Building the CNC

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Mailing Address:
E. C. Marsh
P.O. Box 342
Saint Ansgar, Iowa 50472
ernie@ecmarsh.com

Building the Router Table

Updated 03/20/2008

As things start coming together, I will be posting pictures of the Router assembly. Progress is from the first entry on down.

I ordered a small (get started) quantity of aluminum extrusions, fittings and stuff from the 8020 Inc. Outlet Store.
A couple of timing belts and pulleys from Hubbard CNC Components.
I am considering driving the X and Y with timing belts as they are supposed to be more accurate than the acme screws and are cheaper than ball screws or rack and pinion setups.
Ordered a few bearings and lock collars from Bearing Bargains.

4/6/2007

Got my Lenear Actuator for the Z-Axes (finally) and and it should be easy to configure this one. The stepper motor fits in the motor mount and I have a 10 tooth timing belt and pulley that will give a 2:1 gear ratio.

	For the table I picked up, off eBay a pair of 60" long x 20mm shafts, with 4 20mm open top pillow blocks, and 4 20mm end supports. My nephew fixed me up with 4 24" Lintech 3/4" rail supports which I butted together for 48" of support under each rail. The 20mm rods seem to fit very solid in the support grooves. I can use the end supports to hold the rods firm and this should make a nice sturdy support rail for the table.
	I keep thinking of chopping the rails off to 48" but should wait awhile until I get everything organized.
	Instead of chopping off the rails I went and purchased a pair of 32" heavy linear rails. Went and eBayed the shafts, now I am back to square 1 for the X-table.

	Another eBay find, an auction for 2 rails and 4 THK HSR25 linear bearings each 24" long. I might remove 1 bearing truck from the rails to give a longer travel.

	This is a picture of the preliminary setup plan for the z and x.
4/24/07	All good plans must be changed. I eBayed the 60" rails I had and went with a bit smaller and heavier design. She will have about a 24x24 cutting area which should be more than enough for my present projects. If someday I need a longer travel, it should be easy to extend the table to say 3 or 4 miles or so.
	It was very hard for me to line up the rails as this precision stuff is rather new. The shims are to be replaced by a piece of 1/8" flat stock to hold everything square. The bottom of the gantry will be whacked off to length and clamp the drive belts to the end of the ears.
5/13/2007	The router is coming along pretty good. I have the cutting deck (MDF) setting there for the picture and the router isn't attached yet. Just have it held on with C clamps.
	Another shot of the CNC machine.
	The big old ball screw mounted well. It is way over kill but it was surplus and got it at a real good price.
	Here is a shot of one of the belt clamps to move the gantry around.
	One of the belts in a clamp. I will just put the belt over the pulleys, connect the clamp to the gantry and adjust the tighter. I will have to install the drive pulley and belt before I make a permanent connection. the 48 tooth drive pulley will be here this week and I will be able to mount all the motors and measure the belts for the X and Y axes. Hope to be done for a test run in 2 more weekends.
5/23/2007	It is all put together. Everything looks to be square, level, and straight. Next phase is to wire her up, turn on the power and stand by the Emergency Stop switch. Cutting area is 24" x 24".

	I had to add an extra bearing for the 48 tooth differential pulley. The shaft would bow as I tried to tighten the belt. The whole thing is based on belt drives and we will find out soon how they work. Going to see how it goes with the gantry belt drive. Seems a little odd to have a big old heavy duty table with the heavy belts and pulleys connected to little motors with 3/8" shafts.
6/3/2007	I got the CNC completed yesterday and worked on setting up the table and doing some test cuts. Everything wound up being a 20 x 20" cutting area, forgot about the width of the Z axes.
	I am very happy how everything worked out. I am not able to measure any backlash with the dial indicator when it is under no load.
	My wife Terry got me a great deal at Staples on a computer stand for $6.00. Best deal I have on the whole project.

	Now I need to learn G-Code and the Mach2 software plus cough up another hundred and fifty bucks for the license and will be ready to go for real. I plan on posting a couple of cutting videos as soon as everything is figured out.
8/01/2007	Changed the X drive ball screw to a belt drive. Looks strange but is extremely fast and accurate. To me this is the only way to go as I am very happy with the belts.
	The belt extended the X from 22.5" to a full 24". Now I just have to fabricate a better dust extraction hood. This one works fair but is still not good enough when cutting that nasty MDF.