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- Nov 28, 2016
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Please bear with me... this may get long...
Last week I posted in the 'what did you buy today' thread about some machines I bought cheap, including a K&T Model H horizontal mill. In that post, I referred to it as 'junk'...
There is a reason for that. It has had some 're-engineering' done on it. One issue in particular is that someone had previously removed the spindle speed control mechanism and connected the motor directly to the gearbox input shaft with a double v-belt setup.
My idea is to work around this by powering it through a VFD... but I know almost nothing about VFDs.
As it is setup now, the motor (3hp 208v 3ph) is rated at 1725 rpms which by my calculations (with a 4:1 motor to spindle ratio) should be turning the spindle about 430 rpm, give or take...
When I was machining the new gears for my Hendey lathe on my vertical mill, I had the spindle turning about 80 rpm and that worked out well, so that is sort of my goal... to be able to turn the spindle on the K&T at 80 rpm and still have useable torque.
So, my question is whether a VFD will be able to do what I want, or do I need to play with the pulley ratios to get the spindle slower by mechanical means first.
IOW, what spindle speed should I shoot for running the motor at 60 cycles to expect to acheive my goal after adding a VFD?
Also, I'm assuming if I can reduce the rpms with a VFD, I can potentially increase them also? Is there a generally accepted effective range that VFDs can handle?
If I am way off base with my thinking on this, let me know... like I said, I really don't know anything about VFDs aside from what I've picked up reading H-M.
Thanks -Bear
Last week I posted in the 'what did you buy today' thread about some machines I bought cheap, including a K&T Model H horizontal mill. In that post, I referred to it as 'junk'...
There is a reason for that. It has had some 're-engineering' done on it. One issue in particular is that someone had previously removed the spindle speed control mechanism and connected the motor directly to the gearbox input shaft with a double v-belt setup.
My idea is to work around this by powering it through a VFD... but I know almost nothing about VFDs.
As it is setup now, the motor (3hp 208v 3ph) is rated at 1725 rpms which by my calculations (with a 4:1 motor to spindle ratio) should be turning the spindle about 430 rpm, give or take...
When I was machining the new gears for my Hendey lathe on my vertical mill, I had the spindle turning about 80 rpm and that worked out well, so that is sort of my goal... to be able to turn the spindle on the K&T at 80 rpm and still have useable torque.
So, my question is whether a VFD will be able to do what I want, or do I need to play with the pulley ratios to get the spindle slower by mechanical means first.
IOW, what spindle speed should I shoot for running the motor at 60 cycles to expect to acheive my goal after adding a VFD?
Also, I'm assuming if I can reduce the rpms with a VFD, I can potentially increase them also? Is there a generally accepted effective range that VFDs can handle?
If I am way off base with my thinking on this, let me know... like I said, I really don't know anything about VFDs aside from what I've picked up reading H-M.
Thanks -Bear