Thursday, August 26, 2010

CNC Machine Build - Part II


I bet you'd all thought I'd given up on this! Well, I just got a little sidetracked with a few other projects - the main one being the play-structure restoration and a load of garden "improvements" (I hope the landlord agrees!).

Well, I was wondering if I could finish it before posting again, but I got impatient. Most of the hardware is done, but there's still some fine tuning to do on the axes and I still have all the electronics to sort out.

I've been really happy with the plans I bought from solsylva.com, they are detailed and straightforward to follow. Most of this has been new to me, so I've taken my time (not that I had much choice) and it's been working out ok. It must have been comedic seeing my sleep deprived carcass hanging around the wood or screws/bolts at Home Depot around midnight on Saturdays, looking confused and eyeing everything up suspiciously. I had no idea what all the numbers and specifications meant on the parts when I was first buying them... trying to match up what was in the plans with what was on the shelves took a lot longer than I'm willing to admit.

There were a few choices to make when building the machine:
  1. What wood to use.
  2. What leadscrews/leadnuts to use (ACME rod or hardware store threaded rod).
  3. What bearings to use.
  4. What stepper motors, power supply and controller board to use (main choices seemed to be hobbycnc and xylotex.
Since cost is definitely an issue for me, I mostly went with the cheapest options. So, whatever wood was available at Lowe's/HD (pine and Douglas-Fir); threaded rod leadscrews (I can always upgrade to ACME later); hardware store tee-nuts as the leadnuts; skateboard bearings from Slam N City's ebay store; and I ended up choosing the xylotex 3 axis system kit for the electronics/steppers. I went with Xylotex over HobbyCNC mainly because the HobbyCNC kit appeared to require more work to get it up and running (like buying a separate transformer and fitting it in with the rest of the kit).

Here's a few in-progress shots:



This is after installing the y-gantry on the x-rails.



These are the bearing flanges cut out of kitchen cutting board. I bought some Forstner bits from ebay in order to cut the recesses. There are a few holes in the wood that require either spade or forstner bits as well -> the bits have been handy on other projects like drilling recesses for the bolts on the play-structure and making holes in our upside-down tomato plant buckets (you can see them somewhere in the middle of one of Lin's more epic posts).



This image shows the machine after the x-axes leadscrews and nuts have been added - there's one on each side of the machine. The x-axes stepper motor is connected to the two leadscrews by a belt and pulley system (suppliers and part numbers were given in the plans for these, so there was no confusion).



This is the cage that moves along the y-gantry rails and houses the z-axes spindle plate.




This shows the cage in position with the z-axes leadscrew assembly and stepper motor. The rods in the right hand picture are tension rods to press the bearings into the rails and allow the cage to run smoothly along the y-gantry black piping.




and here's the z-axes complete with spindle plate. The metal band at the front is used to clamp the router onto the spindle plate (as you can see in the picture below).




So, I think all I have left to do is to wire up the steppers, controller board and power supply; connect these to a computer (I'm planning to use linuxcnc on an old disused laptop - so old it has a parallel port!) and then work out how to use the software. Can't wait to carve out my first test pattern!

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