3 Replies Latest reply on Jul 19, 2016 3:59 PM by Harold Brunt

    Disparity in Equation Driven Curve Sketches

    Harold Brunt

      I hope this is simply an oversight for a setting on my part but this is a new problem for me. I frequently use the Equation Driven Curve sketch tool and my go-to formula for several years has been y = (x^2/R)/(1+(1-(1+(k))*(x/R)^2)^.5) where R = radius of curvature, and k = conic constant. Recently I needed to send a file to a machine shop and copied our optical engineer on the email. My OE let me know the STEP file I had sent did not match the original part file we had been working from. When I generated the STEP I created a part by simply doing a copy and paste from the formula field of the complete part to a new part. The curves should be the same. The formula looks like this in the part: (x^2/-7.0)/(1+(1-(1+(-2.0))*(x/-7.0)^2)^.5) with X1 = 0.00 and X2 = 3.5. The template is in mm. If I measure the point at the end of the curve I get the coordinates for each iteration. I also made an Excel spreadsheet to calculate the curve.

      Calculated end point: 3.5, 0.82624

      Original Part file: 3.5, 0.82624

      New Part file: 4.24, 1.00093

      I have OptisWorks with Optical design Add-In and Zemax LensMechanix Add-in so I generated the surfaces with those:

      OptisWorks OD: 3.5, 0.82624

      Zemax LMX: 3.5, 0.82624

      I thought I'd dig through my files and find the archived sketch block in SW2012 that I had saved and created a new lens with that sketch:

      Legacy Sketch File: 3.5, 0.82624

      One more new from scratch file with SW2016....

      New Part File #2: 2.67, .62928

      Now the latest new part isn't like the previous new part?!

      Even if the curve is wrong shouldn't it end at 3.5mm? What has changed and is changing in my templates or in the SW releases between SP 2.0 and 3.0? I'll be getting in touch with my VAR on Monday but thought I'd hit the forum first. Ant assistance or insights would be appreciated.

        • Re: Disparity in Equation Driven Curve Sketches
          Harold Brunt

          I thought I'd do a little more digging into this and take a look at any differences between the first new SW2016 part and the second SW2016 part. What I found was that the first part had the sketch drawn on the Front Plane along the Y Axis where as the second part had the sketch drawn on the Right Plane along the Y Axis. I made another two parts with the sketch on the Front Plane of both and along the X Axis for the one and the Y Axis for the other. Results measured at the curve end point with the part positioned in the assembly:

          Original Part File: 3.5, 0.82624

          New Part File (previous): 4.24, 1.00093 Front, Y-Axis

          New Part File #2 (previous): 2.67, 0.62928 Right, Y-Axis

          New Part File #3: 4.05, 0.95519 Front, X-Axis

          New Part File #4: 2.87, 0.67649 Front, Y-Axis

          So then, different results for each iteration regardless of sketch plane or axis. One thing though is that once the part is generated from the sketch the revolve always rebuilds the same.

          • Re: Disparity in Equation Driven Curve Sketches
            Harold Brunt

            Well I think I'm onto something here. I have been making the parts 3mm thick just so that there was a consistent visual reference. If I sketch the curve using the formula driven sketch tool and then leave the rest of the sketch dimensionless then the part does not auto scale to a dimension other than the calculated end point of the curve. However, even if I bring the part into the assembly and have it fully constrained if I dimension the center thickness the curve end point changes driven by the auto scaling.

            curve-1.JPG

            curve-2.JPG

            • Re: Disparity in Equation Driven Curve Sketches
              Harold Brunt

              Sent the files and description to my VAR and received a follow-up call shortly after. He could not reproduce the issue on his PC so he set up a remote desktop to run mine and we got to the bottom of it. The problem could be reproduced any time I pulled in the Block with the Equation Driven Curve sketch. If I used the pull down and started a new curve (even using a copy/paste function from an old sketch) the new sketch would work fine. So long story short, I can use the Equation Driven Curve sketch but not by bringing it in via the Block saved from SW2012.