Today I'm going to describe replacing the stock PM 25 BLDC drive with one from
Anaheim Automation. The reasons for making this replacement include the
original driver lacks documentation, may be hard to obtain a replacement, it's
slow to stop and reverse the direction of a spindle which limits rigid tapping,
and it lacks a fault indicator signal that can be used in an e-stop circuit.
There is an LED on the board that can be replaced with a opto coupler and that
could be used in the e-stop circuit but the signal comes too late to prevent a
crash so it's really not useful. On paper the Anaheim automation Drive appears
like a perfect replacement and it runs a spindle at nearly 6000 rpm.
There's also a pulse-per-revolution line that may be useful if you're not able to
use the stock PM 25 tach without a divider circuit. The Anaheim Automation
drive has a nice enclosure and connectors and compared to the stock
BLDC drive is much more complex internally.
Tthe simplicity of the stock BLDC drives makes it repairable with the
exception of the STC microprocessor which I've not found a way to read the
firmware out of which means that if you are replacing it you're going to have to
write your own firmware. The Anaheim automation drive has both open and
closed loop modes while the stock BLDC drive is probably only open loop.
Regardless, the stock BLDC drive has better speed regulation following a
speed change than the Anaheim automation drive does in closed loop operation. It
is as though the proportional value of the PID loop of the Anaheim automation
Drive is just too large and you can't change those settings.
Stopping the Anaheim automation BLDC drive requires sequencing of the freewheel
and run stop signals which requires additional relays. It also requires that
the fault latch be disabled on the BLDC drive. The Anaheim Automation support staff
are great and clearly engineers and after several exchanges they offered to
have, at their cost, the drive and motor sent to them for optimization. This
wasn't something I was able do because of the time of the mill would be down
but it was great of them to offer. A couple other observations while the fault
light lights, the fault line never goes high, so it's not useful even in a latching
e-stop circuit. Also at speeds less than a thousand rpm the torque is so low
at the spindle that it's easily stopped so those lower speeds aren't usable.
Thousand RPM, closed loop.
The Anaheim Automation drive may work better with one of their motors but the cost
quickly escalates and doing so replaces more hardware than I intended to. In the
end the Anaheim Automation drive is not a suitable drop-in replacement for the
stock PM25 BLDC drive. Unless you only want to run the spindle at those higher
RPMs it is probably not suitable and given the cost there's more general solutions
available. If you have any questions let me know otherwise I'll be tearing this
down and getting back to work. And as always. thank you for watching.