- Joined
- Apr 4, 2013
- Messages
- 635
Good part of the day,
Right before Christmas the main power supply board on my Grizzly G0720R milling machine let out some of it's magic smoke. I was ultimately able to fix the board, but the design doesn't make me feel warm and fuzzy. The motor seems to be pretty well made, but the controller is pretty crude. Besides having no back-EMF protection to speak of, it's not driving the motor that well either. As far as I can see on the 'scope, the control logic is pretty basic. I.e. the controller is not doing any timing advancing, etc. It's basically turning the transistors on and off after the encoder pulses. This results in pretty rough-running motor, which (now that I know to notice it) is annoying me. On top of that, I don't trust that it won't just grenade again at the worst possible moment.
Incidentally, I have a brand new 3PH 1HP Baldor motor and a matching Poweflex40 VFD that would fit the machine nicely if mounted upside-down. On paper this would be a downgrade: G0720's spec sheet claims that the motor is rated at 220V/2HP (although I don't believe that number, even when adjusted for Chinese-sized horses). On the other hand, my thinking is that with 1HP 3PH motor with 2-step V-Belt pulleys and VFD would probably give me more usable RPM range. I.e. more torque at low speed when in "low gear" and more top speed in the "high gear". Currently max RPM is 1600, which is too slow for me, since I tend to use 1/2" and smaller end mills, all the way down to 1/16". Moreover, my last mill was rated at 600W (about 3/4HP) and I don't remember feeling that it was underpowered.
All that said, I have a few questions:
1. Given different torque curves of 3PH vs. BLDC motors, would 1HP 3PH motor be underpowered for this size of machine?
2. I noticed that a lot of SIEG machines use toothed belts. Is that warranted at such low HP, or can I get away with either a V-Belt or a "serpentine" belt (I don't recall what the correct term for that is)?
3. Is there any danger in increasing spindle RPM to 3000-ish RPM? I.e. are there any concerns with the bearings that come with this machine, etc.?
I'd appreciate you input
Thank you
Yuriy
Right before Christmas the main power supply board on my Grizzly G0720R milling machine let out some of it's magic smoke. I was ultimately able to fix the board, but the design doesn't make me feel warm and fuzzy. The motor seems to be pretty well made, but the controller is pretty crude. Besides having no back-EMF protection to speak of, it's not driving the motor that well either. As far as I can see on the 'scope, the control logic is pretty basic. I.e. the controller is not doing any timing advancing, etc. It's basically turning the transistors on and off after the encoder pulses. This results in pretty rough-running motor, which (now that I know to notice it) is annoying me. On top of that, I don't trust that it won't just grenade again at the worst possible moment.
Incidentally, I have a brand new 3PH 1HP Baldor motor and a matching Poweflex40 VFD that would fit the machine nicely if mounted upside-down. On paper this would be a downgrade: G0720's spec sheet claims that the motor is rated at 220V/2HP (although I don't believe that number, even when adjusted for Chinese-sized horses). On the other hand, my thinking is that with 1HP 3PH motor with 2-step V-Belt pulleys and VFD would probably give me more usable RPM range. I.e. more torque at low speed when in "low gear" and more top speed in the "high gear". Currently max RPM is 1600, which is too slow for me, since I tend to use 1/2" and smaller end mills, all the way down to 1/16". Moreover, my last mill was rated at 600W (about 3/4HP) and I don't remember feeling that it was underpowered.
All that said, I have a few questions:
1. Given different torque curves of 3PH vs. BLDC motors, would 1HP 3PH motor be underpowered for this size of machine?
2. I noticed that a lot of SIEG machines use toothed belts. Is that warranted at such low HP, or can I get away with either a V-Belt or a "serpentine" belt (I don't recall what the correct term for that is)?
3. Is there any danger in increasing spindle RPM to 3000-ish RPM? I.e. are there any concerns with the bearings that come with this machine, etc.?
I'd appreciate you input
Thank you
Yuriy