Z axis inverted!

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nalmeida
Posts: 46
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Z axis inverted!

Postby nalmeida » Fri Sep 04, 2015 6:18 am

So as I told before the littleRP clone is built and I'm doing the last adjustments, it was when I noticed Z axis is inverted.

I built everything according to the Brad's instructions and when I go to creation workshop controls the Z axis movement is inverted, when I press for the Z to go up it goes down and vice versa. I configured for a bottom_up setup and that is fine but when I simulated a print it started printing down to the flex vat, I now am glad it is "flex". I flashed grbl 0,8a through the instructions and I'm using Brad's shield to control the stepper. Should the axis be inverted through software or hardware?

Thanks for your help.

rasamaya
Posts: 5
Joined: Thu Sep 03, 2015 2:41 pm
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Re: Z axis inverted!

Postby rasamaya » Fri Sep 04, 2015 6:55 am

Thats funny I just installed a tilt, and my tilt is going down and then up, so its inverted too.
My Z is fine. Lucky you caught it.

I too would like to know how to invert a motor.

nalmeida
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Re: Z axis inverted!

Postby nalmeida » Fri Sep 04, 2015 8:45 am

I don't know if it's relevant but I'm using the stepper A4988.

I already changed $7=255 in GRBL to $7=128 (Invert mask) but nothing changed

nalmeida
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Re: Z axis inverted!

Postby nalmeida » Fri Sep 04, 2015 10:22 am

Solved this one the hard way, rewired the motor and it's now working perfectly. I don't know if the original inversion was due to the A4988 or a "inverted" cable, all I know is that once I rewired the motor everything went fine.

goopyplastic
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Re: Z axis inverted!

Postby goopyplastic » Fri Sep 04, 2015 12:08 pm

The DRV8825 that I include with the kits will move backwards compared to the A4988. So you can either reverse the motor wiring or change the step/direciton mask in GRBL to compensate.

rasamaya
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Re: Z axis inverted!

Postby rasamaya » Fri Sep 04, 2015 6:49 pm

For my inverted Y Tilt, I just flashed the new grbl and then used the grbl controller to update values from the littlerp support page.

All was magically fixed; mechanically that is.

I am still having issues with sticking to the build plate. I am a master at making goopy blobs in my dish though.

Using a Optoma w316 and a polaroidx4 magnification lens, need to find more time later this week or next sigh

goopyplastic
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Re: Z axis inverted!

Postby goopyplastic » Sat Sep 05, 2015 10:56 am

Have you roughened the build plate with sand paper?
Also you may need a longer base layer time to get it to stick as well.

rasamaya
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Re: Z axis inverted!

Postby rasamaya » Sat Sep 05, 2015 1:47 pm

I dont want to pose my "New Issue" on Nalmieda's thread but it sounds like it was solved.

Sanded yes, I even bumped it up to 10000ms as a crazy test for the base layers.
I am sure I will get it.
Im using tilt, littlerp, The Red SF that comes with it and a coated tray.
My only annoying variable is that I am not using the suggested ACER.
I am using a dlp optoma w13. It has a crappy focus distance, so I use a polaroid 4x lens(suggested by muve3D).

I have tested burning in different shapes to make sure I was getting good UV. My test were primarily on G+ with good success, at single layer shapes.
So I am hoping the projector is all good.

My understanding, is that if we are using makerjuice SF resin or regular build exposure time is 1400-2000, and I should not have to play with this to often.
I just adjust the 1000ms delay in gcode and the cycle(making sure my build play has come to a stop before the next projection). So far my cycles have been in the 4000-5000ms range.

I had more success with less in the vat. How much do you normally have in it? few mm?? For testing, do you use a flash light or led lamp to observe the build or just wait patiently. Open to tips.

I washed and uv cured my lump as a test. The lump was washed in room temp water for 5 sec and I placed under my uv grow lights for a minute. Sound normal?

I keep thinking there is a master instruction pdf I am missing, besides what I at littlerp support. I heard people say they followed Brians instructions, and I have no clue who Brian is.

I will post my rig, and accurate setup/settings in a new thread if I dont get it by next weekend.

Freddy
Posts: 6
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Re: Z axis inverted!

Postby Freddy » Sun Oct 11, 2015 10:52 pm

Hi all,
I have also changed the shield on my unit due to an operator error (unplugging issue) and now the Z has also reversed itself.
Which of the wires need shifting?
My sequence from the unit is...... red grey yellow and finally green.
Thank you in advance for the courteous reply.

goopyplastic
Posts: 236
Joined: Sat Mar 29, 2014 6:16 pm
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Re: Z axis inverted!

Postby goopyplastic » Tue Oct 13, 2015 11:59 am

You can just mirror the cable, so 1,2,3,4 -> 4,3,2,1
However it is not too bad to change the setting in GRBL, I will be making a video guide on doing this as it's come up a few times.


The 8825's are generally backwards compared to the allegro 4889's, you can reverse the motor cable (hard to do if using the keys connectors) or change the step port direction mask in GRBL

You can see how this works here:

https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.8

but basically there is a binary value xxx00000 where the first three bits are z/y/x

You can convert the binary to the decimal value here:

http://www.binaryhexconverter.com/binar ... -converter

so to only reverse z it would be 10000000 = 128

to reverse only y it would be 01000000 = 64

reverse both z/y = 11000000 = 192


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