The New Machine

[Robin Hewitt]

Using a ratio of 2.5 to 1 ( 10 and 25 tooth pulleys) will give me a step resolution of 0.001mm per step.

Hi Rick

AH! Confidence truly is that feeling you get just before you understand the problem :heehee:

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend. You can compensate for backlash, but you will forever expect the tool to dig in.

Ball nuts bed in, they may feel firm but you are probably pushing against the dust seals and kidding yourself. The seals can't hold it when the tool loading kicks in.

If you bolt the column to a brick wall I would suggest a 5 micron step, 200 steps/mm is optimal for accuracy and speed. Half step is good, quarter step is vaguely credible, beyond that everything gets too springy.

Getting high accuracy is more a problem of rigidity than anything else. You can't mill to 5 microns because the tool will bend, you can't skim 10 microns, it will simply ignore you. To get 5 microns your tooling needs to cut a mirror finish. IMHO 5 microns or better has to be ground.

Good luck :naughty:

Robin

[Ricardoco]

Hi Rick

AH! Confidence truly is that feeling you get just before you understand the problem :heehee:

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend. You can compensate for backlash, but you will forever expect the tool to dig in.

Ball nuts bed in, they may feel firm but you are probably pushing against the dust seals and kidding yourself. The seals can't hold it when the tool loading kicks in.

If you bolt the column to a brick wall I would suggest a 5 micron step, 200 steps/mm is optimal for accuracy and speed. Half step is good, quarter step is vaguely credible, beyond that everything gets too springy.

Getting high accuracy is more a problem of rigidity than anything else. You can't mill to 5 microns because the tool will bend, you can't skim 10 microns, it will simply ignore you. To get 5 microns your tooling needs to cut a mirror finish. IMHO 5 microns or better has to be ground.

Good luck :naughty:

Robin

Well as I said if I aim high and do the best i can with what i have its an education and im not sure it will hurt will it. I do wish in my original post i had used the work theoretical...

[Rogue]

.001mm is one micron. Standard ball nuts give you 50 microns, shimmed gives you 20, the only way to get 1 is to use double nuts and spring them. Helps if you can hold the screws in tension with more springs. The Belleville washer is your friend.

By double nuts do you mean the "double ballnut" that somewhere like Zapp sells, or do you mean using two seperate nuts and combining them with the spring?

I've seen the latter in different places around the internet, but I didn't know if the former was simply a commercial version of the latter.

[Lee Roberts]

Sorry for the delay and welcome fragger!

[fragger6662000]

No worries

Sorry for the delay and welcome fragger!

[John S]

Late into this post but converted 4 of these machines now based on the Warco WM16.
1605 ballscrews all round, 3.1Nm motors all round, direct drive on X and Y 2:1 belt reduction on Z
42 volts power supply and 542 drivers. If I had to do any more I'd increase the voltage to 70v and use the 80v 7 amp drivers de-rated to suit the motors.

[cooliced]

Im very interested in this machines capability.

I currently run a CNC converted Sherline Mill and im now realising i need something bigger and better.

Keep us interested in this project please

Stu

[fragger6662000]

If you are thinking of under slinging the motors on x you will loose lots of travel.

Hope you have fun doing the machine as it is certainly a rewarding thing to do. especially when it works!

[Ricardoco]

If you are thinking of under slinging the motors on x you will loose lots of travel.!

it will be in front i suspect, just a tad lower than the bed. although it would have been nice if i could have put it underneath without the loss of travel.

Hope you have fun doing the machine as it is certainly a rewarding thing to do.!

Likewise :tup:

especially when it works!

Well here's hoping. Needless to say i will only post what works...:rofl:

[Ricardoco]

Well here is an idea, im sure there will be people with experience of this sort of thing.



just a basic concept and yes There are covers missing for clarity...

This type of thing is what i was looking into and it all misses the y axis as well so no loss of x or y. excuse the drawing its my first google sketchup