KOMPAS-3D V11 – Part 4Others Saturday, January 2nd, 2010
After doing some basic solid modeling in KOMPAS-3D I decided to try some surfacing. Previously, a reader had asked me how KOMPAS-3D compared to other MCAD systems. I believe the best way to compare features of similar software products is to try and do the same thing in both products and see how easy or difficult the process turns out to be. A while ago, I had compared the surfacing capabilities of SolidWorks and Alibre Design by modeling a rose in both products. So I figured that I could do the same in KOMPAS-3D and see how it goes. Long story short, I didn’t find the idea of doing surfacing in KOMPAS-3D enjoyable at all – for a number of reasons. And to appreciate all of them I would need to take you through what I went through.
The act of surfacing normally starts by creating 3D curves, usually splines, and then using them to define a surface. 3D curves are normally created using 3D sketches. Now, from what I understand, sketches in KOMPAS-3D are 2D only. You can create 3D curves but they are left dangling loose in the history tree. I am not exactly sure why KOMPAS-3D lacks the concept of a 3D Sketch.
Another thing. Something as complex as surfacing should have had a tutorial in the documentation. But none was provided. So I was left to figure things out on my own by using the search feature of the documentation or going through its extensive table of contents. Not exactly the kind of thing I enjoy doing.
Anyways, I decided to create four connected 3D splines and use them to create a surface patch which would define the surface of the rose petal. I clicked the spline toolbar icon and was surprised to see that KOMPAS-3D was asking me to input a set of coordinates. I couldn’t simply click the mouse in the 3D model window and sketch my 3D spline, like I did in SolidWorks or Alibre Design. Surprisingly I can create a 3D Polyline (linear segments) by clicking points in the 3D window, but not a 3D spline.
A little irritated, I took the trouble of entering coordinates and got a set of four connected 3D splines somewhat similar to four 3D curves I created in SolidWorks to get the initial petal surface. Next I fired up the Patch command, selected the four 3D splines and got a message “Cannot perform this operation“. I rechecked the curves to verify that they were indeed connected to each other and tried again. Still nothing. I spent some more time trying to figure out the problem and while doing so ended up reading the documentation for the Patch command, which essentially told me that I was barking up the wrong tree. As it turns out, the Patch command can be used to create a surface patch from curves which either (1) lie in the same plane, or (2) lie on the same surface. So basically, KOMPAS-3D needs to already have the definition of an underlying surface to begin with and simply uses the curves to trim it. So obviously the output that I wanted (surface) was actually the input that the Patch command expected me to give it.
But now I had taken the trouble of creating these four 3D splines and wanted to use them to get a surface, one way or the other. After some looking around I came to the conclusion that it would not be possible. With the four 3D splines that I had, the only surface creation command that could be invoked was “Patch”. So a bit frustrated, I deleted the four 3D splines that I had so painstakingly created and began looking for other ways to create a surface in KOMPAS-3D. Here I would like to point out the importance of a tutorial. Or rather, the lack of one, and the frustration that a user is put through as a result of that.
Now I know that I could create the rose petal using the solid modeling route, like I did in Alibre Design (see “Surfacing in Alibre Design“). But technically, that is not surfacing. And since KOMPAS-3D offers features to create surfaces I wanted to see how I could use them to create my rose petal. I was more interested in comparing KOMPAS-3D with SolidWorks, as opposed to Alibre Design. After all KOMPAS-3D is priced at around $3500 and SolidWorks sits at around $4000. Alibre Design is nowhere close to either of those numbers.
KOMPAS-3D offers the following methods of creating a surface:
Extrusion Surface: Created by sweeping a sketch in the direction perpendicular to its plane.
Rotation Surface: Created by rotating a sketch about an axis lying in the sketch plane.
Swept Surface: Created by sweeping a sketched section along a path.
Lofted Surface: Created by lofting a surface through cross sections.
Patch Surface: Created from a closed contour.
I decided to use the Lofted Surface option. So I created the arc shaped petal solid base, created four parallel planes and sketched four 2D splines on them to serve as the cross sections.
The blue squares signify the planes and the green splines lie on them. I lofted a surface through the cross sections to get a surface. Next I wanted to thicken it just like I did in SolidWorks to arrive at a solid petal. But I could not find any way of doing that. I searched the documentation for quite a while but came up with nothing. I guess the only way to get a solid from a surface is to knit adjoining surfaces together. So in this particular case, common sense told me that I could create an offset surface and then create other surfaces required to enclose a volume and stitch them together to get a solid. But I couldn’t find a command to offset a surface either. Which meant that I needed to create another set of cross sections to cook up another surface and then create the surfaces required to enclose a volume. As you can imagine, by the time I reached this point, I was in no mood of going down that road, as I wasn’t sure whether it would lead me to another dead end. So I stopped. Maybe one day I will revisit this after getting a more clear understanding of what is and is not possible in KOMPAS-3D as regards surfacing.
There is something else that needs a mention here. Take a look at the images in the ASCON Gallery. You will need to click the “Details” link for each item to view larger images. From what I see, people are using KOMPAS-3D to mainly build mechanical parts, not organic objects like the rose that I was trying to model. So maybe I was trying to do something that KOMPAS-3D is not designed to do. From the way the surfacing features are integrated into the software, I get the feeling that surfacing is more of an afterthought, something that has been bolted onto a strictly history based parametric solid modeler.
Another thing. I had to endure a couple of crashes while I was fiddling around with surfacing. Not once did KOMPAS-3D crash or complain when I was modeling the Piston Cup. So I get the feeling that surfacing may be a work-in-progress in KOMPAS-3D.
I understand that modeling a rose like I did in SolidWorks may be entirely possible on KOMPAS-3D. In spite of everything that I tried, I may have missed something. I am just a beginner. If any of you can enlighten me in this regard, I would greatly appreciate it. Please do leave a comment. Either way, I am not sure it would be wise to treat this part of the series as a verdict on the surfacing capabilities of KOMPAS-3D. Its just that I could not find a way to do what I set out to do.