Z Axis Lead screw and stepper Motor

[bob-hepple 59]

Could anyone answer this question before I start stripping the Printer,,

I'm wanting to take the lead screw apart, I looked on GitHub and found the schematic of the UM2 but don't understand how the lead screw is attached to the stepper Motor,, is it one machined piece, which I find it hard to believe, if not it must have a connection...

Thanks in advance for any Help....

[neotko 1,417]

Isn't exactly exactly the same but practically is the same

https://www.youmagine.com/designs/z-screw-cleaning-manual-for-um2-umo

[rowiac 53]

The lead screw is integral with the stepper motor. This eliminates the need for a collar to attach the two parts and avoids any runout that might occur due to dimensional tolerances.

[bob-hepple 59]

MMMMMMMMmmmm worst night mare,, I thought but really hoped this wasn't the case, that means if I want to change the lead screw disassembling the stepper motor, and turning the end of the lead screw down is the option,,,, I take it the stepper motors disassemble OK.

[rowiac 53]

I'm not sure what exactly you are trying to do, but most likely the motor's rotor is pressed onto the lead screw shaft. The bearings are likely pressed on too. You can probably remove all that from the housing pretty easily, but the pressed on parts would be tough to deal with.

[bob-hepple 59]

Thanks for the reply,, I am going to replace the lead screw with a Helix thread, and the nut will be self lubricating.. so before I ordered the Helix thread wanting to make sure what I'm letting myself in fore..

[Waynicus 0]

Thanks for the reply,, I am going to replace the lead screw with a Helix thread, and the nut will be self lubricating.. so before I ordered the Helix thread wanting to make sure what I'm letting myself in fore..

Hi Bob

How did you get on with replacing it? I've got some play with the lead screw and motor.

Thanks

Wayne

[bob-hepple 59]

Wayne

I stopped, I found the lead screw is directly attached to the motor no by a coupling it is machined, I thought the process would be stretching my machining skills, and I had enough of other problems to sort out. I think I still have the PDF of the lead screw if you interested, got it from Git Hub and the step files,,

The helix lead screw is awesom along with the self lubricating nut company Igus

have a look

http://www.igus.co.uk/wpck/9443/productoverview_Trapezgewindemutter?C=GB&L=en

let me know if you want the files.. or and how you get on.

[Waynicus 0]

Thanks for that Bob

It's a job and a half to strip it down from what I can tell. I've packed the lead screw with Magnalube and dialled the printer in a bit more. It's a little better but I think at some point I need to replace the lead screw and brass bush.

[neotko 1,417]

Thanks for that Bob

It's a job and a half to strip it down from what I can tell. I've packed the lead screw with Magnalube and dialled the printer in a bit more. It's a little better but I think at some point I need to replace the lead screw and brass bush.

In my experience a perfect brass nut is hard to find, there are some china nuts with dampening tr8x2

IMO if you have perfect Z square flanged bearings on the bed, the issue disappears immediately. I know @gudo made a dampening nut using two nuts and a spring. So is fairly doable.

https://ultimaker.com/en/community/11123-z-axis-layer-error?page=last#reply-130203

http://www.3dprintingforum.us/viewtopic.php?t=549

[bob-hepple 59]

from what I read igus might not be the best way neotko threads make interesting reading I'm glad I stopped before too late still think the z screw on UM could be better,,

[rowiac 53]

As @neotko states, you can buy cheap anti-backlash nuts at places like ebay for maybe 10USD. If your Z-linear bearings are good you probably don't need one, but it would be simple to make one using two nuts and a spring.

The spring forces the edges of the nuts against one side, eliminating the backlash, rather than using gravity (the weight of the build platform) to accomplish that. This type of nut is often used in DIY CNC machines where backlash can't be tolerated because they operate in both directions rather than just one direction (down) as on our Ultimakers.

[bob-hepple 59]

I Like that idea, I also thought of using Ball screws as on my Mill. a lot of the heavy machines are starting to use ball screws, the Frog Bolt for instance.

[tomnagel 126]

but what use is the anti backlash nut when the z-stage is already pre-tensioned by gravity?

[neotko 1,417]

but what use is the anti backlash nut when the z-stage is already pre-tensioned by gravity?

With some bad beds, gravity isn't enough

https://ultimaker.com/en/community/11123-z-axis-layer-error?page=last#reply-129326

[tomnagel 126]

That is a thing of the past, bad bearings in the UM2go. So if you want to replace things, first consider your bearings. Remove the connection with the nut, and feel if there is friction somewhere along the whole height of the z-shafts. If there are no "heavy points", then an anti back-lash nut does not add value. If there are "heavy points" then change the bearings.

[neotko 1,417]

That is a thing of the past, bad bearings in the UM2go. So if you want to replace things, first consider your bearings. Remove the connection with the nut, and feel if there is friction somewhere along the whole height of the z-shafts. If there are no "heavy points", then an anti back-lash nut does not add value. If there are "heavy points" then change the bearings.

Well, the user has a machine from the past. Also, indeed like I said is always better to have really good flanged bearings, something that until recently was of a very 'so-so' quality. But removing play from the nut can't be bad, or can it? You tell us.

[tomnagel 126]

You tell us.

I just did. It is bad. It costs time and money, and delivers no value. None whatsoever.

[neotko 1,417]

You tell us.

I just did. It is bad. It costs time and money, and delivers no value. None whatsoever.

Wow. That's a good explanation. Thanks!...