Home Built CNC Router and Plasma Table
(8020 Belt Drive)
E. C. Marsh
P.O. Box 342
Saint Ansgar, IA 50472
Building the CNC Router Project
The concept came about because I wanted to manufacture a simple way to fold the CD inserts for CD and DVD back trays cases.
The ready made printable Avery type back tray inserts are quite expensive. A prototype injection molding venture is expensive for a item that would have a limited market.
With my CAD ability and the mistakes I probably would make with the first or second test this is out of the question. For the cost of a prototype I feet I could build a machine to carve out these jigs plus it would have many more applications.
Hopefully this log will give others ideas on construction their machine and point out some of the mistakes that I made in the process.
I started with a budget or $2,500, which was the cost of the first prototype template I wanted to build. I shot that out the water! The completed Router which included a drill press, miter saw, taps/dies, misc tools, a PC, and software (Mach III) drove it up to $5,200. Much more than I wanted but when you get so deep there is no use to stop.
|I purchased a (eBay) Linear Actuator for the Z-Axes 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 (changed to 12) 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.
|Another eBay find, an auction for 2 rails and 4 THK HSR25 linear bearings each 24" long. I used 1 bearing truck from the rails to give a longer travel.|
|This is a picture of the preliminary setup plan for the X and Z axes.|
|All good plans must be changed. I eBayed the 60" rails and went with a bit smaller and heavier design. My new Y rails bolted perfectly to the T-Slot using weld nuts and I was able to slide them back and forth to line things up.|
The table is a 22x22 cutting area, which is 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. Just keep adding T-Slot and extending the belt lengths.
|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.|
|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.|
|The big old ball screw mounted well. It is way over kill but it was surplus and got it at a real good price.|
The ball screw was installed, although very accurate it was to darn slow (30ipm). As progress went on you will see that this was changed over to a belt also. I re-eBayed it.
|Here is a shot of one of the belt clamps to move the gantry around.|
The belt tighter is a PVC coupling with 2 skate bearings pressed in. A 5/8" bolt is the shaft and it is threaded in a piece of 1/4" aluminum flat, which is mounted to the T-Slot. Slide up and down to adjust the belt tension.
|One of the 3/4" L belts in the clamp. I just put the belts over the 24 tooth pulleys, connect the clamp to the gantry and adjust the tighter. My motor mounts are made with 1/4" aluminum angle. The 1/4" motor mounts work very well with no noticeable flex that affects accuracy.|
|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 22" x 22".|
I purchased the router mount from K-2. Had a hard time trying to figure out how to make decent one.
|Later on I wound up removing the e-stop. The darn contacts would bounce and stop the machine. De-bounce didn't work and I decided there wasn't really any use for it other than it looked cool. I don't use any limits or home switches on the machine either.|
|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 was to find out soon, how they work. |
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. The motors are 500 oz/in. steppers.
|I got the CNC completed and worked on tuning and setting up the table to do some test cuts.|
|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.|
|Electrical connections and cable chain.|