From the many posts on the forum, most of us are happy if we can get our VFDs wired up and to function in some useful way. After a bit of use, they become familiar and we start taking them for granted. It's always a good thing to allow the tools to make our work a bit easier, and a incremental approach is fine. Make one parameter change and see how it goes.
Today I was doing a bit of "high speed spindle" lathe work. (3000rpm with ER collets). I had set the ramp time parameter on the VFD years ago for both start and stop to .8 seconds. This seemed to go along with the slower pace of operations like threading etc. It felt smooth and "comfortable".
With the accel and decel configured this way and using the VFD to "over drive" the motor speed (75hz) the lathe was balking while starting and stopping. Not faulting, but stepping up and stepping down in a jerky fashion so as not to exceed the current limits programmed.
I didn't like this, so I reset the accel and decel parameters to 2.2 seconds. The spindle spooled up and down smooth as silk (I'm sure it would stutter and step again if the added mass of a jaw chuck were fitted, but I don't like to run jaw chucks fast if the work will fit in a collet.
Well, with the task accomplished I started to "reset" the ramp times, but then thought.... ramp time is set as time in seconds from start frequency to max (or base) frequency. If the VFD is set to a portion of max frequency, the ramp time should be a portion of the parameter set time. And it IS!
So for threading or other "rapid stop , rapid start" applications, I can have my previous ramp times by selection of a fast mechanical spindle speed , by way of the gear box or pulleys etc. and then set the VFD at say 20 hz, to arrive at a suitable actual spindle speed. Playing one system against the other to arrive at an agreeable result.
Note, that this may not be the best if one were doing "heavy work" pulling lots of power, but when is that the case for work that would benefit from raid spindle stops and starts. For myself, such needs are usually repeat operations on a batch of parts with loading and unloading taking a considerable portion of the operation time. If the loads are "heavy" the longer ramp ties are generally acceptable.
Well, It all made sense to me today, so I thought I would share. 'might all be different tomorrow ;-)
Today I was doing a bit of "high speed spindle" lathe work. (3000rpm with ER collets). I had set the ramp time parameter on the VFD years ago for both start and stop to .8 seconds. This seemed to go along with the slower pace of operations like threading etc. It felt smooth and "comfortable".
With the accel and decel configured this way and using the VFD to "over drive" the motor speed (75hz) the lathe was balking while starting and stopping. Not faulting, but stepping up and stepping down in a jerky fashion so as not to exceed the current limits programmed.
I didn't like this, so I reset the accel and decel parameters to 2.2 seconds. The spindle spooled up and down smooth as silk (I'm sure it would stutter and step again if the added mass of a jaw chuck were fitted, but I don't like to run jaw chucks fast if the work will fit in a collet.
Well, with the task accomplished I started to "reset" the ramp times, but then thought.... ramp time is set as time in seconds from start frequency to max (or base) frequency. If the VFD is set to a portion of max frequency, the ramp time should be a portion of the parameter set time. And it IS!
So for threading or other "rapid stop , rapid start" applications, I can have my previous ramp times by selection of a fast mechanical spindle speed , by way of the gear box or pulleys etc. and then set the VFD at say 20 hz, to arrive at a suitable actual spindle speed. Playing one system against the other to arrive at an agreeable result.
Note, that this may not be the best if one were doing "heavy work" pulling lots of power, but when is that the case for work that would benefit from raid spindle stops and starts. For myself, such needs are usually repeat operations on a batch of parts with loading and unloading taking a considerable portion of the operation time. If the loads are "heavy" the longer ramp ties are generally acceptable.
Well, It all made sense to me today, so I thought I would share. 'might all be different tomorrow ;-)
