Rick
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+ The Combivert inverter that was fitted as standard cannot be used with modern spindle control boards - it has a resistive (0-10k ohm) input control mechanism, not an analogue (0-10v) one. If you do want to keep it, I believe that the new Soundlogic breakout board can drive resistive controls, but I've never tried it. I am going to replace my combivert - which is misbehaving - with a Teco inverter but have not done this yet (the new one wont arrive here till mid next week).
+ One problem is that the combivert board also has the main power breakers and the +24v output that drives all the control relays (coolant and lube pumps, etc etc). Not sure yet how best to deal with that issue - may be simplest to leave the combivert wired in just to provide power for this board. Alternatives I can think of are to use a separate 24v PSU, or to replace the board entirely, or wire the pumps directly into a 240v supply. If you do the latter, you'll need to provide +12v for the low voltage worklight. This lot is something I plan to tackle next week, when the new inverter arrives.
+ Getting the original electronics box / control unit off the top is a challenge - these lathes were built to last (
). You'll need to remove the front and top panels, then the keyboard circuit boards, then remove the PNC circuit board on the right hand end - this has multiple plugs/cables/bolts that run thru the steel frame that prevent you going any further. Carefully disconnect (and label!) the three sets of armoured cables that come up through the hole in the baseplate - these connect to plugs at the back of the control unit power compartment. Once this is all done, you can unscrew the right half of the frame - mine had one screw at front centre (behind the keyboard), two on the top of the right hand panel (one each on the front and back pillars), and two underneath the baseplate, which take a bit of getting to. At this point, the right half of the box will slide off, exposing the turntable. On mine, this was like a pipe flange that had been pressure fit into the main casing of the lathe. If you have this setup, take a 4lb hammer and a cold chisel, put the chisel into one of the slots in the flange and wallop it sideways a few times until the flange starts to rotate in the housing. This breaks the seal, and then you can lever the flange vertically out with a crowbar. Then you can take the frame of the control unit off.+ The wiring of my lathe did not match any of the diagrams that are in the manuals that the Denford folks have kindly placed into this forum. However, the schematic at the back of the PNC3 installation/maintenance manual was accurate as long as I ignored cable numbers and colours, which did not match the actuals. It therefore took me two days to trace all the wiring through, and then about two hours to wire in a breakout board, power supplies, switches, and new stepper drivers and get things working under Mach (it works fine now).
+ On my lathe, the armoured cables coming from the lathe body were grouped into three sets, each going into multiway plugs on the original control unit power compartment. The largest plug (C01) on the left had all the power connections (care: 240v here as well as low voltage) and cables for switching axis power, coolant pump, lights, etc on and off. These operate relays on the combivert board. The middle plug (C02) had the connections for the X-stepper motor at the top, the remainder of the connections being for limit and homing switches. These all connect to the saddle box, at the back of the cross slide. The switch connections all ran through a single 12-way shielded cable. The third plug (C03) on the right had the connections for the Z-stepper motor at the top, and for the spindle encoder at the bottom.
+ I have retained the existing stepper motors but if you need to replace them, NEMA34 motors will fit directly onto the mounting points. The steppers on my machine seem to be basically unused, so I wont replace them unless they have a problem. There is reduction gearing in both drives (small to large pulley on the belts). If your drivers are set up like mine (set with 1600 steps on the driver) Mach will be 800 'steps per' in the motor tuning.
+ I replaced the existing stepper drivers with new 4.2A ones - type PMR542. You can get these from Gary Higgins at Zapp Automation (and if you do, let him know that I told you to call!). If you get the PSU from him, choose the 48v 350w model (S350-48, I think it is). You can power this from the 240v feed that comes up one of the armoured cables from the machine, no need for another external mains plug and lead.
+ I've used a Uniport breakout board for my conversion, and you can get that from Zapp too (or directly from Roy at diycnc.co.uk). I've got a separate small PSU in my controller box to feed this 5v rather than using the USB power connection simply so that I dont have yet another external cable to get in the way.
+ I suggest that you forget trying to use the homing switches - they are seriously weird and I could not get them to work. Mach does not need them anyway - you can use the limit switches for homing, which is what I am doing. If you want/need to wire each limit switch separately, you'll need a second breakout board - use a PCPPS card (also from Zapp / diycnc) and configure Mach accordingly. If you go this route, you'll need an add-on parallel card in a PC that already has one parallel port. Configure the PC so that the addon card is LPT1, and the onboard port is LPT2 or you'll risk running into issues with how the PC/Windows assign pins to inputs and outputs. If however you wire all four limit switches in series, it only requires one input port on the breakout board so you dont need the extra parallel port, which is both easier and cheaper, and still works fine with Mach. In this case, you'll need to rewire the switches in series - I have done this inside the saddle box on the back of the cross-slide.
+ The lube points under my cross-slide were clogged with muck - probably worth checking yours and cleaning or replacing them if need be.
+ I have not tackled spindle speed control yet, but will do this when my new inverter arrives. I'll append my observations on this and on combivert replacement when I've done it.
