Part and Component Overage

Last Updated: April 16, 2019
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During PCB assembly, extra parts may be needed due to manufacturing parasitic loss and component defects. The MacroFab platform automatically calculates how much overage our process will need given the component type and how many assembles are being built.

Why is Part Overage Necessary?


There is a potential for component or part loss in a couple different areas of the PCB assembly process.

Mycronic feeder cartridge loaded on a My200 pick and place.

Mycronic feeder cartridge loaded on a My200 pick and place.

The first loss occurs when loading our automated SMT placement machines with components. The feeders (tooling that holds and advances the parts to the machine) require a certain amount of exposed tape during setup. This exposed part section is called the leader section on the SMT tape and is what allows the tape to start feeding into the feeder. Modern SMT placement machine feeders are very efficient in minimizing the amount of leader needed. Older machines used to require almost 2 feet of extra leader which is a lot of overage!

Chip components (0402 and 1206) packaged in tape form.

Chip components (0402 and 1206) packaged in tape form.

If the component is a part we have not used before there is a component training phase the SMT placement machine needs to go through to learn the new component. This generally requires only two extra overage parts. One part to train the machine and one to verify the training.

Machine teaching for picking up a part out of tape feeder.

Machine teaching for picking up a part out of tape feeder.

Training the machine by test placing an LED package.

Training the machine by test placing an LED package.

Checking the orientation after training a new diode on the pick and place machine.

Checking the orientation after training a new diode on the pick and place machine.

There is a chance of a mispick by the SMT placement machine during assembly. This mispick can cause the vision inspection system to reject the part. For larger parts this is fine as the machine operator can remove the part from the reject bin on the machine but for chip size resistors and capacitors it is hard to identify, separate, and reload individual parts.

Reject bin on the pick and place after a manufacturing run.

Reject bin on the pick and place after a manufacturing run

If a part was lost due to the above problems and an exact number of parts was ordered this would cause a manufacturing delay in the PCB assembly process. To reduce manufacturing delays part overage is a necessary part of the logistics process.

Transparency for part overage


Here at MacroFab, we want you to know exactly what you are ordering. The Bill of Materials tab of your PCB assembly displays the additional quantity and price of part overage required for each individual line item. No labor charge is associated for additional parts for overage.

MacroFab PCB interface displaying the overage for a line item.

MacroFab PCB interface displaying the overage for a line item.

Learn how to Manage your PCB Bill of Materials with the MacroFab Platform.

Turnkey parts overage


You do not have to worry about part overages for turnkey sourced parts. MacroFab will automatically calculate the overage required and order the parts for you. This reduces overall manufacturing delays by making sure all the parts arrive on time and there are no part shortages during assembly or your PCBs.

Consignment parts overage


When shipping components to MacroFab for consignment parts it is required to ship part overage. The MacroFab platform will calculate how much overage you will need to send in. Failure to send in part overage will result in manufacturing delays with your order and could cause the cancellation of the order. Learn more about consignment parts.

Do I get my leftover overage after my order is complete?


Left over Turnkey sourced parts are generally scrapped at the end of the order. Consignment parts are returned to you when the order is shipped out.

If you have anymore questions or have concerns with part and component overages contact our support team.