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Old Jan 05, 2013, 11:14 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
I use both ACad and Draftsight (Draftsight because I can't get my ACad loaded on Win7). ACad is on an older XP. Both systems work practically the same.

First, import a raster image (I use either jpg or tiff images) into my drawing assigning it to it's own layer.

Second, rotate (if necessary) the image to achieve a true horizontal reference. If there is a known dimension on the plan, the image can be re-sized at this time. Can be changed later if necessary.

Third, I do my tracing on Layer O. Trace out a few lines, then hide the raster layer to see how the tracing is looking and what else I might need to trace.

Some CNC or Lazer cutters seem to have problems with splined lines, so a trick I use for smoothing up curved lines is to use the polyline tool to first trace the curved line using fairly large steps. Then spline that line. Select the line and adjust the handles so that the line closely follow the original plan. More handles can be added if necessary.

Then turn on Snaps with "Nearest" selected. You don't want any other snaps on and you want ortho off. Trace around the splined line using the polyline tool again but use very small steps. The snap setting will hold you right on that splined line. This second tracing goes very quickly with the help of the snap setting. Delete the splined line. You now have a polyline that the cutters can work with.
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Old Jan 07, 2013, 07:21 AM
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redC5's Avatar
NE Georgia USA
Joined Jul 2010
68 Posts
BRNR,
Thanks, I appreciate the tip.
I just acquired a tablet with a xhair puck I am going to try.
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Old Jan 07, 2013, 10:22 AM
Laser Cutter Guy
United States, PA, Greensburg
Joined Oct 2009
247 Posts
Quote:
Originally Posted by Brner View Post
Some CNC or Lazer cutters seem to have problems with splined lines, so a trick I use for smoothing up curved lines is to use the polyline tool to first trace the curved line using fairly large steps. Then spline that line. Select the line and adjust the handles so that the line closely follow the original plan. More handles can be added if necessary..
If you change the number of points per spline to a higher number, that should help that issue. It makes the spline more precise by adding more nodes.
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Old Jan 07, 2013, 10:52 AM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
Rob,

That's effectively what I do but I end up with a polyline with very short segments . As I'm not a CNC or Lazer operator maybe you can answer this.....does your cut follow the curve of a spline or does it cut to the handles? I've been told that some machines can't handle a splined line at all....but I'm not sure. I know my method seems to work well.

Don
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Old Jan 07, 2013, 12:14 PM
Laser Cutter Guy
United States, PA, Greensburg
Joined Oct 2009
247 Posts
Quote:
Originally Posted by Brner View Post
Rob,

That's effectively what I do but I end up with a polyline with very short segments . As I'm not a CNC or Lazer operator maybe you can answer this.....does your cut follow the curve of a spline or does it cut to the handles? I've been told that some machines can't handle a splined line at all....but I'm not sure. I know my method seems to work well.

Don
Don,

My laser and CNC will cut curves and splines fine. I have, however, recieved files from others that upon inspection the line segments were drawn wrong, which makes the cut look wrong. I think it comes down to how you draw it. I had a heck of a time getting sketchup files to work right even exported as a dxf.

Never heard of a CNC not being able to cut a curve or spline, it's all in the G-Code. If you want a curve, draw it as a curve not a bunch of rotated straight line segments.
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Old Jan 07, 2013, 02:59 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
Quote:
Originally Posted by RCROBBY View Post
Don,

My laser and CNC will cut curves and splines fine. I have, however, recieved files from others that upon inspection the line segments were drawn wrong, which makes the cut look wrong. I think it comes down to how you draw it. I had a heck of a time getting sketchup files to work right even exported as a dxf.

Never heard of a CNC not being able to cut a curve or spline, it's all in the G-Code. If you want a curve, draw it as a curve not a bunch of rotated straight line segments.
Rob,

Don't want to belabor the point but maybe an explanation based on the picture below will be easier for an old man to understand.....lol

Line 1 is a three segment polyline. Line 2 is a copy of Line 1 that has been splined.

Notice that the handles in both cases have not changed position. If the lines were overlayed the handles would be in exactly the same spot for both lines.

The dashed lines are merely reference lines.

If you were to cut Line 1, I'm sure you would end up with three straight line segment cuts based on the handles. No problem so far....

Now, if you were to cut Line 2, which clearly shows as a curve on the drawing, would you end up with a curved cut or the same cut line as Line 1 based on the handles? Does your machine follow the curve shown or the handles?

Guess I went ahead and belabored the point but I do appreciate your patience with this question.

TIA,

Don
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Old Jan 07, 2013, 03:32 PM
Laser Cutter Guy
United States, PA, Greensburg
Joined Oct 2009
247 Posts
Quote:
Originally Posted by Brner View Post
Rob,

Don't want to belabor the point but maybe an explanation based on the picture below will be easier for an old man to understand.....lol

Line 1 is a three segment polyline. Line 2 is a copy of Line 1 that has been splined.

Notice that the handles in both cases have not changed position. If the lines were overlayed the handles would be in exactly the same spot for both lines.

The dashed lines are merely reference lines.

If you were to cut Line 1, I'm sure you would end up with three straight line segment cuts based on the handles. No problem so far....

Now, if you were to cut Line 2, which clearly shows as a curve on the drawing, would you end up with a curved cut or the same cut line as Line 1 based on the handles? Does your machine follow the curve shown or the handles?

Guess I went ahead and belabored the point but I do appreciate your patience with this question.

TIA,

Don
No problem on the questions, I see what you are talking about now. In AutoCad the "Handles" are called nodes and typically on a spline or arc they are ON the object line, not away from it (similar to what you have in line 1). I am not 100% sure how the laser would react to that for cutting. If you want to E-mail me a dxf sample of those 2 types of lines I'll put it in the laser and see what it does.
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Old Jan 07, 2013, 03:47 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
Quote:
Originally Posted by RCROBBY View Post
No problem on the questions, I see what you are talking about now. In AutoCad the "Handles" are called nodes and typically on a spline or arc they are ON the object line, not away from it (similar to what you have in line 1). I am not 100% sure how the laser would react to that for cutting. If you want to E-mail me a dxf sample of those 2 types of lines I'll put it in the laser and see what it does.
Be happy to do that Rob. I'll get your addy off your web site....

Thanks for the reply.

ooops, can't find your email but sent you a message requesting same from your site....
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Last edited by Brner; Jan 07, 2013 at 04:00 PM.
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Old Jan 08, 2013, 07:46 AM
Laser Cutter Guy
United States, PA, Greensburg
Joined Oct 2009
247 Posts
Ok, Here is what I found.

1.the Draftsight DXF is not a direct import into the laser software. I had to open the file in AutoCad and convert it. No big deal but worth mentioning.

2. after importing, the line #1 looks as drawn but line #2 was all wacky. I had seen this before and knew how to fix it. I had to explode line #2 into arc segments.

3. After fixing line #2 both went through the laser just fine and were cut as shown. I forgot to take a picture but they cut exactly as they were drawn above.

In conclusion, both ways will work fine but line #2 was more refined as it was drawn smoother. The "handles" concern became moot because I exploded the arc and removed the associativity (sp).

Let me know if any of this does not make sense or needs clarified. It's always good to learn something new, lol.

Rob
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Old Jan 08, 2013, 01:59 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
Rob,

I've been playing with this most of the night and found pretty much the same as you did.

1. The problem with opening the DXF may have just been the format I saved it in. As with AutoCad there are many DXF versions (14 to be exact) that one can save to. I wasn't sure which format to use but I believe I saved it to R14ASCII Drawing.

2. I also found that by exploding line 2, it exploded into many "straight" line segments with all the handles following the line. Not sure how you got it to explode into arc segments....might not be available in Draftsight but I'll check my Acad program later for that function.

Handle to handle seems to be the way the cutter works.

Another thing I read on your website is that ellipse's should not be used. Understandable if the cutter goes from handle to handle. I did find a work-around for this too. As I like to use ellipses a lot I'll put this solution in another post.

As you said, it's always good to learn something new...

Don
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Old Jan 08, 2013, 02:18 PM
No bounce, No play.
davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,566 Posts
I would like to use DevCad to get my ATR 42 plans into files for cutting.

The scan comes out with a lot of background "noise" and when I preprocess it just puts too much stuff on the background image.

Any suggestions for cleaning up the image so just the actual part is enhanced?
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Old Jan 08, 2013, 03:17 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
David,

At first glance it looks like you are trying to export a jpg that you've loaded into your Cad program....disregard if I'm wrong here.

I'm not a DevCad user so can't say what that program can do but here's a quick look at what Draftsight and Acad can do....

I pretty much followed my first post on tracing with a couple of tips learned from my exchange with Rob...

No dimensions were given so it's not to scale but could easily be re-sized....

Look around DevCad and see what tools are available for tracing over a jpg.

Don
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Old Jan 08, 2013, 05:08 PM
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davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
3,566 Posts
Quote:
Originally Posted by Brner View Post
David,

At first glance it looks like you are trying to export a jpg that you've loaded into your Cad program....disregard if I'm wrong here.

I'm not a DevCad user so can't say what that program can do but here's a quick look at what Draftsight and Acad can do....

I pretty much followed my first post on tracing with a couple of tips learned from my exchange with Rob...

No dimensions were given so it's not to scale but could easily be re-sized....

Look around DevCad and see what tools are available for tracing over a jpg.

Don
Actually what I am trying to do is import a jpeg from the flatbed scanner into DevCad and use the Auto-Trace feature. I already played around a bit manually tracing and am looking for something that is not as time consuming. There are a lot of parts to do from the three sheet plans.

The thing is that all the shadows and everything show up in the Auto-Trace. I wonder if there is any way to "bring to the front" the acutal lines I want and ignore the shadows.
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Old Jan 08, 2013, 05:34 PM
Just Me
United States, OR, Salem
Joined Apr 2006
842 Posts
Have you tried to copy and paste just the lines you want to a clean area of the screen?

Sorry I can't be of more help but I'm not at all familiar with DevCad or it's functions.
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Old Jan 08, 2013, 08:09 PM
Jim C Patrick
jcpatrick's Avatar
Shenandoah County
Joined Jan 2008
860 Posts
Quote:
Originally Posted by davidmc36 View Post
Actually what I am trying to do is import a jpeg from the flatbed scanner into DevCad and use the Auto-Trace feature. I already played around a bit manually tracing and am looking for something that is not as time consuming. . . . The thing is that all the shadows and everything show up in the Auto-Trace. I wonder if there is any way to "bring to the front" the acutal lines I want and ignore the shadows.
Sorry to disappoint you, but autotrace almost never works for CAD. Every line it produces will have to be tweaked, and you will end up spending far more time using autotracing than manual drawing. If you doubt me, search and look it up in this forum; all the experienced drafters and cadsmen will tell you the same. Your best bet is to trace with polylines as outlined in the above comments.

My only other contribution to this (having done a lot of these conversions) is that it works better zoomed out. Most people, including me when I started, zoom in too close to the bitmap they are tracing.
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