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  #1  
Old Wed 10 March 2021, 07:49
Diplocaulus
Just call me: Gary
 
Kearney
United States of America
BallScrew Z Axis Upgrade Questions about existing stepper, specs for ballscrew

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.
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  #2  
Old Thu 11 March 2021, 03:52
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
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.
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  #3  
Old Thu 11 March 2021, 12:09
Diplocaulus
Just call me: Gary
 
Kearney
United States of America
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.
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  #4  
Old Sat 13 March 2021, 03:37
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
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.
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  #5  
Old Sat 13 March 2021, 08:06
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
added some pictures from my z axis
Attached Images
File Type: jpg fot 2.jpg (48.4 KB, 106 views)
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  #6  
Old Sat 13 March 2021, 08:10
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
second attemp for the pictures
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  #7  
Old Sat 13 March 2021, 08:12
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
and the thirth attemp
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  #8  
Old Sat 13 March 2021, 08:29
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
fift attemp
Attached Images
File Type: jpg 21.jpg (33.8 KB, 106 views)
File Type: jpg fot 8.jpg (51.1 KB, 104 views)
File Type: jpg foto 25.jpg (35.9 KB, 106 views)
File Type: jpg foto 26.jpg (40.6 KB, 108 views)
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  #9  
Old Sat 13 March 2021, 08:31
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
side view of z axis
Attached Images
File Type: jpg fot 8.jpg (51.1 KB, 106 views)
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  #10  
Old Wed 26 May 2021, 10:17
Diplocaulus
Just call me: Gary
 
Kearney
United States of America
Hey Rik, what size motor are you using on the z axis? I got a nice linear rail kit with a ballscrew and I'm probably going to take your advice and go with belts for power transfer.
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  #11  
Old Wed 26 May 2021, 11:27
Diplocaulus
Just call me: Gary
 
Kearney
United States of America
Sorry, Lead screw, not ballscrew.
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  #12  
Old Mon 31 May 2021, 02:23
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
Motor z axis

Hallo Gary,
I use the same motors on all axis. I looked for a motor with same specifications as oriental motor pk299. Then i found ted motor dst86em83a, and bought 5 of those (one spare, or future 4th rotating axis)
They are connected to a 35 volt powersupply. This can be a higher voltage but my motor temperature does not raise above 40-45 dengrees celcius
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  #13  
Old Tue 01 June 2021, 12:45
Diplocaulus
Just call me: Gary
 
Kearney
United States of America
Hey Rik#92, on mine, the lead screw is 1/2" 10TPI, I think 2 starts. What is the screw you're using in your setup? It looks from your pictures like the gear is mounted on a 1/4" shaft, is that heavy duty enough for a standard 2.2kw spindle? That is the setup I currently have, I am having trouble figuring out if that screw is strong enough.
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  #14  
Old Sat 05 June 2021, 07:18
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
upload some pictures of the z axis
Attached Images
File Type: jpg foto 108.jpg (37.0 KB, 60 views)
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  #15  
Old Sat 05 June 2021, 07:27
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
atach pictues

some other pictures of the z axis
Attached Images
File Type: jpg foto 107.jpg (45.3 KB, 60 views)
File Type: jpg foto 105.jpg (44.9 KB, 59 views)
File Type: jpg foto 104.jpg (31.4 KB, 60 views)
File Type: jpg foto 102.jpg (45.4 KB, 59 views)
File Type: jpg foto 101.jpg (73.1 KB, 59 views)
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  #16  
Old Sat 05 June 2021, 07:49
rischoof
Just call me: Rik #92
 
Goirle
Netherlands
after the pictures the story

Did some measurements on the leadscrew. The leadscrew has an diameter of 16 mm, on top is the toothed gearwheel mounted for the tooth belt. the diameter at this point is 8 mm. the toothed gear on the leadscrew has the same amount of tooths as the one which is mounted on the stepper motor for the z axis.
the leadscrew is attached at it's ends to the back plate, and the lead nut is attached to the front plate.
the lead nut holder needed some washers and shims to achieve the correct height. To check if you have the height correct, assemble the z axis and move the lead nut up and down by turning the leadscrew by hand. this should be working very smooth, and you should not feel resistance when it is reaching the lowest and highest position
The aluminum front and back plate have a thickness of 12 mm
The aluminum bars which are holding the linear guiding's are 25x50 mm.
it is important that the spindle is not moving down when you power off the machine and the stepper motors don't have holding torq. The weight of the spindle and z axis can causing this. If his is happening a balance spring can be mounted, or you can change the ratio of toots to 1 to 2 or 3 of the toothpulleys on top of the leadscrew and the z axis stepper motor
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  #17  
Old Thu 10 June 2021, 20:00
pblackburn
Just call me: Pete #98
 
South-Central Pennsylvania
United States of America
With the conversion I did, it is a direct drive to the ball screw. The big thing with a ball screw is the weight should be neutral for longevity. I am driving it with a PK296-F4.5A. I increased the Z retract height to well above the bottom of the gantry.
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  #18  
Old Sun 05 September 2021, 07:48
silverdog
Just call me: Sergio #70
 
Rome
Italy
Quote:
Originally Posted by rischoof View Post
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.
I did not think about the point of gravity building mine

The motor is a closed-Loop Stepper motor 142MM 9n.m 1280 oz.in 6A, the ball screw is a 2010 (10mm/turn)
Tests already made with a 20meter/min speed and 4000mm/s2 accelerations are ok :-)
Attached Images
File Type: jpg Zaxis.jpg (101.9 KB, 18 views)
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