The main purpose of an assembly is to show the components assembled together which translate into the Bill Of Materials with some kind of chronological order. Accordingly to the assembly drawing, to consider a top level assembly complete, you need to have assembled all the sub-assemblies, and each sub-assembly cannot be complete without having assembled all its sub-sub-assemblies, etc… Thus, it is possible to use an assembly not only to make sure that everything is assembled following the right sequence, but to sequence anything!
A prerequisite to this article is to understand the article about the Components Modification. With the described method you can create a sequencing with precedents and dependents. The next phase cannot be completed without completing the previous phase.
Each assembly level corresponds to a step, to a phase, to a stage in the production. But that depends of the level of details you want, how much freewill you want to give to the one proceeding with the top level assembly. Take a look at the article about the Scope of Supply to learn more about it. If you want the person to take care of everything then forget about making any sub-level but if you want to detail it, create as many level as you want.
Let’s say we have this standard welded part that can be painted in different colors. The manufacturing operation is really long compared to the painting so you make batches of this part and paint them only when the customer buys it.
Insert the component in an assembly and specify the color in its parent properties:
The parent drawing specifies just the color as everything else (dimensions, material, etc…) has been sepcified at the part level:
This technique is particularly useful for the treatments that you add to a component. Usually the machine shop that makes the part takes care of doing the post-processing but let’s imagine that in this case they don’t to make a bit more complex example.
We have a shaft with on its drawing specified that we want an Induction Hardening 58HRC~ operation followed by a Hard Chrome Plating 750HV. The machine shop is too busy to deal with the treatments so you have to sub-contract it yourself. To add these operations, right click on the component in the construction tree and select “Form New Subassembly”:
This way, you can include the shaft into a sub-assembly without breaking any mates. Click on “Form New Subassembly” one more time for the second operation.
You can use the “Description” to specify the treatment to save you the hassle to make two drawings just to specify it. It will be visible in the BOM and it is probably self-sufficient. To avoid confusion, remove the treatments that were specified in the shaft drawing.
If you have several parts in the same assembly that also need these treatments, you can even drop them under the treatment assemblies. You will have to make them flexible though to avoid having mates that over define the assemblies.
If finally the machine shop change its mind and decide to take care of it, you can always revert back in using “Dissolve Subassembly”:
Don’t forget to add back the treatments to the shaft drawing.
In the previous examples we have used this technique to replace a note in a drawing but we can go further: the sequenced steps can be a milestone, a contractor service, anything!
For example, we have a device that is completely mechanically assembled but we want to add a wiring phase, followed by a testing phase and lastly a packing phase.
We can also add empty parts that represent the time each step takes. With the help of configurations we can instead of counting it as a unit, count it as hours and display it in the BOM. See the article about the Components Defined by a Measure.
In the previous examples, we have created operations assemblies that could actually become standard and be used anywhere you have one or more components that need these operations if you need that level of details.