On Saturday 18 August 2012 06:55:51 Yorik van Havre did opine:
> Hi Gene,
> Sorry about the late reply
> Your 2 questions are a bit vague, I'm not sure how to answer. By scaling
> do you mean zooming? About dimensions, they are not enabled or
> disabled, you need to add them manually, being in the sketcher or the
> draft workbench.
I expected that a menu would appear on the left side of the screen when I
had added a line/circle/box, one that would allow the editing of the
dimensions, but while a menu did appear that looked like it was editable
for colors etc, no dimensions were listed. So it was not possible to
specify that the box was to be 34mm long, 22mm high, which was to be
extruded to 22mm thick eventually. Those figures are arbitrary of course,
picked out of thin air, but what I wanted to do was to draw a cage for a
ball nut, which is for an 8mm by 2.5mm pitch ball screw. It is intended to
mount on the bottom of the cross feed table of my lathe. The nut itself is
round, .750 inches in diameter, and .675 inches long.
I have it partially carved on my milling machine now, but have made no more
progress since last Tuesday when the owner of our local radio station came
by and asked me to go take a look at his main transmitter since that is
what I have been doing for a living since '62. Chasing electrons & making
them do useful work for a living since 1948.
The transmitter is about 60 years old, and not well cared for, so its list
of problems reads like a restaurant menu. Rapid fixing is compounded by
the scarcity of parts for such an ancient unit. I replaced a 200pf, 5kv
tested, 1.2 amps of current rated mica capacitor in the final's driver
stage yesterday which I suspected of opening up when hot, detuning the
circuit. So it is back on the air, but the 833C's in the modulator are
tired so it isn't modulating well. A fresh set of those should be here
> About the squares, it depends on how they are created
> (sketcher or draft).
ISTR I had tried both methods, but got into an 'I need an undo' state which
could not be exited by any method except sending freecad a kill -9 as the
normal exit was denied, claiming to be in an incompleted edit mode.
After the update since I wrote that, freecad now works to display the
online html docs, it did not before, but I wasn't able to find a back
button to get back to the screen I was working on, and was again only
terminatable with a kill -9. I find, at my age (77), that is so distracting
that it over rides my train of thought. Running two copies on separate
workspace screens might be handy but I've not tried that yet.
> In any case, you'd probably better have a look at the documentation:
That page is advertising version 0.12. Since I am getting version 0.13's
fresh builds about 2x a week from the update manager, it strikes me as
having the potential to be outdated.
Not having a place to enter the part dimensions right up front seems to me
like a huge oversight. I can probably work, and should be working from the
micrometer measurements I can take from the actual part I'm trying to build
a mounting wrapper for even if I have to manually translate that .750
diameter from inches to mm's to do it, but with no place to do it in the
freecad menu system, it is of very little utility, so I am writing the
gcode to build this on a cut by cut basis, doing all my cutting bit
diameter compensations as I go. Relocating the part in the vice when I
have to present a new face as the top to do the next operation is likely to
be a problem, and that is the next 2 steps, cutting out the sides of the
cage so that the cage can be flexed enough to be driven over the nut, then
closed back up enough to grab it. With little or no lengthwise play
allowed, since if there is, I'll have to drill and tap one end of it for
setscrews to eliminate that play since it will translate directly into
backlash that LinuxCNC will have to compensate for.
> About pycam, i don't know which formats it uses, but FreeCAD exports to
> many well-known formats (step, iges, obj, dxf, etc..), surely there is
> one that works.
PyCAM can surely work with one of those. But I know nothing about python.
In years past I have written lots of code, but in native assembly for
smaller cpus, 1802, Z-80 and the 6809/6309, or in C, and most recently
since the hardware is gotten wider data over the last 30 years, even in
bash. But lisp-like languages such as python have eluded my mental grasp.
Old dogs, new tricks syndrome I guess.
> Hope it helps!
Hopefully I will have the time to explore it more later today, its early
for me yet so the instant error is $ENOTENOUGHCOFFEE.
What I am hoping to do here is to relate to you folks who are intimately
familiar with this, the problems a total newbie who pretty much has a
mental picture of what he wants to do, while trying to translate that
mental picture into something I can both print out in 2d views with
dimensions of every line or pair of faces noted, and if possible, actually
have the gcode written by PyCAM. Usable by a newbee who has never seen
autocad run should be the documentations major target. You do have a
'start' button/mode that looks like its defined, but what does one do next?
That is the sort of documentation help a rank newbee needs, but I'm not
The biggest problem with PyCAM and its ilk is that the gcode generators I
have tried to use so far, all "unroll" what obviously can be done with a
conditional loop, generating tens of thousands of lines of code, where by
using named variables and conditional loops and or named subroutines, I can
do that directly in gedit, vim etc, in 50 lines of code that on my little
machine might take 36 hours to run. Not to mention that to fix an errant
dimension in my gcode is a single named variable edit & rerun the code.
Such code generators as I've tried to use so far are idiotically simple as
they don't use named variables and it is simply not practical to go through
an 80k LOC file changing the value for the Y dimension in every 4th line of
code when that value is being incremented by .010" or less for every time
that move is encountered.
So automatic gcode generators have a long way to go yet to 'get there' IMO.
Thank you Yorik. Off to find some coffee & something for breakfast.
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