Create planer line and arc geometry from 2D CMM point scan

[Robo308]

I need to create 2D profile geometry from a 2D CMM point scan. I have a small 'dog bone shaped' extrusion, app. 1/4 x 3/8, that I need to create a 2D .dwg for. We have a new scanning CMM that has output a dxf file of the profile in points.  I have opened this file in ACAD Mech, corrected the 'Z' value, for slight probe variation, so that all are on the same plane (Z=0) and saved it as a dwg . My goal is to convert these points into radii and lines that I can edit.  Is a point file the right type of output or should I have the CMM generate some other format?  Do I need a third party software or plug-in for ACAD to do this?  I am running AutoCAD Mechanical 2013 and Inventor Pro 2013.  I prefer to do this in ACAD Mech but will use Inventor if that is the only way. There is alot out there for 3D Cloud point scans and solid model generation but not much on 2D.  This seems like it should be fairly simple, am I missing something?

[Curtis_Waguespack]

Hi Robo308,
Can you attach the *.dxf file? Most likely someone can help figure out the best approach, but it will likely be dependent on the data you're working with.

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@Robo308 wrote:

Do I need a third party software or plug-in for ACAD to do this?

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There are likely some LISP routines out there already that will read in X,Y coordinates from a text or XLS file. Inventor can also read in the points and connect the dots for you. Can you output the data in one of those formats?

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Robo308]

Here is my first scan.  It has 588 points that are app .04mm apart.  I can generate a scan with many more points if that will help to generate more accurate radii.  The CMM is running Hexagon software and can output many other file types. If there is a better file type to use, please let me know. Thank you for taking the time to help solve my problem.

[Curtis_Waguespack]

Hi Robo308,

Thanks for the DXF file, that helps us understand what you're working with.

Is this something that you will be doing a lot of then? If so the solution that comes to mind is to output an XLS file from the CMM and import that either by using a LISP routine (i.e. custom macro) with AutoCAD or just use Inventor's built in tool for this, and then save the profile from Inventor as a DXF, to be opened in AutoCAD.

Can you provide and XLS file of the practice part?

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Robo308]

I will request an .xls file from our Metrology dept. and post.  Meanwhile, I will try the Inventor tool.  Yes, this is something I will be doing often for a while.  I am converting several tool geometries from 'theoretical' off the print to 'actual' taken from the scans of the extrusion.  This will also give me the opportunity to see how close the actual is to the drawing.

[Curtis_Waguespack]

Hi Robo308,

If you get the XLS file posted, I'll try and have a look again. In the mean time here are the steps for importing the points into Autodesk Inventor and connecting them:

1. On the ribbon, click Sketch tab > Insert panel > Points.
• To create a spline or line through the imported points, click Options, select the appropriate connectivity (Create Lines or Create Spline), and then click OK.
2. In the Open dialog box, browse to the folder where the XLS or XLSX file is located.
3. Open the file.

Once the file is imported into the sketch you should be able to save the file as a DXF so that the profile can be used in AutoCAD.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[AllenJessup]

I found a program that might help. http://www.ransen.com/pointor/default.htm

It looks good for importing point lists. I'm not sure how it handless arcs. There's a free trial so you might want to check it out.

Just brining in a polyline from points is easy with a script. See HERE. The real challenge is the arcs.

Allen Jessup


Civil 3D 2012 SP 3 / IDSP 2014
Dell Precision T7400, Xeon CPU 3.16 GHz
Win 7 Pro, 64-bit,12 GB RAM, Nvidia Quadro FX 4600

[Robo308]

Thanx Allen. I'll see if IT dept will install the trial for me (don't have admin privileges, big corporation).  I tried pasting all points at once in pline, like the link you gave me, and yes, arcs were a problem, all I got was a straight line instead of the 'dog bone' shape.  I'll keep trying....

[Curtis_Waguespack]

Hi Robo308,

Here's some information on the Inventor data format.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[JDMather]

Designers usually use nice round numbers like R40mm or 30° angle.

I would use the points only for reference and sketch overtop the points trying to find the best fit "curves" (lines and arcs).

If you use parametric dimensions and constraints (in AutoCAD or Inventor you can then easily edit the geometry into these nice round numbers that you can infer were the original designer's intent.

Keep in mind realistic manufacturing tolerances and you should be able to figure out the original intent.

I don't think there is an "Easy Button" solution.  I have seen software demonstrations that interpolate best fit curves, but even then I would want final parametric control to fine tune.

[JDMather]

About 5 minutes work - I left a couple of 3point arcs open.

Around 20-25 entities, all machine g-code compliant lines and arcs (no splines).

Tolerance (total) within about the thickness of a sheet of paper.

[sboon]

I used the best fit line and curve tools in C3d to create all of the lines and the larger arcs.  Normally we use these tools to fit geometry to survey data, but it appears that they work here also.  I tried to ensure that all of the points were within 0.002 of the geometry.  I then filleted the smaller arcs, using trial and error to get a radius that appeared to fit the points well.

I did end up with one non-tangent intersection of the two arcs on the right side.  Not sure if that's critical or not.

Steve
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