RE: [CAD_CAM_EDM_DRO] Why calculate steps/unit? Just try it...

<Rant On>

I disagree. I have never figured out the step per unit setting by just
putting in a number and hoping. All the required parameters are very
easy to determine (lead screw pitch, reduction ratio, steps per
revolution) and the math is simple. Take the Sherline in inches. 20 TPI
screws direct drive. So it takes 20 motor turns to go 1" If you are
using standard 200 step/rev steppers and using a 8x microstep you have
1600 steps per motor turn times the 20 turns per inch for 32000 steps
per inch. If you need the movement per step it is just 1/32000 =
.00003125 Now how long will you screw around trying to get that number
right with a type and pray approach?

The math is simple and it works. If your movements do not match the
calculations you have something wrong and it is not the setting. It is
that simple. The steps per revolution are what they are, meaning you
will not have 1599 or 1601 steps per rev on a 200 step motor with a 8X
microstep. The reduction does not change. If you have direct drive it is
exactly 1:1, if you have a 2:1 belt that is what it is, it will not be
1.999:1. If you use 10 tpi screws there are 10 tpi. If it is off you
have bad screws and I would be pretty confident that the error will vary
in different spots on the screw so you fiddling with the setting will
not help. Replacing the screws with ones that are made to the proper
spec will.

<Rant Off>

Tim
[Denver, CO]
Sherline products at Deep Discount
Mach1 & DeskCNC with credit card ordering
www.KTMarketing.com/Sherline
Now selling Visual Mill

> -----Original Message-----
>
>
> Soapbox mode on:
>
> If you are building a machine and calculating ratios it makes a lot
> of sense to figure steps per inch but if you are trying to run an
> existing rig it just seems easier to plug a number and try it. Jog in
> one direction to take up backlash, install an indicator behind the
> direction of move at near max travel and do a .25" jog. The
> percentage difference between what you asked for and what you got can
> be used to modify the steps per unit. You can also just read the hand
> wheel. It seems like a silly intelectual exercise and waste of time
> to try to pre calculate it. Your likely to be wrong anyway.
>
> Soapbox mode off.
>
> Roger S
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html