Hi Rod, OK if my maths is correct everything checks out pretty good. The only thing that is amiss is that your kernel speed no way needs to be 100KHz. The plain vanilla 25KHz setting is more than twice what you'll ever need from the info you've posted.

Whilst a 64V supply would give the "optimum" torque/speed curve for your motors, as you never go much above 1300 full steps/sec your 42V should be fine (according to the torque curve for your motors - different driver but probably close enough). Plus of course your driver's max voltage is 50V anyway.

JFI - are you sure your steps/pers are correct for all your axes? They're slightly "funny" numbers. X is CLOSE to an inch lead, Y and Z are CLOSE to 5mm lead and A is CLOSE to 1mm lead.

Anyway set that kernel to 25KHz and see what occurs.

Ian

Many MANY thanks Ian. I will set the the kernal back to the default of 25KHz.
The steps per for each axis
X- is driven with a belt and I have 10:1 reduction gear on the motor. I worked out the travel based on the size of the end pully driving the belt and also included the gear reduction.
Y & Z are both on an imperial screws with a 0.2" lead - which I calculated to 5.08mm travel per revolution
A - is not active so I guess I should turn it off
After I am satisfied with the reliability of the motors and installed them on the table I had intended to confirm the steps per with some distance validation. I recall something in the doco about that so I'll re-visit that for final confirmation. 

The concern that I have with the reliability of the motors is that the X Gantry is driven by 2 motors - one either side - which are powered and run by independent power supplies & drivers, and I didn't want one to stall and one to keep going. You can just imagine the carnage on the gantry. Apparently there are digital drivers that can be linked to stop if the other stops so I will investigate that.

I have sinced slowed the speed of all axis down and they are now operating reliably but I'm not sure whether it will be too slow or not. I have also swapped the signal cabling from the breakout board to the drivers with shielded cable.

In regards to the speed of the axis can I ask what would be an average speed of travel? I can't set it over 2000mm/ without the motors randomly stopping. This seems quite slow for motors of this size but anything over and they stall. My table is 3000*1500*300.

I'll let you know the outcome of the kernal change - but first I'm going to find out what kernal is - haha

Cheers
Rod

You may well be able to achieve the speeds you had set in the xml you posted. The torque curves for your motors suggest those speeds arn't unreasonable but there's so many variables it's difficult to predict. But remember that speed isn't everything, acceleration is important too. you'll just have to see when you drop your kernel frequency.

Cheers

Ian