probably a stupid question

[mad.sculpture]

Hi folks,
if i go shopping on ebay for complete linear slides to try to make a mill with the least machining and individual parts sourcing how much of an issue is it if the units gearing is not the same ?
You see what would make a complete axis so simply but the chances of you getting an idential ballscrew/complete slide any time soon are minimal.
I've read several cnc on a budget articles and if your building an ideal machine you'd make steps/distance on each axis identical, however other than this factor some of the ebay surplus looks very tempting.
How much of the software you guys use allows different travel/pulse on each axis ?

Didn't know what forum, probable software cure to hardware problem.

I want to end up 4 Axis milling organic sculptures so i don't realy need super
accuracy but it would be nice ...and if i had to i could stretch the model by certain percentages to compensate, but thats such a sloppy solution

Cheers

[Al_The_Man]

Originally Posted by mad.sculpture I've read several cnc on a budget articles and if your building an ideal machine you'd make steps/distance on each axis identical, however other than this factor some of the ebay surplus looks very tempting.

If the software allows individual scaling of the axis, then it should not matter as long as you achieve the resolution you are looking for.
Practically all software will allow individual ratio/scaling.
It is done all the time in the CNC Machine world.
One thing I would look out for in linear ballscrew slides, is to go with the smaller lead screws as opposed to hi-lead that are in the order of .5"/turn and above.
Al.

[mad.sculpture]

thancks for reply,is that just because they'd need much beefier motors and not so applicable if slide already has one mounted?
Is there a too fine pitch at the other end of scale,like impractically slow,there were some realy cheep assemblys the other day but not ball scew and pitch looked a bit fine,not fragile,just lots of tpi. they'd been in a power recline medical chair.
if i built something big it (i'm in 2 minds at moment) may only need to cut foam,although wood or plastic might be handy also

ross

[mad.sculpture]

p.s if a screw has the 0.5 pitch / turn but has an indirect mount that lets the motor drive through a toothed belt (pulley wheel on leadscrew next to nema mount) you could gear it 2:1 does this make it ok?

[Al_The_Man]

That tends to bring it back to a practical resolution.
Direct, the high lead ball screws require lower inertia motors for high accel. rates etc.
Al.