2nd Adjustable Y Limit Switch

Hi everyone,
New to the forms here. I’m a manufacturing engineer and have had my shapoko xxl for about a year now. I have learned a lot from the community forms, Instagram, YouTube etc. and thank everyone who has gave their input.

Shapeoko upgrades:
HDZ
Steel belts
Proximity limit switches
Aluminum threaded table

Problem:
Repeatability after turning machine off and back on. There is very good repeatability on the side that the limit switch is on, but the further you move down the x axis the more error you find. This makes sense due to minor twist in the x carriage. I have tried to move the HDZ to the center of the x and push it back an inch or so before starting the machine to get it to it’s most ‘natural’ position, but it hasn’t got rid of the problem. When the stepper motors turn on they sometimes jump before locking into their nearest position. This inaccuracy has made fixturing somewhat of a headache.

Proposed solution:
Add a second limit switch to the left side of the machine. I believe the reason this is not used is because you don’t want to induce twist that is not already there. Many users, including me, don’t take the time to get the machine perfectly square (even though I watched Winstons tutorial), so having a non adjustable 2nd limit switch may cause problems. Although, having a proximity limit switch that can be easily adjusted may be the solution. Off the top of my head, this could be done by adding shims (or tinfoil for the savvy users) between the limit switch and it’s mount and then manually sliding the x carriage until the red lights go off at the same time. I could get this setup, but don’t know the coding side of things past g code (or Arduino).

Carbide3d let me know if you have thought of anything like this or if it would be easy to somehow code this into the board. I have fixtures for different parts across the whole table and it would be nice to be able to start the machine, run it over to it’s known global coordinates and start the program. Knowing as it moves across the x axis it will continue to accurately cut parts relative to the previously machined fixtures. This could make the machine as repeatable as much more expensive equipment.

If anyone else has any other ideas that could increase repeatability across the whole work table let me know.
Thanks,
Nick

Hi @SeniorCutMaster,

This was briefly discussed in this thread, in relation to the release of GRBL 1.1H version, and how it now supports “Dual motor support for self-squaring gantry homing”, which is exactly what you propose.

I took away from that discussion that…unfortunately, the Shapeoko controller board won’t support that, you would need to upgrade to another controller (doable, but not a piece of cake, so worth thinking twice)

Also, in my opinion you should rather invest a little bit of time to get to a good squaring of the machine than trying to compensate for it being out of square in software (3D printers are different, there is virtually zero force applied on the tip of the extruder). I have a feeling that even if you installed a double Y switch, you may still have to fight other geometrical inaccuracies of the machine, because the “twist” may not only be on the X/Y plane.

Last but not least, can you share the repeatability error value you are seeing ? Some people here do precision work, and it should be possible to dig up “reachable” values on a square machine with proximity switches in earlier posts.

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A variation on that is to implement the mechanical effort from “Poor Man’s Homing” which used to be suggested back before the machines had homing switches by default:

Pull/push the machine solidly up against the front plate and far left corner — this should remove any twist from the gantry and ensure a consistent starting position which is not on a homing switch.

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I did this for the first few months and it worked out. But then I got the HDZ and had a reason to take the machine apart and get everything shimmed and to fill the extrusions with sand since I had everything apart.

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