Thread: Wobblycogs CNC Mk2
03-09-2013 #51Now put a proper bloody cover over the Z axis and give those bearings and screws a break.
That stepper motor mount would be really useful, thanks (my back plate is 190mm wide so it would fit perfectly). The stepper mounting plates are one of the bits I wasn't looking forward to making by hand.
Possibly this is a silly thought but is it worth trying to getting the X and Y axis ball screws machined so that they can be used with a fixed BK bearing on both ends? The price difference of the bearings doesn't seem to be much and it would increase the critical speed nicely. The only problem I can see is that I'd have to be quite accurate with the positioning of bearings.
Any recommendations on stepper motors? I'm currently thinking the 4Nm steppers from CNC4YOU look quite nice.
Regards the 4Nm then I've found the 3Nm motors spin faster and see very little to any difference in torque.!
I've been doing some reading about the electronics side of the project recently hence the lack of updates. I'm currently favouring a Mach based set up using an Ethernet SmoothStepper and the PMDX-126 board. A fairly expensive set up admittedly but one that I hope will be fairly trouble free. I admit I'm tempted to try out LinuxCNC first as I have a pile of old computers hanging around and a fair bit of experience with Linux (I run half a dozen Linux servers) but as an old friend once said to me "Linux is only free if your time is worth nothing" and I've found that to almost always be true.
My rails finally arrived from South Korea (48 hours to get from South Korea to Cardiff, 3 weeks nearly to get from Cardiff to Gloucester!). I got caught for import duty but not a lot so can't really grumble and they were still much cheaper than locally sourced stuff. I've given them a little slide about and everything seems fine. If I press down on the block it slides more easily, I'm guessing this is pre-loading? Is there anything in particular I should look for to check if they are ok?
I'm just about to press the button on the ballscrews and round rails so would be interested to hear where you got your linear rails from as I might bite the bullet, pay the extra, and get these from the outset. also I'm going to get a PDMX-126 BOB so give me a shout and I'll order one along with you and perhaps we can save some carriage by getting 2?
I keep meaning to have a play with Linux but I've been out of playing with PC's for years now so probably know enough to get me into trouble but not out of it!!
The rails came from eBay a seller called fa-system. All told they cost £484, the same kit from Zapp would be £683 (not sure if that Zapp price includes postage). As far as I can tell the rails are still in tip top condition. The Z-axis have clearly seen a harder life than the X and Y which look almost brand new, I'd guess they all still have a ton of life left in them though.
I like the idea of buying the BOB's together, I'm pretty sure that's the model I'll end up going with but I want to have a bit more of a read first. I'd guess I would be looking to order late next week if that's ok?
Have you had any thoughts about spindles? There's an eBay seller "happykisssoul" that's shipping 2.2kW from the UK for a good price (even including insane shipping costs). I've seen a couple of guys say they have bought from him without problems.
End of next week is good with me for the BOB. I've looked at that seller and even bookmarked some of the rails but they would be miss matched sets and the NSK S20 rails that are 1390mm long look like they have a bit of damage to one rail so not 100% happy about getting it. Might just have a look about and see what else is available.
I've made my own spindle which should put out 1.7kW and I've got a 25V 47A PSU to power it....
I think you are right not to touch those NSK rails, the damage is way to close to the bearings for my liking. There are some HiWin and THK clones over on AliExpress that looked ok and the reviews I've found are generally positive.
Does the power supply really have that written on the top? I can't quite tell if it's been "photoshopped" on. You certainly wouldn't mis-read the spec.
I got it made from a chap on the heli forum I'm a member of, it was going to power my LIPO battery charger but I've got a bigger supply for that now The writing is vinyl stickers so could be peeled off if so wished...
Just looked at the rails again and the damage is right at the end of the rail, as it's 1390mm long and I only want 1300mm I could cut that off....
BUILD LOG: Wobblycogs CNC Mk1By Wobblycogs in forum DIY Router Build LogsReplies: 91Last Post: 02-01-2013, 06:38 PM