Buddy and i finished our JGro machine this morning. Want to post some pics but I don't see anywhere to attach them here. I expect one of you will help me out!
We bought the 4-axis board, power-supply and fan kit from Xylotex. 269 oz. in. motors from AutomationDirect (NEMA 23's). Leadscrews were ¼ - 20 threaded rod. We used flange-bearings (wheel-barrow wheel bearings) on each end of the x-axis screw with nuts and washers to tension it and reduce whip. These bearings are poor choices and do NOT take the axial thrust required here. Will replace later. Bearing-block bearings came from VXB at the most excellent price of $21 US for 30 pcs delivered to my door within 5 days of ordering (and there was a weekend and a border-crossing in there!).
Design and drawings were pretty good. Only things we changed were the addition of plastic adjuster blocks for the big pipes of the x axis; the MDF ones stripped their threads during setup. We also changed the leadscrew tensioning setup for the x-axis to take all tension loading off the motor as steppers don't usually have bearings to take thrust loads like that. Easy enough to do. Used some cheap Lovejoy-type jaw-couplings from www.princessauto.com to join motors to leadscrews. Spaced the motors away from the machine body with a couple pieces of carefully cut 2" PVC pipe and long mounting bolts. 10-24 nuts will NOT fit very well at the motor housing so we would suggest long screws here rather than threaded rod which we were forced to use.
So far we have only used a Dremel tool on it but it worked well. Looking forward to a router. We get about 30" a minute out of it which is about all I'd want to push a Dremel at. Lot of guys said we wouldn't be happy with the poor performance of the NEMA 23's but we think they're just fine. Not trying to win any races here.
Some cautions we have for others building it are as follows;
1) Check your stock size. The drawings are based on .75 thick board. Ours was somewhat less than that at .72 and this caused some alignment and fit problems between the bearing blocks and pipe guides, among other things.
2) Didn't have time to check if it was our mistake or not yet, but the x and y axis lead screw nuts seem to be mounted a bit higher than the motors and outboard leadscrew supports. This causes binding and motor overloads near the limits of travel n those axes. Check the drawings before cutting the mounting holes.
3) While tapping the MDF made us nervous and skeptical at first, it actually works pretty well. It works quite a bit better in the face of the stock than through the edges. Be prepared to drill a clearance hole and put a nut on the other side or make a new part; these DO strip out quite easily. If you just assemble and leave it, it should be OK. Repeated disassembly and assembly would not be recommended here. Use a good drill bit and a fresh sharp tap of good quality.
4) We spent a day and a half diagnosing a weird motor reversing symptom and traced it back to how we wrapped the wires. The motors are bipolar units and the wires for each phase should be kept separate. We twisted all 4 wires from the motor together along their whole length. This caused (we assume) an induced charge in adjacent pairs of wires and this in turn caused the motors to change direction after 5 movements or less. eg; we jogged for 1 second intervals, 10 times and the motor randomly reverses direction 3 times and would often lock up before 15 jogs. We separated the four wires into 2 twisted pairs and took the extra precaution of wrapping them in foil. Problem solved.
5) We attempted to use EMC to drive this machine (initially) because, 1) we have a good friend who is Linux-fluent and offered to det it up for us, 2) it's free and 3) supposed to be pretty stable once set up. We had this old donor-computer (333 PII MMX) that we thought would do. We wanted 3 partitions on the HD so we could mount some version of windows and DOS as well so we could ise Mach2 or TurboCNC if necessary. To make a long story short, Linux and EMC got in, Windows and DOS didn't. We ended up installing WinXP in a single partition and running Mach2. We had a lot of trouble finding a version of DOS for download to try TurboCNC. In any event, we wanted to use a thumb-drive or wireless LAN to transfer programs from house computer to shop and neither DOS nor Linux (?) have drivers for these (yet). Least not ones that could be installed and tweaked by us Neanderthal's. House computer doesn't have a floppy and we don't want one. It's still to be seen whether or not Mach2 will run consistantly on this old machine but so far so good.
That's about all for now. There's a bit more I should get down while it's fresh but I'll save it for when i put the photo's up.
Many thanks to Jgro for doing up these plans for us and to Mr. Keinbauer for the inspiration (and cajoling).
Keith Green, Surrey, BC
Ray Webster, Kamloops, BC
and
Rob McCrea, Langley, BC