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Utectok

Arc smoothing in workflow for laser cutting how do you do this in VW

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Hi all first post and all so I might be in the wrong section (mods move it if you need to) but here goes....

I'm working with a plasma cutting guy and the complex files I'm building need "arc fitting" can this be done accurately in VW?

I can do it in Rhino but it seems like I should be able to do it in VW and save a stage? The "arc smoothing" command even set at very high 2d conversion changes the file to much.

Any help would be appreciated.

Cheers Will

Edited by Utectok

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Yes this is a bit of a pain. The "smoothing" commands don't actually "smooth" so much as just *convert* existing verticies.

Having a much higher vertex count than would otherwise be necessary will give better fidelity when converting from Beziers or Cubic Splines- at the cost of a much bigger pain in editing.

I personally prefer drawing curves with Cubic Splines but gave up on this for CNC profile cutting and just draw with Arc Verticies from the start.

The Tangent Arc mode in th Polyline tool makes this not too bad a prospect.

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Ok propstuff this is definitely the best plan unless like me the client wants artwork traced in Illustrator and the resulting file is an exported dwg from AI. So it is full of loads of various data and is a large file (many lines) so retracing in VW is completely impracticable. It seems VW should really offer a output for plasma cutting although I realize many more current companies can create g code straight from ai files this is not the case here in bonnie scotland and they don't seem to be able to deal with splines at all and polys slow the cut time to much for a complex form.

Help!!!

Cheers Guys and gals

Will

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The inability of CNC software to deal with splines seems universal at least here in Au.

I'm guessing modern CNC machines can do it, but the profile cutters here all seem to have stuck with their 1995 V1.0 Toolpath and don't wish to pay the $20K to get a new one.

Have a look at this:

http://scs-inc.us/default.php?page=products&subPage=Products/CAD~CAM~CNC/Default

I've not tried it yet but..............

Can you post a sample of what you're trying to convert?

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Welcome to the Forum, Will. Please click on the My Stuff tab at top of forum window and make yourself a forum signature with VW version, OS flavor and version, and a bit about your hardware. This all helps with troubleshooting and advice.

I have done many VW to waterjet projects. My method is to draw the paths in VW with the polyline tool. I toggle btw corner point mode and the arc modes with the U key.

A few years ago, one cutting project involved about a hundred line drawings, by elementary school kids, in pencil on letter sized paper. These were distributed to a bunch of Urban Planning students who all had access to AI on the campus computers, but not VW. They scanned each pencil drawing to jpg, imported and traced in AI, exported to DWG, and emailed to me. I imported each one to VW- they came in as bezier points, converted all paths to arcs, and rescaled as nec (I think it was about .3AI=correct VW). Then export VW to dwg for the cutter. I also checked this cutting dwg by reimporting to VW for a look. This was not as tedious as it all sounds, and actually there were no cutting errors. It all worked really well.

We found that the "find edges" and "auto trace" functions in available software (AI, VW, Photoshop) returned too many vertices, arranged in zig-zaggy paths. Hence the hand trace.

To reinforce Propstuff's excellent comments: VW's "Arc Smoothing" command converts all vertices of the selected polyline to arc vertices. This presents two problems. Corners are rounded, and some straight lines are interpreted as arcs with infinite radii. For sharp corners, either do the AI trace with 3 closely placed vertices at each sharp corner, or apply VW polyline edit tool in convert to corner vertex mode. Usually, the infinite radius points can be deleted to make the path acceptable.

I agree that lots of cutting shops have old software. It's unclear whether new CNC software can read VW exported Splines and Beziers. Anyone know about this? Also, splines may be different in different aps. Cannot verify, but one ACAD user tried to explain that ACAD splines are not real geometry, are not actual vectors. Anyone know about this?

Check your cutting files!!! Open in ACAD, or at least reimport into VW. When possible, go to the cutting shop and look over their shoulder when they open your dwg. Any file could blow at any seam:

1. I once exported a VW to dwg and sent it to cutter (first time with this shop). My VW drawing had labels and 3 point leader lines with end dots. The cutter opened my dwg, deleted my leader lines and made the cuts. The parts came back with 2" holes where my leaderline end dots were - the VW export had converted my leaderline into two lines and a circle. Fortunately, the cutter was able to provide new disks from same material, and my weld shop was able to fuse them in.

2. Another forum member reported losing lots of material & cutting fees to a cutting error resulting from open polylines exported from VW resulting in closed polys in the dwg cutting file. Big slices across the sheets cut the parts into unusable segments.

Enough rambling. Post back with specific questions or to let us know how it went.

-B

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thanks benson a great help.... I'll try your ideas not absolutly certain how to use "polyline edit tool in convert to corner vertex mode" But I'll muck about!

Cheers Will

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Oh, for many tools, there are several modes. These are the little boxes in the Mode Bar near top left of the VW window. Click the box(s) you need, or toggle through them with the U and I keys. Hover over each and a label will dispaly.

I wrote "convert". Sorry, the mode is actually called "Change Vertex".

And Here is the correct screen shot

-B

Edited by Benson Shaw

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