PDA

View Full Version : Running 4 1605 screws



kev20009
22-02-2017, 09:28 AM
Hi guys not sure if anyone as seen this done, I build a z table for a laser cutter, and tried 4 1605 screws with closed loop belt driven by nema24, put all ball nuts to bottom or top rises smooth go back down, but when it comes back up all screws are out 1 will be top but all others out with bigger gaps than others,

There plenty of these table working, so not sure what screws are used, I now these were overkill but I had 2 so just perchased 2 to match lenth,

Thanks guys for any help. Kev

magicniner
22-02-2017, 10:49 AM
Repeat the up/down cycle several times to see if the error increases with each cycle, if it does you have a mechanical problem.
If you mark the screws at the front top with a marker pen and run up and down several times do the marks all come to the front again at the same time?

Clive S
22-02-2017, 11:27 AM
Check to see if any of the pulleys are slipping on the screws

Boyan Silyavski
22-02-2017, 12:09 PM
Or it could be the stepper/ servo drive is not connected properly to board. STEP signal could be Rising edge or ??? Lowering edge / what was the exact name?/ edge, which if not right, each movement you will loose 1 step. Which if running large toolpaths you could not even see it, but run short multiple tool paths and all goes out of place. BUt as others said make sure its not the pulley slipping

Clive S
22-02-2017, 01:11 PM
Or it could be the stepper/ servo drive is not connected properly to board. STEP signal could be Rising edge or ??? Lowering edge / what was the exact name?/ edge, which if not right, each movement you will loose 1 step. Which if running large toolpaths you could not even see it, but run short multiple tool paths and all goes out of place. BUt as others said make sure its not the pulley slipping

The way I read it, is that he is using 1 stepper with a belt connecting 4 screws and the screws are going out of sync.

I think he is using the 4 screws to just lower or higher his bed. (one at each corner)

If that is the case the rising edge thing is nothing to do with it.

Boyan Silyavski
22-02-2017, 01:46 PM
The way I read it, is that he is using 1 stepper with a belt connecting 4 screws and the screws are going out of sync.

I think he is using the 4 screws to just lower or higher his bed. (one at each corner)

If that is the case the rising edge thing is nothing to do with it.

ok. you are right. i misread what he said. then very simple,all screws are not perfectly square maybe? each screw lowers a bit differently, assuming he has all connected with one belt.


Kev, why dont you show us what exactly you are dong?

kev20009
22-02-2017, 05:33 PM
hi sorry for late reply photos to show,

there is 4 rods and nuts, table taken off to try too get it to work, photo shows rods and belt, and the 2 that im trying is out of sink,

thank you guys for trying to help kev

Clive S
22-02-2017, 05:43 PM
When you set this up did you start with all the nuts at the top before you put the belt on? or loosen the grub screw on the pulley and then turn the screw to the correct position and then retighen

kev20009
22-02-2017, 05:47 PM
Repeat the up/down cycle several times to see if the error increases with each cycle, if it does you have a mechanical problem.
If you mark the screws at the front top with a marker pen and run up and down several times do the marks all come to the front again at the same time?

hi thanks for reply, done the up down several times but gets worse, it doubles the gap on the left rod, put red mark at front of rod and one was just off and the other by a bit so marks never came back, thanks again kev

kev20009
22-02-2017, 05:49 PM
When you set this up did you start with all the nuts at the top before you put the belt on? or loosen the grub screw on the pulley and then turn the screw to the correct position and then retighen

hi clive yes done it where I could turn the belts and pulleys before tighten grub screws, put nuts top bottom and middle with a gauge block,

Clive S
22-02-2017, 06:04 PM
hi thanks for reply, done the up down several times but gets worse, it doubles the gap on the left rod, put red mark at front of rod and one was just off and the other by a bit so marks never came back, thanks again kev

If the pulleys are tight and not slipping are you sure you have the same pitch on the all the screws?

Boyan Silyavski
22-02-2017, 06:18 PM
These are things i do with Locktite, and i mean not the instant glue from grocery shop

kev20009
22-02-2017, 06:33 PM
guys not sure if this is a stupid thing to think, but looking at all the nuts none off the plastic ball carrier matches each other, some are at bottom some are 6to7mm up, so could this effect what im trying, thanks again kev

kev20009
22-02-2017, 09:33 PM
If the pulleys are tight and not slipping are you sure you have the same pitch on the all the screws?

hi glive just checked and pitch 5 mm on all using calipers, yes checked pulleys, only thing I can think is when I put 2 side by side with the start fron,t thread is high to other match line of thread and the start is quarter way round, I have tried every position but still none match when travel stops, thanks again kev