topic Can't join lines to form polylines in AutoCAD Forum

Can't join lines to form polylines

Anonymous — Sat, 02 May 2015 12:50:12 GMT

Hi all, I'm REALLY new to Autocad and this problem is driving me mad. I'm trying join the lines in the attached file to form single closed polylines ie cut paths for a laser cutter. I've tried a lot of the suggestions throughout this forum but nothing seems to work. I have figured out it has something to do with the curves etc and when I delete them and redraw them I can join some lines but there's a lot of curves here! So just hoping someone can spot an obvious newbie mistake.

thanks for lookin!

Re: Can't join lines to form polylines

Anonymous — Sat, 02 May 2015 13:53:06 GMT

Your problem is that your curves are splines, which cannot be joined to other objects. Even some of the straight lines are splines. If you are new to Autocad, try to avoid splines because they are geometrically very complex and are completely unnecessary for something like what you have in this drawing. You have a couple of choices here:

Honestly, they should be redrawn as curves and lines and you will be thankful you did in the long run. There are some circles there that are made up of several splines and there is no reason that should be the case. They should simply be circles. Personally, I would redraw the whole thing with the curves as arcs, all the circles as circles, and the lines as lines or straight polylines. You could also use the fillet radius command to make the corner curves.
If you don't want to redraw everything, you can convert the splines to polylines by using "splinedetit", select the spline, and then choose "convert to polyline". But it only allows you to do one at a time, so I think it would take longer than drawing everything over as curves and circles. And if you take a straight spline and convert it to a polyline and then select it, you will see a ton of grips light up meaning that that polyline is made up of a ton of little segments.

Was this drawing converted from another format or drawn in Autocad from scratch? If it was drawn from scratch, it should have been a very simple line, arc, circle drawing with no splines. There is nothing in that drawing that warrants being a spline from what I can see.

Lastly, many machines (assuming this is an item going into production) will have a hard or impossible time reading spline geometry. Most machining programs like simple joined polyline objects.

Re: Can't join lines to form polylines

Anonymous — Sat, 02 May 2015 19:38:56 GMT

Often, arcs have an extrusion direction that is opposite from others that you are trying to join and will prevent them from being joined. You may be able to find a LISP routine that can "normalize" the offending arcs.To avoid the problem with splines as mentioned above try saving to a AutoCAD R12 (not 2012) format - or DXFOUT to an R12 format.

Re: Can't join lines to form polylines

Anonymous — Sun, 03 May 2015 13:07:50 GMT

Hi no it wasn't originally drawn in autocad, I think it was drawn in
draftsight? or something like that. I am a teacher in a school and the
student wants to use it to build a 3d printer so i was hoping for something
simple. I'm just a beginner in A cad so if i had drawn it, there would
have only been lines and curves because that's all i know atm. Thanks for
your reply.

Re: Can't join lines to form polylines

Anonymous — Sun, 03 May 2015 13:08:50 GMT

Thanks i might see if i can do this.
S

Re: Can't join lines to form polylines

ВeekeeCZ — Wed, 06 May 2015 20:49:49 GMT

Used FLATTEN command to convert splines to polylines couple of times, then EXPLODE, OVERKILL, JOIN, PEDIT, MPEDIT, PEDIT with EXTEND FUZZY 1 and MPEDIT with FILLET FUZZY 1 to connect them together. It is not perfect but almost... see file (1).

Then MPEDIT with FILLET FUZZY 5 and MPEDIT with ADD FUZZY 2. After this it's probably get no better. See file (2).

Re: Can't join lines to form polylines

twaddle.jarrett — Mon, 01 Aug 2022 19:53:10 GMT

I'm having this problem right now and I have never had the issue before. Automatically, from the first time I started this program up for the first time, I have been able to join cut circles and arcs to polylines and splines to polylines, converting one to the other depending on which I initially and subsequently selected. I imagine I fat-fingered a few keys - after all I've typed all sorts of things typing "off" (offset) and have caused an enormous amount of erroneous activities which have left me scratching my head for quite a time, indeed.

Re: Can't join lines to form polylines

twaddle.jarrett — Mon, 01 Aug 2022 19:58:23 GMT

This is something that's a result of trying to manipulate values imported from someone else's file. I don't know what setting I can select all and apply to that would reset the value because I don't know what it is... if I knew the name I'd be able to call on it and problem solved... the issue is that I don't know what question to ask in the first place.