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Author Topic: Question for the CAD gurus.  (Read 1595 times)
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Russ Lister
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« Reply #25 on: November 21, 2018, 06:24:12 AM »

If you trace back the functionality history of cad packages you will see that some things were not available to me when I was working with CNC machinery nearly a quarter of a century ago!
My 2010 version will convert splines but I get some horrible judder when using my vinyl cutter due to the amount of small segments.
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pedwards2932
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« Reply #26 on: November 21, 2018, 06:40:53 AM »

This has been interesting conversation.  I use Inkscape for all my plan drawing and it allows you to flatten the Bezier curves (you select how detailed you want it).  I use a program called T2 for all may laser cutting and it optimizes the dxf and I have never had an issue with how it cuts if I flatten the Bezier.  I find Inkscape to be the easiest program to use for tracing plans.  When I was using Ben Cut Laser you had to convert the SVG files from Inkscape to polylines or it would cut in small sections.  T2 cuts smoothly and I can export from Inkscape as a dxf file directly to T2.
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Russ Lister
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« Reply #27 on: November 21, 2018, 06:45:59 AM »

Yes, some optimisation programs do a good job.
They will resolve a tighter turn with more segments and a shallow curve less .... things are getting better!
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« Reply #28 on: November 21, 2018, 07:01:15 AM »

Interesting.

But it also states:

"It's been my experience that lower end software that is often bundled with the machines is the most likely candidate to have an issue with splines"

and

"The best case scenario is nothing. It may be that the software used to program the machine doesn't have an issue with splines"

This is probably why I have never encountered any issues, I am sort of a assuming that the £500K fibre laser, or the £200K HAAS machining centre that works with the Solidworks derived geometry/splines comes with software or uses software that simply copes with the splines...

Having said that the VMC files are generally FASTCAD derived, and their laser cutters aren't that high end...

So it's potentially the high end professional stuff that can cope, rather than the low end (and maybe beginner stuff) that can't?

You could also be right, things have just moved on.  It is possible that because designers like to use splines, the folks that have to cope with the data generated in manufacturing (and those that make the machines and software) have simply got smarter at coping with them without us having to worry...

Also possibly with a 1TB hard drive costing a few quid nowadays who worries about the size of the required files (that was probably a worry 25 years ago), and the "gaps" are so teeny weeny and therefore "judder" simply doesn't happen because, the accelerations just aren't as high and are well within the resolution of the machine movement...

Andrew

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Russ Lister
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« Reply #29 on: November 21, 2018, 07:17:54 AM »

I agree entirely with that first line Andrew.... I have had to work with output from all sorts of sources and working on someone else's software as a sub contractor. More sophisticated software and machinery does indeed handles things better.
In the scale of things, our little model aeroplane plans are not going to throw up too much of a discrepancy.
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Russ Lister
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« Reply #30 on: November 21, 2018, 07:21:56 AM »

On your last comment, the size of the hard drive has never really been of any relevance. However,  earlier machines were limited to an 8 bit number so taxing JOBS like spline conversions required line numbering to be removed about a certain limit (32k)
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Russ Lister
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« Reply #31 on: November 21, 2018, 07:24:09 AM »

Standing in the freezing cold on someone's else's WiFi so apologies for any typos! Back in the warm now
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Indoorflyer
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« Reply #32 on: November 21, 2018, 11:41:38 AM »

Glenn,
On the Outerzone page for the Sterling Waco downloads, there is an important note regarding the parts drawings: "Parts drawings are offset 0.4 mm for 0.8 mm CNC cutting tip".

Might want to ask over on OZ as well, for simple scans of the parts sheets.
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Glenn (gravitywell) Reach
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« Reply #33 on: November 21, 2018, 04:32:06 PM »

Hi Indoorflyer.  I saw that annotation but didn't know what it meant.  Now I understand.  Thanks much.
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Glenn Reach
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