Re: [CAD_CAM_EDM_DRO] Help please: Stuttering Stepper Motors in Jog Mode

Hello Thomas,

I use an old 200MHz Toshiba laptop with TurboCnc 4.x to run my Sherline
5410 (metric 5400) CNC mill.

TurboCnc requires DOS mode. You must boot up in DOS mode or reboot from
Windows to DOS mode. Otherwise, Windows interrupts will result in
erratic motion and missed steps.

Holding down the jog key may generate interrupts so this might be more
noticeable than Gcode commands.

Interrupts cause more problems at high speed than at low speed. Jog keys
probably result in highest speed. How fast is your rapid speed set?

Another possibility is that your rapid speed might be setup too high.
This won't effect your Gcode commands unless you set your feed nearly as
high as your rapid speed. If you don't need to move faster than
1000mm/minute then set your rapid to 1000mm/min and avoid rapids that
are faster than your system can go.

Tom Hubin
thubin@...

***********************

bear_cnc wrote:

>
> Dear All,
>
> I have recently converted my Denford Orac lathe from Parker CD20 to
> Gecko 210 stepper drives. The lathe is driven from a laptop PC using
> TurboCNC 4.01 software. The CD20's needed 24V pulses hence were
> connected through a breakout board, but the Gecko's are now directly
> wired to the parallel port (+5V to Common and the step and dir pins
> to the step and dir terminals).
>
> The new setup suffers from the most peculiar fault:
> When I jog an axis along by pressing the cursor keys the motion of
> the axis is erratic, jerky. It stutters like a misfiring engine or
> jamming machine gun. The distance travelled has little to do with
> how long you press the key.
> However, when in MDI mode, and I enter G1 Z10 F50, it moves along in
> a perfectly smooth manner. (Same goes for any other F from 5 to
> 1000.) The distance travelled will be exactly 10 mm, or whatever I
> have asked for.
> I pulled the old `scope out and had a look: In MDI mode the pulses
> come perfectly harmonic, not missing a beat.
> When using the jog cursor keys however the scope screen matches the
> stuttering sound and jerky travel: The rectangular wave is totally
> irregular. Amplitude is nearly 5V in both cases.
>
> This is one for the experts: How can the step pulses on the parallel
> port be so irregular when generated via cursor keys, and perfectly
> OK when triggered by software alone?
>
> To be sure, the G210 is OK since it also works perfectly well with a
> TTL signal from a generator, and the laptop is also OK because I
> have tried a different one (different make altogether) and it gives
> 100% the same results.
>
> It's got to be interaction between the drives and the PC, but how
> and what? Why did I never get anything like this with the CD20
> drives?
>
> Any suggestions appreciated.
>
> Best regards,
> Thomas.
>
>