Hi guys, i'm new to this stepper motors world and i'm having some problems when i try to drive my nema 23 under high torque conditions. I'm usign a Tb6600 driver to control my nema. Driver specs (https://robu.in/product/tb6600-stepper-motor-driver-controller-4-5a-850v-ttl-16-micro-step-cnc-single-axis/). I'm also using a power supply that provides 12V and 6A of current to the Tb6600. My goal is to use the stepper motor to fix two intake valves of a four cylinder engine at a certain lift. The stepper motor has enough torque to open and close both intake valves when i order to make a full rotation, however, when i find the steps that give me my desired lift (for example 57), the motor rotates more than it should or less when i put the same number of steps as before. I noticed that the stepper motor gets quite hot, but after testing the motor cold i got the same results as previously. I think the motor is loosing some steps after looking to the shaft of the stepper motor. So, i would like to know what you guys think about this and maybe give me some tips or advices to help me solve this problem.
Microstepping is pretty much essential to reduce resonance (the most common cause of miss-stepping) - try x 8 or x16 microstepping.
Its also absolutely essential to ramp up and down step rates with a large stepper motor, for instance using the AccelStepper library - failing to do this will normally miss-step every time!
Hi MarkT, after testing over and over with the accelstepper library and testing 8 and 16 microstepping, the stepper motor still looses some steps when i make him move to a certain position. I already changed the acceleration and velocity in the accelstepper code a couple times but it didnt make better this situation as well as using a microstepping of 8 or 16. I even installed a belt pulley system to increase torque but the outcome remains the same. Any other thoughts ?
simotech17:
The stepper motor has enough torque to open and close both intake valves when i order to make a full rotation, however, when i find the steps that give me my desired lift (for example 57), the motor rotates more than it should or less when i put the same number of steps as before.
I wonder if that means that motor has just barely enough torque to keep going when it has an opportunity to build up momentum over a full revolution but does not have enough torque to make a partial move against the load.
OR ... assuming the valves are spring loaded there will be an opposing force while the motor is opening the valve against the spring and an over-running force when the valve is closing. Maybe a full revolution actually involves missed steps in the opening phase and extra (skipped) steps in the closing phase so that it only appears to be working properly when it does a full revolution.
I'm not sure how you could verify this other than to do some tests with a much more powerful motor. Or maybe you could reduce the valve spring pressure for testing?
...R
PS ... I presume you are doing your tests at a very very slow step rate to maximize the stepper torque.
More torque or better mechanical advantage, bigger motor or more gearing. You might up the operating voltage of the motor, but then it might get really hot.
Hi guys, answering to robin's reply, yeah im doing the test at a speed of 10 to 20 and i have already replaced the stock springs which were extremely strong for two springs with much lower elastic force required to press it down. The stepper working procedure is exactly like you described robin and i think you are right, the stepper looses steps when pushes the spring down and gain the lost steps when the springs helps the movement. I will try to increase the voltage like zoomkat suggested. I will attach here the two codes that im using for you to see if it can be from the code. i have used the stepper library and the accelstepper. The uncertainty range is between 0.05 until 0.2 mm, for instance if the stepper moves 2mm one time the next time it will move be between 2.05 and 2.2. I know that is a not very significant error but i would like to achieve the same result as before. I'm using a Indicator (distance amplifying instrument) so maybe the uncertainty can be from this instrument and not from the motor.
simotech17:
i have already replaced the stock springs which were extremely strong for two springs with much lower elastic force required to press it down.
You have not said whether you plan to use the stepper motor to control the valves when the IC engine is powered up. Valve springs are very stiff for a reason and they are usually only just sufficiently stiff to do their job properly. Replacing them with weak springs is very likely to result in a mal-functioning engine.