[Notes from a Creator] It was a good day
It would seem that after some teasing, Murphy decided to give me a
break yesterday.
First, the motors arrived right when UPS said they would. Installing
one on the x axis went smoothly, but I ran into some problems once I
started testing and tuning it. First, when I tried to run it it kept
stopping at the same place on the table and clutching out. Turns out
the set screw that was keeping one of the drive sprockets in place had
loosened somewhat and was catching on the chain. For some reason it now
wanted to be tighter than it had been before, which meant grinding a
new flat into it's head to prevent further catching. Once that problem
was solved I started the process of finding the right amount of current
to drive the motor. Surprisingly, even with the current turned all the
way up to 4.3A (the motor should only get 3A), it was still not able to
move at the speeds I thought it should. In looking for a cause of this,
I had the first of the day's breakthroughs.
It turns out the dip switches are "on" when they are in the down
position. This meant two things: that the auto half current function
(which helps keep motors from overheating) was off when I thought it
was on, and that the boards were set to microstep at 25 subdivisions
instead of just 5. While microstepping does give you much more
precision (which I don't really need), it also severely reduces the
amount of torque (which I do). I turn the auto half current function,
set the driver to 2 subdivisions just to be on the safe side, modify
the necessary settings in the software to reflect this, and resume
testing.
The torque of the motor improves significantly, but it's still not
performing as well as I'd expected. I could get it up to about 9 inches
per second, but higher than that and it would choke, regardless of
current. Now, when I was running my previous jobs, I had the machine
running at feed rates of 50 and 100, so I was understandably concerned.
I had no idea what was wrong, and was starting to get very frustrated.
Then it hit me: the units are different.
See, those feed rates of 50 and 100 were inches per minute, not second,
so what I thought was a slow 9 was in fact 540 IPM, way faster than I'd
ever need to go.
It's amazing how one small realization can improves one outlook on life.
After that, it was all cake. I re-tuned all three motors and cut the
next prototype of the card dispenser. The y axis motor got a little on
the warm side, so I had to let it rest half-way through the job, but I
can turn the current down on that one with torque to spare.
There were some issues with the card dispenser job itself, but that was
because of how I had it cut, not any hardware problems. I assembled it
today, and it works quite well:
You can find other pics of it, along with screenshots of other things
I've modeled in Solidworks that are destined to be milled out on a CNC
here.
break yesterday.
First, the motors arrived right when UPS said they would. Installing
one on the x axis went smoothly, but I ran into some problems once I
started testing and tuning it. First, when I tried to run it it kept
stopping at the same place on the table and clutching out. Turns out
the set screw that was keeping one of the drive sprockets in place had
loosened somewhat and was catching on the chain. For some reason it now
wanted to be tighter than it had been before, which meant grinding a
new flat into it's head to prevent further catching. Once that problem
was solved I started the process of finding the right amount of current
to drive the motor. Surprisingly, even with the current turned all the
way up to 4.3A (the motor should only get 3A), it was still not able to
move at the speeds I thought it should. In looking for a cause of this,
I had the first of the day's breakthroughs.
It turns out the dip switches are "on" when they are in the down
position. This meant two things: that the auto half current function
(which helps keep motors from overheating) was off when I thought it
was on, and that the boards were set to microstep at 25 subdivisions
instead of just 5. While microstepping does give you much more
precision (which I don't really need), it also severely reduces the
amount of torque (which I do). I turn the auto half current function,
set the driver to 2 subdivisions just to be on the safe side, modify
the necessary settings in the software to reflect this, and resume
testing.
The torque of the motor improves significantly, but it's still not
performing as well as I'd expected. I could get it up to about 9 inches
per second, but higher than that and it would choke, regardless of
current. Now, when I was running my previous jobs, I had the machine
running at feed rates of 50 and 100, so I was understandably concerned.
I had no idea what was wrong, and was starting to get very frustrated.
Then it hit me: the units are different.
See, those feed rates of 50 and 100 were inches per minute, not second,
so what I thought was a slow 9 was in fact 540 IPM, way faster than I'd
ever need to go.
It's amazing how one small realization can improves one outlook on life.
After that, it was all cake. I re-tuned all three motors and cut the
next prototype of the card dispenser. The y axis motor got a little on
the warm side, so I had to let it rest half-way through the job, but I
can turn the current down on that one with torque to spare.
There were some issues with the card dispenser job itself, but that was
because of how I had it cut, not any hardware problems. I assembled it
today, and it works quite well:
You can find other pics of it, along with screenshots of other things
I've modeled in Solidworks that are destined to be milled out on a CNC
here.