Pulse Unit

[Greolt]

AWC 608
Main Board 8.12.01.28
LCD Board 5.12.01.05
LaserCAD v5.85

I come to laser from the CNC world. In step and direction motion control, steps are referred to as "steps per unit" (step per inch or steps per mm)

On the AWC608 it seems to be otherwise. "Pulse unit" is how it is shown on the manufacturers parameters settings. However it is in reality not steps per unit. It is some other thing.

My X and Y axis are designed and built to be 1000 steps per inch (39.37 steps per mm) But entering 39.37 in "Pulse Unit" leaves it way out, in distance travelled.

In fact I must enter something like 25, to make it travel the commanded distance.

So what is "Pulse unit" ? I have even heard it referred to as "pulse width". Very confusing terminology, normally refers to PWM.

I know the first thing others will say is, you have your calculations wrong. That's what I would say. The calculations are not wrong.

I have been running this laser up till now with Mach3, which I am very familiar with, at 39.37 steps per mm.

So can someone set me straight. What is "Pulse Unit"?

Greolt

PS: I know about "read and save"

[Greolt]

I have received an answer to my query from another source.

"Pulse unit" is the distance of one step in um. Therefore 25 was close. 25.4 to be precise.


The next question or observation I had was to do with the "Pulse unit" setting for Z axis. I need a setting of 0.432. The system will not allow a setting below 1.

This is no big deal because it is the Z axis, however it seems silly not to be able to set it to a correct value.

Greolt

[Ruud Hogenberg]

Greolt,


Reading your interesting finding on pulse vs step.
You would like to know what is the length mm of one pulse?
I think it depends also on the steps per 360degrees on your machine, your stepper motor driver setting.
In your machine it looks to me that one pulse is 25.4/39.37 = 0.639 step

25.4 is also the figure of inch/mm as you know, so pulse could be per inches not um.. (PPI)

For your setting of z-axes, you could change the stepper driver to get a higher figure, but be carefull on that. not sure to increase or decrease the steps.

This is from the Photograv forum, it could also be interesting for you;


QUOTE
The Chinese machines tend to use a parameter called "scan gap" instead of dpi. Here is a listing of how to convert between scan gap and dpi.

Converting Laser Scan Gap to DPI
Scan Gap is how far the laser moves on the Y axis for each pass of the laser. Scan Gap is where you enter your DPI for engraving. DPI is in inches and Scan Gap is in Metric

DPI/25.4 = dpmm (Dots per millimetre)
1/dpmm = Scan Gap

Eg.
300/25.4 = 11.811 dpmm
1/11.811 = a scan gap of 0.0846

Some Converted for ease of use

DPI Scan Gap
1200 = 0.02116
800 = 0.03175
600 = 0.04233
500 = 0.05080
400 = 0.06350
300 = 0.0846
200 = 0.12700
150 = 0.1693
100 = 0.2540
UNQUOTE

Regards Ruud
www.gippetto.com

[Greolt]

For your setting of z-axes, you could change the stepper driver to get a higher figure but be careful on that. not sure to increase or decrease the steps.

The stepper drives I use are Gecko G251s. They deliver ten microsteps. Gecko believes this is the optimum for a stepper motor and is not adjustable.

Greolt

[wtlowery]

I am upgrading a chinese laser and my pulse units can't be changed in Lasercad without a password, anyone know what it is. Version 5.85

[Tech_Marco]

"608"

Marco