Hi,

I am using Flash to control the Egg-bot via tinkerproxy2.0.

I am using this method to send commands like "SM,100,10,10<CR>" to the board.

I only send pun up and down and sm comands like the one above to move the motors.

I use inkspace before I start using flash to calibrate the pen's servo motor.

This works very well with a couple exceptions. Most times moving the egg motor 3200 steps does not rotate the egg a full revolution. Typically it is about about 1/16th of an inch shy of a full rotation, and is very consistent, but sometimes the accuracy can change and vary by as much as 1/18 of an inch (so I can't just consistently add some steps and get a full rotation consistently.

Is there anything obvious that might change the accuracy of a full rotation? Perhaps something I need to do to calibrate the voltage or other detail for the board to communicate with the motors?

I am using Flash to control the Egg-bot via tinkerproxy2.0.
I am using this method to send commands like "SM,100,10,10<CR>" to the board.
I only send pun up and down and sm comands like the one above to move the motors.
I use inkspace before I start using flash to calibrate the pen's servo motor.

Pun up? Inkspace? I'll guess that you mean pen up and Inkscape.

This works very well with a couple exceptions. Most times moving the egg motor 3200 steps does not rotate the egg a full revolution. Typically it is about about 1/16th of an inch shy of a full rotation, and is very consistent, but sometimes the accuracy can change and vary by as much as 1/18 of an inch (so I can't just consistently add some steps and get a full rotation consistently.

Sounds like you don't have good coupling-- a solid connection --between the egg and the egg motor. When the egg is fully seated, it should have almost no "play" with respect to the egg axis. Read through the instructions at http://wiki.evilmadscience.com/Improving_precision

Is there anything obvious that might change the accuracy of a full rotation? Perhaps something I need to do to calibrate the voltage or other detail for the board to communicate with the motors?

There is a tiny "knob" to adjust the motor current on the board, but it doesn't sound like that's the issue here-- just mechanical coupling.

Thanks. I'll definitely give that another read.

If I try to manually turn the egg, there is no play. And each time I draw a line 3200 steps long, it consistently comes up short by the same amount. The amount only changes infrequently, and then it is consistently short by that amount. It seems to me like either the speed at which I am sending it commands, or the periodic return to Inkscape to turn the motors off is effecting the accuracy of the steppers.

Do you think the knob you refer to could be used to calibrate the steps? Is there more I could read about the situations when adjusting that knob is typically needed?

This still really sounds like slippage. Having consistent slippage is quite normal in my experience. If you want to demonstrate to yourself whether or not the difficultly lies with the software interface, make an inscape drawing of a some concentric circles, print it on paper, cut it out, and fix it to the egg motor drive cup. Draw a reference tick mark at an edge of this paper circle. Then stand your Eggbot up on its headstock, place something fixed nearby with a mark lined up with the paper circle's reference tick mark. Then, tell the egg motor to turn 3200 steps.

A number of us in the past have done this experiment when we were unwilling to believe that mechanical slippage of some sort was occurring. In my case, I was nagged that something was wrong in the software -- most likely a bug on my part. I did this experiment and others. Seeing was believing: the circle always turned a nice 360 degrees, always returning right back to where it started.

Dan

Quote by: dnewman

Having consistent slippage is quite normal in my experience.

Mind you, with care you can reduce the slippage until it is very minor. My point was that when I am having mechanical slippage, it's not at all unusual for it to be very consistent.

Dan

ok. thanks. I'm starting to believe this crazy slippage theory

Thanks for helping.