Monday, 2 February 2015

Fasten your Design!

You've created some plastic parts and are now unsure how they will fasten together. Maybe this blog will help.

Many plastic parts contain specialised features such as snap hooks, mounting bosses and a gap at the joint where two components come together.  Let see how we can do this inside SOLIDWORKS.  There's a handy set of tools located in the menu, Insert > Fastening Features.

The model is first split into multiple bodies to identify the upper and lower housing. The shell tool can be used to hollow out the part. It will leave the faces you select open and create thin-walled features on the remaining faces.  
We will use the Lip/Groove feature to create an edge. It is often used in plastic parts to prevent an edge-to-edge joint between two parts.
Select the Lip/Groove feature. Highlight the upper housing to receive the groove and the lower housing to receive the lip.
For the Groove Selection select the face and the edge you wish to apply. Repeat the same procedure for the Lip Selection. You can then define dimensions in the parameters.

Snap Hooks are common features in plastic parts enabling quick assembly without the need for tools or fasteners.


First create sketch points where you wish locate the snap hooks. Select Snap Hook feature, pick the sketch point. Select a reference plane to define the vertical direction of the snap hook. Select another reference plane to define the direction of the hook (use Reverse direction if the hook is pointed the wrong way). Define the dimensions in the Snap Hook Data. Repeat the same procedure for each snap hook.     


Next is to create the Snap Hook Groove. The dimensions of the snap hook groove are driven by the snap hook. You can change the offsets or clearances through the PropertyManager. Again, repeat the procedure for the other snap hook.

Mounting boss can be added for hardware fasteners. When you create a mounting boss it can either be a through clearance hole for the fastener or one with a blind hole for the threads.
First we will create the through clearance hole boss as shown below. You can reposition the mounting boss by editing the 3D sketch.

Now that we have a clearance hole boss, it will be easier to create the corresponding blind pilot hole boss because we can reference some of the existing geometry to orient the boss and define its height.
To define the height, select the mating face option and select the planar face on the mounting boss of the lower housing. 

For added support you can set the fin parameters. A reference plane can be used to orientate the fins. The number of fins will be equally spaced out.

I hope you find this information useful and please subscribe to keep informed of future blog posts.

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