Lead screw question

TLeTourneau · 10 Feb 2020, 18:13

I have a CoreXY printer with a 500x500x9.5mm cast aluminum build plate and I am switching from dual Z axis to triple Z axis. I currently have dual T8x2 single start lead screws, I am wondering if this is an opportune time to switch to T10x2 or T12x2 lead screws (I haven't found any that are 16 or 20mm) seeing that I need to order a new lead screw anyway. The lead screws are suspended from the top of the frame with pillow blocks with the motors at the bottom.

When going with a triple Z configuration are linear guides still recommended? I have seen images each way and I'm not sure how to proceed with that.

Danal · 10 Feb 2020, 18:20

@TLeTourneau said in Lead screw question:

When going with a triple Z configuration are linear guides still recommended?

Yes.

Regarding pitch & starts: Have you calculated steps/MM for your motors and each of your proposed screws to ensure that your typical layer heights are a multiple of your preferred microsteps (almost always 16)?

TLeTourneau · 10 Feb 2020, 18:40

@Danal said in Lead screw question:

@TLeTourneau said in Lead screw question:

When going with a triple Z configuration are linear guides still recommended?

Yes.

Regarding pitch & starts: Have you calculated steps/MM for your motors and each of your proposed screws to ensure that your typical layer heights are a multiple of your preferred microsteps (almost always 16)?

For the linear guides, would you recommend increasing the diameter of those as well? I currently have 12mm linear rods with LM12UU Extra Long Round Flange Linear Ball Bearings, 12mm Bore Dia, 21mm OD, 57mm length.

Yes, both the T10 and T 12 are single start 2mm per revolution which will work for either a 0.1 and 0.2mm layer height.

Danal · 10 Feb 2020, 19:07

@TLeTourneau said in Lead screw question:

For the linear guides, would you recommend increasing the diameter of those as well? I currently have 12mm linear rods with LM12UU Extra Long Round Flange Linear Ball Bearings, 12mm Bore Dia, 21mm OD, 57mm length.

Just "gut feel", those sound fine to me.

On the leadscrews, there's probably no strong reason to pick one v another.

TLeTourneau · 10 Feb 2020, 19:13

@Danal said in Lead screw question:

@TLeTourneau said in Lead screw question:

For the linear guides, would you recommend increasing the diameter of those as well? I currently have 12mm linear rods with LM12UU Extra Long Round Flange Linear Ball Bearings, 12mm Bore Dia, 21mm OD, 57mm length.

Just "gut feel", those sound fine to me.

On the leadscrews, there's probably no strong reason to pick one v another.

But you think going to 12mm or 10mm over 8mm is worth doing? I just want to make sure I understand the recommendation. Thanks for the replies!

Danal · 10 Feb 2020, 19:17

Yes, that matches all the other things you are doing a little better than 8. Not absolutely 'required'; still a good idea.

Phaedrux · 10 Feb 2020, 19:17

@TLeTourneau said in Lead screw question:

500x500x9.5mm cast aluminum build plate

Well that is a very large and heavy bed, so I would say the thicker the guides and lead screws the better. Depends what your budget is.

Also for the lead screws bare in mind that the larger the screw, the more rotational inertia, so your acceleration will likely need to go down to keep from either skipping steps at the start of a Z move, or over rotating at the end of a long z move.

TLeTourneau · 10 Feb 2020, 20:33

@Phaedrux said in Lead screw question:

@TLeTourneau said in Lead screw question:

500x500x9.5mm cast aluminum build plate

Well that is a very large and heavy bed, so I would say the thicker the guides and lead screws the better. Depends what your budget is.

Also for the lead screws bare in mind that the larger the screw, the more rotational inertia, so your acceleration will likely need to go down to keep from either skipping steps at the start of a Z move, or over rotating at the end of a long z move.

Well I don't want to say money is no object, if that were the case I probably wouldn't be modding a TronXY but I have some discretion. I think I'll try these, any input on the parts selection?

The motors are either going to be:
Nema 17 Bipolar Stepper Motor Kit 92oz.in 2.1a 4-lead 60mm
https://www.amazon.com/dp/B00QGBUO1C/?coliid=I1FI9NK78500QA&colid=1EJS5C5NLQWI&psc=1&ref_=lv_ov_lig_dp_it

or

MOTECH MT-1705HS200A 114oz.in 2.0a
https://www.filastruder.com/collections/electronics/products/super-whopper-motor

I think I'll switch to the T12x2 single start lead screws with pillow blocks:
https://www.amazon.com/uxcell-KFL001-Aligning-Pillow-Bearing/dp/B073KT9BY5/ref=sr_1_7?keywords=Flange+Pillow+Block+Bearing+12mm&qid=1581366593&s=industrial&sr=1-7

And keep the 12mm linear rods and use these guides to hold them in place.
https://www.amazon.com/Sydien-Linear-Support-Motion-Bearing/dp/B07DPCZSLH/ref=sr_1_25?keywords=smooth+rod+support&qid=1581366345&s=industrial&sr=1-25

Phaedrux · 10 Feb 2020, 20:42

Honestly I think those motors are probably a little overkill. You've got 3 of them remember, and the 2mm thread pitch means that you won't really need a lot of torque to overcome a steep attack angle like you would on an 8mm lead.

But yes, those both look like good choices. If I had to pick one over the other I would choose the filastruder motor.

Dougal1957 · 11 Feb 2020, 13:13

If you really would like 16 or 20mm lead screw have a look at https://www.dold-mechatronik.de/Trapezoidal-screws-meter