How I solved MY missing steps problem.

[davegrennan]

Since I completed my second build, I was finding that I had quite a problem with missing steps. The usual solution of reducing speed and acceleration helped some but it did not solve the problem. I found that machine runs with curves made it worse. i.e. if the x and y axes were both working at the same time the problem was visible. It resulted typically in a position shift of about 1mm in x and 0.5mm in y over a 20 minute run. Enough to make any machine pretty useless. It got worse on longer runs. This made me suspect that there was noise or emf getting into the system. Then came a bit of an embarassing moment. When I built the second machine I reused the wiring loom from the first machine which was unshielded. I had intended to swap it out but simply forgot to. Anyway after a days hard work the entire wiring was swapped out with shielded cable. All of the shields connected back to a single earth which went nowhere else but the mains earth. I also covered my BoB housing with aluminium tape and earthed this too. I just ran a 1.5hr job hit the goto zero button and it returned precisely to where it started. Proper sorted!! Another thing I noticed is that my spindle rpm which used to wander up and down by a few hundred rpm now only varies by < 5 rpm.

Just thought I'd post this in case anyone else is puzzling over a similar problem. Electrical noise is your enemy and shielding is your friend.

Regards,

Dave.