[mannster]

I have started this thread to share the work I am doing to get a cnc mini mill up and running. The RULES for my project are:

1) Keep costs down to a minimum (*use surplus/used parts when possible)
2) Keep rigidity up, since it is a mill
3) Don't worry too much about short XYZ travel, since it is a *mini
4) Don't worry too much about rapids being slow. (use simple drivers)
5) Try not to get carried away, the important thing is to finish. LOL

This being said, step #1- What to do about the XY axii ?

SOLUTION:

This cross slide was cheap, and more rigid than what I could probably make on my own. (but it does need some upgrades)

[mannster]

This is the cross slide table as of today:



It is used, but still in good shape.

The first thing I needed to do was to replace the steel gibbs with brass. The slide was not moving smoothly.



This was easy enough, and I replaced the larger wingnut with a bolt.

[mannster]

This table has alot of backlash ! I am trying to minimize it by putting a bearing on the acme screw and capturing it where the handles used to be.



The standoffs and the motor plates are quite basic. The plates were drilled to handle both NEMA24 and NEMA34. The part that captures the bearing is also quite basic. The bearings are standard metric skate bearings 22mm OD x 8mm ID cheap and precise (depends on ABEC #) and readily available.



This is a shot of the assembled pieces. This is the same on both axii.



Next, I need to do something about the brass nuts used for this table.

[mannster]

I got rid of most of the backlash of the X and Y axii just by making sure everything was tight, so I am satisfied with that. Now I have moved on to the Z axis, and chose to build something from scratch. I didn't feel up to machining Dovetails so I built a router style head using Thompson rods and frelon linear bearings. It is actually more rigid than I thought it was going to be. The important thing is to keep vibration down to a minimum, and i think the weight of this assembly and the frelon linear bearings will dampen alot of the vibration. The 3/4" rods are 12" long. (see pics)


This was built with mostly surplus parts, but still impresses me with what little slop (if any) it has.

I still have to machine a tool mount. I am going to use a Craftsman All In One Cutting tool.
CRAFTSMAN TOOL LINK
It feels heavy and has a 20,000 and 30,000 rpm speed settings...I am worried that this will be too fast to cut any aluminum or plastics although my primary goal is to rout and drill PCBs .

[balsaman]

Cool. I am interested to see how it comes together. Will you build a welded frame?

Eric

[mannster]

Yes, Balsaman. I intend to make a welded tube support for the Z-axis. It will be about 20" tall, and basically a 4x6 inch steel tube. The baseplate for this machine is going to be a 3/4" aluminum plate. I would have preferred to make the bottom frame out of steel, but for now I need to go with what I have on hand. (*see rule #1) LOL

Thanks for looking !

[miljnor]

I have one of those cross slides and havn't used it in years. I was thinking of doing the same thing, so I will be following along to see how yours comes out.

So far it looks *****en man! keep up the good work!.

[mannster]

Thanks Miljnor ! I appreciate it, I am trying to do at least one thing for this project everyday, I want to finish it soon !

[mannster]

I finally got another big step completed for my project. I welded some 2x4 steel tube and some heavy 1" steel flat bar to make my "pillar" for the Z-axis. The bottom and face have been machined perpendicular to each other. The welded assembly is 20.5" OA height.



I still have a few details to finish up before this project can power up. The power tool mount/clamp, the motor couplers, and the baseplate/platform needs a hole pattern drilled and tapped.

So far it hasn't been too complicated, it is just hard to complete things like this at work during lunches and such. :frown:

But the payoff will be worth it ! :banana:

[mannster]

I got the baseplate done, so I can at least bolt the main components together and get an idea of how it's gonna turn out. Here are some pics:



I intend to get it running, and then I can see what needs tweaking ( I suspect it is going to be the leadscrews on the XY.

So now, I need to:

1) finish the Craftsman Tool mount
2) complete my motor couplers.

[anoel]

Did you buy those bearings and rails from me on ebay? aka... renegade_amps

They look just like a set that I sold cause I abandoned a project. (and as it always turns out could have used them a month later.)

[mannster]

Nope, I had this stuff already. The rail was actually a 2 foot rod that I cut in half.

[JFettig]

Looking good so far, how do you plan on squaring up the machine? mainly the z-axis because the other parts are premade. Is the column only tacked to the base? that might be something you want to finish welding around then machine the surfaces once more.

Jon

[mannster]

The column has heavier welds on the front and back joints. The Side just got a short stitch to minimize warpage left to right. The bottom plate was machined prior to welding, and the front face was machined square to the base after welding. It came out very square, at least square enough for the time being. The tooling plate probably should have been flycut, but I am going to leave this for the final tweaking stage, or perhaps Version 2 Project :devious:

Thanks for your input Jon !

[anoel]

You can add set screw in the four corners of the base of the cross slide. That way you can use them to tram the table to the head. (This is something that Jose Rodriguez did for his homeade mill that Little Machineshop sells a video for. And he was able to get things trammed in at under .0005" in a 4" circle.)

[mannster]

I finally got the tool mount done and bolted on. I installed the Craftsman tool in it and powered it up, it sounds sweeet ! I also got one motor coupler done, and mounted the stepper motor I am going to use. See pics !

[drawbar]

mannster,

You must have access to a bigger manual mill that you're making your pieces with? Your work looks awesome.

Brian

[mannster]

Thanks Brian ! We have a new Sharp Manual Mill with 3 axis DRO, it helps alot when you have to do small parts in a hurry, (like this project )

[mannster]

Whooo ! that took some effort to get it done (but not perfected)

Things I have learned:

1) Helical motor couplers are a MUST ! Especially when you don't have very much current going to the motors. I understand that they keep your motors from getting mistreated by misaligned leadscrews, and a twisting motion is a greater load on the motor.

2) The cross slide is so weak, that when I tightened the fixture plate I made, the gibbs actually binded up, ( I thought it was a leadscrew problem).

3) I can probably start making some simple parts, but a chopper drive would sure help things along.

anyway.... here are a couple pics

[mannster]

I let some time pass cuz I was looking into building some chopper drivers and fixturing so I can try making something on this mini mill. So, I am just trying some tests of pcb board type milling.

test #1 drill 4 holes. Using simple straightforward G-code.