PartDesign Pattern Tutorial

Tutorial: Lattice PartDesign Pattern

Featuring:

• Lattice PartDesign Pattern
• Attached Placement
• Array an attached placement ("subsequencing")

Complexity: intermediate

Requires: FreeCAD v0.17 or later, Lattice2 add-on installed

Overview

We create an irregular array of latches in a PartDesign Body, with latch modeled as another body.

Tutorial

1. Model a latch

Let's create a latch optimized for injection molding. It has a hole in base plate, to simplify the mold.

Do it however you like. But:

• baseplate (not part of the latch) must be the first feature of the body
• the pocket cutting the hole under the latch should have quite a margin for maximum versatility of the latch body.
• do not use fillets, chamfers, thickness, drafts, and native PartDesign Patterns, as these are not supported by Lattice PartDesign Pattern yet.

2. Attach a reference placement

Use Attached Placement to create one:

Or you can use a plain moveable placement aligned by hand or by expressions, it doesn't matter how you create the placement.

Reference placement is like a handle for pick-and-placing your latches. The most convenient place for this tutorial is center of the latch, at its root, right where the edge of the thing to be held by the latch touches it. You can have as many different reference placements as you like, for uses in different situations.

3. Model a part

Use any PartDesign tools, no limitations now.

4. Create a sketch for making an array of placements

Draw an L shape for each occurence of the latch. Make sure to draw the L-shapes in a consistent direction and chirality (for example, start with line parallel to the latch, in ccw direction, and finish with a line setting the direction of latch). Use sketcher's Clone/Array tools to your advantage.

5. Attach a single placement to the first L of the sketch.

Use Attached Placement tool:

Attach the placement to the first L-shape of the sketch, the one which has Edge1 and Edge2.

You will likely have to fiddle with attachment offset angles to get the right orientation. Make sure the paper plane is placed so that if you pick the latch with its reference placement, and put it where you want, the reference placement whould then line up with the placement we are attaching now.

6. Array an attached placement

Boom! Array.

If the array is missing some occurences, you probably attached the placement at step 5 to non-first L shape. You can just change PlacementSubsequense's 'Cycle Mode' to Periodic.

7. Lattice PartDesign Pattern

Select latch body, reference placement, and the array (order of selection matters!). Apply Lattice PartDesign Pattern

You should get a broken result...

The result is broken, because LatticePattern replicates the baseplate of the latch body. This causes self-intersection. You can change LatticePattern's 'Selfintersections' to true to obtain a non-broken result with all the baseplates, but we want to get rid of them. so...

8. change LatticePattern's 'SkipFirstInBody' to True

And we are done!

Notice that we have holes in our part. LatticePattern doesn't fuse up the whole body - it replays every feature of the latch body

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Lattice Pattern generally has the same restrictions as PartDesign Patterns do. However there are important differences:

• Lattice Pattern can copy other Lattice Pattern (i.e., avoids the need for Multitransform container)
• Lattice Pattern does not support mirroring yet, at all.
• Lattice Pattern can copy PD boolean feature, if it is not in Common mode
• Lattice Pattern can copy features from other bodies, and whole bodies worth of features (as shown in this tutorial).

Lattice Pattern has a few more properties that alter its behavior, not mentioned in this tutorial. It alows to invert signs of features, for example.