My 1st CNC Router

[robertf03]

I've been kicking around the idea of building a miniature CNC mill for a while and decided to finally get started on it. Most of my ideas came from the Tom McWire article on instructables.com, and I'm mostly building this as practice so I don't make any mistakes if I decide to do a big budget mill.

I intend to do mostly circuit board milling and drilling, maybe some plastic too. The "router" is a cheap 12v harbor freight cut off tool. The 12v part of it interested me, since I can very easily add on/off controls with the same power supply. The steppers are 3 NEMA 17's and I plan on using 1/4" 20 for the lead screws. I priced out linear bearings and decided for this project I'll just use roller blade bearings and channel and hope for the best.

The design is still in its infancy, and I'll clean it up and modify it as I'm waiting for the steppers to get here in the mail. The table in the model is 12"x 12", but I will probably reduce it to 8" x 8".

Except for a few missing braces and actual mounts for the steppers, here is what I'm planning on doing.

Any obvious problems in the design?

[2muchstuff]

Your choice of spindle worries me. Even using a Dremel tool would be an improvement in quality. If cost is an issue search Craigslist.

[lovebugjunkie]

Not sure I follow your design but it looks like your table will be moving in the x and y direction. Not sure how you would support it with bearings in both directions in the U channel. Also the U channel will catch a lot of "dust".

[robertf03]

I didn't think I'd be real happy with that design, so I scrapped it. I really just wanted something to experiment with, but i think this will be more fun and changing to the moving gantry makes the work area bigger.

I offset the X axis linear slides, and the Z axis linear slides thinking that it will counter any play in the bearings. I will probably be using brass bushings for now and upgrade to thomson stuff in the future if this design works. I was going to use TGP shafting, but hardened shaft isn't that much more expensive from the local bearing place. I'm thinking .500" shaft, 4 linear slides on the Y axis (the one under the table), 2 on the X and Z.

The cheapo cutoff tool spindle is only shown because I already drew it, I'll get something bigger and more dependable once its built and working.

The rails will be adjustable for alignment, its just not shown in the drawings. I'm not counting on MDF to locate the rails.

Any suggestions or things I need to change?

[gangster429]

I’m going to build Tom McWire board too. It’s cheap and easy.
http://www.instructables.com/id/Easy...lling-Machine/
http://www.instructables.com/id/Easy...and-Driver-ci/
did you build it already does it work good?
Does it work with Mach3 ?

[robertf03]

I did not build the first design, but I do plan on using his circuit design. I'm not sure if it works with mach 3. I'm pretty new to the CNC thing and the only thing I can tell you about software is that my local fab shop rejects dxf files with splines.

[johnmac]

My first table was 12"x12" with 1/4x20 screws and top speed is way too slow. It has other faults, but replacing the screws now will be a real pain.

John

[robertf03]

You are probably right about the all thread. I was trying to do this on a budget, but now I'm starting to lean more towards building this to keep for a long time.

I forgot that I owned a rotozip, so I'll be using that instead of the cut off tool. In another post someone linked an ENCO acme thread sale. The motors are on the small side, and I'm not in a hurry so 3/8-12 is looking like the stuff I want.

I got the base built, and the steppers are tested. I need to pick up some parts to finish the controller and get the lead screws on order.

[johnmac]

I have read that the plastic housing on the RotoZip can allow flexing. With that in mind, make the mount replaceable. Some of the name brand trim routers seem to make good spindles. I built mine with a Dremal tool, and replaced it before I even got the limit switched hooked up.

John

[robertf03]

I plan on making the spindle mount easily interchangable.

What are you currently using as a spindle? And what did you use for your limit switches? I was thinking about some microswitches that kill power to the steppers.

[johnmac]

I currently use a harbor Freight trim router. The limit switches are micro switches wired thru my Stepperworld driver to the software. If the limit switches kill the steppers directly, you won't be able to back away from a tripped limit switch with the motor.

Kcam keeps track of the direction when a switch is tripped, and will allow a reverse direction. Mach3 also has a "soft limit" that can be set ahead of the "hard limit".

My second machine is in the planning stage now. It will have a 36"x48" table with a 7" Z.


John

[robertf03]

What is the runout like on that spindle? Have you tried aluminum and if so, how did it work?

If it hits the limiter wouldn't that mean the nc code or zeros were off, or the machine has jogged and the part is already trashed? Like I said earlier I have almost no experience with the software yet. My previous place of employment had a dedicated CNC shop using Mazaak stuff, but I was just a simple manual lathe and mill operator and didn't get to mess with the automated stuff.