Saturday, July 20, 2013

Router lathe – upgrades and wood sign

Router lathe – upgrades and wood sign.

Here's a wood sign I made for a friend's woodworking shop, Artsubstrates. This is the first time I've wrapped a 3D shape around the rotary axis. It worked better than expected.


(note: from here on is going to be pretty dull for anyone not building a cnc machine. ...and maybe for those who do, as well.)
I generated the text using "FEngrave" a great piece of software for generating gcode for signs. It does one thing and does it very well. Highly recommended. Then I used another piece of software to take the output from FEngrave and wrap it around the rotary axis.

Recent upgrades:

Some upgrades were required to convert from arduino 2 axis control to 3 axis CNC. Added was new z  axis assembly with stepper motor and controller, new belts and pulleys on the rotary axis to increase the gear ratio, and limit switches on the linear axes.

New Z axis assembly with motor.
The new Z axis assembly has 3/8" aluminum plate for the base and the carriage platform, 5/8" O1 tool steel rods for rails and UHMW bearings to slide on. I made another UHMW nut and used the acme threaded rod left over from the X axis. I'll have to re-think the UHMW bearing though -- they slide really smoothly by themselves but take a lot of adjustment to get the carriage to slide without binding with all 4 attached.

Limit switches on Z axis
Motor and switch wiring

Showing the limit switches and motor wiring on the Z axis. I used ethernet cable and jacks for the limit switches, and heavier 22g wire for the motor.

New rotary axis belts
 The big automobile timing belt and diy pulley were replaced two XL timing belts and pulleys. increases the motor/ axis ratio from the previous 4:1 to 16:1. This provides a lot more holding power against the router and gives smoother rotary axis travel and much finer resolution. With the old belt, there was more backlash that I liked and at larger diameters, one step on the motor translated into as much as .003" of travel. With the new belts and gear reduction, resolution at large diameters is still very fine and I see less chatter during heavy cuts.

The current belts are neoprene with polyester fibers, which do stretch a little and is more noticeable with the double gear reduction. I purchased new belts with kevlar fibers that have very little stretch, but haven't installed them yet.

All this is because these 285 oz/in motors are OK for the two linear axis, but a bit puny for the rotary axis. A motor upgrade on the rotary axis may be in order, but would require a bigger power supply and new controller as well -- not in the current budget.

Wiring to the electronics enclosure. 5 pin XLR connectors with 22g stranded cable for the motors and ethernet cable and jacks for the limit switches and e-stop button. There's a vented cover for this enclosure, but after an overheating incident where the cooling fan lost power and the controllers started making real funny noises and smelling bad, I don't have the courage to close it up yet. I'm thinking of putting in a temperature monitor, but that may be overkill.


  1. How does it work? Have you done any more upgrades?

  2. It works well -- and I finally put the cover on the controller box, but I'm not sure if that applies as an upgrade.


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