Does anyone know if it's possible or feasible or reasonable to use an Arduino for speed control of an electric motor to drive the main spindle of a Lathe? I'm not talking about making the Lathe CNC, (that would involve stepper motors on the Cross Slide and lead screw.) I'm just talking about driving the main spindle.
The Background is that I have one of those cheap Chinese mini-lathes. These lathes are powered by a 350 Watt variable speed brushed DC motor which is controlled by a potentiometer through a speed control/driver PCB Board. This motor is underpowered and stalls easily when cutting steel. And the speed control board is very sensitive to overload situations and is burned out easily (which is the current state of my speed control board).
So since I have to replace the board now, this seems like the perfect time to replace the stock motor with a more powerful one - preferably brush-less. And since I know very little electronics but am an experienced professional programmer, I was thinking that instead of one of these finicky, delicate driver boards to control the motor, perhaps an arduino, with the right interface could do the job.
My understanding is that the main challenge of driving the spindle of the Lathe is to keep speed (rpm) and torque constant under varying and heavy load, and to be able to provide high torque at low speed.
As I said, I'm an experienced professional programmer with a degree in Computer Science and I have toyed with the Arduino and found it very straight forward to program. But I am just an amateur when it comes to electronics and electric motors. So before I set out to learn enough about electronics and electric motors to do this project, my question is; "Is it even possible or feasible to do this"
it is 100% possible to do this, and personally i highly recommend it. without knowing the specifics of the mounting, size, or voltage of your dc motor i would reccomend this motor controller which can be easilly controlled by using PWM. (note you will also need a power supply of the correct rating)
to get feedback to adjust the speed accordingly a rotary encoder should be used.
then all the additional stuff you would need would be a display (preferably an i2c one), and another rotary encoder, this time one like this.
on the note of high torque at low speed, perhaps using a servo (or closed loop stepper) would be best. normal (cheep) dc motors generally have to either have a gearbox or be larger to achieve this.
r0bb1e:
Does anyone know if it's possible or feasible or reasonable to use an Arduino for speed control of an electric motor to drive the main spindle of a Lathe? I'm not talking about making the Lathe CNC, (that would involve stepper motors on the Cross Slide and lead screw.) I'm just talking about driving the main spindle.
The Background is that I have one of those cheap Chinese mini-lathes. These lathes are powered by a 350 Watt variable speed brushed DC motor which is controlled by a potentiometer through a speed control/driver PCB Board. This motor is underpowered and stalls easily when cutting steel. And the speed control board is very sensitive to overload situations and is burned out easily (which is the current state of my speed control board).
So since I have to replace the board now, this seems like the perfect time to replace the stock motor with a more powerful one - preferably brush-less. And since I know very little electronics but am an experienced professional programmer, I was thinking that instead of one of these finicky, delicate driver boards to control the motor, perhaps an arduino, with the right interface could do the job.
My understanding is that the main challenge of driving the spindle of the Lathe is to keep speed (rpm) and torque constant under varying and heavy load, and to be able to provide high torque at low speed.
As I said, I'm an experienced professional programmer with a degree in Computer Science and I have toyed with the Arduino and found it very straight forward to program. But I am just an amateur when it comes to electronics and electric motors. So before I set out to learn enough about electronics and electric motors to do this project, my question is; "Is it even possible or feasible to do this"
As a self taught machinist, I suggest you do not want a motor driven by a pulsing DC power. You want steady never varying speed, otherwise you end up with "chatter" marks on you project. Hard enough to keep them from appearing, anyway.
Stalling might indicate your tool may not be sharp, or is not positioned correctly, or wrong shaped tip, or other errors. I am sure you have a rigidity problem with the lathe, but that is a design/manufacturing problem you cannot correct.
super7800:
it is 100% possible to do this, and personally i highly recommend it. without knowing the specifics of the mounting, size, or voltage of your dc motor i would reccomend this motor controller
That controller and it is not rated for 120 volts chopped DC output the that motor needs.
You might want to check the specs of the motor before trying to connect an Arduino to a mains voltage driver.
it outputs a 120 volt chopped DC like a treadmill. some motors are low voltage and only need the output to be 90VDC.
Look up PMDC motor drivers.
The voltage at the pot can be 160 volts so be careful in testing.
when someone has to ask about working with mains voltages, my point of view is that if you are not trained on AC and not experienced, you should not by playing with it.
Paul_KD7HB:
As a self taught machinist, I suggest you do not want a motor driven by a pulsing DC power. You want steady never varying speed, otherwise you end up with "chatter" marks on you project. Hard enough to keep them from appearing, anyway.
Stalling might indicate your tool may not be sharp, or is not positioned correctly, or wrong shaped tip, or other errors. I am sure you have a rigidity problem with the lathe, but that is a design/manufacturing problem you cannot correct.
Paul
chatter is a function of harmonics. you can put magnets on the mass of the part and alter the frequency of the part vibration (old trick) and old machinists have lots of options. changing the rake of the cutter can alter the finish. also the proper edge of the cutting tool has a lot to do with chatter. doing 96 inch diameter condensor ends for submarines we used to use the magnets that ATT used for holding 50 pair phone cable. grey blocks like horseshoes. did wonders.
holding a wooden stick on the part can also dampen the harmonics and eliminate chatter. just hard to stand still when one cut takes over an hour.
the 7x10 lathes have a motor that is driven with a chopped DC driver and you can swap out the motor for one that will work with pure DC, or even to one that will use AC.
I believe that the 7x10 hobby is more about modifying the lathe than to make any actual parts.
the main shaft has a serated encoder for feedback that in inside of the casing (think old mouse wheel encoders)
as for the strength of the machine, it is not going to take deep cuts in steel. it is a hobby machine, not a SouthBend or Clasing that has dense cast iron as the main casting.
There is an old American Indian, Uncle Rabid, that used to repair the old driver boards.
he would buy your old one so he could fix and sell it. Low overhead and great guy.
IIRC, his daughter was the one that did the shipping.
LittleMachineShop may still be the leading supplier for all things 7x10 (7x12) and have the boards available.
I believe they even have a troubleshooting guide for the drivers.
It may be as simple as failed MOSFETS. and that is something you can do easily.
I want to mention that I have both a Mini Mill and a Mini Lathe. In both machines I have fried the controller boards.
The Mill uses an xmt-1135 board which is one of the two boards you can buy from Little Machine shop
The Lathe uses a KBIC120 board which is not sold by LittleMachineshop
On the Mill, I looked at the board and it was obvious that the big Power Resistor fried because it had oozed a tacky tar like substance. It was easy to de-solder that resistor and solder in a new one and it seemed to fix the problem in that I could start the motor but now the motor stalls with just the slightest load so i think there is more wrong with the board. The motor seems fine because I can get it to spin with just a 9 volt battery.
On the Lathe it initially seemed like the the combination potentiometer/power switch failed because I no longer got a definite "Click" when turning it clockwise from the off position. This click resets the board and turns on the power. I got a new one and it seemed to fix the problem at first but after turning on the motor a few times, I could no longer get power to the board even though I get the "Click". So it appears that more than the switch was the problem. In investigating the problem I came across these 2 YouTube videos:
This guy has exactly the same control board in his lathe as mine. He has had two of these boards fail on him and at $125.00 apiece, he decided not to get a third one. So he went ahead with a conversion to a pulley setup with a powerful three-phase motor which he says cost him less than a KBIC120 board. This setup seems great but it requires a lot of room outside of and behind the lathe.
Just like the fellow who did this video, I don't want to continue buying these boards at $120 each only to have them continually fail. And while the solution that he developed seems to solve all the problems, I'd rather not create the setup he used because it requires a lot of room. But if I can't find an alternative I may have to go with his setup on the lathe, but for the Mill it would be very awkward if not impossible.
Thus what I'm looking for is a solution which uses a more powerful motor of about the same physical size as the stock motor and an electronics system that is simpler and more reliable.
r0bb1e:
Thus what I'm looking for is a solution which uses a more powerful motor of about the same physical size as the stock motor and an electronics system that is simpler and more reliable.
I can understand the desire to get a more reliable electronic system but why do you need a more powerful motor? Doesn't more power run the risk of overloading other parts of the machine?
I have a very small chinese lathe but I don't use it much and not for anything heavy so (touch wood) I have not blown the control board yet.
Would a simple setup with a suitable high current h-bridge, a speed detector and an Arduino running a PID control program be suitable?
Sounds like way too much load for the little fella.
You may well end up spending heap just to have something else further down the chain break as Robin2 says.
Might be time to start looking at something a bit bigger from Taiwan perhaps.
They seem to make slightly better quality gear.
the minilathe/minimill community is almost as strong as the Arduino community and it is much older. having started before the BasicStamp.
not sure of your needs or space, but used American lathes are often available and can cut much-much deeper.
and yes, much-much-MUCH larger and heavier. a 7x10 mini lathe is smaller than the headstock of my 9x20 South Bend.
the 3-phase option is great if plan to cut steel or other hard metals. definitely worth keeping your eyes out for a bantam 3-phase motor.
The minilathe control boards have always be a constant issue. And there is a huge resource about how to test and repair these. as well as upgrade. many guys will run their lathes for years without any problems.
Google mini lathe control board for lots of great information.
I think the lathemill forums will be a much richer resource of how to test and repair your lathe.