5bar scara Problem configuring z probe using fsr switch

gnmrc_

@Phaedrux ok thanks so:

I’ve built a 5bar scara arm, I can home the 2 arms in the home5barscara.g but when I try to do a G0/G1 move to set the hotend position to the center to home z, the arms overshoots the required position. If I only home the arms than send a G92 Z## the arm works as expected.

In this thread there are also the config and homing files, plus the videos of the machine behaviour.

Thanks for the help,
Gianmarco.

gnmrc_

@fcwilt Ok, I’m going to report back asap.

Thanks,
Gianmarco

gnmrc_

@fcwilt so this is what I get from m208:

g28
Axis limits (mm)s X-162.7:250.0, Y-108.5:250.0, Z0.0:200.0
Axis limits (mm)s X-162.7:250.0, Y-108.5:250.0, Z0.0:200.0
Error: Failed to home axes Z

Thanks for the help,
Gianmarco

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@fcwilt so this is what I get from m208:

g28
Axis limits (mm)s X-162.7:250.0, Y-108.5:250.0, Z0.0:200.0
Axis limits (mm)s X-162.7:250.0, Y-108.5:250.0, Z0.0:200.0
Error: Failed to home axes Z

Thanks for the help,
Gianmarco

Thanks. That all looks normal.

It seems that your kind of printer has some unique requirements - like changing the name of of HomeALL.g to something else.

So who knows what else is going on. In a "normal" printer you would have some code to home the Z axis in your HomeALL.g file. But after the X and Y are homed they can move to wherever is needed to home Z.

But in your case to move to X=0 Y=0 you have to force Z to be homed with a G92 - which makes no sense to me at all.

I gather from your config.g file you have a Z Probe which, in theory, would be used to home Z.

Since the G92 allows you to move to X=0 Y=0 have you tried adding the code to home Z with the probe?

Can you specify in G92 close to the actual position of Z? If so you can still move forward and home Z with the probe and the actual Z position would finally be established.

Or maybe you have to home Z first somehow?

Just out of curiosity what took you down the path to a SCARA printer in the first place?

Frederick

Phaedrux

if you send G30 on it's own does it attempt to use the probe?

gnmrc_

@Phaedrux Yes, the heated bed is moved up, but due to the zprobe not being inside the bed area the heated bed crash. But if I manually activate the probe the homing is completed.

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@Phaedrux Yes, the heated bed is moved up, but due to the zprobe not being inside the bed area the heated bed crash. But if I manually activate the probe the homing is completed.

One "disadvantage" of homing Z with the probe is X and Y need to home first so the probe can be moved into position.

I don't like that so all of my printers have a physical Z endstop switch or sensor so I can home Z first thing and be sure it is safely out of the way when homing X and Y.

Then I use the Z probe for setting the Z=0 Datum, leveling the bed, creating the height map, etc.

Have you consider going that way - adding a endstop switch to the Z axis - it sounds like it might solve all of your problems.

Frederick

gnmrc_

@fcwilt yes in the homing file I tried to use a dummy G92 comand to trick the machine in to moving, but with no success. There is something that I’m missing but I can’t figure it out.

So I wanted to build a SCARA printer because I think that there is a lot of unexpressed potential in this kinematic but due to it’s complexity there aren’t a lot of people that wants to build one of this printers and improve them. This type of printers are left in an embrional state, particularly the 5bar one, the only 2 guys that I have seen make them work are Joerg and Pontus Borg but 3/4years have passed since the last videos and post about those printers.

Thanks for the help,
Gianmarco

gnmrc_

@fcwilt for semplicity of wiring I would prefere to have only the probe, but due to all this problems I’m really considering this solution.

Gianmarco

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

yes in the homing file I tried to use a dummy G92 comand to trick the machine in to moving, but with no success. There is something that I’m missing but I can’t figure it out.

I clearly misunderstood. I thought the G92 did allow homing to complete.

Just out of curiosity how about a test where the G92 for the Z axis is before the two G1 H1 moves. Then you could see if the G1 X0 Y0 move needed H2/S2.

If that worked once you could get to X=0 Y=0 then you could use the Z probe to accurately set the Z axis.

Thanks.

Frederick

gnmrc_

@fcwilt Nice idea, I’m gonna try and see if this trick works.

Thanks for the help,
Gianmarco

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@fcwilt Nice idea, I’m gonna try and see if this trick works.

Thanks for the help,
Gianmarco

I haven't been much help so far.

To date what I have mostly done is help you to find new and interesting things that don't work.

Frederick

gnmrc_

@fcwilt It’s not true, we are trying to solve a problem that seems easier than what it really is on a complex and not so well documented machine. You gave a really big help trying to figure out what the problem is, and giving option on how to solve it.

By the way if you want to build one I can give you the cad files so you have the machine too and we can complete the build of a well documented and easy to work scara arm.

Gianmarco

fcwilt

@gnmrc_

Actually I would like the CAD files - I'm always up for a challenge and I like new and interesting things to work on.

Frederick

gnmrc_

@fcwilt ok I’m gonna send it to you, but I have no idea in how to do it. Can I link them here in some way?

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@fcwilt ok I’m gonna send it to you, but I have no idea in how to do it. Can I link them here in some way?

Are they large?

You can attach files to messages here but I don't know if there is a size limit.

Perhaps you can email them?

Or I have a DropBox account. Maybe there is a way you can leave them there. I would have to research how to do that.

Frederick

gnmrc_

@fcwilt Yes they are too big to link them here, the dropbox could be the best way.

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@fcwilt Yes they are too big to link them here, the dropbox could be the best way.

Do you have a Dropbox account? I know how to share files (yours to me) but I don't know how to allow you to put files into my Dropbox.

Frederick

gnmrc_

@fcwilt no but we can use a google drive in the same way right?

fcwilt

@gnmrc_ said in 5bar scara Problem configuring z probe using fsr switch:

@fcwilt no but we can use a google drive in the same way right?

I don't know. I have it but to do certain things you have to sign up for a paid account. It's not much it's still another $72 annually - minimum.

Do you have Google Drive?

Frederick