Delta homing issues (SOLVED)

Brian.Everts

Good afternoon gents.

sorry to be asking for help on my first post, but im scratching my head with this

Hardware is as follows:

Genuine Duet wifi

Firmware Electronics: Duet WiFi 1.02 or later

Firmware Version: 2.02(RTOS) (2018-12-24b1)

WiFi Server Version: 1.23

Web Interface Version: 1.22.6

Kossel style Delta, vertical rail height (from the bed to the end stops) is almost 900mm

Smart effector

Haydn Mag ball carbon arms with a length of 490.66mm

Bed Dia is 300mm

Linear Rails

0.9 degree motors

Zesty Nimble on the smart effector.

My issue is that i can home but once i do the web interface lists the axis's in the following manner:

X= 0 Y= 0 Z=350.1

And if i try to initiate a "delta calibration" move only the X & Y motors move.

Would someone with obviously better knowledge of delta's than i be able to pass comment on what my issue might be, i will try to attach copies of my config.g, bed.g & homedelta.g files

I know its cheesy but many thanks in advance for helping a newbie with his first delta.

Brian

T3P3Tony

@brian-everts said in Delta homing issues:

My issue is that i can home but once i do the web interface lists the axis's in the following manner:
X= 0 Y= 0 Z=350.1

this is normal as this is the location of the effector in the co-ordinate space of the printer rather than being the position of the individual axis (which are no doubt all the ways up at the endstops)

Please update your bed.g to use six factor calibration (I don't know if this is the issue causing only X and Y to move - I doubt it - but S3 is not right):
https://duet3d.dozuki.com/Wiki/Calibrating_a_delta_printer#Section_Setting_up_the_bed_g_file

Is that the bed.g file from the RepRapFirmware configurator, unedited?

Brian.Everts

@t3p3tony

thanks for the prompt reply. yes i used the config tool, i didnt change the bed.g file but i did do a comparison between it and David's kossel example file which is in the sd card you guys send out.

i will look at the bed.g section and digest until i can get me head round it.

thanks again.

Brian

T3P3Tony

The line to change is:

G30 P12 X0 Y0 H0 Z-99999 S3

Change this to

G30 P12 X0 Y0 H0 Z-99999 S6

Brian.Everts

@t3p3tony

Thanks for that, i changed it, that seems to have cured the issue, the calibration sequence now starts, but it has presented another issue (typical)
in the the nozzle doesnt actually get to the bed before it reports that it was not triggered and tries to move to the next point.

one step forward, i will try speeding up the the probing speed as it looks like it "timing out" due to my very slow probing speed.

Regards

Brian

dc42

@brian-everts said in Delta homing issues:

@t3p3tony

Thanks for that, i changed it, that seems to have cured the issue, the calibration sequence now starts, but it has presented another issue (typical)
in the the nozzle doesnt actually get to the bed before it reports that it was not triggered and tries to move to the next point.

one step forward, i will try speeding up the the probing speed as it looks like it "timing out" due to my very slow probing speed.

Regards

Brian

Temporarily increase the probing dive height, for example to 50 (it's in mm). It's the H parameter in the M558 command in config.g.

Brian.Everts

Hi David

Thanks for the input on the M558 command I tried that and im afraid to say that didn’t help.

I worked out a work around (rightly or wrongly) you can advise me on its validity.

Once I got the machine to actually start the calibration procedure I observed that the height the Z axis would “dive” to always show zero in the web interface and that dive height in mm corresponded with the amount of mm in H switch in the M665 command, the H switch states: H = height of the nozzle above the bed when all three carriages are just high enough to trigger the end stop switches. Measure it as best you can, to within about 5mm. Calibration will adjust it.

Now I measured that as advised after homing all three carriages, and from the bed surface to the tip of the nozzle is 355mm, and with that value in the H switch of the M665 command the nozzle would never get close to the bed when I initiated the auto calibration sequence, so I made the connection between the two and I tried increasing the H value, I reached a value of 444 mm which now allow the nozzle to reach a reasonably close distance above the bed.

Why would the original (correct) H Value not allow the nozzle close to the bed? And why does the incorrect value allow this to happen…

So is my workaround crazy or can I leave it for now?

Im now working through writing a macro to help me to carry out all 12 trigger height corrections.

Detla’s are crazy machines to get your head around but so fascinating too.

Brian

dc42

It sounds to me that you have the incorrect steps/mm value for the towers in the M92 command. For example, you may have entered 80 when the true value is 100.

Brian.Everts

@dc42 said in Delta homing issues:

It sounds to me that you have the incorrect steps/mm value for the towers in the M92 command. For example, you may have entered 80 when the true value is 100.

Hi David

I will double check that, i followed the reprap calculator.

Brian.Everts

Hi All

So i have my homing issue fixed, thanks to all who helped.

I used the RepRap config tool and it appears to have set the Switch incorrectly in the beg.g file.

I also checked the steps per mm as advised by David, im running 0.9 degree motors so the steps per mm was wrong, the RepRap config tool appears to assume 1.8 degree motors are being used and unless its hidden somewhere, i couldnt find where to tell the tool i was using 0.9 degree motors.

so i will mark this as solved, thanks again to everyone who assisted.