PartDesign Bearingholder Tutorial I: Difference between revisions

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== Setting up the skeleton geometry ==
== Setting up the skeleton geometry ==


The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change.

The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.





Revision as of 18:36, 9 June 2013

Bearing Holder Tutorial - Finished bearing holder (top)

This is an introductory tutorial to modeling with the PartDesign workbench in FreeCAD. The purposes of the tutorial are to introduce you to two different workflows for creating a cast part with drafts and rounds. Depending on what other CAD programs you have been using, one or the other might be familiar to you. As a working example we will be modeling a simple bearing holder.

This is the first part of the tutorial. It will use what might be called the 'single body' workflow, using the (simpler) top part of the holder as an example.

Design data

The holder should be able to hold a diameter 90mm bearing with a width of up to 33mm (e.g. DIN 630 type 2308). The bearing requires a shoulder height of at least 4.5mm in the holder (and on the shaft). The top part of the holder will be bolted to the bottom with two 12mm bolts. There should be a groove on both sides of the bearing able to hold a standard shaft sealing ring DIN 3760: 38x55x7 or 40x55x7 on one side, 50x68x8 on the other side.

The holder will be a sand cast with a minimum wall thickness of 5mm, a draft angle of 2 degrees, and a minimum fillet radius of 3mm.

Setting up the skeleton geometry

The idea of skeleton geometry is to capture the basic design dimensions in a single datum feature (e.g. a plane or an axis). When the design dimension changes, all that needs to be done is to change the skeleton feature. If the model is well built, then all its feature will recompute to reflect the design change.

The alternative to skeleton geometry is to have a table of the basic design dimensions that assign a symbolic name to each dimension, and then use the symbolic name wherever the dimensions is required to build the model. FreeCAD does not allow this approach yet.