Toolpath problem - is this intended behavior?

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Binkmeister
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Toolpath problem - is this intended behavior?

Post by Binkmeister »

I'm trying to use PhotoVcarve to do landscape cuttings, and have run into an issue with how the toolpath honors cutting depth.

https://youtu.be/ytzcM3MrI6Y

I'm doing a 1.5" deep rough cut of a mountain on an Xcarve machine with a 1/4" ballnose bit. PVC generated gcode using the Vectric Vcarve postprocessor. I had problems wit jitter, which I've minimized by using the shortest possible bit and adding a beveled edge to the design, but I discovered there is one major issue with cutting depth in some instances. The video above shows exactly what's happening. On the right side, the path properly cuts at 0.05" passes, but when it goes back left, over the top of the mountain, rather than doing multiple .05" passes, it does one massive cut, which creates huge stress on the machine. The linespacing is 20%.

Question (for developers): Is this intended behavior? And is there something I can do to prevent this from happening?

This is the only remaining issue I have. Thanks for any help or suggestions.

- Kelly

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Ms Wolffie
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Re: Toolpath problem - is this intended behavior?

Post by Ms Wolffie »

WOW
You cut all that in a single pass?????????
My machine would die long before that.
Cheers
Wolffie

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Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

No, sorry that wasn't clear, I did not cut that in a single pass. The depth of cut was set to .05", which worked fine - except where the machine did NOT cut at 0.05". That's the problem - the toolpath is sometimes cutting deep instead of doing multiple passes. That's what the video is showing. The first part of the video is fine, where it goes back and forth and dips .05" each pass, but when it comes back left, it does not properly cut .05". That's why the machine is tearing itself up, and I want to see if that's the intended behavior - I can't imagine it is.

Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

To illustrate my question, here's a graphic of what's happening on my project.

Image

1. Cross-section of my project.
2. Green lines are the toolpath, which correctly routes out the right side of the design.
3. Problem area: The red line shows how the toolpath dives deep on the left side, routing out the entire area in red in one pass. This is the problem.
4. Here's the expected toolpath, but it's not happening.

weber765
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Re: Toolpath problem - is this intended behavior?

Post by weber765 »

Can you look at your g-code and find where it is commanding the Z axis to cut full depth ? If so, you could try re-posting your program and see if it corrects itself.
There should be an incremental command to cut to depth. Look at the g-code that cuts correctly and see how its done. If it does not re-post correctly you may have to edit your g-code manually. I struggle with g-code myself so I would not be able to help you much with that.

weber765
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Re: Toolpath problem - is this intended behavior?

Post by weber765 »

I just tried a junk program I wrote and I can see where you are having problems, I do not know how to get around.

If you look in the gallery section under " perfect use for PhotoVcarve " there is some work posted by Charlie_L that looks like what you are trying to do. You might try contacting him and see if he has any suggestions.

weber765
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Re: Toolpath problem - is this intended behavior?

Post by weber765 »

Hi Binkmeister

I just figured out how to do what you are trying to do and it works ! It may sound a little redundant but here is how I did it.

Open you file in Photo Vcarve and set perimeters to cut .050 deep and save as whatever 1.
then change perimeters to cut .100 and save as whatever 2
then change perimeters to cut .150 and save as whatever 3.
ect. ect. ect until you get to final depth.

then machine each file in numerical sequence and it should do what you are looking for.
I verified it worked by opening the files in Aspire on over the other and it works fine.

It may be the long way around but it works.
Glenn

Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

I think you're right, that sounds like it would work. I ran some quick numbers, and it's about 1/3 slower than doing it piecemeal rather than in one pass, but this would probably also solve other issues. It'd be a bit of a pain to generate 28 gcode files, but I could probably write a script that concatenates them together pretty easily.

Thanks for the suggestion!

It would also be nice to hear from the developers, and see if the way the current software acts is what was intended.

weber765
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Re: Toolpath problem - is this intended behavior?

Post by weber765 »

Writing the code is pretty quick you only have to change the depth each time and if you have Vcarve or Aspire you can import each Photovcarve file over the previous file. You then can post all tool-paths at the same time in 1 file. If you do not have Vcarve or Aspire you should be able to combine all the separate files together in notepad.
Also to speed things up you might be able to decrease your step over but ramp your feed rate up a lot, it is called chip thinning in the metal working trade and is used all the time to reduce machining time.

I Hope this works out for you
Glenn

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Adrian
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Re: Toolpath problem - is this intended behavior?

Post by Adrian »

Binkmeister wrote: It would also be nice to hear from the developers, and see if the way the current software acts is what was intended.
This is primarily a user to user forum although Vectric staff do post here occasionally. If you want an answer from the horses mouth it's best to email support@vectric.com directly.

Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

Adrian wrote:
Binkmeister wrote: It would also be nice to hear from the developers, and see if the way the current software acts is what was intended.
This is primarily a user to user forum although Vectric staff do post here occasionally. If you want an answer from the horses mouth it's best to email support@vectric.com directly.
I thought I'd seen somewhere that they monitor the forums, but good suggestion. I had a very good response from them a couple of weeks ago about something else.

rsetina
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Re: Toolpath problem - is this intended behavior?

Post by rsetina »

I'm looking at the length of the bit and what looks like the long shaft of the router. To me it looks like there's a ton of pressure being put the the bit and long router shaft. It's like a long fulcrum, if you understand where I'm coming from.
Rick

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NormanAlbert
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Re: Toolpath problem - is this intended behavior?

Post by NormanAlbert »

I too have had this problem. Don't understand why it happens but it's unnerving when it does. Is there a fix? Norm

Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

NormanAlbert wrote:I too have had this problem. Don't understand why it happens but it's unnerving when it does. Is there a fix? Norm
Good to know I'm not the only one experiencing this. I've sent my files to Vectric Support but haven't heard back yet. In the meantime, Glenn (weber765) has a suggestion for a workaround, see above. It takes longer to prepare the files, and takes longer to run, but *should* eliminate the deep dive problem I illustrated in this thread. I haven't tried it yet, but probably will this week.

Binkmeister
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Re: Toolpath problem - is this intended behavior?

Post by Binkmeister »

Apparently, this behavior is a bug in the software; they didn't anticipate people using it to carve such deep projects. It's been reported to the developers, but there's no immediate fix anticipated. In the meantime, I'm going to try Glenn's workaround and see if that works. (I generated the code but haven't cut it yet.)

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