The New Machine

[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

[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.

[Jonathan]

I'm pretty sure Robin will mean two nuts sprung, hence the Belleville washers. I think the commercial versions are just shimmed. To eliminate backlash you need them to be pushed apart using a spring applying a force greater than any cutting force plus acceleration, F=ma, you anticipate.

[Rogue]

[whisper]I think someone on this forum is considering it / has done it...[/whisper]

I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

[Robin Hewitt]

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?

Either, if you use a double take the shim out

[i2i]

on another note what do you think of the idea of a counter balance on the Z...
Rick

Denford used to do this on the early triacs, they stopped it quite quickly.

[Ricardoco]

I'm playing with the idea, primarily because I think it looks good, effectiveness be damned! :twisted:

On a related note, I also asked similar questions about the under-table mounting, the consensus seemed to be that it wasn't a problem. The following thread might have useful things for you: http://www.mycncuk.com/forums/showth...or-under-table

I will be using the Double ballnut if needed when i fit the ground Ballscrew but for now with the rolled i will use just the 1 with the ability to encorperate a double in the design..

LOL well here is the Vcarve output for the endplate for the Z with a side mounted stepper, or if prefered it can be hung on the end infact ive desinged it so you could hang it on the left rignt or even underneath,Ive not included the tensioning system yet as im still working on it. I still think it looks bodged on the end but that is just my opinion lol




I will make the prototypes out of a non metalic material i suspect...

Oh and ive made it incorperate the ballscrew Double A/C bearing housing as well.