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Help picking lead screws for a CoreXY design

Posted by badrobit 
Help picking lead screws for a CoreXY design
July 14, 2017 07:50AM
Hi All,

Long time lurker and after lurking here for a long time I have started designing my own CoreXY printer. I am currently working on the bed design and I have decided that I want a system that uses 3 lead screws two on the front two corners of the print bed and one in the center of the back. Each of these will be individually driven so that I can do bed leveling automatically. (I know this is frivolous but it's something I want).

I am currently trying to work out lead screws and nuts and I have been looking at igus. Currently, I am looking at their 10x2 right handed aluminum threaded rod with this nut.

Not being a mechanical engineer (I am a software eng) I was looking to get feedback on this combination.

Re: Help picking lead screws for a CoreXY design
July 14, 2017 05:45PM
Perhaps a read of the Core XY section?
The statements against independent driven screws on Z axis?

Aluminum leadscrew? Only going to use it a little while huh?

Perhaps a find on eBay instead of a retail leadscrew?

confused smiley
Re: Help picking lead screws for a CoreXY design
July 14, 2017 11:05PM
You want to use aluminum because of the lower inertia?
I'm driving three robotdigg 1204 ballscrews with one NEMA17 and acceleration and speed is excelent.
Although their pitch is 4mm, I believe the much lower friction improves accuracy.

If you want direct drive, make sure you pick the right couplers. The Prusa style couplers are compressible in z-direction.

Edited 1 time(s). Last edit at 07/14/2017 11:07PM by o_lampe.
Re: Help picking lead screws for a CoreXY design
July 15, 2017 03:52AM
The screw and nut combo will work together as long as they both have the same threads...


The lead of that screw is 0.08 m. That's 80 mm/rev. That's a very steep screw, intended for high speed movement (probably why it's made of aluminum). It isn't going to provide much leverage so your motor is going to be working very hard to lift the bed. We typically want much lower lead in the Z axis so that we can get higher resolution in Z and to make life easier for the motor. A more typical lead in Z is 2 (or 4) mm/rev which provides 40x (20x) resolution and 1/40th (1/20th) the load as your screw.

With 80 mm/rev, 200 steps/rev and 16:1 ustepping, the bed is going to move 25 um/ustep (except you can't be sure it will move with 1 ustep input). In general, you want a whole step resolution to be a fraction of your print layer thickness.

Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
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