re: Compucut ?

Rab,

Interesting to hear that you are already running a Roland on HPGL.
Expanding your use of HPGL is certainly a choice if it is already
working for you. Compucut could work similarly.

The gcode advantages over HPGL (and I'm a comparatively newcomer) would
be that gcode is expressly designed and extensively used for machine
tool control (3d, multi axis), whereas HPGL was designed for plotter
control (2 axis, + pen up/down). I have just leaned that HPGL protocol
may be extended to 3D, however it does not have the support that gcode
has. HPGL would have to have "M codes" added, "plane" modes, tool comp.
and other additions added to be similar in capability. I see the
utility of being able to use HPGL generated by many programs to drive
machines. What is lacking IMO, is control of the order and direction of
cutting. If a "post processor" is required for HPGL code to be useful
in machining, then why not just convert it to gcode instead?

On the bipolar/ unipolar question, stated very basically, unipolar uses
half or less of the windings at one time, while bipolar uses both
windings. The bipolar windings are of lower impedance, and hence,
higher currents and faster rise times of those currents are possible,
allowing higher stepping rates. Bipolar drivers are more complex, and
usually are implemented with choppers. The chopper allows higher
voltages to be used to drive the windings, thus faster rise times, with
limiting when the proper current is reached. Bipolar drives are
typically capable of higher powers and speeds. Refer to Mariss' white
papers (geckodrive site) for a more through explanation.

Hope this information is useful! Others can expand on these simple
explanations. But remember, if it works for you, RUN IT! These
comments are merely meant to be informative, not to convert you!

Alan KM6VV


Rab Gordon wrote:

>
> Thanks for the replies,
> Could anyone explain the advantages of G-Code over HPGL ?
> My current machine, a Roland uses HPGL to cut in 3D very
> successfully, although I have nothing to compare it with, it contours
> well enough for me. It seems that compucut would work similarly ?
>
> I don't understand the unipolar v. bipolar thing yet, is there a big
> difference ?
>
> Rab
>
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