Monday, November 14, 2011

Making a Modular CNC Mill Spindle (MyDIYCNC Build log #4)

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When I left off in my ongoing My DIY CNC build log I had a few problems remaining. The spindle was not up to the task of really any quality milling, and some axis still had issues with not being parallel. After some thought for the future I decided to divide and conquer the issues. I dealt with the parallel axis issues on their own (mostly just taking apart, realigning, and putting back together).

For the spindle, though, I went back to the drawing board.

My spindle carriage must:
  • make it easy debug problems
  • make it easy to trial solutions
  • simplify changing spindles in the future (think laser etching, or 3d printing)
  • still be rigid enough to create quality work.
I decided to take the existing spindle mounts off the z axis carriage, and create a modular carriage adapter plate that allows for switching spindles with little effort. The rest of the post is a guide to modularize my DIY CNC spindle to support easily switching spindles between milling, 3d printing, laser cutting, or any other tool.
For this project you will need:
  • z axis carriage removed from CNC
  • 3x 1" bolts, with matching wingnuts, and washers.
  • small countersunk screws for attaching new spindle mounts to the spindle plate.
DIY CNC Z axis carriage, spindle removed
Step 1: Flatten existing carriage.

Remove the z axis carriage from the CNC and remove the attached spindle attachments so you have just a flat plate.
Spindle plate template about to be cut
Step 2: Create mate plate

Create a second spindle plate that will "mate" with the spindle carriage.  This plate will mount the actual spindle, and be held onto the carriage with 3 bolts.

Note the corner cut out to avoid the leadscrew mount on the carriage (visible in the photo above).

I'm using 1/4 inch MDF from home depot.
Spindle plate sitting on carriage
Step 3: Align spindle plate

Align the new cut out spindle plate with the carriage and tape into place.
(tape removed in photo post-drilling)
Another picture of the spindle plate + carriage
Step 4: Drill mating holes

With the spindle plate taped to the carriage, drill holes the size of your mounting bolts.  Be very careful to choose spots leaving enough room for the spindle to be mounted.  

Also ensure the bolt heads can be accessed with a wrench to hold in place while tightening the spindle plate with the wingnuts.

Also be sure to plan to leave enough space near the mounting bolts on the spindle plate from to have room for the wing nuts that will hold the plate to the carriage.
Step 5: Deal with fallout.

This picture is a view from the bottom of the z axis carriage.  The problem it's showing is that the plate mounting bolts hit the edge of the z axis parallel bars mount.  This limits z axis travel by about an inch, so file down the parallel bars mount until the bolts can pass smoothly past without causing problems.
2 spindle mounts, taped, and match drilled
Step 6: Create new spindle mounts

Measure the diameter of your spindle tool and cut two matching mount pieces out of the MDF.

Align the spindle mount edges that will attach to the mounting plate and tape them together.  Drill a hole large enough to fit your spindle through both.  This should create a nicely aligned "matching drilled" hole in both spindle mounts.
Step 7: Insert spindle, attach mounts to carriage

Last step of spindle plate assembly is to first tightly insert the spindle into the mounts, then align the mounts on the spindle plate. 

Pre-drill through the back of the spindle plate into the mounts.  The MDF may split so be sure to align the holes directly into the center of the mounting plate, and be sure to pre-drill holes big enough that the mounting screws will fit without expanding the holes much.  My MDF split a bit but is still holding strong, so I added a layer of tape and moved on.

Countersink the mounting screw holes before inserting the screws so that the back of the spindle plate can be flush with the carriage.
(For some reason I got excited and failed to get a picture of this step)
Step 8: Put it all together

Insert the spindle plate mounting bolts into the holes you drilled in step 4, then reinstall the z axis carriage into the CNC.  Insert the spindle plate into the mounting bolts and pull it flush to the carriage.  Tighten the plate to the carriage using the wingnuts on the bolts.  You now have a modular spindle attachment for your CNC!

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At January 15, 2012 at 3:05 PM , Blogger Austin Blanco said...

Just wanted to find out if you'd had any success with your modifications. I'm in the same boat. Finished my DIY CNC about 6 weeks ago, but I can't get a level bed yet. Keep tweaking to tighten up the axes, but on the other side doing this makes thins bind. Here's my build log if you're interested -


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