FSR / Proximity / Z probe or..........

Good day all

Did my 1st few prints on my Kossel mini clone and it almost print better than my top notch Prusa I3 with almost twice the speed.
The prints really came out great - CALIBRATION WAS A PAIN - I only did firmware changes (Delta arm mm etc) and played around with the mechanical endstops set screws on top of each arm. Did not play around with eeprom, m666 and and...
After a print I must re-set one of the endstops, because the nozzle are a paper thickness too low or high on 1 of the towers. Then I can print again and after that I must play around with the same or another endstop again to get my nozzle a paper thickness from the glass.

So now I want to go the auto Z calibration way, but don`t know which way. I have a Ramps 1.4 board installed with Marlin 1.02. Can you guys maybe send me in the correct direction. I have read about FSR sensors, Proximity sensors and z probing. I`m leaning towards the fsr sensors, but don`t have any knowledge on any auto z leveling to compare with. I don`t mind playing around with firmware, but don`t want to struggle days on end to calibrate z height.

If you have a suggestion please add a link of the neccessary equipment needed.

Thanks guys

If your delta is calibrated accurately, then you probably only need to set the nozzle height at the centre of the bed before each print. Here's how to do it without a Z-probe:

1. Make sure you do not have any G28 homing commands in the start gcode of your slicer program.

2. Make sure the axes are homed.

3. Heat the nozzle and bed to operating temperature. Send the nozzle to X=0 Y=0 Z=0.5mm. Place a piece of ordinary 80gsm paper on the bed under the nozzle.

4. Lower the nozzle in increments of 0.05mm until it grips the paper but you can still slide the paper around. Then send G92 Z0 to the printer, to define that point as Z=0.

5. Command the nozzle up a few mm, remove the paper, and print.

I currently use a mechanical (microswitch) Z probe on my Kossel, which I will soon be replacing with a differential IR probe, and after that I have another type of height sensor I want to try. I haven't tried FSRs yet, but I have seen good reports of them.

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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].

I have FSR's on my Rostock Mini which I like. Kits are available from TriDPrinting or Utlibots in the $30-$40 range, or you can just buy a trinket and a few sensors from somewhere like Adafruit.

However, is it always the same tower that needs adjusting? I am wondering if the screw is loose and moving during the print. Perhaps try a little locktite first?

No it`s most of the times a different axis or at g x0 y0 z0. But it`s minimal - Normally before I print I check my level. I home, then g x0 y0 z1 and move z slowly down to 0 with the paper test. I home and do the same for xyz towers and sometimes one of the towers or middle will be a paper thickness too high or too low after a 3-4 hour print. If this happens, I must re-upload my firmware with the corrected build height(If the problem is in the middle) or I must re-set that specific tower endstop switch a tiny tiny bit. This is really a pain - And I know I can do it more efficient with g or m codes, but I don`t know all the tricks of the trade. But when it eventually prints, I cannot ask for better quality.
Maybe someone can give me some shortcuts

Edited 1 time(s). Last edit at 04/17/2015 04:32PM by Bking1340.

Try sending M666, and with any luck it will report the existing endstop offsets. Then you can send it an M666 command with X, Y and Z parameters specifying the new endstop offsets you want. If the centre height is out, you can either adjust this using the M666 or M665 command (depending on the firmware), or use the G92 trick I described earlier.

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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].

Thanks dc, think this will make life easier till I can play around with some fsr sensors. I have some small savox digital servo`s laying around, maybe I must try a z probe move aswell.