1.5.0 gcode creation error

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aabill
Posts: 2
Joined: Thu 11. Apr 2019, 13:21

1.5.0 gcode creation error

Post by aabill » Thu 11. Apr 2019, 15:01

Hello

I purchased recently and I am VERY impressed by the quality of WingHelper (and I'm a super-critical retired IT guy!!). However, although I will later use it for built-up wings my main reason for buying it is to produce gcode for my CNC hot wire cutter.

Unfortunately there seems to be an error in the gcode exporter. It produces correct code for a not tapered wing but for a tapered wing the code produced would cut a wing with correct root size but reduced tip size. For example, a simple test wing with root chord 300mm and tip 150mm produces gcode to give 300mm root and 100mm tip.

Platform is Linux (OpenSuse LEAP 15.0) (although I'm pretty sure the problem is not platform-related)

Attached is test data so you should be able to replicate the problem. It contains two simple tests of a tapered wing, one swept and the other not. Also the "real-world" example which produces even more extreme results. I used a hot-wire cutter version of grbl-panel to visualise the gcode, but it's easy to see and quantify the errors just looking at the gcode files with a text editor.

Any further info required? I'm happy to help in any way, even down to looking at source code...

Kind regards
Bill
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WingHelperData.tar.gz
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alex.pozgaj
Posts: 86
Joined: Tue 29. Sep 2015, 20:08

Re: 1.5.0 gcode creation error

Post by alex.pozgaj » Sat 13. Apr 2019, 09:51

Hello Bill,

I'm flattered to hear such great feedback from a super-critical IT guy (which I also am :) ), thank you!

Regarding your observation, please help me narrow down the problem. I took a look into your AG50 example, replaced the Z coordinate name by V (that's what LinuxCNC accepts in my setup) - it's hard to actually tell, but from what I see, it doesn't seem to be obviously bad. Can you please, based on the AG50 example, help me understand the issue?

What I have seen in your file is that the machine width you set is 1000, while the panel length is 730. With a strongly tapered wing like yours, it can happen, if the machine width is so much larger than the panel length, that the wire path for the last rib moves in a very strange way, sometimes even traversing backward respectively even "inverting" the rib sides. However, this is to be expected, because the *actual* end of the panel is not at 1000mm, but rather at 730 (plus the side offset, of course).

I prepared a drawing to explain the situation better - "A" depicts the real length of the tip rib, while "B" shows the apparent length at the end of the machine (i.e. the length traversed by the wire at the right portal); green lines depict the wire position at the beginning and at the end of the rib:
NGC-Area.png
NGC-Area.png (31.92 KiB) Viewed 666 times
Could it be that you got tricked by that effect into believing there is something wrong? How did you test - actually cut the foam, or did you visualize the output in a test program like LinuxCNC?

I might be overseeing something obvious here, of course. :)
Aleksandar Pozgaj
Wing Helper e.U.

aabill
Posts: 2
Joined: Thu 11. Apr 2019, 13:21

Re: 1.5.0 gcode creation error

Post by aabill » Sat 13. Apr 2019, 13:56

Alex

Thank you so much for your prompt reply by email. I had indeed neglected to change the machine width from the default 1000mm to 800mm which of course as you illustrate, results in much reduced movement of the UV gantry. Schoolboy error on my part and I apologise for even suspecting an error in your programming!! I am delighted that I can now proceed to use WingHelper in my workflow.

Kindest regards
Bill

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alex.pozgaj
Posts: 86
Joined: Tue 29. Sep 2015, 20:08

Re: 1.5.0 gcode creation error

Post by alex.pozgaj » Sat 13. Apr 2019, 22:40

No problem Bill, I'm glad it worked, it could have been a bug as well. To be honest, as I developed that part, I also thought that can't be right. Took me a debugging session to understand how it works. :D

I hope we get to see your plane once you build it!
Aleksandar Pozgaj
Wing Helper e.U.

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