simonr Posted May 3, 2012 Share Posted May 3, 2012 Although my Lathe has been running Mach3 for a few years, when I converted it, I needed it up & running very quickly and just lashed it all together (very untidily). I'm just about to start re-converting it and making a neat job of it! I thought it would be useful to any of you considering a CNC conversion on a Lathe or Mill. For those who don't know what Mach3 is, it's like Megasquirt for Machine Tools. It allows you to control any machine using a PC as the brains with either stepper or servo motors moving the axis. http://www.machsupport.com/ for full details. You can download a free version which is fully functional but limits you to a few hundred lines of code. I thought it was so good, I bought a licence to say thanks as much as anything! I've decided to replace the original stepper drivers which work perfectly with new Geckodrives http://www.geckodrive.com/. I used one to drive the 4th axis on my mill and it's so much better than the original lathe drives, they seemed a good option. What they give me is quiet, smooth operation and 5x the resolution, so it will be able to resolve 0.001mm. I'll post photos etc as parts turn up! Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted May 3, 2012 Share Posted May 3, 2012 I shall watch this with interest Quote Link to comment Share on other sites More sharing options...
ejparrott Posted May 3, 2012 Share Posted May 3, 2012 Me too! Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted May 3, 2012 Share Posted May 3, 2012 Me three! Are you using any pulse generating hardware? I saw that the mach3 website now lists kit that has an Ethernet interface. Quote Link to comment Share on other sites More sharing options...
simonr Posted May 4, 2012 Author Share Posted May 4, 2012 This is what the control cab of my lathe looks like at the moment! As you can see - it's not tidy! When I put it together is was much better, but a succession of modifications including a new monitor which didn't really fit in the case - and it's a mess. I ordered a 3U 19" rack mount equipment case from RS as well as Bulgin 400 Series connectors and last night started assembling it. The case comes as a kit that's fiddly to put together - but is very good & solid. I've mounted a 24v 15A Power Supply (top left) which will run the GeckoDrive Stepper drivers (top right). The Gecko's are mounted on a slab of Aluminium as a heat sink. I've found they are fairly efficient and run cool, but I'm going to be running them at their max current (7A) so they will need a bit of cooling. As you can see I've left a space for a 3rd Gecko in the middle. This is just to allow things like an auto tool changer in future. As I said before, Mach3 uses a PC as it's brains. It needs to be an older XP (ideally) machine with a Parallel port. I've been using a Dell Optiplex which cost £20 on eBay and it's proven ideal. I have added an additional Parallel port card to it, just to give me a few more inputs & outputs to play with. A standard Parallel Port gives you 8 Outputs & 5 Inputs. It's perfectly possible to control a lathe with a single port though. The parallel port needs to be connected via a 'Break Out Board' or BOB. This isolates and protects the PC from the lathe as well as making the wiring a darn site easier and providing some useful functions. The main thing it adds is a 'Charge Pump'. When you switch a PC on, it makes all the Parallel Port outputs high for a second or so. If one is connected to your spindle for example, it would make it spin up briefly - so potentially dangerous. Mach3 generates a 15kHz signal on one of the parallel port pins (Pin 17 generally). The BOB detects this and if it's present, enables the outputs. This means that if the PC crashes or Mach3 is not running, all the outputs are disabled. There are several BOB's on the market. Previously I used a C11T from CNC4PC But, I had a few problems with it. I think it tries to be too clever and also the Parallel port connector is wired differently to standard - so you have to make your own lead (which they don't tell you). After a lot of hunting & reading on Forums, I decided to order a Campbell Designs board It's big advantage is it contains all the required power supplies (5v & two isolated 12v) as well as two additional relays. I had to add a couple of relays to the CNC4PC board. The last bit I've ordered is not really necessary, but it's nice to have. From PoLabs. It just allows you to control the machine more manually by turning the dial without having to reach up to the control cab. My plan is to add a socket for it to the Mill (Bridgeport Interract, also using Mach3) as well as the lathe. I suspect it will be more use on the Mill though. More as and when some of this arrives! Si Quote Link to comment Share on other sites More sharing options...
simonr Posted May 4, 2012 Author Share Posted May 4, 2012 Me three! Are you using any pulse generating hardware? I saw that the mach3 website now lists kit that has an Ethernet interface. On the Milll, I use a SmoothStepper motion controller which connects via USB (though they have an Ethernet version as well). It's very good, but very sensitive to electrical noise - and as you can imagine, there is a lot of stray noise in a mill. When it crashes, everything stops & you need to re-boot the PC which is unhelpful! The only other motion controllers all seemed to be out of my price range. I think if I were converting the Mill again, I would stick to Parallel port control. The mill uses a BOB and servo drivers from CNCDrive in Hungary - and they are fantastic! Very well thought out and work exceptionally well. However, they are more geared to Servo Axis drives than Steppers - so I decided to go with the Campbell BOB instead. Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted May 4, 2012 Share Posted May 4, 2012 The BOB's from CNCDrive seem considerabbly cheaper than the campbell one, any reason other than the country of manufacture? Quote Link to comment Share on other sites More sharing options...
ejparrott Posted May 4, 2012 Share Posted May 4, 2012 Have you looked at Motion Control Products? Quote Link to comment Share on other sites More sharing options...
simonr Posted May 4, 2012 Author Share Posted May 4, 2012 They do less! I agree it's a big cost difference and the other boards by comparison are not very good value. If you are using CNCDrive servo drivers, you just connect the drives to the BOB using CAT5 Network cables - so the wiring is really easy & neat. The Servo drives have a USB interface which gives you all the tuning & diagnostic info needed - so the BOB doesn't really need any LEDs. However it only has two relays - and you really need at least 4. On the mill, I added a second board with 8 relays - which obviously adds to the cost & complexity. Relays common to all machines: 1. Main Power / machine enable 2. Coolant 3. Spindle direction 4. Spindle on/off Additional for real Anoraks 5. Flood/mist coolant 6. 3 Phase contactor 7. Door release 8. Chuck open/close 9. ATC Lock 10. 4th Axis Lock 11. Tool Grab Si Quote Link to comment Share on other sites More sharing options...
simonr Posted May 4, 2012 Author Share Posted May 4, 2012 Have you looked at Motion Control Products? I really hate them! They made the original servo drives and spindle controller for my mill. They gave me so much trouble and to fix a blown drive, it cost me over £500. When it spontaneously died again - said they only warrantied repairs for 2 weeks. They are expensive and provide little support for anything more than a few years old. I dare say their new products are better - but the CNCDrive components were so much cheaper and have more intellegence built in. Granted they are not as robustly built - but in a sealed control cab that only I am going to open, it doesn't matter. I completed the whole of the Mach3 conversion on the mill for less than the cost of one new Servo Drive from Motion Control. Si Quote Link to comment Share on other sites More sharing options...
landroversforever Posted May 4, 2012 Share Posted May 4, 2012 Following this with interest . Si, was the lathe originally CNC or did you convert an old manual machine to Mach3? Quote Link to comment Share on other sites More sharing options...
robertspark Posted May 13, 2012 Share Posted May 13, 2012 Simon, Could you post a few more pictures of your setup please of how you converted your mill and lathe to CNC. Pictures can speak a thousand works, unless they're copyright of course. Many thanks. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted June 14, 2012 Share Posted June 14, 2012 Any more work Si? Just pondering converting my Boxford lathe to CNC and Mach 3...its still in bits at the moment post-house move, so now might be a good time to do it. Anyone a good source of ball screws? Quote Link to comment Share on other sites More sharing options...
robertspark Posted June 14, 2012 Share Posted June 14, 2012 Do you really want / need ballscrews? Mach3 can compensate for backlash, or so I read (not done my conversions yet). The big source (most well advertised) seems to be Marchant Dice (all the same company below) http://www.marchantdice.com/ http://www.worldofcnc.com/ http://stores.ebay.co.uk/Marchant-Dice-Ltd Not used them personally, I did look at a plasma cutting table a while ago and them for bits, but decided that I didn't have the space for an 8x4 table (yet). Decided o go away from ballscrews on that one and use rack&pinion (cost, size of ballscrews etc, etc) and you can add rack anytime you want to lengthen it.... build a 4x4 table with an extendable section. And :http://www.ondrives.com/linear-ballscrews-bearing-support-units.html Quote Link to comment Share on other sites More sharing options...
simonr Posted June 14, 2012 Author Share Posted June 14, 2012 For a Mill or Lathe, you do need Ballscrews (ideally). Although Mach can compensate when it changes direction, what you loose is rigidity and accuracy. Particularly when you are cutting hard, the table will try to move as the cutter bites into the material. You see this particularly when you are cutting an interpolated curve. When either axis reverses, you get discontinuities & ripples. Backlash comp cannot cure this. I'll write up a bit more soon & post more piccies. The conversion is now finished - it only took a few hours once the board from Campbell turned up. However, there is a lot of the detail which I think will be useful to others. The board is fantastic and works really well - but the manual is terrible! The gecko stepper motor drives I've used are so much better than the original ones with 5x the resolution and the motors run much more quietly & smoothly but with more torque. The original stepper motors on the lathe are pretty big, but they were made before Neodymium magnets so need to be big to deliver the torque. You could use modern motors half the size to get the same performance. I have been thinking about Plasma tables! The resolution & Kerf (cut width) of a plasma are in the order of about a mm - so the positional accuracy does not need to be much greater than that. My main idea is to laser cut the sides of the table including the rack - and just use a high resolution (400 step per rev) motor plus micro stepping drive (to give 4000 step per revolution) with direct drive to a gear which walks along the rack. This should give better than 0.1mm. The big advantage of this is cost. The sides can be cut & folded for rigidity. The bridge between the two racks, so long as it's not too long can just be a length on M16 stainless studding and two ground shafts. The torch is moved across the bridge by turning the studding on a carriage sliding on the ground shafts. The ground shafts are also used to connect the gears driving the racks on either side. 3 x 16mm bars (one being the studding) will easily support the torch in the middle I think. The plan is to make something about 700mm square with 600mm square cutting area. It can then be made to clamp to the sheet so if I need to cut something bigger, I can move it. If the program includes cutting four holes in the corners of the cut area, these can be used to reference the cutter if it needs to be moved (using drop in tapered pins). I figure 700mm square is big enough to cut most of what I want and small enough that I can lean it against the wall when not in use! I'll post the cad files for the table once I've drawn them! Si Quote Link to comment Share on other sites More sharing options...
robertspark Posted June 15, 2012 Share Posted June 15, 2012 thanks si, comments + insight much appreciated Quote Link to comment Share on other sites More sharing options...
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