KMB1m VFD Upgrade

I have a Hurco KMB1m 3 axis CNC that has a manual speed adjustment via an adjustable sheave pulley system. It's similar to the one on my
Bridgeport, and likewise has a High/Low range. I'm planning to install a 1ph to 3ph VFD to eliminate the static phase converter in use now. The spindle start up is kinda slow on the static, as is reversing. Questions: Once the VFD is installed what kind of max RPM above base should I allow? I'm thinking of ditching the variable belt drive and putting in a 1:1 gear belt from the motor to a new spindle pulley, (I would keep the How/Low gear reduction unit in place). Anyone do this on a BP or the Hurco? I happen to have a set of solid bore gear belt pulleys about the correct size...
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Keep the static converter and use it to start the idler motor of a rotary phase converter. I wouldn't anticipate any CNC problems from a rotary if you obtain an idler motor of at least 2 x the HP rating of the Hurco. See rotary phase converter in metalwebnews.com.
Bob Swinney
I have a Hurco KMB1m 3 axis CNC that has a manual speed adjustment via an adjustable sheave pulley system. It's similar to the one on my Bridgeport, and likewise has a High/Low range. I'm planning to install a 1ph to 3ph VFD to eliminate the static phase converter in use now. The spindle start up is kinda slow on the static, as is reversing. Questions: Once the VFD is installed what kind of max RPM above base should I allow? I'm thinking of ditching the variable belt drive and putting in a 1:1 gear belt from the motor to a new spindle pulley, (I would keep the How/Low gear reduction unit in place). Anyone do this on a BP or the Hurco? I happen to have a set of solid bore gear belt pulleys about the correct size...
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I already have a 10hp capacity rotary phase converter, but I don't really want to run 3 phase service and a control circuit for the phase converter over to where the mill is located, in any case I won a 5hp 1phase in to 3 phase out ABB VFD on Ebay which is en route. So the the VFD will get used, it's just a question of if I pull off the variable speed belt drive from the mill. Mainly would do this to get auto speed control via the ABB's A/D input from the Hurco's Servo board.
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oldjag wrote:

Install the VFD and leave the variable speed sheaves in place - at least until the drive belt wears out and you have to replace it anyway. If your mill is anything like our Wells-Index, the job of replacing the belt is quite a challenge.
You'll probably never use the reduction gears again since the VFD will give torque controlled speeds down to a crawl.
The ramp-up and ramp-down speeds and dwell times on reversing are adjustable from the VFD. If this is your first VFD conversion, you'll be amazed...
Carla "The English language doesn't just borrow words from other languages. It follows them down dark alleys, hits them over the head with old beer bottles and rummages through their pockets for loose grammar."
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oldjag sez:
"I already have a 10hp capacity rotary phase converter, but I don't really want to run 3 phase service and a control circuit for the phase converter over to where the mill is located . . . ."
I have no direct experience with VFDs but I do feel entitled to an opinion re. RPCs. If you have a 10 HP idler RPC, appropriately "voltage balanced" and use it to run a 3 HP Hurco, then you should have no problems with voltage sag, or etc. Didn't you say it presenly runs ok from a static phase converter? Remember, you can run more than 1 machine from a RPC, but only 1 at a time from a VFD.
Bob Swinney

in any case I won a 5hp 1phase in to 3 phase out ABB VFD on Ebay which is en route. So the the VFD will get used, it's just a question of if I pull off the variable speed belt drive from the mill. Mainly would do this to get auto speed control via the ABB's A/D input from the Hurco's Servo board.
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The 10 hp phase converter runs a Leblond Lathe, a Bridgeport, a bandsaw and a delt/disc sander so it's pretty well utilized now. The static phase converter in the Hurco I'll probably get rid of or may use it with a 13" Clausing late, but I'm not sure it will work with the Clausings 2 speed motor.
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