Manual reset y axis

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jerteach
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Manual reset y axis

Postby jerteach » Mon Jun 11, 2018 5:38 pm

My Raise 3D, N2 has worked great for a year. Last night it had a bad fail and now the y axis needs to be manually reset before each print.

What I mean by manually resetting the y axis is that it thinks home is near the middle of the bed. I can't reset it using the software tools (It will not move any closer to the y axis home, but will happily move the other direction), but I can just physically move the print-head in the y direction back to the home location. When I do that the next print works fine, but at the end of that print the print-head y axis homes near the middle of the bed again.

The x and z axis home is fine. Printing is also fine.


I think that during the bad fail the y axis forced the belt to skip for about 3 inches (Probably made an awful noise).

I can live with the issue, but if anyone can make an easy suggestion I would be most grateful.
B.Sc (Chemistry), B.Ed (High School) Diploma Counselling
40 years coding. Teach: Robotics, Coding, Animation and 3D Printing. I research Music Notation
Train: Rugby Players and Recurrent Neural Networks
Twitter: @rocksetta https://twitter.com/rocksetta

Jetguy
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Re: Manual reset y axis

Postby Jetguy » Mon Jun 11, 2018 5:53 pm

Simple answer, your limit switch is broken and or stuck and that is why the motor when homing cannot move towards the switch.
The Y axis limit switch is in the upper left hand side of the printer near the front.

Jetguy
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Re: Manual reset y axis

Postby Jetguy » Mon Jun 11, 2018 6:02 pm

This topic was about moving that switch slightly, but has a picture.
viewtopic.php?f=4&t=4791&p=26159&hilit=limit+switch#p26159

Here, a user broke the lever off the switch viewtopic.php?f=4&t=826&p=7845&hilit=broken+switch#p7820

Another topic on a broken limit switch viewtopic.php?f=5&t=720&p=6736&hilit=broken+switch#p6736

The part is also carried in the store as a spare part
https://www.raise3d.com/collections/3d- ... stop-board
Attachments
Endstop-Switch-2_600x600.jpg
Endstop-Switch-2_600x600.jpg (8.86 KiB) Viewed 223 times
switch2.JPG
switch2.JPG (18.65 KiB) Viewed 223 times
switch1.JPG
Y LIMIT SWITCH.jpg

Jetguy
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Re: Manual reset y axis

Postby Jetguy » Mon Jun 11, 2018 6:10 pm

Also, additional technical information:
The switch being a simple 2 wire connection is wired normally open (switch not triggered, circuit is open)

If the switch is damaged, and mechanically stuck jammed in the triggered state, one option is to unplug it. Note, the connector may be held with hot glue, or on newer printers, a different glue. This was meant to prevent it from unplugging during shipping. Hot glue will break free with a drop of alcohol, it does not dissolve the glue but breaks the bond to the plastic parts. On the other glue type, you basically have to carefully cut with a razor blade.
Unplugging and running with no endstop is possible. What will happen is, the axis will ram the mechanical end point and just skip steps until the controller times out. This is noisy and annoying but WILL NOT damage the printer. It literally could skip steps for a month straight month with no damage, the motor and controller couldn't care less. Again yes, this would be loud and annoying, but truth is, would be able to to run a hands off automatic print and actually have it work, again, just being noisy at the start and at the end if your gcode contains homing commands.

Jetguy
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Re: Manual reset y axis

Postby Jetguy » Mon Jun 11, 2018 6:31 pm

Also, since you teach "Teach: Robotics, Coding, Animation and 3D Printing."
Opportunity moment to share with your students. Again, if you are teaching robotics and 3D printing, here is an opportunity to explain and understand how this actually works and why you have the problem you have.

This is an open loop control system of stepper motors and homing limit switches. When you turn on the printer or start a print, it literally has no idea where the axis is. Since there is no position encoder, the current position is just considered a random value. All you can know with a stepper system is moves relative to the current position assuming you locked the stepper (stepper driver is in enable mode) and no steps are skipped.

Point being, when you start a print, the printer homes to the axis limit because the starting gcode gives that command.
Homing is literally move in this direction until the axis limit switch is triggered. At that time, since we have a good assumption that the axis is physically at the limit switch and as firmware specific function of the Marlin home, it also update the active position in logical memory.
Another note specific to the firmware, the homing/limit switch is not used as a limit switch during printing and only is "sensed" during the homing command.
Again, you start a print job, the G28 homing command tells the controller to move until it hits the limit switch and internally performs a second command of more or less a G92 (update current logical position) in this case, to 0mm for that axis. Then, because the stepper is now enabled, all moves after this rely on the giant game of Simon says, move 30 steps forward, 10 steps back, 8 steps right, and so forth.

In this case, the limit switch is stuck closed in the triggered state. So, when you command to home or certain jogging commands use relative distance commands, they will not allow the axis to move towards the triggered endstop. This the the basic telltale sign of the fault and root cause (system is sensing an endstop triggered when the axis is nowhere near the endstop).

This also affects your end of print because again, when the homing command is invoked as one of the standard lines in the ending gcode at the end of the print, the endstop is again, sensed as triggered, so whereever it is (in the middle of the build area) now is sensed as triggered.

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jerteach
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Re: Manual reset y axis

Postby jerteach » Tue Jun 12, 2018 3:41 pm

Wow. Thank you for the great answers. Yup, the endstop is bent around and being tripped by some part.
B.Sc (Chemistry), B.Ed (High School) Diploma Counselling
40 years coding. Teach: Robotics, Coding, Animation and 3D Printing. I research Music Notation
Train: Rugby Players and Recurrent Neural Networks
Twitter: @rocksetta https://twitter.com/rocksetta

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jerteach
Posts: 81
Joined: Wed Mar 29, 2017 9:44 pm
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Re: Manual reset y axis

Postby jerteach » Tue Jun 12, 2018 4:35 pm

So the y endstop got bent about 70 degrees and was being activated by the beam beside it. Very difficult to see so I had to take it off. Removed 2 hex screws at the bottom of the endstop.

Here is what it looked like straight off the machine

bad-bent2.jpg

.


.



I bent the endstop part of the small board back to it's correct position

good-fixed2.jpg





and put it back on. Works fine.

Thank you community, for your help and exellent description of the problem.
B.Sc (Chemistry), B.Ed (High School) Diploma Counselling
40 years coding. Teach: Robotics, Coding, Animation and 3D Printing. I research Music Notation
Train: Rugby Players and Recurrent Neural Networks
Twitter: @rocksetta https://twitter.com/rocksetta


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