Re: Triac and Mach3

On 28 July, 01:12, Kevin <kevin.newsgro...@xxxxxxxxxxxx> wrote:
I'm back on this one again, having made some changes and tried a few
things.  The problem is a lack of accuracy, after a long program the
position drifts.  I have replaced the computer, as it was playing up -
but I'm fairly sure that wasn't influencing the problems.  I have also
calibrated the backlash in the leadscrews, as I found about 0.02mm of
backlash in X and 0.01 in Y.  Again, I don't think this is the root of
the problem though -because that wouldn't be affected by the
microstepping settings of the drives.  I'm happy that the power supply
is OK to drive the steppers (as long as speeds are kept to 800mmpm or
so).

The problem isn't "odd steps" being lost, it seems far more regular
than that.  Running a program, then changing the microstepping
settings on the drives and running the program again seems to point to
a pattern of step loss.  I'm wondering of the first step after a
change of direction is being lost, or something similar.

The closest I've come to a solution is increasing the speed mach3 is
running at and setting the drives at a very high microstepping
setting.  This doesn't cure the problem, but as I seem to be losing
the same number of steps it makes the error smaller.  Far from ideal,
as it still causes problems if the program is large enough.

Any suggestions welcome, also as to a more scientific testing
procedure.

Regards
Kevin

Kevin,
Some things to try but don't try them all at once.

First thing to try is the Pulse width, go to Config, Motor Tuning and
set the pulse width to 5, press save axis then OK. You only need to do
it on one axis as it's common to all.

You can change whether Mach sees the leading or trailing edge by going
to Config, Ports and Pins, Motor Outputs and swapping the Step low
setting.

We have done about 5 Triacs now and whilst not noticing lost steps,
but then again we don't run the machines for long periods before
returning to their owners we have had no reports of such [ mind you I
wonder if they even get used at times ? ]
What I have noticed is that as you have said, the speeds have to be
kept low on these 800mm / min is about average. However seeing as we
fit the same electronics as we do to the Sieg machines which happily
run at 1500 to 2000 mm/ min the only difference is that the Sieg's get
the newer square pattern motors fitted.
Non of the Denford's have had motor changes because they already have
motors fitted and itis a fact that those old round 34's are far
inferior to the modern square 23's.

Roy at DIY-CNC.co.uk sells some 23's rated at 3 Nm with 8mm shafts,
they will run on 2.5 amp in series but ned a 5 amp drive to run in
parallel.

John S.
.

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