Splines (again) in Autocad LT

Quik&Easy · 发表于 2022-7-7 17:30:13

A search of the forum for "splines to plines" shows that this is an ongoing problem for us newbies.

I have read the recent thread a couple of times and now find its relevant to me as well. I received a drawing for estimating purposes and find that it has the splines/plines problem, a real problem for me with a need for 2D image only. I'm using ACLT 2011.

I've attached samples of what I'm working with. This project is comprised of 11 separate drawings, similar to the partial samples I've attached.

Drawing 2A is before going through the save as a R12 dxf and re-open, etc.
2C is after reopening and holy cow, thats a lot of plines. Its also a lot of work to edit and eliminate the numerous vertexes and still remain sure I'm keeping to the contour. This is an artistic project so some deviance from contour would be OK, I'm not tied to a tolerance of .001 or anything like that. I have exploded a section of the C drawing and see that its all straight lines about 1.76" long rather than any type of arc at all. For visual reasons, I'm quite sure the client will be able to see the numerous straight lines vs. a few arcs in these outer contours. I'll certainly be able to feel them if I run my hand along the finished edge.

Is there a "splines for idiots" explanation of how the spline was drawn in the first place (or how it ended up a spline rather than a pline); I don't know how the drawing was achieved, whether it was drawn in AC or somehow converted via something like Illustrator. Is there a "pedit" for idiots as well? I have that command in LT, it opens up an option box, but I don't know what to do or how to use it from that point forward. A few pointers would be very much appreciated.

My task is to cut these shapes from steel plate.

I will be able to provide an estimate for the cutting based on the flattening via R12 method but this project can provide me with a valuable learning experience about combining 3d into 2d with the software I'm running. Only if I get the project will I actually have to perform this conversion for real.

Sorry about the "novel-length" post but I wanted to give all the info thats related.
part Piece 1 - zo test 2c.dwg
part Piece 1 - zo test 2a.dwg

nestly · 发表于 2022-7-7 17:43:22

First of all, I'm no Spline guru, in fact Splines make my head hurt.

You should not have to export/import your splines to convert them with LT 2011, you should just be able to convert them directly with either PEDIT or SPLINEDIT, As for the number of vertices, I have no idea how to reduce those other than using a low "precision", but you can get a smoother effect by changing PLINECONVERTMODE to 1, which will result in a polyline that uses arc segments, rather than line segments.

eldon · 发表于 2022-7-7 17:56:10

Whereas I cannot help you with Splines in your version of AutoCAD, one of the drawbacks of converting Splines to Polylines with the R12 DXF method is that the number of vertexes increases.

To reduce this number, one has to use a lisp called Weed which reduces the number. Unfortunately, LT cannot run this lisp, so perhaps you could seek out someone who could do this for you.

Just to give you an idea as to how it reduces the number of vertexes, I applied it to your posted drawing, and have posted it back.

P.S. If you use the Fit option in Pedit, the line will no longer be a series of straight lines
part Piece 1 - zo test 2c-Weeded.dwg

Quik&Easy · 发表于 2022-7-7 18:12:04

Thank you, gents. That file is a huge reduction in vertexes and will probably work just fine. I'm also going to save it as a 2007 dwg and see if the post processor I use will recognize the spline to create g-code or if it will choke on it as being a 3d entity. Will report back later. Thanks again for the help.

nestly · 发表于 2022-7-7 18:28:59

I'm not sure it's necessarily the DXF conversion that's causing so many vertices. PEDIT/SPLINEDIT in AutoCAD2011 converts it to a polyline with nearly 600 segments using the default settings. The best PEDIT can do is ~50 at the lowest options, and ~4800 segments at the highest precision. New splines that I create then convert have about 1/10 as many vertices?

Quik&Easy · 发表于 2022-7-7 18:33:50

I took the original file, which came as a DXF, not sure which version, and saved it back to a 2007 DWG. Took that file to my post processor to create the Gcode for machine movements. Surprisingly, there are some letters that are not included in my sample files, those letters were all interpreted as straight lines, tons of them (whereas they should have been just a few arcs and straight line segments) while the splines along the outside contours were interpreted at roughly 20 arc segments each and looked pretty smooth. This may work just as it is. Very surprising.

[综合讨论] Splines (again) in Autocad LT

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