[freecncplans]

I am kind of confused why you are persistent not using rack and pinions and must use ballscrews? I don't like it when people come in and just use blanket statements like these and assume that something is not worth using when they have no clue.
Sean

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if module of gear is1.25, rate of reduce 1:2, pulse equivalency is 0.0216mm/step. but we use ball screw, it's 0.0025mm/step. surface is quite different. we had compared two kind of results. if only one result engraving sample, you can't recognize it. On other hand, gear has gap when direction is oppisite, the gap will cause result worse. we had made test by engraving stone, wood, soft and hard wood. more pulse equivalency is small, result is fine.

[ivojnob]

I am kind of confused why you are persistent not using rack and pinions and must use ballscrews? I don't like it when people come in and just use blanket statements like these and assume that something is not worth using when they have no clue.
Sean

I agree with Sean. Sure ballscrews are good, but that's not what I'm using. I said in my second post that I have my R&P parts. That part isn't up for discussion. I'm looking for help building the best machine I can with the parts I have. 5 years ago I thought about using all thread and doing it cheap. I'm glad I convinced myself not to bother, and I'm pretty sure I can make a good machine with R&P drives. (wrong) Lots of other people have!

[DHSYCNC]

I am kind of confused why you are persistent not using rack and pinions and must use ballscrews? I don't like it when people come in and just use blanket statements like these and assume that something is not worth using when they have no clue.
Sean

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when building small size machine, ball screw is good because ball screw is short and machine bed is not bend. But when building big size machine,like more than 2800mm of lengh. machine will be bend. So we will choose rack and pinion. As we know, rack and pinion has gap and accuracy is lower than ball screw.
To keep high accuracy, we must choose ball screw. To keep high speed in big machine, we must choose rack and pinion. On the hand, if using stepper motor, it max speed is 800RPM, can we choose it to build big machine with ball screw and speed is up to 20mm/min? if don't know pulse equivalency, how to choose drive and reducer? it's clue.

[louieatienza]

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when building small size machine, ball screw is good because ball screw is short and machine bed is not bend. But when building big size machine,like more than 2800mm of lengh. machine will be bend. So we will choose rack and pinion. As we know, rack and pinion has gap and accuracy is lower than ball screw.
To keep high accuracy, we must choose ball screw. To keep high speed in big machine, we must choose rack and pinion. On the hand, if using stepper motor, it max speed is 800RPM, can we choose it to build big machine with ball screw and speed is up to 20mm/min? if don't know pulse equivalency, how to choose drive and reducer? it's clue.

If you're really concerned about backlash in a high-speed r&p, why not a helicak rack and pinion, with either a split-or dual-pinion (to eliminate backlash)?

[DHSYCNC]

If you're really concerned about backlash in a high-speed r&p, why not a helicak rack and pinion, with either a split-or dual-pinion (to eliminate backlash)?

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thanks a lot. we're going to choose helicak rack and pinion.

[DHSYCNC]

If you're really concerned about backlash in a high-speed r&p, why not a helicak rack and pinion, with either a split-or dual-pinion (to eliminate backlash)?

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we want to choose control system to compensate it. It's simple and easy. If not get good result, we have to choose above rack.

[ivojnob]

Torsion box started...

[ivojnob]

Finally got around to picking up some 5' x 12' sheets of 3/4" MDF (they were out of 5' x 10'). Cut all of the internal and external strips for the torsion box and dry fit the internal framework. I chose to do half lap joints on the parts as shown in one of my first posts. The fit up is very good. Next on the list is getting the bottom torsion box skin set up nice and level so that I can start the final assembly of the box.

[louieatienza]

Finally got around to picking up some 5' x 12' sheets of 3/4" MDF (they were out of 5' x 10'). Cut all of the internal and external strips for the torsion box and dry fit the internal framework. I chose to do half lap joints on the parts as shown in one of my first posts. The fit up is very good. Next on the list is getting the bottom torsion box skin set up nice and level so that I can start the final assembly of the box.

That's looking great! The 5x 12 sheets must've weighed a ton!

BTW I take you're a bon jovi fan? (I'm a big Jumble player...)