Kinetix scaling

Hi guys!

I´m a beginner with Kinetix6000 servo drives so please excuse for foolish questions...

I hava a Kinetix6000 servo drive which moves a spindle.
It´s configured as an rotary axis with 0-360 deg.

There is an gearbox between the drive and the spindle with an 13.22/1 ratio (13.22 motor revs are 1 spindle rev).

I configured in the axis parameters, tab Drive/Motor --> calculate as follows:

Position Unit Scaling: 36000 deg per 1322 Motor Rev
Position Unit Unwind: 360 deg per 1 Unwind cycle

Is that setting correct? I made a MAM motion direct command with 3600 deg absolute and the spindle moves about 10 1/2 revs.

Perhaps the gear box ratio is not correct what I got from the construction but i want to check if my settings are correct.

Thank you!

Hi all. Does no one have some ideas? Thanks!

you may be right and have a scaling problem
Before you did the MAM did you MAH or MRP the current position to zero?

I usually use MAM incremental in this case

The scaling values you put in would normally work

if 10.5 spindle Revs approx the ratio is about 12.6 something is wrong
Best thing to do is to get the exact ratio from the GB supplier - I find that I have to read the GB nameplate to be sure and have the accuracy.


The Gear box ratio is probably irrational eg 13.222222...

Next thing to do is work out the ratio yourself - I hate this for a spindle as you usually get the ratio wrong and the position drifts due to scaling error. The mechanical guy I work with gives me the exact ratios eg 13:3


One method that I use when I do not trust the gear box nameplate ratio and cannot get the exact ratio
(ie the ratio is irrational or not enough accuracy)
1) Set the scaling to Motor Revs - Rollover in the 100000 range
2) Mark the Output shaft of the gear box - so you know that one rev has occurred Exactly - I get a scratch mark made
3) use MAM incremental so the output shaft of the Gear box turns exactly one Rev - you now have a gear box input rev to output rev ratio.
4) To get additional accuracy in the ratio multiply the number by 10 and check your stop position - Repeat for 100 and 1000

If you see an irrational number appear then work out the divisor
ie how many revs of the motor to an integer rev count of the output shaft - Excel is great for that

Another Method
usually there is a home sensor on the GB output
1) Move the home sensor to Registration input
2) Get a MAR instruction to work and always have a MAR enabled
2a) have a counter on how often the MAR gets retriggered
3) You can now measure how many motor revs between Registration trips
do some averaging over a large number of GB revs for the ratio
Again I try to work out the irrational ratio

Trends are your friend - trend the .actualposition and registration position
Also the counter (gives you GB output shaft revs) - this permits the shafts to be moved by hand as another way to get scaling ratios

Your gearbox doesn't happen to be SEW Eurodrive is it? They are great at building irrational ratio drives. I've had to use method 2 that MichaelG describes on a couple of SEW's. I counted 99 teeth on the final output gear.

steveb1475 said:

Your gearbox doesn't happen to be SEW Eurodrive is it? They are great at building irrational ratio drives. I've had to use method 2 that MichaelG describes on a couple of SEW's. I counted 99 teeth on the final output gear.

Click to expand...

Exactly! The gearbox is from SEW Eurodrive. And you were right. The mechanical construction gave me the ratio 13.22. But this was a rounded value. The exact value is about 13.215849...

Why the hell SEW constructs GB with such ratios?
Anyway, i will try out the exact ratio tomorrow but i think this is the problem.

@MichaelG
Thanks for your tips! They are very useful for future use.

Greets
Steve