(Solved) Firmware doesn't reach limit switch.

[StarShadow 0]

I installed Ultimaker2Marlin firmware on my printer. (Ultimaker 2 replica)

When I start it up, it runs the first time setup. It homes the z axis successfully and guides you through leveling the build plate. Once the leveling is done the build plate moves all the way to the bottom, but the problem is that the plate stops before it even gets to the switch and the firmware tells me that the switch is broken.

I can only assume this happens because the board incorrectly counted how high the plate was when you leveled it. The z end stop works perfectly fine but for some reason the firmware stops moving the plate before it can touch the switch and tells me it's broken.

I have tried this multiple times and I can't figure out why it's happening.

Can someone tell me if there is some other firmware I should try, or if there is something I can change in the firmware to fix this problem? Any help would be appreciated.

While I don't know how to code for Arduino I do know general code.

Looking through the configuration I see values for Z_MAX_POS and Z_MIN_POS

Would changing any of these help to solve the problem? I would think that this would tell the firmware that the z axis is actually larger and it won't stop thinking that it passed the switch.

Edited March 16, 2016 by Guest

[gr5 2,002]

Something is wrong. There are several possibilities that I can think of:

1) You have the um2go firmware on a um2. I think you can check that out in the menu where you display the version.

2) The Z motor wiring is not connected well (one wire of four is broken) - probably not as it would probably *only* go down and never up.

3) The "steps/mm" is messed up somehow. I can't remember which version of Marlin allows you to mess with this but if you never messed with it then it probably has the correct value.

4) Wrong stepper motor in the Z and it is moving at half speed (twice as many steps/mm as the normal Z motor). Or wrong z thread - seems unlikely.

5) Too hot - were you using it in a very hot room like say 90F? The stepper driver can overheat and stop stepping briefly causing the bed not to move as far as the computer thinks it moved.

[gr5 2,002]

Oh um2 replica! Well hook up pronterface and a USB cable and tell it to move 10mm and see how far it moves. I suspect you simply have the wrong steps/mm value.

[StarShadow 0]

Oh um2 replica!  Well hook up pronterface and a USB cable and tell it to move 10mm and see how far it moves.  I suspect you simply have the wrong steps/mm value.

 

I solved it, the problem was the printer didn't know that I have a slightly larger build area. So I had to increase the Z_MAX_POS variable and recompile the firmware.

[gr5 2,002]

Oh. I was wondering why you wrote "solved" in the title but didn't seem to have an answer. Now I get it.

[StarShadow 0]

Oh um2 replica!  Well hook up pronterface and a USB cable and tell it to move 10mm and see how far it moves.  I suspect you simply have the wrong steps/mm value.

 

It turns out you were right, I didn't notice while playing around with it, but once I finally finished putting it together and printed a 20x20x5mm prism, I noticed it was only half as tall as it should have been.

So I decided to actually measure it and found out that the z is off by half. If I tell the z to move 100mm it moves ~52mm

So thanks for giving me that solution early on.

I'm using the motor that came with the heated build plate upgrade, so I don't know why the ultimaker2marlin firmware would have a wrong steps/mm value as default.

Edited March 19, 2016 by Guest

[gr5 2,002]

UMO+, UMO, and UM2 have I think 3 different steps/mm. Sounds like you have UMO+ steps/mm.

[gr5 2,002]

Oh also, the Z axis on the UMO "ramps" circuit board should have the stepper jumper different than the other 3 stepper drivers. Anyway don't worry about it - just adjust steps/mm by an integral multiplier (multiply by exactly 2x).

[StarShadow 0]

Oh also, the Z axis on the UMO "ramps" circuit board should have the stepper jumper different than the other 3 stepper drivers.  Anyway don't worry about it - just adjust steps/mm by an integral multiplier (multiply by exactly 2x).

 

I used a very precise measuring tool to measure how far the plate was moving. Based on that, I calculated what the steps/unit should be and now it's as close as I can get it.

I found that the most accurate steps/unit was 402.42

[gr5 2,002]

I recommend 400 but 402 should be fine.

[StarShadow 0]

I recommend 400 but 402 should be fine.

 

Multiplying it by 2 was the first thing that I did.

But when I used a precise tool to measure, I found that it was actually moving something like 9.6xxxxx instead of 10mm. So that's how I calculated the new steps/unit value that made it accurate to 0.001mm