X Homing Problem

Hello Guy's!!

I've managed to assemble my ormerod printer

But now I'm having a problem homing the X axis.

I want to start saying that my optical probe it's working, using G31 command I can get around 977 when really close to the foil, and the value drops as I go up.
The problem is understanding homing.....

If the extruder is place in the middle of the bed, when I do G28 X0, the Head goes away from the Z axis support and doesn't recognize the foil in the bed.

If the extruder is placed close to the Z axis support the G28 X0 command sends the head towards the Z axis support and finds the little piece of foil that I placed as suggested here in the forum.

This makes me doubtfull, it's the head suposse to go away or towards the Z axis support when homing X? It's X=0 in the edge of the bed or close to the Z-axis supoort?

From what I can understand it should go away, since X=0 should be on the outer edge of the bed(am I correct?).

Secondlly, why isn't my homing working? the sensor is working, at the Z position that the homing is made I can see (using G31) around 100 over the foil and 70 out of it, should be enough to detect the foil? Also I tried in all light conditions, since they can change the probe values and nothing...

I was able to home "by hand" and do the circle test program, but when I try to print something, since normally the first command it's homing, and it doesn't work, my x home value gets messed up and I can print anything.....

Could somenone please help me putting the Z-probe working correctlly?

One other remark, with the original firmware, chaning the light conditions made the homing work, since I update the firnmware (yesterday) it stoped working, so probably it's a firmware issue no?

Cheers to you all!

And thanks in advanced

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JVMelo
If the extruder is place in the middle of the bed, when I do G28 X0, the Head goes away from the Z axis support and doesn't recognize the foil in the bed.

That happens to me if the machine is in bright sunlight. Drawing the window blind avoids it. The problem is that the z probe reading (as returned by G31) is already higher than the threshold, which is 400 by default, or whatever you set it to in your G31 command.

Quote
JVMelo
If the extruder is placed close to the Z axis support the G28 X0 command sends the head towards the Z axis support and finds the little piece of foil that I placed as suggested here in the forum.

That is the correct behaviour.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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JVMelo
If the extruder is placed close to the Z axis support the G28 X0 command sends the head towards the Z axis support and finds the little piece of foil that I placed as suggested here in the forum.

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dc42
That is the correct behaviour.

Sorry for my possible dumbness...but if the X=0 it's near the Z support, positive X values will make it go against the Z support, not away.....so it doesn't make a lot of sense.

Quote
dc42
That happens to me if the machine is in bright sunlight. Drawing the window blind avoids it. The problem is that the z probe reading (as returned by G31) is already higher than the threshold, which is 400 by default, or whatever you set it to in your G31 command.

As i said i tried all ilumination possible, even with all lights out! And it didn't work, can you tell me the correct Z height and what command should i send to define the threshold?
Will it be something like G31 Z2.0 P400 (with the values that I get) ?


Thanks

I have stopped using the Z probe. Home your X and Y axis, manually zero your Z then do your bed compensation (I have been skipping this step for smaller prints) and then you are good to go.

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Ormerod 313

Hi JVMelo - the bed axes make sense if you stand at the end of the machine with the Y motor nearest to you and the Z post on the left and look down on the bed - 0,0 (x=0, y=0) is the bottom left of the bed looking from this position - so moving the head to X=0 sends it to the left, postive values send it across to the right. Positive values of Y move the table toward you, and have the effect that the head is moved upwards relative to the bed. Homing both Y and X moves the bed away from the Y motor, and moves the head towards the X motor.

Hope this makes sense

Ray

The Z height at which you do x-homing should not matter provided it is at least 5mm or so from the bed, so that the IR reflected from the bed is below the threshold. The later firmware versions use a macro on the SD card to do x-homing, and that macro raises the head a few mm at the start and lowers it at the end. What firmware version are you using? Send an M115 command to find out. If you updated the firmware, did you also pick up the new files in the sys directory if the SD image?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

JVMelo, judging by your question I am wondering whether you have made the same mistake as me.

Have you got the X-axis connector the right way around? If you look closely at the wiring page of the instruction X-axis connectors are inverted compared to Z, Y and E servos.

For some time I had my connector the wrong way around and it would not home X. Instead is would go away from the Z axis and jam against the stop.

The Z-probe is used in a different way to home X, it does not look at the aluminium tape on the bed but instead a plastic tab on the Z-carrier.

Edited 1 time(s). Last edit at 01/14/2014 07:03AM by arnaud31.

Wow, this is why I love Open Source, it can be a pain getting things right, but the community it's always the best. Thank you all guys.

Quote
rayhicks
Hi JVMelo - the bed axes make sense if you stand at the end of the machine with the Y motor nearest to you and the Z post on the left and look down on the bed - 0,0 (x=0, y=0) is the bottom left of the bed looking from this position - so moving the head to X=0 sends it to the left, postive values send it across to the right. Positive values of Y move the table toward you, and have the effect that the head is moved upwards relative to the bed. Homing both Y and X moves the bed away from the Y motor, and moves the head towards the X motor.

You are correct! But in my case the positive movement on X moves the Head left not right, so I think....

Quote
arnaud31
JVMelo, judging by your question I am wondering whether you have made the same mistake as me.

Have you got the X-axis connector the right way around? If you look closely at the wiring page of the instruction X-axis connectors are inverted compared to X, Y and E servos.


For some time I had my connector the wrong way around and it would not home X. Instead is would go away from the Z axis and jam against the stop.

The Z-probe is used in a different way to home X, it does not look at the aluminium tape on the bed but instead a plastic tab on the Z-carrier.

Arnaud you must be correct! I notice the lack of coerence when moving positive and negative values (and also with what was said in the forums), probably the motor is wired the other way around, if that it's true it makes a lot of sense the home not working. I'll check that when i arrive home later this night. (look at the wiring and for sure it's the other way around)

Regarding....

Quote
dc42
The Z height at which you do x-homing should not matter provided it is at least 5mm or so from the bed, so that the IR reflected from the bed is below the threshold. The later firmware versions use a macro on the SD card to do x-homing, and that macro raises the head a few mm at the start and lowers it at the end. What firmware version are you using? Send an M115 command to find out. If you updated the firmware, did you also pick up the new files in the sys directory if the SD image?

I updated my firmware yesterday with the latest version, I did not update the SD Cards file, I'll look to it again this evening.

Once again thank to you all for your most apreciated input, for sure i'll be able to put it to work this evening.

Cheers to you all!!

Edited 1 time(s). Last edit at 01/14/2014 07:17AM by JVMelo.

@JVMelo

You seem to of had the same problem that I had, I assumed where the other stepper motors in the same way on the Duet board that the X stepper would be the same but this isn't the case, the X stepper motor is connected the other way round, look at the image from the building docs:


As you can see its the only one that is connected the opposite way.

So the X axis would never home, instead it moves and hits the outer edge.

Paul

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RS Ormerod No 436

I mentioned in other posts, but I'll say again for the benefit of those who have not read those threads that after I printed a new X-carriage (on which the Z axis light probe mounts) in black plastic, it unexpectedly made all the difference to the Z homing reliability - with the extruder touching the glass (Z=0) the reading is well within range, so you could even make 0 your set point (I'm using 1mm). Painting the surround to the Z probe black should have the same effect - maybe just take it off and colour the plastic surrounds with a black marker pen. I did however have to put foil on the X axis homing tab, which had not been necessary on my machine before.

One other thing I found today is that the sensor board screw holes are large enough to allow the sensor board to rotate a few degrees, so that the sensor face is not parallel to the bed. This causes a big reduction in its sensitivity.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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TMD_RS436
the X stepper motor is connected the other way round

1
Ok guys, put it to work, the X-Motor had the plug inverted! Thanks TMD_RS436!

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dmould
I printed a new X-carriage (on which the Z axis light probe mounts) in black plastic, it unexpectedly made all the difference to the Z homing reliability.

Black it's a light absorber ,so the ambient refractions around the sensor are dimmed, it makes all sense, had same problem with some optical communication, and black plastic also did the job.

Well..a very greatfull thank you to you all.

Admin....you can close now

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dc42
One other thing I found today is that the sensor board screw holes are large enough to allow the sensor board to rotate a few degrees, so that the sensor face is not parallel to the bed. This causes a big reduction in its sensitivity.

and it has caused me to scrap a 15 hrs print because the bottom corner of the z-probe pcb eventually started scrapping at the print...

Edited 1 time(s). Last edit at 01/15/2014 04:17PM by arnaud31.