News:



Advertise Here
  • May 09, 2021, 08:25:18 PM

Login with username, password and session length

Author Topic: cad drawing  (Read 411 times)

Offline Al Williams

  • Trade Count: (0)
  • New Pilot
  • *
  • Posts: 9
cad drawing
« on: February 24, 2021, 03:14:34 PM »
This should probably go in the cad section but I do not know where!
I am a 2D cad operator at work and I am looking for the best way to trace plans.  For example a wing rib.  I have used the pline command and picked points along the curve and then splined the line.  This works but is tedious.  I have also used the spline command which need a lot less points and looks very good.

I take the plans to work and scan them as a PDF I can import them into a drawing as a PDF or save the file as a Tiff and import that.  I have found that the plans were drawn by hand  and parts may not be very accurately consistent as we can do now with Autocad.  For example, the wing rib length in the rib details does not equal the length in the wing layout.    Using cad I can correct this by redrawing the ribs or the wing layout.
 
I like to scan in the plans so I always have a copy.  This way I can print out multiply copies to cut up.  I could do this without Autocad.   By putting the scans into autocad I can correct any discrepancies I find.

So back to the original question, what is the easiest way to trace the curves?

One of the younger engineers at work said there is a way to import a scan as a line drawing but he could not do it.

Thanks 

Online Dave Rigotti

  • 21 supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 142
  • "Electric...The future of anytime stunt"
Re: cad drawing
« Reply #1 on: February 24, 2021, 04:17:41 PM »
What CAD program do you use at work?  Maybe someone here can help.
Dave Rigotti
AMA 66859
Chesterland, Ohio

Online George Truett

  • 2018 Supporter
  • Trade Count: (0)
  • Commander
  • *
  • Posts: 236
Re: cad drawing
« Reply #2 on: February 24, 2021, 04:36:50 PM »
Years ago I was converting a lot of plans into CAD.  I used a program called Img2cad which I see is still available.  It will convert your scanned PDF or JPEG to a DXF file.  It works fairly well but it picks up everything on your drawing like crease or smudges (or anything else).  The converted files come out huge because there are many, many more points than needed.  You will spend a lot of time cleaning up a converted file, getting rid of extra points, fixing lines and replacing all the text.  Newer versions may work better, I haven't used it in 10 or more years.

Offline Keith Miller

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 208
Re: cad drawing
« Reply #3 on: February 24, 2021, 09:24:25 PM »
For example a wing rib.  I have used the pline command and picked points along the curve and then splined the line.  This works but is tedious.  I have also used the spline command which need a lot less points and looks very good.

I take the plans to work and scan them as a PDF I can import them into a drawing as a PDF or save the file as a Tiff and import that.  I have found that the plans were drawn by hand  and parts may not be very accurately consistent as we can do now with Autocad.  For example, the wing rib length in the rib details does not equal the length in the wing layout.    Using cad I can correct this by redrawing the ribs or the wing layout.
 
So back to the original question, what is the easiest way to trace the curves?

One of the younger engineers at work said there is a way to import a scan as a line drawing but he could not do it.

Thanks

Hi Al -
I use SolidWorks, but the initial sketches are done in 2D.
You and I do it similarly, and I've found it's the best way for me.
I scan the rib into a jpg or pdf and then lay that image down in the CAD drawing as a "layer".
I then scale that layer to match reality (in SolidWorks, pasting in a jpg or pdf doesn't guarantee scale).
Then, as you describe, I trace the curves with splines; sometimes just one is needed with a flex point at the apex; sometimes additional flex points are needed.

To convert a bitmap image (jpg, scanned pdf) to a vector file, I've tried CorellDraw and Adobe Illustrator in the past, and the converted vector drawings just have tons of points in them that make for more work than needed.
 /DV



Offline proparc

  • 2015
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2387
Re: cad drawing
« Reply #4 on: February 25, 2021, 11:19:44 AM »
There are a myriad  of ways to trace the curves in Autocad. Nurbs and Bezier curves are the tools of choice for this sort of thing. Mirror copy is CRITICAL in redoing plans because of the lack of accuracy in older hand drawn plans. If you have a small plan, I can probably do it for you VERY accurately because, I am so friggin old, I have probably flown the darn thing!!
Milton "Proparc" Graham


Advertise Here
Tags:
 


Advertise Here