2005 Articles

Short a standard, machine specs and performance are derived different ways.

Our industry has no standard criteria for the qualifying factors used in determining equipment performance specifications, or even for what equipment specifications should be supplied to the customer. There are no rules all equipment suppliers can use to determine performance specifications. Some activities, sporting events for instance, have standard rules that all participants must obey – and that can be used for performance comparisons. We do not.

Specifications such as accuracy, repeatability, speed, cycle time, up time, mean time between failures (MTBF), mean time between assists (MTBA), set up time, etc. are based on a particular set of factors from that particular supplier. Users must read and understand the qualifying factors on each piece of equipment from each supplier. For example, the quoted cycle time of printing equipment from a particular supplier may include the printing time of a particular size board using a particular squeegee stroke speed. The quoted cycle time of a printer from another supplier may be faster or slower based on a different set of qualifying factors. For component placement equipment, the placement rate from each supplier is based on specific criteria such as board size, distance between components being placed, component size and complexity, feeder carriage movement, nozzle changing, etc. A placement machine with a specified faster placement rate may in fact have a slower placement rate for any particular operation, depending on the requirements. The same variation in methods to quantify performance specifications is true for reflow ovens, wave solder equipment, dispensers, AOI systems and even conveyors.

A significant consideration to investigate is how the supplier generated the data to support their equipment’s performance specifications.

• Were the data generated using statistically valid tests?
• Were standard-released machines built using the standard manufacturing process used in the performance standards testing?
• How was the data gathered and verified?
• How often are the equipment specs verified?
• Are the specs recalculated after a significant modification to equipment design?
• What does the supplier consider a significant design modification?
• What is done to verify specs if a new supplier for a major component of the equipment is used?
• Was a gauge R & R study performed on every measurement system used in the tests to collect the equipment’s performance specification data?
• What was the performance-to-tolerance (P/T) ratio of each measurement system?

Understand the details of precisely what is done to generate the equipment’s performance specifications. If required, seek the assistance of someone knowledgeable in statistics.

Determining what equipment has the best performance specification requires more than just comparing the specification sheets from the various suppliers. If the person responsible for selecting process equipment does so by comparing performance specifications published in suppliers’ literature, they are not doing their job. You must question the supplier on how the value of that specification was determined. Ask for valid data to support the claims.

For years our industry has had third-party verification of equipment safety issues through organizations for compliance to legal standards such as CE, UL and CSA. Third-party verification of some equipment performance specifications is now available. For example, CeTaQ supplies equipment and onsite testing services to evaluate, calculate and verify the accuracy and repeatability of printers, dispensers, component placement and other equipment used in electronics manufacturing. Such third-party testing provides standard, statistically valid, documented data. Having equipment performance specifications verified by a valid third party minimizes the specification investigation process and generates confidence in the supplier’s published specifications.

The final chapter in equipment performance specification is how the equipment supplier verifies that every machine shipped complies to or exceeds published specifications. What testing is done on the factory floor? Many of the same questions asked about how the supplier generated the data to support their equipment performance specifications should be asked of the performance verification process for each machine prior to shipment.

During my career at Motorola, we were not allowed to place a new machine in a production line until we verified its performance to specification. We would unpack the new machine and run our own performance testing using the supplier’s specifications. Often the machine would not meet the supplier’s standards the first time out. Working with the supplier, we would make the necessary adjustments and rerun the tests.

At times, after several adjustments, the machine would pass our performance test and be placed in a production line. We called this verification testing “Prevention versus Reaction.” The philosophy should always be to prevent defects from occurring, not react to defects after they are created. Understanding and verifying equipment performance specifications is one step in a preventative manufacturing philosophy.

Joe Belmonte is project manager, advanced process development, at Speedline Technologies (speedlinetech.com); jbelmonte@speedlinetech.com. His column appears semimonthly.

• Prev
• Next