Delta printer homing problems

dc42

Is your Y endstop really triggering 12mm higher than your X and Z endstops? If so, I suggest you correct it. It's not hard to get all 3 endstops to trigger to within 1mm of the same height.

Are you using steel-cored belts? If so, the steel core in the Y belt has probably fractured.

Willmish

@dc42 The head is still moving smoothly and I've analised the tower which had the slight jump. Also how do you know that it's the Y tower that could have a fractured belt?

I'm not sure how to tell whether they are triggering higher or lower, they hit the endstops at different times but as soon as they do the coordinates get set to X12.5 Y-9 (something has changed here) Z174.40

EDIT:
Also the config-override.g file has changed, I do not know what caused it to do so
Should I modify it to one of my previous versions (I have saved the memory of the SD card from a few days ago) or should I leave it as it is?

dc42

The config-override.g file only changes when you use M500 to save the current delta calibration and heater model settings - that's what the file is for. So if the printer works OK after auto calibration, then run auto calibration and then run M500 to save those calibration settings.

If you don't want to use config-override.g at all, then remove the M501 command from config.g. Then auto calibrate, and copy the new M665 and M666 settings into config.g by hand.

Willmish

@dc42 said in Delta printer homing problems:

u use M500 to save the current delta calibration and heater model settings - that's what the file is for. So if the printer works OK after auto calibration, then run auto calibration and then run M500

the printer runs the M500 command automatically after calibration, as you can see in the attached bed.g file. Will sending it by hand change anything? Also after calibration head moves definitely better than after homing though now during paper test, the sheet of paper is hard to move at the edges of the bed (though at least the nozzle isn't drilling the table as it was before)

Question 1: If running the M500 command won;t change anything, is it wise to remove the config-override.g file?
Question 2: Is the explained above state of the bed (a bit uneven) acceptable or should I keep digging?
EDIT:
I'm still using the G92 X0 Y0 command
EDIT2:
I ran the M500 command and it did change the config-override file and the Y changed to around 10. There is a slight difference in the printers movement, it now moves around 0.3 lower than it used to (it used to gently
Press the bed at 0 now it triggers the z probe. Also the X and Y movement differs slightly but is similar to previous behavior

dc42

There is something very wrong with your mechanics if the Y endstop switch triggers 10mm higher than the others (or even 8mm higher). What sort of endstop switches are they, and how do the carriages trigger them? What type of belts are you using?

Willmish

@dc42 I'm using GT2 belts (6mm wide). Attached is the photo of one of my endstop switches
They are triggered by the top of the carriage (which you can see in the picture).
They simply press on the metal part of the switch.

dc42

If they are ordinary glass-cored GT2 belts, they should be OK. The steel-cored ones are less flexible and the cores will break on a delta because of the small pulley diameter.

I find it best to remove the metal arm of the microswitch, so that the carriage presses directly on the button. That gives you a more precisely-defined trigger height.

Willmish

@dc42 said in Delta printer homing problems:

Hi, I tried removing the metal arm, but it's attached firmly to the endstops (photos). Also they are all equally bent on all towers so I don't think they would produce such a big uncertainty. I tried fiddeling with them for a bit.

Also, each time I home the printer and then calibrate it, the X, and Y value (during homing) change. As I mentioned earlier, they are wrong since I know the printer homes at X0 Y0 Z174... so I enforce it to think this way (by using G92 X0 Y0 instead of G1 X0 Y0) which still produces an error. Here are the values throughout my testing (X, Y):
13.2 -13.1
13.0 -14.6
12.9 -15.4
12.9 -16.1

The config-override.g file didn;t change during the testing

PlasticMetal

The arms will come out with a slight twist from some small pliers. I would think arms that long would have way too much flex for repeatable homing. I believe you'll get more reliable and repeatable switch action without the arms.

My old delta had the arms. I removed them when I built my new delta, and homing repeatability is at least as good as before, if not better.

Willmish

@plasticmetal Thanks a lot for the tip, I will try it over the weekend and hope for the best! Though it still kinda bothers me how is it so off, should I fiddle in it's config?

Willmish

It's been a while since I have posted anything, the X and Y error continues to grow, it's around 20 in Y now. Since I didn't want to rip out the metal arms of the endstops, I am ordering new ones with easily removable metal arms: https://www.amazon.co.uk/gp/product/B079JDB4PW/ref=ox_sc_act_title_1?smid=A282CIVY4X0P53&psc=1
In the meantime I have printed a few things, all of which turned out correctly, even though the first layer is a pain in the ass. (THe head isn't moving parallel to the bed)
That's all for now, I will update this thread after I get the new endstops.

Gary

@Willmish said in Delta printer homing problems:

G92 X0 Y0

I've got exactly the same problem x 24.2 and y 2.3 homed. Edited homedelta all to zero, but g32 way above bed.

Willmish

Hi @Gary,
I forgot to upload my solution to this thread, because luckily I've been able to solve it.
It turned out to be simpler then I first assumed. Basically, the error occurred due to another error in the measurements in calibration. This was then stored in the override.g file. I was suspecting that there might have been an error there, but each time I tried deleting it, it was already stored in the machines RAM.
Here is a step by step guide, explaining how I fixed it:

Temporarily delete/comment out the M500 command in the bed.g file. (It causes the machine to store the new values after calibration)
Delete the config-override.g file and do an emergency stop of the machine.
Restart it, (hopefully there shouldn;t be a config-override.g file) and add the M500 command back in, then perform a delta calibration.

This should have: removed your previously stored values in config-override.g for good --> allowing for new values to replace them, so the printer will home properly.

Also, you don't need the G92 command, it was only a temporary fix