Z axis Buggy configuration

We've made some progress, but the Z-Axis is buggy. When using the Reprap firmware the only way I can get the Z Axis to spin (and not just sit there and hum) is to crank the Z_STEPS_PER_MM to 20 or lower (our calibrated value should be 1454.545454), This although not accurate at all allows the Z Axis to move in either direction. The min and max feed rates seem to have no bearing on the speed at which the Axis moves.

Gen3 electronics, v1.8 firmware.

We've tried using ReplicatorG to load firmware to the unit (Cupcake firmware) and the axis and MAX/MINS work properly there.

Has anyone run into this?

Thanks in advance

I believe the problem is that reprap firmware uses the speed of the last move to try and move the Z-stage which can not run at that high of speed. To deal with this skeinforge has an option to limit the speed of the Z axis. Its in craft under the Limit tab.

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Hmmm. I've been using the console to send gcodes directly to the mendel. I'll have to try it with replicatorG. Have you seen anything code side that may cause it? I looked around but didn't see anything.

I believe if you look your Gcode it will look like:

Quote
No Z speed limit between layers

G1 X-2.7 Y-0.15 Z0.2 F2400.0 E4.0299
G1 X-2.57 Y0.82 Z0.2 F2400.0 E0.9828
G1 X-1.67 Y1.72 Z0.2 F2400.0 E1.2731
M103
G1 X-0.97 Y2.43 Z0.58 F4800.0 <--- Z move at travel rate in skeinforge
M101
G1 X-1.07 Y2.38 Z0.6 F2400.0 E0.115 <--- Z move at feed rate in skeinforge
G1 X-1.46 Y2.18 Z0.6 F2400.0 E0.433
G1 X-1.86 Y1.86 Z0.6 F2400.0 E0.5165

Once you enable the limit feature in skeinforge it will look like this.

Quote
With Z speed limit between layers
G1 X-2.7 Y-0.15 Z0.2 F2400.0 E4.0299
G1 X-2.57 Y0.82 Z0.2 F2400.0 E0.9828
G1 X-1.67 Y1.72 Z0.2 F2400.0 E1.2731
M103
G1 X-0.97 Y2.43 Z0.58 F40.9745 <--- Z move at max set speed in skeinforge
M101
G1 X-1.07 Y2.38 Z0.6 F174.7307 E1.58 <--- Z move at max set speed in skeinforge
G1 X-1.46 Y2.18 Z0.6 F2400.0 E0.433
G1 X-1.86 Y1.86 Z0.6 F2400.0 E0.5165

Edited 1 time(s). Last edit at 06/04/2011 07:40PM by Sublime.

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Excellent thanks Sublime. I'll try that tomorrow when I get home.

I think you still have to turn off acceleration in the Five-D firmware or it would start the z-move at the feed rate from the previous command (F2400).

Yeah, I turned acceleration off, with it on it would start at a slow speed then quickly spin the stepper faster then it can go... I'm going to try feeding a feed rate with the g code, once I get my computer restored.

Thanks for your input guys.

Acceleration works the other way too: from fast to slow. If the last feed rate give is higher the the current one, then it starts at the faster feed rate and then slows down to the new feed rate. This is the problem. The reprap host generates G codes that issues the new feed rate before the z move. For example, G1 F60.0. Skeinforge does not do this.

brnrd Wrote:
-------------------------------------------------------
> Acceleration works the other way too: from fast to
> slow. If the last feed rate give is higher the the
> current one, then it starts at the faster feed
> rate and then slows down to the new feed rate.
> This is the problem. The reprap host generates G
> codes that issues the new feed rate before the z
> move. For example, G1 F60.0. Skeinforge does not
> do this.


Skeinforge has the ability to do exactly what the reprap host does, read my post's above concerning the limit tab.

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@subline: The limit tab does not do the same thing. I used your example above. With acceleration on, the z-move that you labeled will start with a feed rate of 2400 (the previous command) and slow down to a feed rate of 40.9745 (the command to move the z axis). Before it can slow down, the z motor would have already missed steps. This was my experience before I turned acceleration off. THe reprap host would have issued a separate G1 F60 command and then a G1 Zxx command to move the z.

BTW, does any firmware still use M101 (extruder on) and M103 (extruder off) included in your example? I have my alterations file in SF set to remove these.

Edited 1 time(s). Last edit at 06/05/2011 03:14PM by brnrd.

I did not realize it was so sensitive to the previous move even with a new F command. Good to know and I guess its all the more reason to use a different firmware.

And yes Teacup uses the M101 and M103 to activate automatic retraction every time the extruder is supposed to start/stop.

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I've got my system back up and running, and if the z-axis issue is indeed that I'm not feeding the F code, I think I may have this thing running! If I do I'll upload a copy of my code so ppl won't go through the same frustrations I did just to get a basic unit running.

uhh.. Gen 3 electronics..

Adam.m.Nelson Wrote:
-------------------------------------------------------
> I've got my system back up and running, and if the
> z-axis issue is indeed that I'm not feeding the F
> code, I think I may have this thing running! If I
> do I'll upload a copy of my code so ppl won't go
> through the same frustrations I did just to get a
> basic unit running.
>
> uhh.. Gen 3 electronics..


I'm not sure what you mean. But the z-move problem with Skeinforge and Five-D firmware on Gen 3 is a known problem with a known solution:

1. Turn acceleration off in the firmware. I think this is in configuration.h
2. Enable the Limit option in Skeinforge and set the maximum z-feed rate to what your Mendel can reliably handle. I have mine set to 1.5 mm/s.

Cheers!

Yay z-axis works! But some where along the lines the extruder stopped working. I'm currently searching for a solution, but havn't found anythign remotely close to this issue.... suppose I should start a new thread.