MCADCafe Weekly Review November 24th, 2017

SOLIDWORKS: Continuity and Curvature
November 22, 2017  by Rony Godoy

I like nice curves and I cannot lie. And in SOLIDWORKS we can control exactly how smooth our curves are. When it comes to curves in SOLIDWORKS, there is a difference between what is smooth and what looks smooth. This blog will discuss how we can analyze our curves and control how smooth they really are by using surface evaluation tools and different spline tools.

The quality of a great surface lies within the curve that defines it. These curves are ideally created and controlled through splines. The spline sketch tool creates a smooth curve through the position of control vertices, or CV’s. Controlling the quality of our splines will ultimately control the quality of our surfaces. Splines can be analyzed using the curvature combs tool. The curvature combs tool graphically shows the amount of curvature at a given point on a sketch element. A smooth curvature comb is desired to produce the smoothest surface. As shown below, both splines look the same until we look at their curvature combs. The spline with the smoothest curvature combs (i.e. no flat spots or dips exist) will produce the smoothest surface.

SOLIDWORKS: Continuity and Curvature SOLIDWORKS: Continuity and Curvature

To create smooth curvature combs, splines should be created with the least amount of points possible. Just as seen above, both of these splines are identical. The difference in curvature combs is due to the fact that the spline on the left was made with just 2 points, whereas the spline on the right was made with 5.

If multiple points are required, then the spline should be modified by using the control polygon tool as opposed to the spline handles. This can be activated by right clicking on your spline and clicking on Display Control Polygon. The control polygon will allow the spline to be manipulated while keeping the curvature combs as smooth as possible.

SOLIDWORKS: Continuity and Curvature

An even better method for creating a spline with multiple points is by using the style spline tool. This spline tool creates a spline by drawing its control polygon and using that control polygon to control the shape of the spline. This allows for smoother curvature combs since we’re using the control polygon instead of the spline handles. As stated above, controlling a spline through its control polygon allows for smoother control of the curvature combs which ultimately will create a smooth surface.

Curvature can be mathematically defined as the inverse of the radius (i.e. k=1/r where k is the curvature). There are three different degrees of curvature that we are concerned with in SOLIDWORKS. Curvature is defined as the The first degree is called contact (or C0 continuity) and is when two entities meet. These entities will ultimately create an edge, so there is no smoothness on the surface created by them. At the sketch level, this means the curvature combs will not touch or have a smooth transition between each other.

SOLIDWORKS: Continuity and Curvature

The second degree is called tangent (or C1 continuity) and is when two entities touch, and the angle of both curves are equal. This would be a situation where a tangent sketch relationship is created between two entities. Although this provides a smooth surface, the transition would be noticeable as seen in the image below. This situation would be acceptable for most applications, but is not aesthetically pleasing.

SOLIDWORKS: Continuity and Curvature

The third degree is called curvature continuous (or C2 continuity) which is when the two entities have the same curvature amongst each other. The radius of their curvature combs is equal as well as their angle. This type of curvature would provide the smoothest type of surface in SOLIDWORKS.

SOLIDWORKS: Continuity and Curvature

Part 2 of this series will further discuss how to further analyze surfaces and can be found. For more information, check out our YouTube channel, get a SOLIDWORKS 3D CAD quote or contact us at Hawk Ridge Systems today. Thanks for reading!

Hi everyone! In this blog, I’m going to showcase a brand-new feature available in SOLIDWORKS 2018 to help you design faster! Have you ever had an idea and either not had a mouse or wanted to sketch it freely rather than using a mouse? With this new release and your Windows 10 touch-enabled device, now you can live out those wants with Touch Based sketching.

I’m working on the gas cap for my RC car and I’ve decided that I want to really make it unique by adding a design to the front of it. I’m going to put a cloud to symbolize a gas cloud (and because there’s a reason I became an engineer instead of an artist.) I also found a picture that I want to use as a sketch picture and that’s in a sketch that I’ll unhide.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 1: Gas Cap Isometric View

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching

The first thing I want to point out is the new Sketch Ink Command Manager tab, which where all of my touch sketch commands will be. This can be turned on like any other command manager tab, right-click on an existing tab and select it from the list.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 3: Sketch Ink Command Manager.

I’ll start my cloud sketch by selecting the gas cap face and hitting Sketch. There’s a pulldown to allow me to select a 2D or 3D sketch, touch sketching works with both. Next, you can customize your pen color and thickness. Use the slider to adjust the latter.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching

Next to that is an eraser tool if you need to delete any errant strokes, and the select tool to select geometry. The eraser works similarly to Power Trim, where swiping over existing geometry with it turned on erases it. The select tool turns your stylus or finger into a mouse pointer.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 5: Remaining Sketch Ink Commands

The Touch button is next to that. I’m using a stylus, but you can use this mode with your finger. Without that button pressed, swiping on my screen causes the model to move around. Therefore, to start sketching I’m going to click that button. Next, there are 2 ways to sketch entities: Auto Shape and Auto Sketch Entities. I’ll use Auto Shape to sketch the cloud, converting my pen strokes to smooth geometry. These are just conceptual, but I can use Select and hit Update to Entities which will change them to sketch entities.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 6: Cloud drawn using Auto Shape.What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 7: Update to Entities command.What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 8: Updated Entities.

If you prefer to go straight to sketch entities, use the Auto Sketch Entities button. I’ll switch over to that and sketch a lightning bolt. This will also imply sketch relations. Now I have a sketch that I can use to create a feature like a boss or cut, or a split line.

What’s New in SOLIDWORKS 2018: Touch/Pen input for Sketching Figure 9: Using Auto Sketch Entities.

As you can see, touch sketching can bring more of your ideas to life with pretty minimal effort. For more information, check out our YouTube channel, get a SOLIDWORKS 3D CAD quote or contact us at Hawk Ridge Systems today. Thanks for reading!



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