One of the most effective time and labor savers for a product development effort is the use of a selective part list produced from the company's Item Master.
In an earlier Best-Practices post, I discussed the Item Master in some detail and promised to write another feature that introduces a subset of the Item Master, commonly referred to as the Preferred Parts List (PPL). (See: Comprehensive Item Master & Related BOM Item Structure.) Imagine a design that has close to zero part failure issues over the lifetime of the product. This translates to efficiencies at every stage of development and production and extends to end user experiences and subsequent company reputation.
Each company should identify the part characteristics to be used for generating a PPL and, generally speaking, the more comprehensive the list, the more reliable the end product. Like any other engineering effort, the more work put in on the front end, the less work is required on the back end.
Initial cost is only one consideration for the PPL and may be offset by the value gained from less repair rework and replacement costs over the lifetime of the product. Obviously, the company's philosophy and quality practices come into play here. At the very least, the vice-president of engineering must be willing to enforce the practice of using the PPL or individual engineers; otherwise, the purchasing department may be tempted to introduce the most readily available or lowest-cost parts that have no field performance history. The criteria for selecting parts for the PPL can be any or all of the following.
- Performance history:
- Alternate source.
- Regulatory compliance:
- Reliability numbers:
- Life span:
- Economic order or lot quantity:
Low cost, but not necessarily lowest cost.
Actual field experience or extensive relevant testing.
Parts can be purchased from multiple sources, (vendors or/and distributors).
Same form, fit, and function for parts, but different manufacturers' names and part numbers. (Different manufacturers' crossover part numbers must be equal.)
Failure in time (FIT) or mean time between failures (MTBF).
Pre-screened or tested parts.
The cost might be slightly more in order to obtain the desired lead time.
Business preference or contract obligation.
Let's look at six different stages in the product's life and examine our subsequent savings:
- Research and design:
- Eliminating a newly introduced component's unknown performance will expedite Design Validation and Testing (DVT) efforts.
- Shorter development cycles realized through less component failure issues and time taken for troubleshooting and reworking breadboards and prototypes.
- Quicker proof-of-concept results.
- Parts used from PPL are more likely to be available from on-hand inventory, and small development quantities can be kept in engineering's stock location.
- Less problematic with part availability concerns.
- Since the part is used in pre-existing assemblies, even greater discounts can be achieved by increasing part order quantities that include the new design requirement.
- More volume from a single supplier tends to curry the favor of that supplier and opens the doors to the benefits of special favors beyond just pricing. The supplier may go out of its way in order to keep a valuable customer happy. This could take the form of free parts in small quantities or samples and preferential treatment for retrieving allocated parts on an expedited basis, if necessary.
- Less line failures using proven parts.
- Test fixtures already programmed with applicable Vector/Boundary Scan information.
- Assembly personnel already very familiar with part handling requirements.
- Higher level of confidence in product representation because of proven performance.
- By using environmental and regulatory pre-approved parts, the certifications are already on file and can be quickly retrieved to expedite purchasing authorizations by customers that have compliance mandates in their countries.
- Fewer returns achieved with higher reliability.
- Experience with commonly used parts promotes a deeper understanding of part behavior and common failure mode and symptom identification.
- Customer satisfaction with longer life product and fewer returns.
The points made above are a combination of different characteristics required to be added to the PPL. Higher reliability guarantees are only attained by making “Reliability” an entry on the PPL. Purchasing benefits come as a result of “Availability” and “Lead Time” requirements. By fine-tuning the PPL to your company's internal processes and the customer's expectations, the time-to-market is shortened significantly, and the sales effort is greatly enhanced because your products' reputation precedes the sales.
Don't forget where it all begins. The design engineer who selects the components must choose as many parts as possible from the PPL. If a non-PPL part is to be considered for use, that use must be approved by a components engineer (CE), and the part may be added to the PPL only after a CE qualification process approval. By selecting even a majority of the parts from the PPL, the benefits realized from the arguments presented above should be sufficient to encourage the company to validate and enforce the practice of using a PPL.