I think if you up the voltage ( which is really the current to the motor, the voltage reading is just an easy way for us to set the board) the motors will be more likely to be the limiting factor than the controller board.
FWIW, my motors and controller heat sinks set as per the recommended 1.2V run very slightly warm to the touch w/ no extra cooling. I had a motor burn up on me when I first built the machine. I tweaked the voltage very slightly for a short period of time, and noticed no difference in available speed, but apparently the motor didn't like it. I took the stepper apart, and a set of coils was fried.

 

wow, thanks man....i will leave it alone then. thanks agian, randy.

 

the electronic idiot/challenged is back....i will be getting my new steppers today, ther 185in. ounce rated. my question is how many steps to set-up at? i was reading about the step set-up, and as far as i can figure out the 1/8 step will be a more accurate, but slower speed than lets say a 1/4 step. can someone tell me if my understanding of this correct? if so does the torque change as the steps do? even set at 1/4 step the accuracy is .00007in. man we dont achieve that at work on half million dollar machines!!....what steps you fellas got your stepper motors set at? thanks, randy.

 

yes kwok, you would have to re calibrate...thats not a issue with me. im just trying to figure out why ther is different steps to choose from, and why. randy.

 

Randy, I found this good article on micro-stepping that may answer some of your questions

A common misconception is that microstepping increases machine accuracy.

Microstepping was developed to allow a stepper motor driven machine to have a smoother trajectory from one step to the next. It was invented (but never patented) in 1974 by Larry Durkos, a mechanical engineer for a medical equipment vendor while working on a blood analysis machine with a 20" diameter vial conveyor turntable which tended to spill the liquid due to the jerkiness of the full step mode drive. Nowadays microstepping is commonly used to increase theoretical machine resolution while minimizing noise and vibration.

Actually, microstepping is very inaccurate, for three reasons.

One, microstepping is accomplished by shifting the current in one motor coil from one polarity to the opposite polarity in some finite number of increments, to achieve one full step as a series of micro steps. The problem is that the exact position of the rotor between steps is not tightly or linearly proportional with current. Microstepping controllers must apply an approximately sinusoidal current waveform to obtain approximately uniform motion with each microstep. Any given motor's response to any given amount of current is arbitrary, based not on current, but on the motor's electrical and mechanical characteristics. So no two stepper motors ever have exactly the same response or reach exactly the same microstep position as any given amount of current is applied. So having imperfect motors (and imperfect wiring) and approximate current values applied, one can only achieve an approximate microstep position.

Two, friction and load variation causes a shift in the actual position obtained against any given amount of current applied. Problem number one is such that even with a perfect friction free motor with no load, the exact rotor position is ambiguous. Problem number two then eponentially exacerbates problem number one in accounting for how real world friction and load variation works against being able to acheive any given position with any given current on any given motor. A loaded motor will not reach the same position as when unloaded with the same amount of current applied, because some of the current is used to overcome the load resistance, so less current is available to reach the desired position.

Under the arbitrary conditions of problem one, and the varying conditions of problem two, microstep positions are much less accurate than full or half step positions, which don't vary with current or load like microstepping does.

Third, during a microstep, the current applied is partial, which means the torque developed is partial. Simply put, the motor is weaker when less than full current is applied, as opposed to when full current is applied in a normal full step position. At certain microstep positions, mainly half way between a full and a half step, the loss of power (torque) leads to a dramatic loss of ability to reach the next desired microstep position from the previous, under load.

If we consider that full stepping provides 100% rated power, we can estimate the approximate power output of less than full step operation as follows. Half stepping yields 70% of full power. 1/4 microstepping yields 40% power, 1/8 microsteppig yields 20% full power, 1/16 yields 10%, 1/32 yields 5%, 1/64 yields 2.5%, 128 yields 1.2%, and 1/256 microstepping can only achieve 0.6% of full power toward reaching and holding at an intermediate step position. Depending on the load, intermediate microsteps might only move a fraction of the intended (unloaded) distance. Only when the step sequence coincides with a full or half step is the rotor position likely to be where intended.

The benefit of smoother operation and higher theoretical machine resolution with microstepping is offset by much lower power and not much accuracy compared to full or half step operations. Not only does the microstepping controller cost a lot more, but it also requires a much larger motor and more power to achieve the required torque to move the designated load through microstep positions.

For heavily loaded motors and/or for higher positional accuracy it is often more practical to gear down the drive system to achieve micro sized motion using full or half step operation. Half stepping with 1:4 geardown provides the same machine resolution as a 1/8 microstepper with much higher accuracy and torque, and especially more holding torque. The miniscule backlash in a 1:4 kevlar reinforced timing belt drive is comparable in magnitude with a microstepper's inherent positional variation. Any gearing inaccuracy due to backlash is very consistent whereas microstepping inaccuracy varies with rotor position. Gearing multiplies consistent full motor torque to the load, while microstepping torque varies with rotor position, and rotor positional accuracy varies with loading.

Now, microstepping does have three advantages over geared down whole step mode operation.

One, it is quieter and smoother. As the microstepper applies reduced current, the resulting motion is less energetic, and each step is that much less instantaneous, so the same amount of kinetic energy (motion) occurs over a longer time frame. Much like moving something by hitting it with a hammer. If you hit it with full power (full stepping) the load will move farther and incur more shock than if you just gently tap on it (microstepping). But as the load increases, tapping is less effective. Mid step microstepping is more like tapping while moving over bumps. The taps are less effective in some places and more effective between bumps. Using a geardown is more like using a come-along. The motion is not as shocking and it doesn't matter if the load is large or small, and the rate of motion is more consistent, reliable and predictable.

Two, microstepping is faster than half or full stepping. Even before it is geared down, a whole stepped motor's top speed is lower than if it were microstepped because the velocity is more intermittant. Both start from each full step with the same speed, but all steppers essentially stop at each subsequent step, and take off again to proceed to the next step. With whole steps, the stop and go action is very abrupt and definite. With microstepping the action is less abrupt and each step position is less definite, so the rotor inertia does not stop as abruptly or completely. Much like a rolling stop at a stop sign compared to a complete stop.

Three, microstepping can be used to produce much smoother very slow motion. Even with high gear reduction, low speed full stepping operation is really jerky. Microstepping between full steps reduces that low frequncy vibration. So microstepping can be employed in a full step strategy to get the best of both modes. The only problem with that is that most generic control systems do not have any features to impliment mixed step mode operation.

Generally speaking, for light loading, high speed, and slightly less than perfect accuracy under load, microstepping is the way to go. For heavier loads and higher precision, microstepping is less effective, though not entirely without merit. A hybrid solution that utilizes microstepping to effect whole step movement is best.

Hope that helps you out.
Mark

 

well mark....lols, i will try 1/2 and 1/4 stepping. see what one works better....thanks for the post, randy.

 

mark, thanks for the post...my printer is running so good at 1/4 step i really hate to touch it...x and y are running at 70ipm, and the z is at 40ipm....ran your snow flake program for two hours...runnin smooth. hey got the dude at work grindin the zip tools. randy.

 

Man that is awesome Randy! I just saw your last post what a great looking/preforming machine. Nice one
Mark