Cheapcnc Design

[mikeschn]

This is the open source thread for a cheap cnc design... benchtop size...

I did one of these last year, but it was not nearly robust enough... So I figured I'd bring it to the open source group and see what you guys think I did wrong, and then we can come up with a new, more robust cheapcnc design.

The only criteria for this design are that we want to use drill rod and bushings. Beyond that, anything is fair game!

Here's my original version of the cheapcnc machine...

Mike...

[greybeard]

Hi Mike,
There have been several references to "drill rod" in US postings. Here in the UK the only reference I find is to Oil Drilling !!
Is this the raw material for making drills, or are you using very long drills as lead screws

[mikeschn]

Hey Greybeard,

Drill rod is blank shafting that can be used to make drills. It's basically untreated steel rod.

Look at this attachment from McMaster Carr...

Mike...

[ger21]

I think by going with the drill rod and bushings, you're setting yourself up with the same problems. The rod has to be supported somehow to eliminate the problems you had before. I'm a bit leary of recommending my method because I don't have it finished yet, but, I think it will work pretty good. Here's one using similar construction.
Second MDF machine

It's cheaper, and it's easy to build. Just my 2 cents.

If you want to stick with the drill rod, that's fine.Make sure you can support it, though. Just set some basic rules and stick with them.

[mikeschn]

Does anyone have an idea how we can support a drill rod, and use split bushings, affordably?

I don't think a cheapcnc type machine can afford 4 of these on every axis. (see attachment)

[kw26]

Hi Greybeard,
Try "silver steel" for "drill rod" in the UK and Oz.
Cheers,
KW26

[Mcgyver]

Do not use drill rod, use precision ground shafting.

Why?

-its cheap
- its hardened, DR isn't
- its round, DR isn't necessarily
- it has a better finish than drill rod
- and the top reason for using PGS, its tolerances are are zero over, drill rod is +-. DR often won't fit! Pressing an oilite into a reamed hole of perfect size produces a bearing ID that can't handle a half a thou over sized dia.

imo it would be very difficult to even agree on the objectives let alone a design. Think of how hard it would be to do in a workplace where there are pay cheques and boss to keep things in line. People will not spend their leisure time on something they disagree with. Want to see what can happen? Check out the thread on making a communal pcb mill at the parallax basic stamp site – there, the objective was predefined but what a mess!

As was posted, the idea of building a culture of open source designs is the best idea. Having a variety of designs will help people create what’s right for them and inspire many. Kudos’ to peeps like Phil and Alan and others for contributing to it – that sort of action will have the greatest effect imo. My view is that the culture should encourage people to share their designs and frown on amateurs trying to sell their designs. Me? I don’t have a design to share yet so try to contribute by answering machining Q’s

OOPS, bottom half of this was intended for open design thread

[mikeschn]

Originally Posted by Mcgyver Do not use drill rod, use precision ground shafting.

I agree

Originally Posted by Mcgyver As was posted, the idea of building a culture of open source designs is the best idea. Having a variety of designs will help people create what’s right for them and inspire many.

In a way I think that's what we are trying to do. If I can find any two people who agree on a type of cnc machine, then we'll draw it up, and let folks here work out the problems in the design. The end result hopefully is a set of plans, and even more hopefully, a machine that has been built to validate those plans.

Mike...

[pminmo]

I believe either drill rod or gas pipe is acceptable for a machine as you have titled. ENCO www.use-enco.com has drill rod consistently on sale along with acme rod and nuts. Just make sure you size appropriately. Many machines have tried to use 3/4" DR for an X axis to support a moving gantry (my 1st attempt also) and 1/2" for Y and it just isn't enough. 1" drill rod is $14 there, 1.25" is $17. 7/8" is $12 and 3/4" for $8. The one thing about drill rod is it's easy to upgrade the machine to precision shafting of the same diameter it a person wants more precision. Same can be said for 1" gas pipe using roller bearings. my 2 cents

[mikeschn]

Originally Posted by pminmo Just make sure you size appropriately. Many machines have tried to use 3/4" DR for an X axis to support a moving gantry (my 1st attempt also) and 1/2" for Y and it just isn't enough. 1" drill rod is $14 there, 1.25" is $17. 7/8" is $12 and 3/4" for $8.

So what size did you use on your x axis, and how long was the PGS (precision ground shafting)?

How about your Y axis? what size and how long?

And what kind of bushings did you use?

Thanks,

Mike...

[eqreservoir]

Do not use drill rod, use precision ground shafting. Why? -its cheap??????????

I guess cheap as relative to what. I looked at mcmaster carr and the prices didn't seem that good as compared to drill rod. Maybe I was looking at the wrong stuff. Do you have recommended sources?

Herman

[Mcgyver]

i think last time i bought it was $0.45 cdn per inch for the higher class .500" (there are two classes available), cut to lengh. i didn't mean to imply that it was cheaper than drill rod, only that as the right choice for the task at hand, it was not a lot of money. got mine from canadian belting, but any industrial supplier would do.

its not so much that its more precise (although it is) its more that the tolerance is only - whereas dr is +-