Custom Design Circuit Board Electronic
Pcb-Set-Up Time Of Operations
Design for manufacturability for CNC machining
The objective is to design for lower cost. The cost is driven by time, so the design must minimize the time required to not just machine (remove the material), but also the set-up time of the CNC machine, NC programming, fixturing and many other activities that are dependent on the complexity and size of the part.
Set-Up Time of Operations (Flip of the Part)
Unless a 5th-Axis is used, a CNC can only approach the part from a single direction. One side must be machined at a time (called an operation or Op). Then the part must be flipped from side to side to machine all of the features. The geometry of the features dictates whether the part must be flipped over or not. The more Ops (flip of the part), the more expensive the part because it incurs substantial “Set-up” and “Load/Unload” time.
Each operation (flip of the part) has set-up time, machine time, time to load/unload tools, time to load/unload parts, and time to create the NC program for each operation. If a part has only 1 operation, then parts only have to be loaded/unloaded once. If it has 5 operations, then load/unload time is significant.
The low hanging fruit is minimizing the number of operations (flip of the part) to create significant savings. For example, it may take only 2 minutes to machine the face of a small part, but it will take an hour to set the machine up to do it. Or, if there are 5 operations at 1.5 hours each, but only 30 minutes total machine time, then 7.5 hours is charged for just 30 minutes of machining.
Lastly, the volume (number of parts to machine) plays a critical role in amortizing the set-up time, programming time and other activities into the cost of the part. In the example above, the part in quantities of 10 could cost 7-10X the cost in quantities of 100.
Typically, the law of diminishing returns presents itself at volumes of 100-300 because set-up times, custom tooling and fixturing can be amortized into the noise.
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