Uploading DELTA_RADIUS has no effect.

[Hans2]

I am calibrating my new Prusa Delta Rostock 3D Printer G2s and everything seems to be going ok up to the point that I have to change and upload DELTA_RADIUS in the firmware. I now do have a convex surface on my Z plane. If my printhead is in the middle, it is 1.39mm lower than when the printhead is at one of the three other points which I have calibrated. According to the manual I have to reduce the DELTA_RADIUS value to compensate for this difference, which I did in the configuration.h file. Uploading the firmware seems to be going fine (I do get the message 'Done uploading') But I don't see any difference in the behaviour of the printer. The Z plane stays convex, no matter which value for DELTA_RADIUS I write in the firmware. What am I doing wrong?

[Mark]

have you leveled the heatbed first?

[Hans2]

Yes, I have levelled the heatbed. Firstly with a caliper to make sure the distance between the heatbed and the acryl base beneath it is the same near the three screws. And then as described in the manual by sending the printhead to three places close to the towers and making the distance to the heatbed the same by setting the screws which control the upper limit switches..

[Mark]

Well it doesn't make sense.....did the bed itself bending or not?

[Hans2]

The bed is flat and looking good. It has never been in any kind of mechanical stress.

[Mark]

well ...can't figure out what the problem is...

[Hans2]

Found the problem. The USB cable I was using for programming was too long. Sometimes programming seemed to be okay according to Arduino 1.0.5, sometimes programming failed due to time-out. After changing the cable with a short cable, uploading always went ok and printer was reacting upon it. Now DELTA_RADIUS is set to -8 and my Z plane is flat. Up to the next part now.

[Mark]

you mean the original USB cable is too long and caused that problem? maybe is just the USB cable's problem, not the length?

[Hans2]

No, I was using a longer high-speed cable which caused the problem. Now I am using the cable which was delivered with the machine and uploading is going fine. I have also printed my first objects which does not go well enough. I need some more calibration.

[Mark]

Always use the original one.