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Topic: Calibrating towers to the build plate (Read 5568 times) previous topic - next topic

Calibrating towers to the build plate
Disclaimer: I haven't been able to test this. This is based off of reading about calibration on other delta printers. Give it a go and let us know how it works for you. I'll be able to try it myself this weekend.

So it's important that each tower is calibrated to the build plate surface to assure proper and level printing.
Here is some gcode you can use to move the print head to 4 points (in front of each tower & center) to test if your towers are calbrated correctly.

Easiest way to test that the height is correct is to use a piece of paper and slide it under the nozzle when z=0.
You should be able to feel light drag from the nozzle but the paper should still be able to slide easily under.
If it pins the paper down or if it doesn't touch the paper, you'll need to adjust accordingly.

LocationG-Code (script)
Tower Ag28 g0 f800 x-43.30 y-25 z0
Tower Bg28 g0 f800 x43.30 y-25 z0
Tower Cg28 g0 f800 x0 y50 z0
Centerg28 g0 f800 x0 y0 z0

What does this gcode do? Well lets break it down...
  • g28 homes the printer carriage.
  • g0 is a move to an absolute location.
  • f500 controls the speed of the move. See note below.
  • x, y, and z are followed by the corresponding cartesian coordinates.  The x and y coordinates should be points directly in front of each of the three towers.

So calibrate Tower A until the paper slides between the nozzle and print surface with only light drag. Test a couple times and adjust as needed. Then move on to Tower B and repeat those same steps before finally doing Tower C. Once all three towers have been calibrated, do the same test at the center (0,0). You should be able to now test any of those four locations and have it pass the paper test.  8)

(NOTES: While the 101hero glass plate itself has a diameter of 150mm, My math is based off of using a setting of 50mm as my build radius.
Travel rate is set to 500mm/min, though theoretically it could be higher (upper limit should be: 14mm/s * 60 = 840mm/min). But for now, slower is safer.)
  • Last Edit: 31 Dec, 2016, 00:52:45 AM by DigitalWhitewater

Re: Calibrating towers to the build plate
Reply #1
S3D needs the gcode separated and in uppercase to work. I tested the speeds, and 700 seems to be fast enough and still safe:

Tower A
G28
G0 F700 X-43 Y-25 Z0

Tower B
G28
G0 F700 X43 Y-25 Z0

Tower C
G28
G0 F700 X0 Y50 Z0


Center
G28
G0 F700 X0 Y0 Z0

Re: Calibrating towers to the build plate
Reply #2
I mapped each to a button on repetier. Used the 800 speed with no problems. Going from the value (14mm/s) in cura, I think any f value under 840 is safe.

Re: Calibrating towers to the build plate
Reply #3
Maybe I just have too fat of hands for this hobby, but those little screws are a pain in the ass to access.

Re: Calibrating towers to the build plate
Reply #4
I did the levelling, buit I think now the distance is too big for the first layer. the head should really touch the paper properly, so that it's just barely skimming over the build plate without touching it, otherwise the adhesion is messed up.

Re: Calibrating towers to the build plate
Reply #5
Thanks for the info/update!

Re: Calibrating towers to the build plate
Reply #6
It seems that others have this issue too, i.e. when calibrating at the coordinates you provided (diameter 100mm) then you get too much lift-off in the center. Maybe we should calibrate with a diameter of 80mm and stick to smaller prints.....

i.e. something like:

Tower A
G28
G0 F800 X-34 Y-20 Z0

Tower B
G28
G0 F800 X34 Y-20 Z0

Tower C
G28
G0 F800 X0 Y40 Z0


Center
G28
G0 F800 X0 Y0 Z0
  • Last Edit: 09 Jan, 2017, 20:46:33 PM by brandstaetter

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Re: Calibrating towers to the build plate
Reply #7
The lift off would be down to the cooling process more so then anything else. If there was a way to get directed air to the part that's just been printed so that the part was cooling is a more uniform way, it would probably take away a lot of the lifting issues. PLA contracts as it cools which is going to cause stress and bowing at the best of times.

I think most people are still using fans mounted at the edge of the printer. This means that there is possibly going to be areas of still air where the flows meet and compete.

My fluid mechanics is quite rusty (18 yrs of rust ::) ) but I'm nearly sure that there is a high probability of dead air in the print area.

(Please note the word rusty, it really has been a long time  ;) )
  • Last Edit: 09 Jan, 2017, 20:58:05 PM by Admin

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Re: Calibrating towers to the build plate
Reply #8
@brandstaetter If you make the z axis longer in cura, would that allow the head to come lower?
That should make the printer use more steps to get to 0,0?

Re: Calibrating towers to the build plate
Reply #9
The lift off would be down to the cooling process more so then anything else. If there was a way to get directed air to the part that's just been printed so that the part was cooling is a more uniform way, it would probably take away a lot of the lifting issues. PLA contracts as it cools which is going to cause stress and bowing at the best of times.

I think most people are still using fans mounted at the edge of the printer. This means that there is possibly going to be areas of still air where the flows meet and compete.

My fluid mechanics is quite rusty (18 yrs of rust ::) ) but I'm nearly sure that there is a high probability of dead air in the print area.

(Please note the word rusty, it really has been a long time  ;) )

I'm not talking about the print lifting off the plate, I'm talking about the nozzle not keeping the same distance over the plate, although it's calibrated to be exact near the 3 pylons, it has a bigger gap over the center. It moves in a slight arc with the high-point above 0/0/0.

Re: Calibrating towers to the build plate
Reply #10
@brandstaetter If you make the z axis longer in cura, would that allow the head to come lower?
That should make the printer use more steps to get to 0,0?
how would I do that?

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Re: Calibrating towers to the build plate
Reply #11
The lift off would be down to the cooling process more so then anything else. If there was a way to get directed air to the part that's just been printed so that the part was cooling is a more uniform way, it would probably take away a lot of the lifting issues. PLA contracts as it cools which is going to cause stress and bowing at the best of times.

I think most people are still using fans mounted at the edge of the printer. This means that there is possibly going to be areas of still air where the flows meet and compete.

My fluid mechanics is quite rusty (18 yrs of rust ::) ) but I'm nearly sure that there is a high probability of dead air in the print area.

(Please note the word rusty, it really has been a long time  ;) )

I'm not talking about the print lifting off the plate, I'm talking about the nozzle not keeping the same distance over the plate, although it's calibrated to be exact near the 3 pylons, it has a bigger gap over the center. It moves in a slight arc with the high-point above 0/0/0.

I understand you now, that's a bit of an issue all right.

 
@brandstaetter If you make the z axis longer in cura, would that allow the head to come lower?
That should make the printer use more steps to get to 0,0?
how would I do that?

As far as I know, the set up in cura where you set the dimensions x,y,z for the build plate.

Since we are able to set the with and length accurately,  would changing the z axis set the steps to lower the head further.

Re: Calibrating towers to the build plate
Reply #12

 
@brandstaetter If you make the z axis longer in cura, would that allow the head to come lower?
That should make the printer use more steps to get to 0,0?
how would I do that?

As far as I know, the set up in cura where you set the dimensions x,y,z for the build plate.

Since we are able to set the with and length accurately,  would changing the z axis set the steps to lower the head further.

No, that won't work. you could tell the motor to go to a coordinate above 150 or whatever the zmax is, but it will be ignored by the firmware. same as telling it to go below 0. The dimensions are hardcoded in the firmware...

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Re: Calibrating towers to the build plate
Reply #13
Ok. Wasn't sure how much was hard coded on the board.

Re: Calibrating towers to the build plate
Reply #14
I think you can work around the hardcoded limits with relative movement instructions though...