problem with z-homing & limit switches

[thereza]

When I do an x/y homing, it goes till it hits the limit switch, backs off, and sets the position at 0. For the Z it just goes to the limit switch, stops, and does not set the value to zero. it also behaves strangely at this point.

here's the output of x homing

Code: Select all

==> {"gc":"G28.2 X0"}
{"r":{},"f":[1,0,18,77]}
{"sr":{"coor":0,"dist":1,"stat":9}}
{"qr":32,"qi":1,"qo":1}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posx":-4.667,"feed":2000.00,"vel":2000.00}}
..
{"sr":{"posx":-37.000}}
{"sr":{"posx":-42.309,"vel":148.87}}
{"sr":{"posx":-42.333,"vel":0.16}}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posx":-42.028,"feed":100.00,"vel":100.00}}
{"sr":{"posx":-41.703}}
...
{"sr":{"posx":-38.215,"vel":0.51}}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posx":-598.000,"feed":2000.00,"vel":0.00}}
{"qr":32,"qi":0,"qo":1}
{"sr":{"posx":0.000,"feed":0.00,"coor":1,"dist":0,"stat":3}}
ReadyEvent stat
{"qr":32,"qi":1,"qo":1}
Homing X done.

vs z

Code: Select all

==> {"gc":"G28.2 Z0"}
{"r":{},"f":[1,0,18,77]}
{"sr":{"coor":0,"dist":1,"stat":9}}
{"qr":32,"qi":1,"qo":1}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posz":-4.660,"vel":0.03}}
{"sr":{"posz":-84.000,"feed":0.00,"vel":0.00,"coor":1,"dist":0,"stat":3}}
ReadyEvent stat
{"qr":32,"qi":1,"qo":1}
Homing Z done.

Note the last sr has a pos of -84 vs. the x-homing went to zero. also it didn't back off like it did for the other axis

The other thing that's super annoying is that if the unit starts up with a limit switch depressed, and it mores to un-depress-it then it triggers a limit switch fault. it seems to detect any change of voltage vs. just a negative swing.

I'm going to upgrade the fimrware to see if it helps - has anyone else had this problem? I"m not sure if the version number is in here, but this is the ready msg.

15:57:59.352> {"r":{"fv":0.970,"fb":438.02,"hp":1,"hv":8,"id":"1H4973-HU2","msg":"SYSTEM READY"},"f":[1,0,0,5409]}

[thereza]

upgraded and it's still acting stupid. Also, seems to only work on the edge version.

to reproduce this problem, home z then click test z - as soon as it moves down a bit and releases the limit switch, it throws an error and shuts down. this is getting really annoying. will have to look at the firmware source now.

Code: Select all

==> {"gc":"G28.2 Z0"}
{"r":{},"f":[1,0,18,77]}
{"sr":{"coor":0,"dist":1,"stat":9}}
{"qr":32,"qi":1,"qo":1}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posz":-1.130,"feed":1000.00,"vel":1000.00}}
{"sr":{"posz":-4.377}}
{"sr":{"posz":-7.624}}
{"sr":{"posz":-10.871}}
{"sr":{"posz":-14.118}}
{"sr":{"posz":-17.365}}
{"sr":{"posz":-20.612}}
{"sr":{"posz":-23.858}}
{"sr":{"posz":-27.105}}
{"sr":{"posz":-30.352}}
{"sr":{"posz":-33.599}}
{"sr":{"posz":-36.843,"vel":981.17}}
{"sr":{"posz":-37.844,"vel":0.03}}
{"sr":{"posz":-83.300,"feed":2000.00,"vel":0.00,"coor":1,"dist":0,"stat":3}}
ReadyEvent stat
{"qr":32,"qi":1,"qo":1}
Homing Z done.
G0 Z0
==> {"gc":"G0 Z0"}
{"r":{},"f":[1,0,15,74]}
{"sr":{"posz":-37.844,"vel":0.37,"stat":5}}
{"qr":31,"qi":1,"qo":0}
{"sr":{"posz":-34.703,"vel":2807.50}}
{"er":{"fb":440.14,"st":204,"msg":"Limit switch hit - Shutdown occurred"}}
G0 Z20
{"qr":30,"qi":1,"qo":0}

[JuKu]

> I'm going to upgrade the fimrware to see if it helps.

You are on uncharted waters here, The software is only tested against firmware version 438.02. The ready message shows this at "fb" field (firmware build).

Please send a $ command at the "Text to send" window. This dumps all the TinyG settings to the log window, and either post here or e-mail to me. It might be that the default settings is missing something. This is not how my machine works and your is supposed to be identical, so missing a setting is my first guess.

[JuKu]

Btw, are you noticing any differences or anomalies (except the issue at hand) with the updated firmware? Testing the newest edge is on my todo list, but you got there first.

[thereza]

Found the problem. Seemed that I had the max/min limit switches backwards. In my mind, max made sense being at the highest point. What's annoying is that the display seemed to work and the only error message was homing done - not 'wrong limit switch hit' or something more useful.

Right now my main problem is that the A motor is getting super hot and doesn't seem to want to work correctly. It also makes a lot of noise with the frequency changing depending on how much current it's set for. I'll try swapping the channel on the tinyg board to see if the controller IC is burnt out.

Also when I hit the test buttons, for X and Y it just goes full speed and slams into the end.

And I had to turn the homing speed down for Y - else by the time it hit the limit switch, it would have too much momentum and couldn't stop before hitting the end.

Can you send a photo of the POTS on the tinyg board to see what type of current settings you use?

[Lars]

Hey Thereza, for the A axis channel I would turn the current limit pot all the way down.

[JuKu]

The test functions assume that the machine is homed. They then exercise the movements almost to max values and back.

My current settings are, for no particular reason: x: 100%; y: 90%, z: 60%; a: 30%.

Lars is right, the A axis does not require any force to turn, so a small current setting is right.

[thereza]

I think the A motor stepper is broken then. It gets super hot and has no turning power at all. I removed the motor and attached it directly to tinyg motor 3 and it had the same problem. I plugged the Z axis into motor 4 and that worked fine, so I'm pretty sure that the stepper is broken.

Can some measure the resistances between the various channels?

I'm getting 3.5 ohms between green/black and 5.3 ohms between blue/red.

Also, I've taken the top off and taken a thermal image of it - it looks like there is a problem with one of the coils. It hit 300 deg within 15 seconds of being powered up.

delme.jpg (69.33 KiB) Viewed 6161 times

[JuKu]

I'll replace it. Please send me your address by email or PM.

[JuKu]

Found the problem. Seemed that I had the max/min limit switches backwards. In my mind, max made sense being at the highest point. What's annoying is that the display seemed to work and the only error message was homing done - not 'wrong limit switch hit' or something more useful.

Agreed, a message would be good, but the TinyG with the firmware we are using does not tell this. They updated the firmware recently as you noticed, but I haven't tested it yet. I'm not expecting any issues, but the software talks to TinyG in rather deep details in some operations.
(edit: clearer wording)