers and 32 sockets was 23 minutes, plus a couple of minutes to change the cutter. So maybe around an hour for a typical turnout. Clearing the blank areas of base could be speeded up with a bigger cutter, but first I need to get a larger collet for the machine.

I'm quite pleased with this result so far. I think this idea is workable, and worth trying in plywood as an alternative to laser cutting. Certainly it is a lot less expensive than getting a laser cutter, and the idea of building the rails onto a single one-piece base panel is appealing. No fiddling with individual timbers or templates.

Also the CNC miller is a nice thing to have, I'm very pleased with it. :) But the manual handwheels on the leadscrews are an absolute essential -- how folks work without them is a mystery to me, even though most of the makes on Amazon show them without. Well worth the small extra cost for the Mostics machine.

cheers,

Martin.
 
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Martin Wynne

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I used an offcut of old chipboard shelving as the wasteboard. I have bolted it to the table with countersunk screws and M6 T-nuts so that I can use the full machining area on top. The screws need counterboring a bit deeper if I ever plan any through cutting. The T-nuts are those nifty ones having a ball spring so that they stay put while setting up -- Amazon is your friend. :)

cnc_table1.jpg



cnc_table2.jpg


The machineable area is 300mm x 180mm (the red lines). These 3mm MDF panels are 210mm wide (A4 width) by 300mm long, which conveniently leaves a 15mm margin for screwing them to the wasteboard with 3 screws along each side, clear of the work area (fix the middle screws first to ensure it goes down flat). The next job is to make a drilling template for future panels -- it's strange how there is always a next job. :)

The secret weapon is the Stanley-bladed window scraper, which is just the job for removing the surface burrs after machining. A sort of sideways slicing action works best, at a low angle. it's quick to do. For this panel I followed up with a (new) nylon kitchen scourer instead of a sanding block. The jury is still out on that. That scraper came from the pound shop and belongs to the BIBO, it's still on the original cheapo blade. Somewhere I have a block plane which takes single-edge razor blades, which might make an even cleaner cut, if I can find it -- it will be handy for the boat kit.

For the next test piece I will make a bit of video of the machine working.

Now to make some chairs with plugs which fit the milled sockets, and see how the track gauge turns out (this is EM). Then to repeat the whole process in 3mm plywood -- I fear it might warp badly. And there is still the hardwood veneer idea to try. I'm also wondering if the MDF might cut more cleanly if sealed first, although that would prevent using the water-based stain or watercolour paints.

Martin.
 
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But the manual handwheels on the leadscrews are an absolute essential -- how folks work without them is a mystery to me, even though most of the makes on Amazon show them without. Well worth the small extra cost for the Mostics machine.
.

Martin,

Those of us with no feedscrew handwheels have an MDI (I think that means "Manual Data Input) interface on our control software so that we can drive the machine by inputting lines of GCode. It actually works very well once you get used to it - one of the benefits being that you can move at full G0 speed to any point on the table.

Referring to your other message, shelving like Contiboard is remarkably constant in thickness and makes an excellent spoil board. The only down side that I picked up years ago is that it can blunt cutters if you cut into the covering. I use thick-ish double sided tape to hold parts to the Contiboard which gives a few thou safety gap between work pieces and the spoil board top. I've also found that thicker MDF sheet (6mm and upwards) is also remarkably constant in thickness and I now tend to use it when clamps or screws are used to hold the material and there is the possibility of breaking through and cutting the spoilboard.

Jim.
 
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Martin Wynne

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@Jim Gu7thrie

Thanks Jim. I will change to plain chipboard or MDF for the wasteboard if I plan any through cutting or jig boring. One option with the supplied wood-carving V-cutters would be to add a ballast shoulder and cess alongside the track, if I can figure out a way to hold the work in the process. Double-stick tape over a large flat area is difficult to remove. I have seen the idea of applying wide masking tape to both the work and the wasteboard, and sticking the tapes together with cyano.

The machine is probably easier to use without handwheels if you control it from the computer, but I'm using the little offline controller, plus SD card -- the computer is in a different part of the house. I can move at full G0 speed by holding down* the buttons, but precise positioning is painful -- changing the jog step size takes about 3 button sequences. A mistake on the buttons could be costly! It's feasible for X-Y just about, but setting the Z-depth that way is next to impossible. Fortunately when using the button controls, the system switches off the steppers between moves, so it's easy to use the handwheels for fine adjustments. This means it's important not to touch the X-Y handwheels while changing cutters. Setting zero involves switching the entire system off and on again which is unbelievably primitive (unless anyone knows different when using the offline controller?).

* if holding down the button, make sure the jog step is no greater than 5mm. Otherwise the button repetition rate will get ahead of the stepper and it won't stop when you release the button.

On the full-size CNC machine I'm used to being able to raise and lower the knee for Z adjustments, or adjust it while cutting, so I'm a bit lost without it. :)

cheers,

Martin.
 
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Martin Wynne

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I think I'm making some progress with this, despite the cruelty of the camera.

This is a curved B-6 turnout in EM with square-on timbering, milled in 3mm MDF -- imagine the spaces filled with ballast:

mdf_sockets6.jpg


mdf_sockets5.jpg


For this latest test piece I tried sealing the surface of the MDF with shellac before milling. I cut the timbers a bit deeper (1.0mm), and made separate roughing and finishing cuts around the timbers. They are consistently 4.04 - 4.07mm wide, which is as good as laser-cutting, and a small tweak next time (and using the same finishing cutter) could get them even closer to exact scale 4.00mm.

Surprisingly the harder sealed surface made little practical difference to the milling, apart from making it a bit noisier. I thought it might make for a cleaner top cut with a less "furry" raised burr, but there was no obvious difference. Counter-intuitively it made it harder to slice the burr off cleanly with the window scraper. So I had initially concluded that sealing the surface was a mistake. But the saving grace meant I could sand the burrs more firmly with the sanding block without sanding away the top surface of the timbers or rounding the edges, with the result seen above, achieved quite quickly. That was 400 grit abrasive paper.

It would be worth trying the finishing cut with a "downcut" end-mill with left-hand flutes to eliminate the burr (as used on copper-clad to prevent ripping the copper foil), so I may get some to try:

https://www.amazon.co.uk/Genmitsu-Coating-Tungsten-Carbide-Milling/dp/B08CDBBWMF

The S1 sockets are consistently 2.15mm wide (design size 2.10mm) so again a tiny tweak next time should get them closer, although we may be approaching the resolution limit of the miller.

The cut depth is more variable, between 0.9mm and 1.2mm. Fortunately for this application it doesn't matter, but if it did I would have to consider skimming the wasteboard with a fly cutter to get more consistent cut depths.

Now I must stop playing with my new toy and get back to re-coding the chair plugs so that I can make some matching chairs and try them. I also need to find some ballast and paints (I must have some somewhere) to see how it all looks. :)

I think this idea is going to be doable, and makes an interesting alternative alongside FDM-printed timbers and laser-cut plywood.

p.s. the holes in the base are from some test sockets cut on the other side of the MDF panel.

cheers,

Martin.
 
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Martin Wynne

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I've made an interesting discovery that the water-based shellac surface sealer which I used on the MDF can also be used as a penetrating adhesive for MDF and probably also plywood.

It's very thin and can be applied around a chair in situ with a fine brush. It will then "flash" under the chair and into the MDF in a similar way to a solvent, and quickly disappear. When dry the chair is firmly sealed in the socket.

The chair plugs are intended to be a press fit. But that requires a close tolerance on the socket, which may not be so easy to achieve in plywood and MDF. Being able to seal any slightly loose chairs in position will be very useful.

The sealer is not cheap as a wood sealer goes, but it's a fraction of the cost of a low-viscosity cyano adhesive. Amazon is your friend:

https://www.amazon.co.uk/gp/product/B08GZGVRYS

cheers,

Martin.
 
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Martin Wynne

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I have now made some chairs to fit the milled sockets:

cnc_chair_corners2.png


cnc_chair_corners1.png


It's an angled corner relief rather than a radius to make for easier adjustments. I was afraid the exposed corner of the chair base might prove too fragile or fail to print, but it's ok as you can see. No sun today, so very difficult to photograph MDF and resin chairs -- if you try hard you can imagine ballast between the timbers:

cnc_with_chairs.jpg


They are a nice push fit in the milled sockets, but all the dimensions can be adjusted as required.

I have also fixed a couple of bugs in the chair design when the rail foot is wider than the rail head (e.g. C&L rail), and also the island on the bottom of the key (thanks Timbers).

I'm hoping to release 228z later today so that folks can tinker with some of the latest options.

Now I must get back to the timbering bricks for FDM. :)

cheers,

Martin.
 
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Martin Wynne

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Morning sunshine.

mdf_sockets8.jpg


I should have gone a bit lower with the finishing cut to remove the furry remains of the rouging cut. But it all disappears under the ballast.

Martin.
 
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