Thanks for your post. When we mill out the boards, we use an NC automated system, essentially meaning the machine just follows a set of instructions and moves to the specified coordinates. Therefore, there is not much difference between simple shapes like a rectangle or a triangle. The difficulty arises when there are either many unconnected milling slots in the middle of the boards for example, having many USB connectors or having a long milling path, e.g. a “complicated” outline or when used to mill out the internal areas of a panelised design. In the latter case, even rectangular boards could have excessive amounts of milling if designed as such. So we recommend using v-cuts for long flat edges as much as possible.
This of course depends on the specific design so there is no one size fits all approach and the pay first, review later approach is not ideal. This kind of situation is not limited to milling and so the only way to accurately quote your boards would be to ask us first if you suspect your design is non-standard.
To answer your specific questions:
if that is subject to specif pricing or if it is included in the standard service;
A moderate amount of milling is included in the standard service, exceptions will be pointed out by engineers during file review and the pricing depends on the complexity of the milling. This is ultimately up to the engineer’s judgment.
in which layer should we submit the board layout. For instance Mechanical 1.
Yes, include all board mechanical information in a dedicated outline/mechanical layer to avoid confusion
if we can use the standard fusion pcb order form to submit this kind of requests.
Yes, of course. If your boards require extra fees, the engineers will point this out during file review. You may choose to cancel your order at this point or change the design if not acceptable.
Hope that helps!