Manufacturing engineers and project managers who are charged with acquiring special factory automation for their plants usually use some variation of a ?standard machine specification.? These standard specs can be great time-savers. However, without the right precautions, they can drive up the cost of automation unnecessarily?and invisibly.
Standard specifications have a way of growing and evolving over time. Eventually, what was originally intended to apply to every automation project is no longer a good fit for any of them. The typical ?universal? specification grows out of experiences like these:
- A project manager brings in some equipment from an overseas source and discovers that it was insufficiently protected from corrosion during the ocean voyage. He adds a paragraph to the standard spec requiring all incoming equipment to be crated, wrapped and sealed, with desiccant placed inside the wrap. What if the next machine only has to make a short trip by truck from the automation builder?
- A manufacturing engineer buys a special machine with a marginal programmable logic controller (PLC), and decides that she won?t make the same mistake again. She adds a line to the standard spec requiring all equipment to have a specific brand and model of high-capacity PLC with data communication capabilities. What if a later project only requires a stand-alone machine with a minimal number of control inputs and outputs?
- An engineer signs a purchase agreement with an automation supplier, only to find out, too late, that he and his supplier have different opinions about what constitutes a sufficient number of design reviews. The engineer revises the standard spec to include a minimum of five design reviews?concept 1, concept 2, interim 1, interim 2 and final?to be held at the buyer?s facility. What if the next project is a relatively simple, semimanual machine?
- A manufacturer purchases a complex, multiprocess automation system that is intended to run a range of product variations. As the qualification phase approaches, he finds out that the supplier only budgeted 2 days for qualification, and intends to charge extra for more run time. The manufacturer revises his standard spec to require a minimum of 1 full day?s running time for each product variation or changeover. What if the manufacturer?s next automation purchase is a single-station, semiautomatic machine that accommodates several product variations through a simple tool change?
- An engineer orders a special machine from a low-cost builder, then realizes that the base the supplier quoted for the machine will be of bolted construction with a marginal top plate. After paying extra for a more appropriate base, the engineer adds a line to the standard spec requiring machine bases to be made from welded, structural tubing and a steel top plate with a minimum thickness of 1 inch. What if the next purchase is a semimanual machine that can easily be bolted onto a standard, low-cost steel base or a workbench with a wooden top?
For the five questions posed here, the answer will be the same: The price of the equipment purchased with the standard specification will be unnecessarily high. Unfortunately, the buyer may not realize it. An automation builder that is asked to quote on a standard spec may recognize and question suspect requirements. But, if the buyer has not established a good working relationship with the builder, the builder will most likely quote on the high-priced requirements.
There is no doubt that manufacturing personnel learn valuable lessons from every project, and they should document that new knowledge so it can be used on future projects. But, indiscriminately loading the lessons-learned into one ?standard equipment specification? is not the answer. Instead, engineers would be wise to develop a series of standard specs based on the complexity of the equipment.
Special factory automation can be segregated into five levels and five grades, depending on its complexity and expected life. These levels and grades are major contributors to the price of the machine.
Level I equipment is strictly manual. All parts positioning and manipulating, and any work done to the workpiece, comes from human exertion.
Level II equipment is semimanual. Parts are manually located and removed from the processing device. However, power for work done to the process is supplied in part by a mechanical, electrical, hydraulic or pneumatic device.
Level III equipment is semiautomatic. All processes are done automatically, but an operator feeds components to the device. The operator is required to feed the machine on a one-for-one basis. That is, with each cycle, one or more parts are fed into the machine, and a single assembly comes out.
Level IV equipment is automatic. The operator normally handles product components in bulk, loading them into a device that orients and feeds them to the process. In addition, the output is handled in bulk or in multiples. Many times, the products made by a fully automatic machine are inspected and packaged, ready for shipment.
Level V equipment is highly automated. Economical in rare circumstances, a highly automated system approaches the much-touted ?lights-out? manufacturing milestone.
Besides complexity, equipment can also be classified according to grades, depending on how long it is expected to last. After all, not every product and process is intended to remain in production for decades.
Alpha-grade equipment is top of the line. This designation is reserved for systems expected to remain in production for more than 8 years. Alpha-grade systems are engineered to accommodate change to another product version or to newer process technology.
Beta-grade systems are engineered to have a productive life of 2 to 10 years. They may have minimal flexibility to accommodate a similar product in the future.
Gamma-grade systems are intended for short-term production, less than 3 years. Because the emphasis is on first-cost efficiency, the prime movers in these systems are typically pneumatic. As a result, gamma-grade systems have relatively low production rates compared with alpha or beta grades.
Prototype-grade machines or tools are built to support experiments to demonstrate or develop a concept or process. A prototype is defined by a short life expectancy, typically days or weeks. After the experiment is completed, the prototype often is scrapped, or disassembled to salvage its major components.
Pilot-grade equipment is built to demonstrate the efficacy of processes over time, usually accommodating ongoing changes from the product development process. Pilot equipment is frequently used for limited production, and to serve as the basis for scaled up production.
These level and grade classifications can be used to set up a series of standard specifications. Obviously, the configuration requirements for a level II machine will be vastly different from those for level V. Levels and grades can be specified in different combinations, but not all grades of equipment are built in all levels.
Standard specifications should be tailored to specific equipment levels or groups of levels. That means keeping three or more separate specification templates. The table of contents headings for all of the templates should be similar. But, only the configuration or performance issues that apply to each equipment level should be entered in the specification template for that level. In this way, engineers won?t unwittingly ask for expensive and unnecessary features in their production equipment. There should be no more instances of specifying a high-end PLC for use with a manual benchtop tool.
Even a standard specification needs to be reviewed each time it is used to ensure applicability to a specific project. View the standard specification as a template-to be refined and detailed at each use. Then, after it is tailored to the project at hand, identify it and save it as such.
A Specification Is Not Enough
Communicating with a prospective machine builder takes more than a written specification, even when the specification is tailored to the project size. A necessary accompaniment to the specification is the request for proposal (RFP) letter. The RFP letter addresses project issues that are not normally defined in the equipment specification, such as project scheduling, product drawings, product samples, existing processes and proposal requirements.
If you supply sufficient¿but not excessive¿project-specific information each time you submit a proposal for a project, you won¿t unnecessarily restrict the supplier¿s innovation and you will receive a proposal that reflects appropriate concepts, and fair and accurate pricing.