Easiest way to prevent parts falling out is use the same method as Billings Boats. At reasonable points you leave about 1.5mm gap in the cutline . Simple to cut through afterwards and will work for both CNC Laser & Router cutting.
Not really required for larger parts - unless you are into commercial kit manufacture - just the parts likely to fall through the cutting bed or sucked away by the dust extractor.

"...To prevent parts falling out,
There is a low tack film sheet that airbrush painters users that you could stick to the under side of the wood...."

There may well be. But it turns out to be easy to just specify a cutting depth which has exactly the same effect. I was surprised at how precise these machines can be.

And I'm running off such archaic software that I would have to do tabs all manually - a lot of work....

Also tell the cam software to leave tabs to hold parts in the parent stock......

To prevent parts falling out,
There is a low tack film sheet that airbrush painters users that you could stick to the under side of the wood.
I don't know if it is expensive.
Or maybe some low tack masking tape.

Martin.

A strong magnet would work - but in fact I have found that:

- cutting 1/16" and 1/8" balsa sheet
- using a 0.5mm cutting tool and a 12v boat motor

the sideways cutting forces are sufficiently small for a simple raised lip around the cutting table to hold the sheet in place.

One difficulty with passing round files of 'cutting instructions' to people so that they can create their own kits is that the cutting machines are all different. They will all accept 'G-Code' of some kind, but that code effectively says things like 'Go to position 25"x2" and cut a circle radius 2 inches'. Now, if you have a machine that only has a 10" cutting bed, you can't do that. You have to reposition the part so that it fits onto your cutter. So I've passed a DXF file to Nick - this is a CNC file with the shapes drawn on it. He will have to take each shape and position it on his machine where he want to cut.

I have designed my machine to be able to take a standard sheet of 4"x36" balsa, because I expect to do most of my cutting that way. If other people have cutting beds which can do this, i can pass them cutting files directly.

Another difficulty with cutting everything out of a single sheet is that one part may fall out of the sheet while cutting is going on in another part of the sheet. The best way I have found to avoid this is to not cut completely through the balsa sheet - leave a small gap of about 5 thou. Then you can easily push the shapes out later...

Hi DodgyGeezer,
I have been reading through this log and it reminded me that when I was a surface mount operator we used to use magnetic pillars and magnetic rubber strips to hold PCB's in place.
Have you tried magnets?

Martin.

"...I suppose depending on the cutting head you will be able to cut thin sheet plastic?...."

The basic machine is just a precise 3-D positioning device. You then tie anything you want onto the end, depending on the job you want to do. A router or a laser will cut wood, a milling bit will cut metal, a knife will cut vinyl or paper. A plastic extrusion head will let you build up plastic shapes, a pen would let you write letters, and I suppose a paint brush would let you create watercolours...

For every material there is a workholding requirement, and a set-up and run optimisation process to undertake, but the principle is simple.

Very good idea, If you do Get someone to listen the next excuse will be health and safety!

Martin.

I have cut plastic, acrylic wood and aluminium so far without problem. It is all down to cutter speed, feed rate and depth of cut, the same as with any power tool....

I have been pestering our local council to utilise empty parts of buildings as a makerspace but so far my pleas have fallen on deaf ears. No money available being the main excuse.....

Hi DodgyGeezer.
I suppose depending on the cutting head you will be able to cut thin sheet plastic?
The more I see and hear about CNC and 3D printing the more interesting it seems.

Martin.

"....I am sure that you will end up with a lot of customers when see these...."

While it is, of course, quite reasonable to charge for materials and time, I am looking forward to a future where the base patterns for a model boat kit will be available for free off the Web. You can download a lot of free patterns already, but I haven't seen anything I would call a 'real boat kit'.

CNC cutters and 3-D printers are already available at most schools, and local councils now operate 'MakerSpace' workshops where this kit is made available to the public.

Hobbyist designers could turn out the cutting files - all a modeller would need to do would be to buy the sheets of wood and feed them into the machine to have a kit coming out the other side. Not too sure how to do fibreglass hulls, though...

Thanks Martin. I have found that a hobby can easily become a chore once you start getting customers so I stick to doing stuff for family and friends, and even doing that can become a pain when you don't like saying no.......

They're excellent.
You could be extremely busy as I am sure that you will end up with a lot of customers when see these.
They would take a very long time to do that by hand.

Martin.

It is easier than you would think. I only got into 3D printing 2 years ago, once you see how it works the rest is easy. Main difference between a CNC router and a 3D printer is that a 3D printer adds material to make an object and a CNC router removes material.

Mesmerizing to watch! what a beautiful finish it leaves, would love to try one, but I feel a little too tech for me😌.

cheers Peter😐

I will order one of those. I can soon print up a custom mount for it. I will get some balsa and ply in stock and have a go. Here is a video of the Ox in operation😊😊

I can send you the .dxf split into A4 size pages fairly simply - will PM it.

".....I have the files to make a dragknife that works with a stanley blade, it is 3D printed and has a steel shaft mounted in ball bearings. Some commercial ones are over 250 quid!....."

Sounds like a lot of work. Here is the one I got - I see the price has gone up to £4.49!

This comprises an aluminium housing with a magnetised steel shaft in it mounted on ball bearings, and 15 precision knife blades in carbide - different angles for different thicknesses of material. I have mounted it in a Delrin collar, and it looks as if it will perform perfectly. Lot less time and trouble (and cost) than making your own...

https://www.ebay.co.uk/itm/15pcs-30-45-60-Degree-For-Roland-Cricut-Plotter-Vinyl-Cutter-Blade-Holder/131906788936?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

I would love to get the plans I drew 'checked out' by a third party who has a precision cutter. My early ones are rather poor - I think I am getting better, but I am still likely to make mistakes. The PT boat would be a good choice - not too much wood and it makes up quite nicely. Of course you would still need to make the fittings - but direction is given on the web site. The figures shown below are cheap Chinese railway figures - about £2 for a dozen - modded and painted up...

I have the files to make a dragknife that works with a stanley blade, it is 3D printed and has a steel shaft mounted in ball bearings. Some commercial ones are over 250 quid! Do you have files for the eze built torpedo boat? I could give that a go....

Good to hear that it's all functioning well!

I have only been using mine for model boat parts. If there's any EeZebilt you would like to make, give a shout and I'll send you a .DXF file for the parts.

I have had a little test with an engraving end and a bit of scrap oak - pic enclosed. And I have bought a set of vinyl-cutting knives and a mount (total ebay cost £4.27!), but I haven't done any vinyl cutting yet. I should be able to make my own numbers/letters etc. These things are very flexible...

Bit of an update on my CNC router. All up and running now and I am well chuffed with the results. I abandoned the Arduino based controller and opted instead for a Duet 2 WiFi board, a 32 bit controller with on board drivers. The machine can be loaded with a job directly from my computer/laptop/mobile phone and progress monitored from same. I have also added a 7 inch Paneldue touch screen display for when my daughter is hogging all the internet bandwidth. It has been going for a couple of weeks now and I haven't stopped making stuff, all for other folks! I need to find some DXF files for model boats now. I have a set of plans for a Lysander aircraft that my mate wants me to cut out for him, so far my efforts to convert PDF into useable vectors have come to nought.

I'm running off a 36v supply with a pair of 6A outputs...

PSU has 3 x 24V 10A outputs. I had most of the bits kicking around, just had to print off the plastic case. Just kept checking for square as everything was tightened up.

A much flasher PSU than I have!
Did you have any difficulty getting the rails dead parallel and level?

Quick progress report on 'The Beast'. Now at the rolling chassis stage, got to fit GT3 pulleys and belts, progress made on electronics and psu.⚡⚡⚡

Sounds like you might not have been waiting long enough for the Arduino to boot and load GRBL, so the port refused to connect, and then just stayed 'busy'....

If it happens again, try opening and closing another port, and then going back to 8. That seems to reset the flag...

I abandoned the job yesterday. Just come back to it now, I shut down all the open windows, restarted my PC, plugged everything in and away it went. I just tried 1 motor at a time and all is good. I can now wire the rest of the drivers up, make some new stepper motor leads up to the correct length, draw a nice box up with DSM and print it out, Happy days!

Congratulations! What was the problem?

VICTORY IS MINE!!! It lives, it lives!

Aha - I get that a lot. You have told UGCS that the Arduino is on port 8 at 115200 baud, haven't you?

The first thing to note is that the Arduino takes an age to boot up. So plug it into the com port and wait a good 30 secs for it to settle down - or look at the lights on it and wait for them to show that it has booted and loaded GRBL.

Even after that I can still get difficulty connecting. Do you have several available ports? I tend to get UGCS to open another port, then close that one, then open the correct one, and that often helps the connect.

I suspect that interference on the line can cause quite a few issues - I have ferrite line filters at all available points. But the big problem I had was realising that the Arduino retains its settings over a power-off, so you can't just reboot and start again from scratch. If you have set it up incorrectly (as I did several times) you have to re-set it up properly before it will operate... and the com ports also seem to remember that they were busy and refuse to become free...

'How did you get on? We are all agog here...!' Well, everything lit up as it should, but zilch as regards motion. I have an idea it is a software issue I am having. GRBL uploaded without a hitch. When I try and connect Universal G Code Sender, it says 'can't connect, COM 8 ( Where Arduino is connected ) is already in use, access is denied. I am assuming that the Arduino needs to be on the same com port as UGS... Getting splinters in me fingers from scratching me bonce now...

Good point - I would refer to the UK HSE FAQ, which says "... However, the levels of free formaldehyde in boards made within the EU at levels of formaldehyde class E1 are thought to be insignificant. .."

http://www.hse.gov.uk/woodworking/faq-mdf.htm

MDF cutting is always very dusty, though. It outputs a fine dust which becomes a paste when wet, and is very difficult to get off things, including out of your respiratory tract! While I find that many advised safety precautions are well over the top, I do try to avoid breathing in any MDF dust at all. The advice provided is usually more driven by legal and regulatory requirement than a real appreciation of danger.

I built my CNC machine in a spare bedroom, intending to move it to a shed for operational use. However I find that it is so clean and quiet in operation that I could leave it where it is - it produces much less dust than manual cutting and planing/sanding to shape used to do. That is, of course, with thin cutters and 1/8" balsa. No doubt with wider cutters and MDF sheet the dust levels would go up.

And, of course, my wife has other priorities....

Unfortunately MDF manufactured in SA has a very high Formaldehyde content - even the yellow board imported from South America seems to be not much different. One whiff of the dust can leave you feeling ill for days.(Bit backward here as for instance water based paint is only now becoming available in a very limited range .)

Incidentally, I wouldn't worry about formaldehyde assuming you are using UK MDF. Levels are insignificant - but I don't suppose that will stop the scaremongers...

Lots of dust makes a mess everywhere, though, and it can irritate your throat...

The amount of dust depends on the diameter of the cutting tool, and where it goes depends on the cooling air being blown from the motor.

I am using sub-millimetre diameter cutters, so there is hardly any dust. And the motor is a slowish Johnson model boat one running at 10v, which makes very little draught. You can see the tiny ridge of dust either side of the cutting line on some of my earlier pictures.

I had set up a cutter-mounted vacuum device, but haven't needed to use it yet.

How much dust is there when cutting balsa ? MDF is problematic as its made using formaldehyde and the dust is really damaging to the lungs. Laser cutting is not a problem with MDF as it burns. but has pollution problems and requires a scrubber on the exhaust .
Most of the sites selling CNC routers seem to advise you to have a cover to minimise dust! Was thinking of changing to a desk top laser for engraving and using a router for cutting but very wary of dust associated problems.

How did you get on? We are all agog here...!

Yes - and you want to balance out the current available from your power supply to go to all drivers equally. I have 1/8 microstep on X and Y axes, but 1/2 on the Z axis. You usually want that one to go faster with less resolution...

Current is set via DIP switches from 0.2 to 5 amps, mine are set to 2.5Amps to match the current rating of the motors. Microstepping is also set via DIP switches, I have set mine to 1/8. Each driver has it's own 24V input so higher current is handled by the driver and not the CNC shield. I will try and video the results when I fire it all up (not literally I hope), I only have my phone camera, which isn't very good should be good for a laugh....

Do you have to set the limiting current to 'low' via a pot on each driver before turning on first? I am using Pololu drivers, and they suggest calculating your max current per stepper, then setting each driver to low and gradually increasing. There is a little adjustable pot on each driver board for doing this...

I don't get 100 grubscrews at a time, I meant all sorts of screws. I have been fiddling about with wiring this afternoon, getting the drivers hooked up to the CNC shield. Just got to connect PSU to driver and CNC shield and it will be either Whoopee!! it works or a look at my on line banking for funds for more circuitry.... I am going to prove the wiring with just 1 motor/driver set up first....

Ah well, grandmothers and eggs... 😌 Still, I did say that the collet was cheaper than 1 grubscrew - not 100...

I found that mine worked first time, so you probably won't need the platform. You seem better equipped than I am for the rest of it 😉

I can, however, report that holding balsa sheet in this way is very effective. It is a sheet of ply bolted to the base, with another sheet of ply 4" wide on top. The sides have hard balsa edges rising about 1/4 inch above the ply, which are held in with a spruce strip. A 4" sheet of yellow correx is there to provide a soft base for under cutting. If I cut outside the workpiece the cutter just goes through the balsa sides, so no damage done.

4" or 100mm sheets of balsa drop into the 1/8th recess on top, and are held by the side balsa, which is slightly sprung inwards. If necessary they can be packed around the edges, but the recess is sized to hold them tightly. They are firmly held against the cutter, do not move at all, and the workpiece can be removed and replaced precisely in the same position if necessary. If you want you can put a weight on top of the sheet during cutting to hold it perfectly flat, and move it when the cutter is going to go over it.

Cable managment all sorted. Electrics mounted on base, drag chains on X and Y axes part of the design, I will print them myself. I always get a shipping order for screws, usually a few hundred at a time, postage still the same. I have 20mm MDF and 20mm ply to hand for the spoil board and loads of milling clamps to go toward work holding kit, clamping arrangements will depend on what I am doing. I have also built a little platform for me to jump off in case I have to jump up and down on it in a rage when it won't work. I have several DTI's, Dial gauges, Depth gauges, and Height gauges lying around so have all I need to get her clocked in when the time comes. I am looking forward to seeing it burst into life. Many thanks for the tips...

".......I am on a bitof a learning curve at the moment........"

A few lessons I learned:

1 - Get a good, solid base-board which isn't warped. The local timber yard may have off-cuts of 3/4" ply. You will want to assemble the mechanics on a proper base, and it helps to have it available first. You will want to paint it anyway, so it will need time to dry.

2 - Get a dial indicator. An easy way to check for precision in assembly is to attach a dial indicator to the end of the Z axis and run it over the base board. It's good for other fault-finding and calibration as well. There are cheap ones on Ebay.

3 - Plan out all the wiring. I put my limit switches in as an afterthought, and found that I had wires which couldn't go in the places I wanted them to go.

4 - Wiring loom control. Consider Drag Chains, Heat-shrink tubing and Braiding. All items are very cheap from Ebay. If you don't put the wiring in at assembly you won't be able to put it in later once everything is connected up...

5 - If you use a drag chain for the USB connection, you will either have to make sure that it's wide enough to take a USB plug passing through it, or cut the plug off, pass it through and re-solder it afterwards. If you do the latter, note that the shielding in a USB cable is aluminium, and won't solder. So you will need to use a connector plug which has a physical connection to the shielding, because interference can ba a problem on these machines....

"....Good cheap screw supplier...."

I looked there for grub screws. There were 58 entries. Of the cheapest orders of these, only 12 were cheaper than the Chinese mini collet set. And not by much.

Once you counted in postage, the cheapest grub screws you could get from a good, cheap supplier in the UK, at £3.20, were about twice the price of a complete mini-collet set from China, which comprised a shaft, locking head, selection of 8 different sized collets, two grub screws and an allen key....

Oak or Mahogany for stable signs, I do plan on fitting limit switches at first anyway. I am on a bitof a learning curve at the moment. Once I have the machine up and running I will no doubt get the hang of it.
Good cheap screw supplier..
https://www.gwr-fasteners.co.uk/m3-socket-cup-point-grub-screws---high-tensile-17166-p.asp

"How is the cutting tool held in place? Do you use just a rigid coupler with grubscrews or a minature collet system?"

A miniature collet system. Cheaper than one grub screw (if bought in this country!). Here is an ebay link to one for £1.28. You have to get one with the right hole size for your motor shaft, of course. There are several standard sizes. This one is 2.35mm ... Go to ebay and search for 'mini drill collet'. You can see a picture here...


https://www.ebay.co.uk/itm/8Pcs-0-5-3mm-Electric-Drill-Bit-Collet-Mini-Twist-Drill-Tool-Chuck-Set-Golden-BE/332680957934?hash=item4d75548fee:g:vJ8AAOSwGUBaRQRg

Aluminium for stables? Perhaps a slab of oak would be more appropriate? I am cutting slices off old oak fence posts for use as coasters and think I can engrave them using the 'boat motor cutter' - so long as the cut is not deep.

A laser would be ideal - but the cost and the danger mean that it needs a bit of thinking about.

I must look up the Rumba and mega2560. One issue I have with the Uno and GRBL is that the software does not do 'tool radius compensation'. You have to do this in your conversion, and Dfx2Gcode does not do this either. I do not know if there is a GRBL version running on the 2650 which does do this. Essentially you need a GRBL which implements G41/2 commands, or you will have to do the compensation in your original drawing. I am using sub-milimeter cutting tools for balsa, so the compensation required is negligible and can be ignored, but when cutting ply I may need to worry about it.

Your TMC2130s may not need endstops, but the limit switches are also used for homing. You will find that if you want to cut lots of parts out of a single sheet of material, it helps to be able to home accurately. GRBL allows you to have a 'master machine home' and then several subsidiary homes. So, when cutting, I start with the cutter in the master home position in the top right corner, then move it to a secondary home position which is directly over the workpiece top right, then do all of my cutting in relation to that secondary home position...

I guess I could make mounts for small spindle motors on the 3D printer. How is the cutting tool held in place? Do you use just a rigid coupler with grubscrews or a minature collet system?