2-axis ghetto cheap

[Mr.Chips]

Originally Posted by blades Hey guys, thanks for the kind replys! Wasn't too sure how well this ultra-simplistic setup would be received. Mr. Chips: no, no ball screw for now (part of my ultra-low-cost design). I originally thought about using some new 10 pitch acme screws, but decided with the smaller motors to see how it works with the OEM 16 pitch. Ball screws would have required machine modifications, which I wanted to avoid at this time (part of the KISS principal again)

I am not a machinest (I think I can't even spell it) but every Mill handle I have turned has has tons of free play when changing directions, and if you tighten the gibs would it still make it usable? How would you manage this? But then possibly there are ways? Pun unintentionally intended I think.
Hager

[blades]

Hey Mr. Chips, it's "machinist"
The typical wear characteristics of a well-used mill will have more slop & backlash in the middle of the table travel area, because that's where most of the use is taking place. The best you can do is to adjust the gibbs (or ways) to eliminate slop on the ends of the travel, then compensate for the extra slop in the middle of the table by gently "riding the brakes" to take up the excess slop. If you adjust the gibbs to have no slop in the middle of the table travel, it will be too tight on the ends of the travel.

If the slop you're feeling when changing direction on the table is backlash, (that dead amount of free-play in the handle when the table isn't moving when you crank), it's caused by either the leadscrew & nut wear & imperfection, or by the bearing preload on the handle that drives the leadscrew, or some combonation of both. THIS, my friend, is where ballscrews REALLY shine! Once they're in and adjusted, backlash is extremely minimal and usually stays that way. CNC and ballscrews belong together like bread & butter. My setup is a cost-driven compromise, because I'm using the standard leadscrews that came with the machine. The primary comprimise is in terms of accuracy, but I'm ok with that.

[blades]

Well, today I didn't have to work after all, so I hooked up the driver & PC to test it out.

It works!! Now for the real impression: I was a little disappointed, but not at all surprised, at the lack of power from the motors. It was very easy to stall them out by hand, or by lightly applying the locks. I'm really not surprised by this, and can see why Hoss and others recommend a minimum of 250-ish oz or so motors. You really need a little reserve power to ensure that the motor doesn't stall and miss any steps. These motors I'm using will get the table from point A to point B, and will most likely work fiine for taking very light cuts.

I'm currently only running on the CNC program that came with the board, but it doesn't support G-code, hence no linear or circular interpolation.

In spite of the low power, I am extremely happy with the results of this project so far. It will be well suited for someone who wants to get their feet wet and play around with CNC. It's probably great for a beginner at CNC, but NOT a beginner machinist. I say that because you have to be well experienced at machining to fully understand the limitations of this setup. I also would NOT recommend this setup (kanton, are you reading?) for part of a 3-axis conversion. Don't try and go this cheap if you're wanting 3 or 4 axis, you'll be sorely disappointed. This setup would be PERFECT for someone who works with PC boards and wants to machine traces & drill holes. The program that comes with it would work great for table positioning for drilling hole patterns.

chukkie: great idea! But it would probably require a more powerful motor than the ones I'm using on this setup. That little fine feed wheel doesn't turn all that easy on my machine.

I am still very much committed and excited about this project, and will continue to improve it. I will install some sort of belt guard before I attempt any actual machining, and I also need to see if I can get Mach to talk to the controller board. I will also see what I can do to improve the overall smoothness of the table & leadscrew operation, which will help the motors.

In the mean time, here's another pic, and a VIDEO of it running a test program.

[skmetal7]

I like the simple approach to 2 axis CNC blades!! Did it take you like 5 mins to make everything! haha

Make sure you keep the bearing blocks, leadscrews, and ways oiled, I know on mine it can be hard to turn when it starts to run dry, especially at the ends of travel.

Are you doing anything to combat backlash? I think I have at least .010" of it on any given axis on mine.

[blades]

Originally Posted by skmetal7 I like the simple approach to 2 axis CNC blades!! Did it take you like 5 mins to make everything! haha Make sure you keep the bearing blocks, leadscrews, and ways oiled, I know on mine it can be hard to turn when it starts to run dry, especially at the ends of travel. Are you doing anything to combat backlash? I think I have at least .010" of it on any given axis on mine.

LOL! Yeah, it definately looks like 5 minutes worth of parts, doesn't it?

Good thought on oiling the ways & leadscrews, as they are a bit dry on my machine after taking everything apart and cleaning/deburring. That will probably help a bunch.

Haven't really addressed backlash yet. I will minimize it as much as possible with careful adjustment, and will have to rely on Mach (or whatever program I end up using) to compensate for it. I really don't have that much though, I think around .004 or less when I checked it before.

[chukkie]

Blades do you have a link or part numbers for the timing pulleys and belt you used?

I just purchased X2 and I think I will do a conversion like yours but with the Z-axis on the fine feed and larger motors.

[blades]

Sure thing chukkie, keep us posted!

I got the parts here:

A 6R 3-067037 $5.00
A 6A 3-22DF03708 $11.79
A 6A 3-22H3708 $11.49

[chukkie]

Thanks blades

I will start a new thread when I get all the parts in.