Reply with QuoteThanks for the kind words Lewis, but I'm sure you are.
CR.
Crevice -Originally Posted by Crevice Reamer
I have recently come across your site and am starting to read through it. All I can say at this point is "I'm not worthy".....
Thanks for the kind words Lewis, but I'm sure you are.
CR.
http://crevicereamer.com
Too many PMs. Email me to my name plus At A O L dot com.
It's just that after flailing around trying to learn as much as possible about this cnc stuff, coming across your site is like having been in the desert and then trying to drink water from a fire hose. Outstanding work! I am sure I am like many before me that have discovered your site in that I would like to thank you for such great assistance to us who are trying to come up to speed.
Lewis
Any of the suitably sized Advanced Motion amplifier drives should control them, these take hall effect input.
For example the B25A20 model 25A peak 12.5A cont. 40-190VDC supply
It can be controlled the same way as a VFD with ±10vdc input via either a pot. for manual or with a Mach PWM to Analogue control some BOB's supply.
It must be the B prefix and not BE or S and if you want a built in power supply to feed directly off of 120 it would be the B25A20AC version.
I have seen various power sizes quoted for these motors, so there must be a few different models used?
Depending on the present supply voltage a suitable model could be selected up to 320VAC.
They can be run in the Hall velocity mode so that the commutation also acts as tachometer for accurate speed control.
5v on board to supply the hall voltage.
They can often be picked up on ebay fairly cheap.
BTW, the BLDC drives will also drive a DC brushed motor just as easily, obviously no hall commutation is used or needed.
Al.
Last edited by Al_The_Man; 05-17-2011 at 04:20 PM.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Al - Excellent info - thanks. I'm reminded of the Spike TV ads though when I look at this datasheet...."there is much to be learned". I'm an EE but never spent much time with motor controls other than simple DC PWM stuff. Going to crack out the books tonight though and try and make sense of it all.
If other are interested and would like to chime in on this - here's the datasheet for the unit that Al has suggested -
http://www.a-m-c.com/download/datasheet/b25a20ac.pdf
Thanks again Al. Whereabouts are you located in Canada ? I'm in NB.
Lewis
There are others also, Copley Controls, Aerotech etc.
Clue: Currently the Wetlands.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Hope you are not one of the poor souls that have or will soon have lost everything. I've been watching the news on this daily.There are others also, Copley Controls, Aerotech etc.
Clue: Currently the Wetlands.
Al.
Fortunately no.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Al - I have a question after perusing the a-m-c website and looking at some manuals etc. Could one of these drives with the BLDC on the SX3 be used to do rigid tapping ? It seems to me there is positional feedback of sorts from the hall sensors. I guess I don't know enough yet as to the process of stopping, reversing the motor etc. but it just occurred to me and I thought I'd ask.Fortunately no.
Al.
Thanks,
Lewis
The purpose of the hall sensors is to tell the controller which segment of the revolution the rotor is in.
The controller then turns on the coils needed to turn the rotor to the next segment.
When it gets there, the hall sensor outputs change, and so the controller changes the coil configuration.
Take a look at this: brushless_motor
It's a good thing I figured out how to step this animation along one at a time. I was starting to go into some seizures trying to follow it in continuous animation....
Thanks for the link.
Perhaps an encoder is needed to get the positional feedback for rigid tapping ? And another question - just how low/high could one rotate the BLDC motor if it was controlled by one of these drives ?
RPM is relative to applied voltage, IOW if your supply for the drive is equal to the motor rated voltage then the motor rpm will be whatever the manuf rpm spec is for that motor.
The ideal situation for rigid tapping is an encoder on the final spindle shaft, the Z axis is then geared off this encoder.
The Dynomotion Kflop and EMC are capable of this.
The motor should be capable of operating from zero to whatever the max rpm is.
It is after all intended for servo operation.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
LOL. Sorry about that. I originally found that image on the ServoMagnetics web site a few years ago, and was trying to find it again.
It was bigger, and started in the stopped state (or running much slower). They also had a few other animations of more poles and a brushed one for comparison.
Sadly, the servomag site is gone.
The motor having sensors is a good thing - it means it can run at low speeds.
Sensorless contollers use the back-EMF generated in the un-energised coil to sense the position. This makes the controller more complicated, and means the motor needs to be moving above a certain speed for the controller to be able to sense the position.
Having sensors eliminates that complication.
Being a controller issue, a sensorless controller can drive a motor with, or without sensors - They're just not connected if they're present. However, a sensor controller needs the motor to have sensors.
So, THEORETICALLY, any brushless motor controller capable of driving the load should be able to run the SX3's motor. But until someone takes the chance, we'll not know.
I don't see any real problem with leaving the speed control as it is, unless you need a faster spindle. I'm not sure of the motor's specs, but I do know that because there's no electrical connection to the moving part, BLDC motors in general can run ludicrously fast. I've seen claims of 100,000+ rpm, with main limiting factors being the shaft bearings, available current, and the structural integrity of the rotor assembly!
I can believe this - seeing as there's no friction from brushes and the like it's basically like a maglev train. Not sure I need 100k on the spindle, but 5-6k would be nice.
You're right though on going with the stock setup until I get to the point of tinkering to get more control / speed out of the machine. At least I know that if the thing dies after it's out of warranty, I have a plan B. I'd much more be interested in exploring the BLDC drive approach than buying another stock setup if it led me on the road to full spindle control and rigid tapping. Heck I might even try it out anyway the more I think about it. Funny how the slope gets more slippery and steep the more you learn about this stuff.....
There is one other thing I have been wondering about with the SX3s - it seems the head spindle bearings are different in some way to the X3s - if I was to jack up the speed, I'd be inclined to swap out the bearings. Anyone have a link with a procedure and/or P/Ns for this ?
Lewis
Al - are these Dynomotion cards similar to the MESA cards that I have seen referenced in the EMC2 literature? They look to be 200k/400k FPGA cards that once configured, claim to do "anything I/O".
The Dynomotion Kflop and Kanalog are stand alone CNC controls that close the loop, it is a multi axis controller, I/O and front end software, there is also a plug in for Mach if you want a more detailed front end software, it operates via USB from the PC.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
The lower spindle bearing# is 32907 which I found at EB Atmus, the upper bearing# is 32006, which i found on ebay, and the bearing that sits in the upper pulley housing is a 6006 IIRC
Do a search for spindle bearing replacements here in the benchtop section
JTCUSTOMS
"It is only when they go wrong that machines remind you how powerful they are."
Clive James
Yes indeed, the search function is your friend. I used a different set of phrases this time and found a few detailed threads on this - but from what I found there's a general consensus that "if it ain't broke don't fix it" - still, I'd like to have this information for reference. I'm not sure it's a job for a rank beginner like myself, but I do have a few machinists I know that I can badger if needed.
I'm still plodding my way through all the links that this thread has revealed, but I'm starting to feel that the SX3 is the one to choose between the X3/SX3 - even if I do move to CNC it after a bit of time with it.
Thanks again for the assistance.
Lewis
All in all it was not difficult at all, replacing the stock bearings made a big difference in surface finish, and spindle temperature was lowered as well
A great upgrade in my opinion
I personally did not like the look of the motor hanging off the side of the X3 head, the SX3 spindle motor is a nice and tidy looking machine (unlike the behemoth that sits atop my SX3 now) and the power output was great
I tried stalling the spindle with my hands at several different speeds and I couldnt, and you could hear and feel it compensating the rpm for the torque output
Good luck
JTCUSTOMS
"It is only when they go wrong that machines remind you how powerful they are."
Clive James
This has been an exercise in frustration for me over the years I have owned my Grizzly SX3 - there have been many false starts for solutions to spindle and speed control. So the info that Al_The_Man provided earlier in this thread came as welcome news that perhaps using a different off-the-shelf driver would be a viable alternative.
I found an AMC B25A20AC drive on Ebay and bought it - should arrive in a week or so. In the meantime, I have begun to collect wiring information from the Grizzly docs. Here is a diagram showing the hookups to the current motor - I would be interested in any advice on how the AMC should be connected to replace it.
Looks like I will be the guinea pig on this - I have already reached out to Al_The_Man via PM, and he has given me some very helpful starting advice. I will log my results in this thread as I see what happens.
