Michael,
the documentation is of course the first thing where to look for the
information you need.
But having been there myself I know it can be quite overwhelming ...
> I've been reading in parts of the documentation and troubleshooting
> pages that some of these issues could be due to step length and such
> being set up incorrectly.
>
In you previous posts, beginning of April, you already mentioned that
you changed the stepper timings and inverted the step signal. Step
timings of 2,000 us (is that 1,000 for the step len + 1,000 for the step
size or 2,000 + 2,000) are not that fast. Usable for most drivers and
motors (I've got big (slow) ones driven at that (2,000 + 2,000) rate
without losing any steps). As I found out inversion of the step (and
dir!) signals may make the difference. Most stepper drivers use opto
couplers connected between the I/O bit of the parallel port and the +5V
supply (I took that from a USB port on the PC). As long as the stepper
motors are not moving, the step signal is low and it is only being
pulsed high if a step signal is needed - this means that there is a
current flow through the LED in the optocoupler when the motors are
idle. Having a (fairly high) current driving the opto couplers all the
time may just be too much for the port. On my FPGA board I had to invert
both the step and the dir signal - the dir signal only becomes active
when driving the step signal.
> Do these numbers look normal? The MAX_VELOCITY and MAX_ACCELERATION
> look strange to me.. but then I don't know what normal is..
>
these values are in (inch?) per second and inch per second squared.
MAX_VEL = 0.1 means 6 inch per minute - seems a bit on the slow side for
my machine (I have 25 mm/s = 59 "/min). With these values you should at
least never hit
> The backlash is a little high - it's on the list.. but otherwise what
> should I be looking for here as "normal".
>
Backlash is what you would have to turn the handwheel before the mill
starts moving. 0.008 inch (0.2 mm) looks OK - that is normal on my hand
operated mill.
> 2) I seem to be having some issues with my Z axis loosing steps (X and
> Y seem to be pretty stable). When making a series of up and down
> moves for some engraving, the depth gets reduced as the program
> progresses.
>
That is funny. Most of the times when loosing steps this is due to
combined speed and load which would mean that loosing steps in the Z
axis would mostly result in deeper engraving. But (see remark on the top
of this mail) inverting the dir signal may do the trick.
> 3) Is the step generation dependent on the stepper motor driver, or
> the stepper motor itself?
>
Both. The driver has maximum values specified, this mostly limits your
step size and step len signals (and the max. stepper frequency) but the
motor is mostly slower than this so the max accel and max vel are really
determined by the motors.
> Any advice or pointers to any good resources would be greatly
> appreciated. Remember.. I'm a NOOB at this, detailed explanations
> would be GREATLY appreciated.
The docs - I discovered that a lot of questions that I had would have
been answered by reading the docs. Only problem I had was that there was
so much documentation and so little time to read ...
Good luck,
Rob
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