CNC router for model making

I have wanted to build a CNC router since I started making model boats kits about 1992 I started reading and tinkering and along the way learned a great deal about CNC I have converted a Sherline and a Prazi as part of this experience. I now use the Prazi regularly to make model parts.

I started collecting parts to make this router several years ago. I found a set of 36" long linear ball slides and several servo motors at the MIT radio club flea market. The most usefull part of this router was a piece I found in an electronics surplus store. It was an aluminum slab about 16x22" and 3/4" thick. It had 2 pairs of round linear bearings and rods arranged in an XY fashion, carrying a platform that held a microscope. I assume it was used to read some kind of photo or chart. I bought the whole thing, including the microscope, for $20. I wish I had taken a photo of it, but the gantry Y carriage is the basic moving part of the original device.

The stand was welded from 3/4" square steel tube. This was my first serious job with a mig welder and I found it rather easy to use after just a few minutes of practice. Some of my welds are less that pretty, but they all held.

In this view the basic frame and gantry are complete, the Y axis lead screw is in place.I started to make acme screws and moglice nuts for this, but the acme rod I had on hand was bent and I didnt want to fool with straightening it, so I ordered the Thompson ball screws from McMaster-Carr. A 6ft screw is about $80 and the nuts are $22 each.
I ordered 4 nuts, planning to make them a pre-loaded pair, but to get the project done quickly I just installed one. After gettin git running I have measuerd backlash to be in the .001 range, more than adequate for a wood router, so I dont expect to install the second nuts.

Here most of the major moving parts of X and Y are assembled. The lead screws are in place and the servo motors mounted.

A view from the other end

I tried to do a real tidy job of the electronics. The chasis is another piece of 'scrap'. It arrived as the shipping pannel on some computer racks at a job I was doing before I retired.
I used Geck drives, and a power supply I bought at a garage sale for $10. I also used a Pmdx breakout board. This was real handy to handle the limit switches and a relay to control the spindle motor.

I made a vaccuum table to hold thin wood sheets. The 3/4" strips make air channels and support a piece of peg board as the top. The pegboard is held down with a few wood screws and can be changed in a few minutes when it gets to scarred.In this photo the pegboard is slid back to expose the strips.

I made a simple mount for a Dremel style tool. This one is a Black & Decker model that was only $20 at Home Depot. I am also going to make a bracket to hold a bigger laminate trimmer. The B&D will cut completely through a 3mm sheet of plywood with a 1/8" dia cutterat 30 in/min. I cant tell how long it will last, but it does not seem to be struggling with this load.
Here was the first test piece with the vac table holding down a piece of 3mm plywood. I was surprised, and pleased to see how well this holds down. The unused table holes are covered with a sheet of drawing mylar film.
I am going to make some simple eccentric clamps that will slip into a hole in the peg board and wist against the edge of a workpiece to help hold it from sliding.

I will be doing some work with the machine, to see what cutters I can use, and what kind of feed rates work. But I think this is going to be a handy tool.

Update, December 05

I began using the router to cut some parts for a model traincar for a friend. I quickly found the 1" angle iron rails that supported the table had considerable sag when the tool was out in the center of the work area. I replaces those angles with pieces of 1"x3" and now have very little deflection. In this photo I was cutting some 3/4" plywood formers for a locomotive boiler.

I also changed to a Ryobi Laminat trimmer instead of the Dremel style tool. I had read many articles that said a Dremel makes a lousy spindle- they are correct!

I also used cheap router bits for a while, and found they left a ragged cut. I recently bought some good, American made, solid carbide bits and get much cleaner cuts.

The vacuum hold down, powered by my shop vac works well but is really noisy. Someday I hope to find a cheap vacuum pump and try that.

My servo motors are also very noisy when at a stop. These were used motors from the flea market and I really dont have any specs on them. They do seem to have enough torque, but the encoders ae very high count and that limits my max speed of travel. I bought some new motors, but because I did such a nice job of all the cabling I cant bring myself to hack out all the wires and replace the motors. Someday the noise will get to me and I'll make the change, but otherwise this machine works well, and I expect to just use it to make parts.

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	The stand was welded from 3/4" square steel tube. This was my first serious job with a mig welder and I found it rather easy to use after just a few minutes of practice. Some of my welds are less that pretty, but they all held.
	In this view the basic frame and gantry are complete, the Y axis lead screw is in place.I started to make acme screws and moglice nuts for this, but the acme rod I had on hand was bent and I didnt want to fool with straightening it, so I ordered the Thompson ball screws from McMaster-Carr. A 6ft screw is about $80 and the nuts are $22 each. I ordered 4 nuts, planning to make them a pre-loaded pair, but to get the project done quickly I just installed one. After gettin git running I have measuerd backlash to be in the .001 range, more than adequate for a wood router, so I dont expect to install the second nuts.
	Here most of the major moving parts of X and Y are assembled. The lead screws are in place and the servo motors mounted.
	A view from the other end
	I tried to do a real tidy job of the electronics. The chasis is another piece of 'scrap'. It arrived as the shipping pannel on some computer racks at a job I was doing before I retired. I used Geck drives, and a power supply I bought at a garage sale for $10. I also used a Pmdx breakout board. This was real handy to handle the limit switches and a relay to control the spindle motor.
	I made a vaccuum table to hold thin wood sheets. The 3/4" strips make air channels and support a piece of peg board as the top. The pegboard is held down with a few wood screws and can be changed in a few minutes when it gets to scarred.In this photo the pegboard is slid back to expose the strips.
	I made a simple mount for a Dremel style tool. This one is a Black & Decker model that was only $20 at Home Depot. I am also going to make a bracket to hold a bigger laminate trimmer. The B&D will cut completely through a 3mm sheet of plywood with a 1/8" dia cutterat 30 in/min. I cant tell how long it will last, but it does not seem to be struggling with this load. Here was the first test piece with the vac table holding down a piece of 3mm plywood. I was surprised, and pleased to see how well this holds down. The unused table holes are covered with a sheet of drawing mylar film. I am going to make some simple eccentric clamps that will slip into a hole in the peg board and wist against the edge of a workpiece to help hold it from sliding.