teacup firmware steps per meter problem

Hi, I've got a bit of an issue. The calculations I have done myself and the ones I have used off of [calculator.josefprusa.cz] both equal the same but when I put them in teacup firmware and upload the distances aren't what they should be.

I am also using Pronterface's directional buttons.

So I have 1.8degree nema17's, 14 tooth gt2 pulley (2mm pitch gt2 belt), 1/16th microstepping on x and y, 1/8th on z. M8x1.25mm thread on Z.

For the Z axis the website gave me 1280 steps/mm, times 1000 to get steps/m for teacup = 1280000. This caused the motors to just squeal and not move. After adjusting the put I got them to move with many missed steps but they were going way to far for the amount I issued. I tried changing it to 128000 and it was a lot closer. Using dial calipers and a calculator I managed to get it almost spot on at 162368. Is it often the case it has to be tuned this way? I thought the math being over 26.8% out was a little weird.....

For the Y and X I calculated 114285 to be the number of steps / meter. What is strange is the X axis looks pretty correct (havent measured it) but the Y is completely out, looks to be over 5x out. Only needs 30mm on pronterface to move the entire range...

I'm not great with programming or scripts etc, I do have a little experience. But this is confusing me. Why is Y moving so much more than X with the same gearing/motor/microstepping/settings?

Thanks,

I had a thought that is might be the stepsticks... So I swapped X and Y's stepsticks around and all of a sudden X moved like crazy and Y moved tiny. Looks like the step stick I have in Y and Z are both screwed some how..?

Might need this topic moved to electronics section...

A bit more testing and found that two work correctly and the other two don't seem to micro step. All tested in the X axis port, so it isn't the Gen7 1.3 board it is the StepSticks.

Quote

Is it often the case it has to be tuned this way?

Yes for belt driven axes (within a few %), no for rod driven axes. You have to get rid of missed steps entirely. If they appear, they appear in unpredictable ways.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Sounds to me like your step stick current limits are not set correctly.

You need to trim the little pot on them so that you have enough current to prevent missed steps but not so much current that you overheat the drivers and they shutdown (which also causes missed steps!). On my machine it was quite a small window in which they would operate, I basically wound the current right down then told the axis to move a large amount. Then turn the pot up until the axis is moving smoothly, plus a little extra as a safety margin.

There are probably some better ways to trim this such as using an oscilloscope or possibly by calculation - perhaps others can advise on this?

I have also found that little heatsinks on the step stick driver chips plus a 40mm fan blowing over the top of them helps a lot. Basically this increases the upper current limit before overheating so you have a larger window in which they will operate correctly.