Nozzle hitting bed when z probing

Ahoy!

Whenever I do Z probing, it has to get so close to the bed that the nozzle will actually hit it. I can do probing along the outside edge of the bed, but I have to go all the way out to X230 (>=228). When using reasonable threshold values, it stops at about Z -1.2, so I basically just set the "height" of the probe to a negative value (default = +1.8), thus:

G31 Z-1.2 P500

I tried lowering the threshold value to get it to trigger higher up, but I have to go as low as ~200 to have it trigger before the nozzle hits, and at those values it gets very unreliable (+/- 0.3mm or so, which makes it pretty useless). Tried putting white stuff on top of the Kapton tape instead of under to get some more reflectivity, didn't change things noticeably. I'm pretty certain the probe is mounted "as intended" with the two screws, looks just like in the pictures.

With some trial and error and trickery, I can at least reliably use it for Z homing, but obviously not for bed level compensation. I just do that manually, but that has to be re-done pretty often, and I want to have a couple different bed plates to switch between (that likely wouldn't be completely identical).

So, is my Z probe "nearsighted" or something (having to get 3mm closer than intended to the bed)? Do others actually trigger at 1.8mm as per the default value? I see a lot of threads for replacing/hacking the IR probe with something better (or it might help just moving it down about 3mm), is that what it takes to be able to do automatic bed level compensation?

How high is the face of the IR sensor above the bottom of the nozzle? It should be 1 to 2mm. If it is higher, check that the print head is level in the Y direction (a sagging print head is a common problem), and that the nozzle is screwed far enough into the heatsink block.

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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].

Well, problem very likely solved. TL;DR: the "nozzle mount" (the part between the x carriage and the hotend assembly) was upside down.

The z-probe triggers when it is about 2mm above the bed (as best as I can tell, it's hard to get in there and properly measure) just as it is supposed to, but at which height the nozzle and fan duct were well below the print surface. I took the hotend off just to see if something was off, and realized I had mounted the nozzle mount upside down. It still held the hotend assembly, but a couple millimeters down, and I guess not quite as snugly. I'm just reassembling it things and haven't run it yet, but now when I move the Z axis so the nozzle just touches the bed, the sensor is about 1mm over it.

Not related to the topic, so apologies, but Firefox (V28.0) consistently crashes if I click the "nozzle mount" in jstck link in above post!

Just interested if anyone else see's this?

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Ormerod #007 (shaken but not stirred!)

Quote
Treth
Not related to the topic, so apologies, but Firefox (V28.0) consistently crashes if I click the "nozzle mount" in jstck link in above post!

Just interested if anyone else see's this?

Yes same here, Opera 12.16 no problem

Erik

I would guess that is due to the STL 3D viewer thingy (I think it's done in JavaScript) on the target page.

Hi guys another nozzle bed crasher.
As Ian (tech support RepRap) is aware my duet (No. 384) blew up. Ian was hopeful that the Z sensor was serviceable, hmm it may be.
I have set the Z height using a piece of printer paper (0.1mm 0.004") getting the same resonance as already described. Set and confirm this G92 Z0. Get pos. all good.
Everything on the printer works. So I am assuming that the firmware/software is good. I did have a problem where Pronterface kept telling me that access was denied. Turns out that you should shut the arduino or other software before you open Pronterface , no problems after that.
So the next thing is bed plane compensation. I followed the first set up and made the necessary config changes and added bedset.g to simplify the future. So print bedset, home all axis nozzle crashes the glass. Get pos to show Z axis z shows 1.4. G92 Z0 get pos Z shows 1.4. So I moved the x and y about a bit and homed z again several times getting various numbers but no zero. Ahh I thought try G31 and see what numbers show. The output varied by about 30 over about 20 tries without moving any axis. Just to be sure interference was not playing a part I pulled the curtains shut, turned the lights out and angled the monitor away from the printer.
Now I know I am new to this but if there is no consistency in the z height any attempt at printing will fail as the nozzle may set itself too high or low on the first layer, with the attendant problems, and on subsequent layers too high will lead to poor finish and too low will mean the nozzle crushing the print. After all this the z sensor does not seem to have a problem zeroing the x axis.
I will email Ian to see how much a new Z sensor is and give it another go but if that fails it looks like a £600 door stop that will have to go back to RS.
Any help would be appreciated.
Lesli

Hi Lesli,

I'd love to suggest that you buy one of my modulated sensor boards. But if your sensor is giving very low readings with the sensor far above the bed and the lights off, and increasing readings as you lower the print head, then it is working and you don't need a new sensor. So here are some suggestions:

1. Are you still using aluminium tape on the corners of the bed? If so, get rid of it and use white PVC tape or white paper instead. The aluminium tape gives readings that vary a lot with tiny XY movements.

2. Have you set the 4 bed compensation points such that they place the sensor head (not the nozzle) in the middle of the white squares [EDIT] and well away from the bed clips?

3. Have you edited homez.g and homeall.g on the SD card to make the z-homing point the same as the first bed compensation point?

Edited 1 time(s). Last edit at 04/05/2014 06:14AM by dc42.

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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].

Hi dc42
Thanks for your quick reply
For your number 1
I found that if I set the z height as per the instruction, over the white square, every time I moved away from the white square the nozzle would settle lower, presumably trying to attain the same numbers, and crash the glass. A work around for that was to tell the printer the z axis was in a different position and then it would work. That's a white square not ally tape.
For your number two
I did try following that and the first print took nearly all the kapton tape off the glass. Not good.
For your number 3
This I have not tried but I will this afternoon and let you know the results
Thanks again for your help

Lesli

Quote
Boxgame
... and added bedset.g to simplify the future. So print bedset, home all axis nozzle crashes the glass.

If this is not a spelling mistake but the name you gave the file this could be a part of your problem as the correct name is setbed.g

Erik

Hi ya Ormerod168
Thanks for that
Yes my mail had a trypo in it. Dyslexic fingers
Lesli

Hi again
Just a thought
As the setbed/bedset is just a file for printing you could call it xyzleveller and then print that. Surely it's the content that is important.
Lesli

Quote
Boxgame
Hi again
Just a thought
As the setbed/bedset is just a file for printing you could call it xyzleveller and then print that. Surely it's the content that is important.
Lesli

Yes, but my point was that if you forgot you called your dog Butch and you yell out "kittycat" it surely won't come (lolz!)

Erik

Lesli, one other question: what firmware version are you using? Some of my older firmware versions didn't do bed levelling properly. My more recent versions do (latest is 0.57y-dc42), and RapRapPro's 0.57a should be OK too.

I recommend that to test bed levelling, you do the following:

1. Run setbed.g (or whatever else you have called it).

2. Raise the nozzle to 5mm and print circle.g. It should draw a circle 5mm above the bed, and you should see small movements of the Z axis to correct for the bed not being quite level.

3. If that looks good, drop the nozzle to 1mm and repeat. If that looks good, try 0.2mm and you should see the nozzle just skimming the bed.

Only do a real print after bed levelling when you are satisfied that the bed levelling is working properly

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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].

Hi again Ormerod168
I take your point but as you have to access the sd card to "run" the bedset??? file, however you spelt it a click is what chooses it. I suppose if I clicked snowman expecting it to do the bed compensation then I really would be in trouble.
Have a great afternoon

Lesli

Hi there dc42
I am using the RepRapPro 0.57a. Do you think yours would be better? If it would be where would I get it?
I have followed it all again and the closest I can get the bed levelling to is 0.2mm 0.008".
Is seems as though the wooden base on the Ormerod is moving under the heat. This puts different loads on the screws and this does not help.
I have just printed of the snowman with no strings etc but the extruded temp was down at 193 C after a gcode edit. Seems a lot different to what I have read about. The bed temp was 65C to start with but I edited the gcode and brought it down to 60C after 3 layers.
Thanks for the help you have all given this afternoon.

I hope this keeps up the "good" work

Lesli

Quote
Boxgame
I am using the RepRapPro 0.57a. Do you think yours would be better? If it would be where would I get it?

Without dc42's firmware I would have send the ormerod back in a box many moons ago..

dc42 latest firmware, chose "raw", download

[github.com]

From the documentation:

Leave the main power to your RepRap off, and connect the Duet to your computer with a USB cable. Make sure that the Arduino IDE Serial Monitor or Pronterface are NOT connected to the Duet board.

Press the ERASE button on the Duet. Then press the RESET button.

Wait at least 10 seconds for the Duet board to start up.

Find out which USB port on your computer the Duet has been allocated

You will find bossac.exe in your Arduino IDE 1.5.5\hardware\tools folder
when you run bossac it needs the firmware file in the same folder

insert you COM number to the string and copy to memory, open command prompt in the same folder, right click insert string, pres enter

bossac --port=COM[?] -U true -e -w -v -b RepRapFirmware-057y-dc42.bin -R

Edit: notice you COM number will probably change after erase, as in not being the same COM port you normally use to connect with pronterface

Quote

I have followed it all again and the closest I can get the bed levelling to is 0.2mm 0.008".
Is seems as though the wooden base on the Ormerod is moving under the heat. This puts different loads on the screws and this does not help.

Yes the MDF bed is not stable, this is what I did, you only have to drill one hole:

Sagging MDF, the Q & D fix that anyone can do
[forums.reprap.org]

..or you could buy a new aluminium one from Edit: Dave

Erik

Edited 2 time(s). Last edit at 04/06/2014 10:10AM by ormerod168.

Quote
Boxgame
Hi there dc42
I am using the RepRapPro 0.57a. Do you think yours would be better? If it would be where would I get it?
I have followed it all again and the closest I can get the bed levelling to is 0.2mm 0.008".
Is seems as though the wooden base on the Ormerod is moving under the heat. This puts different loads on the screws and this does not help.
I have just printed of the snowman with no strings etc but the extruded temp was down at 193 C after a gcode edit. Seems a lot different to what I have read about. The bed temp was 65C to start with but I edited the gcode and brought it down to 60C after 3 layers.
Thanks for the help you have all given this afternoon.

I hope this keeps up the "good" work

Lesli

If you still have the wood bed support, it will be a nightmare, can I suggest one of my laser cut bed support kits, they have been well received by all so far

Totally transforms the Ormerod.

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Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

Hi Boxgame,

Yes the mdf bed support does move with the heat. Best to reinforce it or replace it with aluminium as others have suggested. Meanwhile, heat the bed to operating temperature before you run bed compensation.

Bed temperature is not too critical unless the print is not sticking to the bed. Head temperature of 193C is about right. I use 195C for the first layer and 190C for the rest. The original setting of 205C was for older firmware which had the wrong thermistor parameters.

Edited 1 time(s). Last edit at 04/06/2014 06:12AM by dc42.

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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].

Hi Ormerod168
Thanks for that I will give the firmware a go later.
After the printer worked reasonably fine until I went to bed I was surprised this morning to find that the bed had risen by 0.9mm. Not good.
I will look for an aluminium plate to mount onto the MDF.


Talk soon

Quote
Boxgame
Hi Ormerod168
Thanks for that I will give the firmware a go later.
After the printer worked reasonably fine until I went to bed I was surprised this morning to find that the bed had risen by 0.9mm. Not good.
I will look for an aluminium plate to mount onto the MDF.


Talk soon

You need to get rid of the mdf altogether, the two bed ribs are ok but the mdf support plate is worthless, it moves with temperature, humidity, whenever it feels like it

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

Hi Dave
Do you have a price for this bit of plate?
When fitted will I need longer screws and some springs?

Lesli

Hi

The plate is £15 plus p&p which is £3 for the uk.

It comes with three screws and three nuts, no springs are needed.

It's a straight swap from the wood item.

Let me know if you would like one.

Dave

---

Another RS Ormerod Mk1 meets the world

Retired now but I used to make....
CNC Machined Mk1 aluminium bed support plates for the Ormerod
CNC machined X-plates and ribs for Mk1 & Mk2 Ormerods
CNC machined bed support arms for the Mk2 Ormerod.
Dual Hot-End heatsink blocks.

Quote
ormerod168

Quote
Boxgame
... and added bedset.g to simplify the future. So print bedset, home all axis nozzle crashes the glass.

If this is not a spelling mistake but the name you gave the file this could be a part of your problem as the correct name is setbed.g

Erik

That's interesting Erik..... I didn't realise the Firmware read a Bed setting file from the SD card....
I don't use compensation any more... My bed is level, and I ditched the setbed.g file weeks ago to make room for other stuff,
but when I did use it, I thought I had to Print it, to take in the readings....
Interesting...

Kim..

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Please send me a PM if you have suggestions, or problems with Big Blue 360.
I won't see comments in threads, as I move around to much.
Working Link to Big Blue 360 Complete

You do need to 'print' the bed setting file to use it, and you can call it anything you like. Mine preheats the bed and homes the axes as well as running G32.

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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].

Since we're on the subject of bed compensation, where is really the best place to set it (assuming I want to do manual compensation with values I measured myself)? If I have it in homez/homeall, I have to get the SD card and update the files every time I change it. If I have it in sedbed.g, I'll forget to apply it half the times I'm starting a print. And if I put it in the "custom g-code" in slic3r, I have to update all gcode files if I change it.

I assume something along the lines of "M23 setbed.gM24" wouldn't work too well in the header of a print or any of the homing files, since that would just interrupt whatever file you're currently printing.

To me, it seems a neat solution would be if there was a "G28 B" command (or maybe "E", since by some stretching of terms you can call it "homing the extruder axis"). Just as G28 reads and "prints" the various homing files, it would run setbed.g, and I could just include that command in the custom G-code for each file I print (or possibly homez/homeall).

Afternoon Dave
It sounds like the plate is a good idea and I would like one.
How do we go about it?

Lesli

Quote
jstck
Since we're on the subject of bed compensation, where is really the best place to set it (assuming I want to do manual compensation with values I measured myself)? If I have it in homez/homeall, I have to get the SD card and update the files every time I change it. If I have it in sedbed.g, I'll forget to apply it half the times I'm starting a print. And if I put it in the "custom g-code" in slic3r, I have to update all gcode files if I change it.

I assume something along the lines of "M23 setbed.gM24" wouldn't work too well in the header of a print or any of the homing files, since that would just interrupt whatever file you're currently printing.

You could try putting:

M98 Psetbed.g

in the custom gcode, after homing the axes (or home the axes first in setbed.g, which is what I do).

EDIT: corrected the M98 command

Edited 2 time(s). Last edit at 04/07/2014 01:05PM by dc42.

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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].

With the MDF bed I found there was no point in having a fixed setbed.g file - I had to measure the 4 points before every print as they changed so much. I did have a "setbed.g" file, but kept it on my PC rather than the SD card, and edited it with the measured values before every print, and then sent it via Pronterface. Since replacing the MDF with the triangular aluminium frame I no longer have any need to do bed compensation - the bed is adjusted to be as level as possible and it stays there (it's not exactly level because the glass is domed, but good enough). This also saves a lot of wear & tear on the Z lead screw and nut, which now only moves to change levels.

Dave
(#106)

Quote
dc42

Quote
jstck
Since we're on the subject of bed compensation, where is really the best place to set it (assuming I want to do manual compensation with values I measured myself)? If I have it in homez/homeall, I have to get the SD card and update the files every time I change it. If I have it in sedbed.g, I'll forget to apply it half the times I'm starting a print. And if I put it in the "custom g-code" in slic3r, I have to update all gcode files if I change it.

I assume something along the lines of "M23 setbed.gM24" wouldn't work too well in the header of a print or any of the homing files, since that would just interrupt whatever file you're currently printing.

You could try putting:

M98 Psetbed.g

in the custom gcode, after homing the axes (or home the axes first in setbed.g, which is what I do).

EDIT: corrected the M98 command

Ooh, sweet. That M98 command should do pretty much exactly what I want. Thanks, will try it out.

Edit: Seems that while the firmware parses the M98 command, it doesn't actually do anything with it. I'll take that as a "to be implemented"...

Edited 1 time(s). Last edit at 04/08/2014 05:51PM by jstck.