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I am trying to grasp the purpose of Mechanical layers in Altium Designer. I have seen a tutorial on youtube where the presenter created one new mechanical layer and put information onto it that he said will go into the draft documents.

In any case, since there can be so many mechanical layers in Altium designer and the Mechanical 1 layer is there by default, what is the purpose of Mechanical 1 layer and the remaining possible mechanical layers besides creating outline for draft documents?

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3 Answers 3

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It's a give-and-take relationship, but as a PCB designer I'm mostly given mechanical constraints to work with from mechanical engineers as they stake their claim to available space. I might will definitely argue about the board outline, screw-holes, general space etc, and as such I need dedicated places to convey this information to my colleagues, my suppliers, but also myself.

  • I use Mech 1 for 3D component bodies - both simple extruded primitives for things like passives, but also more detailed, manufacturer-provided step models. It's worthwhile being accurate here. Component-housing collisions and interferences are not fun.

  • I have a separate mechanical layer for the outline of the PCB (File > import > DWG is a highly used command) as well as keep-outs.

  • Depending on the manufacturer and the board, I have a specific layer for the cutting outline, ie the path the 2mm routing tool should take. Sometimes I let the manufacturer decide what's best, but other times I might want a specific clean edge in a certain location.

  • When designing flexirigid PCBs, I use separate mechanical layers for outlining the flexible and rigid regions (top FR4, polyimide...) This is also useful when conforming to IPC-2223, such as keeping a minimum distance between plated holes from rigid to flex, as I can clearly identify where the overlaps are.

  • I also use a separate layer to sketch out bend locations and jot down the radius/angle

  • Another mechanical layer has dimension callouts that are used when generating documentation from a specific output job container to make clean PDF prints

They can be for whatever you need them to be ultimately. Experience will dictate what is useful to you, and creating PCB templates with expectant usage of these layers will likely prove to be valuable.

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  • \$\begingroup\$ Is there a reason you do not use layer pairs instead? \$\endgroup\$
    – quantum231
    Jun 8, 2023 at 20:16
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It's pretty much up to you what it is used for. Typically it's used for the 3D body (a .stp file).

I use Mechanical 1 for bodies and Mechanical 5 for PCB outline, for example, and the built-in IPC-compliant wizard puts elements on Mechanical 13 (body) and Mechanical 15 (location cross and outline).

Some folks such as Robert Feranec (who does instructional videos independently) use Mechanical Layers 1 for the 3d body and Mechanical Layer 29 for information.

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  • \$\begingroup\$ If a person creates layers like "M3 Top Dimensions" "M4 Bottom Dimensions" "M5 Top Constraints" "M6 Bottom Constraints". Is it better to use Component pairs instead? \$\endgroup\$
    – quantum231
    Jun 8, 2023 at 20:18
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Put whatever you want on that layer that is non-electrical. I normally don't put anything on Mechanical 1 since sometimes imported entities (e.g., DXF files) end up on that layer, or, I'll force imported entities to end up on Mechanical 1.

Altium has documentation on working with mechanical layers.

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