Time to go from Delrin Nut to Ball Screw?

[justCNCit]

Hello,

My machine has been operating pretty good for a while but the lead screws may not always be perfectly aligned. Not sure how much this contributes to wear, using Dumpster CNC's 1/2-10 5 start thread. The nuts seem to be wearing out about every 6 months. The machine gets decent use, like 10-20 hours a week probably. At this time the deflection on the oldest replaced ACME nut is .005" side to side, for a total error of 0.010" which is unacceptable in the work that I do. The other one which was replaced probably 4 months ago is at +/-0.002 about.

Does anyone know if these nuts are wearing out prematurely, I can't easily tell, but it does seem logical. If so I should probably spend the $$$ on ball screw and nut combination from McMaster? This is available in 5 start from what I can tell.

What kind of options may be available for other drive system? Since the screws will have a tendency to whip no matter what.



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[ger21]

Plastic Nuts like the Dumpster CNC nuts are really only good for up to about 25lbs of force. At higher loads, they will have backlash, whether they are worn out or not?

Are you using a lubricant on them? If you oil them, then they shouldn't be wearing out that fast.

I certainly wouldn't be buying ballscrews from McMaster-Carr. You can get Chinese ballscrews for about 1/5 the price, if not less.

https://www.ebay.com/itm/brand-new-S...kAAOSwv0tU9So4

Rack and pinion might be a better choice, but would probably require a lot of mods to your machine.

[diycncmill]

The best option for long ball screws are driven nuts.
Unfortunately this requires some reconstruction - but this would be the right way to do it.
This is how they work:

[justCNCit]

I blew all the MDF out of the nut (had a very messy job last night) and restored it to 100% with next to no backlash like the other.

I have lithium grease wonder if that is the correct lube for these? The whole thing didn't make sense as it did seem to go from 100% to completely worn out in one day. Also my lead screws are positioned very badly in the design of the machine to be covered with dust all the time.

[ger21]

I use a light oil.

The dust is probably not helping.

[triumphstephen]

Just typed a whole thing but then lost it. If you get this twice, my apology.
Set up a couple of 1/4" tubes on either side of the nut, attached to the nut and run a small amount of air through them to blow the dust off the screw before the nut gets to it. Uses very little air, a Chinese laser air compressor would probably be enough. Use dry lube on them (silicon spray) so the dust doesn't stick to the screw. Lube a little more often than you would using oil.