MAXNC 10 controlled by Mach3: Two problems

[MachFlowMike]

As I mentioned in my previous post, I'm new to the whole process (CNC machines, g-code, and posting on this forum) so if this thread should be somewhere else, feel free to move it, or ask me to repost.

I recently got my MAXNC 10 up and running using Mach3 software (full version). I have two problems. First off, when I'm jogging (even sometimes when I'm machining) and I try to move a long distance (more than an inch or so), the machine will initially start to move, but will come to an abrupt halt. When it does this, the machine will be emitting a sort of humming-ringing sound, like it's trying to move but just cannot. Since I have an open-loop system, Mach3 still thinks the machine is moving. Can anyone tell me why this is happening?

Secondly, and more importantly, there seems to be a really weird unit problem with my machine. If I move the machine an inch in any direction, Mach3 thinks I'm moving it 8 units. I'm not sure that it's EXACTLY 8, but it's certainly somewhere between 7.99 and 8.01. I have been correcting for this using the "scale" option, but I'd really rather find the root of the problem.

EDITED to say: I've been reading section ~5.5.1 of the mach 3 manual where it talks about steps per unit. I'm a bit confused though, and welcome any guidance.

Any and all help is much appreciated. Thanks.

mike

[Greolt]

Originally Posted by MachFlowMike First off, when I'm jogging (even sometimes when I'm machining) and I try to move a long distance (more than an inch or so), the machine will initially start to move, but will come to an abrupt halt. When it does this, the machine will be emitting a sort of humming-ringing sound, like it's trying to move but just cannot.

It is stalling. Reduce the velocity and acceleration in "Motor Tuning" by at least half.

Once you have it going them you can increase it a bit at a time till it is good.

If I move the machine an inch in any direction, Mach3 thinks I'm moving it 8 units. I'm not sure that it's EXACTLY 8, but it's certainly somewhere between 7.99 and 8.01. I have been correcting for this using the "scale" option, but I'd really rather find the root of the problem.

Again in the "Motor Tuning" you need to set the steps per unit correctly.

On the Settings page there is a button just above the Reset called Axis Calibration which will help with getting this accurate.

Greg

[samco]

I would read this

http://timeguy.com/cradek/cnc

from what I understand - the drives on the maxnc 10 are very weak to say the least. (something to think about)

sam

[MachFlowMike]

Originally Posted by Greolt It is stalling. Reduce the velocity and acceleration in "Motor Tuning" by at least half. Once you have it going them you can increase it a bit at a time till it is good.

I figured that's what it was, I fixed this problem pretty quickly, thanks. There is, however, a bit of a problem still (see below).

Originally Posted by Greolt Again in the "Motor Tuning" you need to set the steps per unit correctly. On the Settings page there is a button just above the Reset called Axis Calibration which will help with getting this accurate. Greg

Again, I figured this was the problem here, but I'm still confused. I suppose it boils down to me not understanding what "micro steps" are, and why 10 is a good value to choose for micro steps, and where I'd even set that value to begin with. I do indeed have a 1.8 degree step motor (200 steps/rev).

Either way, I used the "axis calibration" feature and it worked great (I just had the spindle push a set of calipers to get an accurate reading). When I move the spindle one inch, Mach3 thinks it moves one unit. The only problem is now when I reset the program, the motor tries to move WAY too fast. This is the same thing that happens if I were to run "axis calibration" and then go into the motor setup menu, and even if I don't change anything, when I come out, things are all weird. My knee-jerk reaction is that this is a software bug. At this point my steps per unit are on the order of 8000, which just seems really off to me. I'm not sure why.

Any more advice? Thanks!

PS - samco: I'm well aware of the shortcomings of the MAXNC 10. If it were in the budget to buy a better machine I would've done it by now

[ger21]

When you change your steps per unit, you're also changing the rapid speed, even though it doesn't appear to change. The reason is that the speed was incorrect prior to the step/unit change. Slow down your velocity.

[Greolt]

Originally Posted by MachFlowMike At this point my steps per unit are on the order of 8000, which just seems really off to me. I'm not sure why.

If using 10 microsteps then that makes 2000 steps per motor rev. If you had 4tpi screws that would make 8000 steps per inch

I suppose it boils down to me not understanding what "micro steps" are, and why 10 is a good value to choose for micro steps, and where I'd even set that value to begin with.

Microsteps are set on the drivers. Some drives are pre set, others are selectable by small dip switches. Check the docs for your drives.

And yes 10 is usually a good number. You could go less but you won't gain anything with more.

As Gerry said slow down the velocity.

Greg