[Farmers Machine]

I am going to retro fit my gantry cutting torch to higher power servo motors in the X axis so that I can maximize the output of a plasma torch. Now it has WESTAMP DC servo motors on it that are rated 13 inch pounds and 1000 RPM. Speed above 45" per minute that have to come to an abrupt stop in the X axis will over shoot the mark and the control will pause on excessive position error. I have a 6000 lb. Cat forklift that can not pick the gantry up in the center, so it is very heavy. It is an ESAB Puma 12 feet in Y. Current model is the Avenger. It was used in a steel mill to cut 14" thick plates on a rolling line as I was told. My guess is about 10" per minute. It works fine at 20/25 " per minute with the oxy fuel torch, but the plasma is to slow and it welds the slag back in the kerf. Shinning a flash light between the motor housing and the drive pulley it appears to be about a 5/8" shaft diameter. I talked to Yaskawa, and the engineer said that the new ESAB machines have 3 KW motors on each track of the X axis for total 6 KW but can cut at 400" per minute with success. A 3KW servo motor has a 35 MM shaft 1.38". That is almost the size of the timing belt pulley going to the gear box on the rack and pinion drive. I don't see having to cut at 400" per minute but 150" would make the machine a whole lot more productive on thin sheet work, with a plasma torch. With the weight and rigidity of this machine, I was thinking of mounting a Bridgeport style milling head for drilling bolt holes and piercing holes in heavy plate.

New AC servos are only rated in KW with out reference to inch pounds or inch ounces. I was wondering how to convert to see what I have now in comparison, and to what I actually would need.

Thank You for your input.
The Farmer.

[Karl_T]

KW is a power measurement. Or torque times RPM

inch pounds is a torque measurement.

So, you need to know what RPM they are giving the KW rating at. From there, get on google and find a convert program to get the units right.
HORSEPOWER TO TORQUE CALCULATOR


This only gets you in the ball park. What you really care about is torque at low RPMs. It will not be quite as good as the above calculation gives you...

[Karl_T]

morning - a bit more help. Lets guess 4000 RPM above

so 3 KW * .746 (hp/KW) = 2.24 hp
above calulcator gives 3 lbft or 36 lbin

[Farmers Machine]

So what is a better Servo at 1500 RPM max, an AC digital or an old school DC with brushes?

[Karl_T]

Well if cost matters, go with a large DC servo and AMC servo amp.

Personally, I'd shop the used market. The big stuff goes for peanuts. Not much demand.

Karl

.