Hardwood CNC from wood on a budget, Possible?

[Christian Knuell]

Hi,

I've seen a few build in MDF and thought could I build in maybe ply (I'm not a fan of MDF) or would it really need to be welded steel for hard wood like maple and ash?

Plywood is even worse than MDF because MDF at least does not warp and bend too much just because of temperature or humidity changes.
Steel is not necessary for hard wood but I'd at least use aluminum extrusion.

Christian

[EddyCurrent]

Plywood is even worse than MDF because MDF at least does not warp and bend too much just because of temperature or humidity changes.

I'm not sure I agree with you regarding plywood being worse, good birch plywood I mean, but I do know that among other things moisture makes MDF swell. Also if there's that much moisture in the air then the hardwood being cut will also be useless, especially for guitars.

Steel is not necessary for hard wood . . .

but it's a lot cheaper than aluminium and ideal for the base.

[JAZZCNC]

Plywood is even worse than MDF because MDF at least does not warp and bend too much just because of temperature or humidity changes.

No sorry can't agree on this. Unsealed MDF changes shape if you so much as show it a cup of coffee let alone any decent amount of moisture. Ply wood will take much more moisture before swelling.

BUT to IMO both have only two places in CNC.? . . .Spoil board or to keep the workshop warm.!!

Steel is cheap and easier to work than people realise. Profile is fine but to get the best from it you need all the connection elements, T-nuts etc, and this makes it much more expensive. It's also harder to work than people realise, it's awkward drill/Tap and unless slots used then it can be difficult for mounting things too it with out adaptor plates.

Combination of steel and Profile works well IME, gives a good balance of strength and ease of build without getting silly expensive.

[Neale]

Let me add my twopennorth as someone who has built and used an MDF CNC router, essentially to the JGRO design. There aren't many people prepared to admit that...
I have a cutting area of about 800x400, from memory. It uses skate bearings on steel tubes and threaded rod. On the plus side - it works. On the down side - only just. It's difficult to get a flat bed, to adjust the bearings and keep them adjusted, and generally to maintain any kind of consistent accuracy. There are better MDF designs but I doubt that they will entirely remove all these problems. As Jazz has said, show this stuff a cup of coffee and it distorts. Take the coffee away, and it will sulk and distort again, but probably not back to where it was. Warm/cold/damp/dry - any change in weather and you will be re-tweaking. All that, actually, might be bearable except that you have to keep cutting speeds so low to avoid major structural distortion - or failure - that big jobs can take hours rather than minutes. OK, I use threaded rod as leadscrew material which limits X axis speed to about 800mm/min, but frankly the thing couldn't take much more anyway.

As far as accuracy is concerned, I cut a series of interlocking 9mm ply panels for an architecture project and had reasonable repeatability, although not absolute accuracy - that is, I cut some samples, tweaked the dimensions slightly, and then cut a series of pieces that fitted reasonably well. It works pretty well for engraving, as long as you can level the work.

I'm halfway through a build of a steel framed machine using profile rails and ballscrews. Is there a message in that?