BallScrew Z Axis Upgrade Questions about existing stepper, specs for ballscrew

[Diplocaulus]

Hi All, I have a couple inquiries about upgrading a Z Axis to a ball screw unit. VXB has recently started selling axis kits (https://www.vxb.com/Linear-Motion-Modules-s/2140.htm), which are attractive at the prices and U.S. shipping/warranty. They don't have many answers about them, so I was hoping to run a couple things by the forum. The current Z Axis on our machine was modified for increased Z height. I'd say it was done a little quick and dirty, the spider has a 2mm misalignment in the lowest set of rollers that I haven't been able too get out, and the frame for the z axis height increase that was added isn't super sturdy. We also have to run the z axis at a fairly slow speed so it doesn't skip steps, which is probably from further misalignment in the modification. We cut foam and coat over it so it's not a huge deal but I was thinking a ballscrew unit would fix all of those problems. I was planning on building a square tube mounting point for the ball screw kit to increase rigidity, but wanted to know if the stepper motor I currently have on the z axis would be suitable for the ballscrew. We have PK296A2A-SG7.2 steppers on all axes, and I guess if I could take the one that is mounted currently and just rotate it and mount at the top of the ballscrew, then recalibrate for steps per rotation and tuning, would that be everything I'd need to account for in the modification? The ballscrews come in 5 or 10mm leads, so I'm not sure which would be better for this application, or what diameter ballscrew would be sturdy enough for the standard 2.2kw chinese spindle. If anyone has answers or could guide me to them I would greatly appreciate it.

[jhiggins7]

Hi Gary. I have NO experience with linear slides. I'm posting here just to let you know that we're still around and monitoring the FORUM.

Those VXB linear slides ARE very interesting. Reasonable prices, indeed. The other products we've used from them are good, so I would expect these slides would be good as well. What length stroke are you planning to use? Just off hand, a 5mm lead screw seems small. And, the price increase for a 10mm is trivial. What about clogging with foam cuttings? As for motors, I think you are going to have to investigate. What size is the mount on the linear slide. What are 57/86 Stepper Motors? How do you couple between the stepper motor shaft and the linear slide shaft? The coupler has to have some flexibility.

[Diplocaulus]

John, you're asking a lot of the same questions I have. So far, I think I've figured out that I wanna be leaning towards a NEMA 34 setup for the weight of the spindle and mount, and adaptability to the geckodrive we use. The 5mm and 10mm numbers are the angle of the screw threads, or lead, as it were, so you have to kind of figure out what speed is ideal for your use and your motor. I need 16" of travel to accomodate 6" material and 6" bits. They sell a flexible coupler that allows a tiny bit of play between the shaft and ballscrew, because getting those dead on would be pretty impractical.

[rischoof]

Hello
I have made two z axes with linear bearings and leadscrew
The first one had long travel (40 cm) and had the motor on top.
Problem was that the point of gravity was at a high position and this was causing shaking from the whole unit.
So i made an second one, build from standard components, and kept the gravity point as low as posible. The leadscrew is driven bij a belt, then i didnt need an expensive clutch, and i could mount the stepper motor lower
Use a spindle with a low pitch to avoid sinking of your slide by the weight of the routerspindle. In my builder log (rischoof) are pictures from the old and new one.
i will upload later this day some detailed pictures.
If you have the aluminium plates at the correct size you only need a press drill to drill the holes to make this one.
It,s powered by the same stepper i use for x and y axis,( with belt reductions)
I didn t install an weigt compensation sping (damper) to compensate the weight of the router spindle.

[rischoof]

added some pictures from my z axis

[rischoof]

second attemp for the pictures

[rischoof]

and the thirth attemp

[rischoof]

fift attemp

[rischoof]

side view of z axis