[BobF]

My machine looses steps. When it does the motor makes a strange noise, almost a grinding sound. It doesn't happen all the time and it seems to be mostly the Z axis althouh sometimes X does it also.
I am using a hobbyCNC kit with the 305 ounce motors. I have it set for 1/4 steps. I have tried lots of motor tuning changes - mostly acceleration, and reduced the speed.
What might this be?

[ger21]

Cut your acceleration in half and see if it makes a difference. Also try 1/8 steps. If it's resonance, 1/8 steps might help. Otherwise, you might just be pushing the motors too hard. What voltage supply are you using?

[BobF]

I am using the supply recommended in the instructions. The transformer is 24 volts AC which is about 35 volts DC and 10 amp.
I have dropped the acceleration down several times and that did not seem to help much, if any.
The only time this seems to happen is when you start a move. If I am jogging, I just stop and restart and normally its fine the next time. Once the motor is running, there is no issue. I thought acceleration was the problem, but I have reduced it to very small amounts and that doesn't seem to stop the problem or even really reduce it.
I will try 1/8 steps and see if that helps.
Could the idle current reduction have anything to do with this?

[pminmo]

Yes it's feasable that idle current reduction could be the culpret if it's "automatic". Easiest test is to disable it and see if it makes a difference.

[Toymanf]

If you are a member of the hobbycnc yahoo group, then you can perform a search there. Search for "Delay"

I will tell you that the actual problem seems to be the transition from synchronous to asynchronous mode. If you change to 1/2 step mode the problem virtually disappears. Looking at the data sheets for the chip revealed a warning that the use of syncrhronous mode(which is tied directly to the idle reduction timer on the hobbycncpro board) is only recommended during 1/2 stepping timing conditions. This info was only on ONE of the three data sheets I have seen.

The Hobbycncpro board still switches between asynch and synch modes, even with the idle current reduction diabled, due to the board layout.

In my application, the board works great as a 1/2 step controller. Any other mode is unusable due to the delay and resulting lost steps when switching modes.

If you can live with 1/2 step mode, give it a try. It is much better. The underlying problem of a slow transition time is still there, but in the 1/2
step mode, it only shows up with a very slow feedrate such as .5 ipm.

Thats my 2(and a 1/2)cents
Frank

[BobF]

OK,
I reset my controller to 1/2 steps and turned off idle current reduction.
So far so good. I have not had the problem recur since.