New Taig, 8 ipm maximum rapid speed?

[fivaxis]

I just got my Taig setup, I am using Flashcut and I cannot get over 8ipm. If I go any faster the motor will freeze and it will say the computer can't communicate with the Flashcut box.

I've messed around with the feedrate and ramping settings and that's the best I can get. I am wondering if it could have to do with the stepper motors? The ones I have are supposed to be 166 oz, I don't know for sure though it looks like they had labels on them that were ripped off. There was one that is bigger and I put it on the Z axis, however it doesn't go any faster.

Would I get faster rapids if I went to a different/stronger stepper motor? Could it have something to do with Flashcut?

www.fivaxis.com/cnc2.jpg

[jdholbrook]

For what it's worth.
I use a Xylotex board and his 270oz steppers on my Taig and I get around 40ipm rapids.
Bigger steppers are not the answer. In fact somewhere there is a thread pointing out that the best speed was obtained using 127oz steppers. (I believe that was the size).
Can you run Mach3 with your interface board? Worth a try if you can.

[fivaxis]

Ok I'm starting to think its a computer/communication problem. I'm using a laptop with a serial port, I'm going to try it on my desktop to see if it works.

[fivaxis]

I tried it on the desktop, same exact thing. I guess I will try Mach3.

edit- Well I can't figure out the first thing about Mach3.

[nicad]

The controller has no idea if the motor is spinning or not. The motor stopping with an error is the result of a problem elsewhere...

Since the software reports an error, the problem is with with the cnc controller hardware, software, or computer. I would contact Flashcut, since it is their controller and software.

Mach3 is not compatible with that system.

[jdholbrook]

It seems as if you are narrowing down to the problem.
I wanted to post the article I read showing the different speeds vs stepper torque.


/quote
By Tony Jeffree:

I did a very interesting test the other day on my Taig mill.

I bought one of the original Taigs with 140 oz-in motors, rated at
1A/phase
(something like 7 volts to drive that through the 7 Ohm coil
resistance) -
it was the first of their mills to be imported to the UK a few years
back.
A couple of years later I upgraded to their current 200 oz-in motors -
still 1A/phase, so even higher coil resistance - ~9 Ohm IIRC. I
recently
decided to give the mill a makeover, firstly to improve on the drive
coupling and bearing end-float adjustment arrangements (which can be
surprisingly bad on the standard mill - my worst axis had about 5 thou
backlash), and secondly to convert from Taig's old "bi-level chopper"
drive to
a modern microstepping drive. Having re-vamped the mechanical side to
the
point where I can no longer measure any backlash, I decided to see what
maximum step rate I could achieve with three alternative motors, using
a
driver capable of unipolar half-stepping at up to 2A/phase and a 24V
supply
(actually one of my Divisionmaster units).

The first motor was one of Taig's "standard" 200 oz-in 1A/phase motors.
The
max half-step rate with this motor before losing steps was 1250
half-steps/sec, equating to around 9.4 IPM (20 TPI leadscrews).

The second was a 254 oz-in, 2.5A/phase, so with the reduced (2A) drive,
effectively a 211 oz-in motor, so very comparable to the first in
holding
torque. This managed 4000 half-steps/sec or 30 IPM.

The third was a 140 oz-in, 3A/phase motor; again, with the reduced
drive,
effectively down-rated to 93 oz-in. This managed 7000 half-steps/sec,
or
52.5 IPM.

The differences here are basically down to differences in motor
inductance;
the higher the inductance, the worse the high speed performance will be
for
a given supply voltage. So, given unlimited driver voltage, these
differences would not be a problem. However, in the real world, where
drivers suitable for a machine like the Taig (e.g., the Xylotex board)
are
often limited to a supply of around 30-40 volts, choosing a motor that
has
lower torque and low inductance is often a better deal than choosing
one
that has high torque but higher inductance.

Needless to say, I will be using the 140 oz-in 3A/phase motors for the
final
configuration, but will be driving them at their rated 3A/phase and
will be
using a ~40V supply and a microstepping drive. If you do the math on
what a
motor like that can deliver through a 20 TPI leadscrew, you reach the
conclusion that this combo can quite happily generate a force of around
100-140 Kilos at the tool tip (factoring in leadscrew efficiency and
the
dynamic torque the motor can generate). I feel that should be more than
sufficient for a mill the size of the Taig, and certainly, the ability
to
do rapids at >50IPM is way more than I will ever need (or will feel is
safe!) on this machine.

/quote

James