5 Tips for Buying Your Next Electronic Assembly

Finding a new supplier to purchase your custom electronic assemblies from can be a daunting task for anyone new to the process.  Even if you have experience you may find subtle differences between suppliers that leave you wondering if you’ve made the right choice or not.  There are a lot of steps to the electronic contract assembly process and it is likely that both your engineering and quality departments should be part of your final electronic assembly contractor selection.  Whether it’s your first time finding a supplier or you just need some reminders this article should point out some key items to keep in mind.

Location

Communication

An item that can ease the need for close proximity is a singular point of contact within your supplier.  Is it clear who is managing your project?  Are you going to feel like you are bounced between a planning engineer, process engineer, testing engineer, component engineer, quote analyst, sales person, etc?   Finding a central point of contact that can bridge all these departments for you and is knowledgeable across the whole spectrum can help make your life much easier.  So treat your evaluation like an interview and ask to talk to who you will be working with on your project.  You should feel as comfortable with them as a trusted team mate you would hire to work side by side with.

File Management

 Often you can get a quote for a PCBA with just a set of gerber files and a Bill of Material.  But if you are getting competitive quotes make sure that everyone made the same assumptions if this is all you gave them.  Additional items like fabrication drawings (specifying alloys and PCB thicknesses), permissible BOM substitutions (letting them know what they can substitute can improve your lead times and final pricing), assembly drawings (finer details of the assembly process should be pointed out upfront so you and your vendor don’t argue about additional charges, time, or quality issues later), testing documents (often forgotten at time of quote but something that should be discussed upfront and tentatively budgeted for initially), quality standards you expect (this can drive cost differences depending on the depth of your needs), custom component information and pricing (to properly quote any custom components or upper level fabrications make sure you supply the files and let your supplier know if you already have target pricing or a supplier already tooled for your custom component if you’re planning on a full electro-mechanical assembly ).  Revisions are important, even if your company is small and does not have a robust revision system consider a simple system and rename your electronic files with today’s date and use that time stamp as your revision.  Or start today and name them all revision 1.  Revision control of even the smallest of changes makes looking back on changes to your project much easier to control and trace for all parties involved.

Supply chain and forecasting

Today’s electronics supply chains are very volatile.  Things you have been used to getting shipped overnight from your favorite supplier may all be gone and have a 50 week lead time tomorrow.  Be aware of the components on your design that cannot be easily substituted, consider purchasing a buffer quantity of that part to keep in your own stock, consider what could possibly be changed so you have multiple options.  Supplying your supplier with forecasts and placing purchase orders far enough in advance to get parts on order will greatly reduce timeline stresses later on.

Material storage

Ask if your supplier has good storage and material tracking software.  Are they utilizing good practices for minimizing Electro Static Discharge (ESD)?  Do they have good practices in place for tracking and protecting devices with high Moisture Sensitive Levels (MSL)?  Can they separately track and store components you purchased and supplied for you product that you own?  These are all good questions to get yes answers to from your potential supplier.

Summary

There may be many more very important issues and details to consider when choosing your next electronic assembly manufacturer.  Starting with the above short list will ensure that you are already off to a good start though.  Are some of the above terms new to you?  Do you have questions?  EPD Electronics is here to help.  Feel free to reach out anytime and let one of our very experienced staff answer any of your questions.

Many Thanks to Chance Turner at EPD Electronics for this article: EPD Electronics - www.epdelectronics.com

What are Internal Keyways?

Internal keyways on rings, usually in the form of gears, and external keyways on mating shafts have long been the preferred method of transmitting driven power through mechanical systems. The mating keyways on the shafts and rings are sized up as the components become larger, so as to transmit an appropriate amount of power in keeping with the mechanical strength of the components that are joined.

As in many fields of industry, standards have developed so that machined features, including keyways, can be made cost-efficiently and so that manufacturers can respond in a timely manner without the need to create costly specialized tooling for each keyway job. The American standard for keyways is ANSI-B17.1. And it is available where mechanical industry standards are sold.

What Keyways Do

Now before we delve into the details of ANSI-B17.1, let’s talk more about what keyways are designed to do. A female slot is cut in both the external surface of a shaft and on the internal surface of a ring. The location of these slots determines where the ring will ride on the shaft when keyed together. Into the void on each part is placed a square bar of metal called the “key”. The key is sized so that the key would have to be sheared in half to cause failure of the joint. Since shearing a rectangle of metal is a difficult process, it can be seen how this can make a strong, lasting joint. Increasing the length of the key increases the area of metal that must be sheared to cause the joint to fail, so increasing the key’s length is an easy way to increase joint strength.

Since the strength of the joint comes from the cross-sectional size of the key and not the tightness of its fit, the tolerancing of this feature need not be overdone. B17.1 calls for a total width variance of .003” and a total depth variance of .010”. Off-the-shelf keyway tooling is made to perform to these tolerances and using the sizes tabulated in ANSI-B17.1 helps ensure an economical part for which standard tooling is readily available. Tightening tolerances above these standards usually results in difficulties in installation in the field and not a stronger joint.

How Keyways Are Made

Internal Keyways are made with machines that have a single-point, reciprocating tool that follows the axis of the shaft and mechanically moves in with each stroke to create the keyway depth. Internal keyways can be made by both specialized keyway machines and CNC machines with tooling adapted to apply keyways, but it is the fixed tooling that determines the keyway width despite the fact that the CNC machines are programmable, so the .003 width tolerance should still be adhered to even if a CNC machine is used to apply the internal keyway.

Finally, the machines and processes that make internal keyways work best when the internal keyway runs completely thru the part from end to end. Measurement and chip flushing are vastly improved over a keyway design in which one or both ends of the keyway are closed off, called a “blind” keyway. While it is possible to make blind keyways, it adds considerably to cost and difficulty in manufacture. Securely capturing the key is usually easily accomplished by making the external keyway in the shaft a pocket rather that an open-ended slot. Thus, the key is still captured but the pocket feature is more easily made on the external surface of the shaft, rather than in the confined recesses of the ring part.

Courtesy: Matthew Mawhinney | Gazzam Machine | http://www.gazzammachine.com/