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The High-speed High-mix Production Environment Emerges
December 31, 1969 |Estimated reading time: 9 minutes
Whereas high-volume, low-mix assembly once was the primary activity, it increasingly is relegated to prototype development and high-mix, low-volume products.
By Scott Wischoffer
The North American printed circuit board (PCB) assembly market has undergone dramatic changes since the early 1990s that have reshaped the way PCB manufacturers regard the design of their production environments. In the early part of the decade, the market consisted of two basic segments, roughly of equal proportion: OEMs, who built their own finished products, and contract manufacturers (CM), who performed that function for OEMs on a project basis. However, product lifecycles and development times then underwent a contraction while manufacturers in all markets focused on defining and limiting operations to "core competencies." As a result, the capital investment required to acquire and maintain state-of-the-art production lines became a less attractive prospect to large enterprises in the computer, telecommunications and other digitally-driven industries. Rather, their response was to allocate a greater percentage of internal resources toward research, design and product innovation; manufacturing per se was outsourced increasingly to the CMs.
A New Way of ThinkingIn recent years, a considerable number of former OEM manufacturing facilities have been purchased or absorbed by large CM houses as part of an evolvement in which the latter are getting bigger. Also, the industry quickly is becoming networked and globally based as the major players move aggressively to add production capability in dispersed international regions in which inexpensive labor is the major attraction (Mexico, China and Taiwan being the most prominent). This shift has left North American manufacturers in a dramatically changed position where once high-volume, low-mix products constituted a majority of their business, today that activity increasingly consists of prototype development and high-mix, low-volume assembly.
Traditionally, manufacturers built lines for high-mix, low-volume production using entry- or mid-level machines. The theory was that the cost of high-speed equipment is unjustified in this environment. Flexibility typically took precedence over speed, but numerous factors are combining to create a reassessment of such thinking in three areas:
Competitive Market Forces Are Demanding Speed. As manufacturing resources consolidate on a global scale, time-to-market pressures are bearing on all aspects of the PCB manufacturing process. While it is true that high-speed equipment may be unjustified in an environment restricted to low batch sizes and placements per board, reality exposes various projects now bid upon by CMs to be increasingly diverse. Accordingly, a manufacturer's ability to extend the range of batch sizes and placements often can serve to improve the competitive position. Also, high-speed solutions can drive down manufacturing costs, floorspace requirements, the number of necessary lines and the cost of labor associated with PCB assembly significantly.
Current High-speed Machines Are Built to Accommodate Flexible Changeover Requirements. As the industry has evolved to a market dominated by CMs, the major high-speed equipment makers have focused their product development not only on speed and accuracy, but also on designs that permit such equipment to be easy to use, program, maintain and changeover. For example, a chip placer equipped with a high-speed board-loading system that reduces total cycle time also comes with a gang feeder replacement system that permits rapid changeover from one board to another (Figure 1).
Figure 1. Current high-speed board loading systems can reduce cycle times in high-mix environments.
High-speed Equipment Now Addresses the High-mix Environment. In doing so, the myth of "high-speed, high-volume only" is exposed. Because the high-volume, low-mix market had been so fertile for high-speed-equipment providers, the high-mix operations were largely ceded to manufacturers of entry- and mid-level machines. Changing market dynamics, however, have now forced the former providers into the latter arena only to find that the incumbents have worked hard to isolate high-speed solutions from the high-mix assembly setting. Nevertheless, as the market becomes aware of how flexible the high-speed systems have become, such isolation is likely to disappear via the new ability gained by CMs to leverage in the low-mix environment.
Figure 2. The gang feeder replacement systems can exchange up to 70 fully loaded feeders with 70 different feeders in less than 45 seconds.
The Gang Feeder Changes the PictureOf these technological advances, the development of the gang feeder replacement system is the most important factor for the high-mix production facility (Figure 2). This new system permits up to 70 fully loaded feeders to be exchanged with 70 different feeders in less than 45 seconds. The process uses a cart, called a pallet-change unit (PCU), that docks to the rear of the high-speed chip placer. In operation:
- Once locked into place, the PCU will release the feeder table so that it may be rolled out to the cart.
- The cart then is exchanged for another fully loaded verified cart, and in less than two minutes, the feeders on both sides of the machine (up to 140 individual part numbers) can be replaced.
- The rail width and the program then can each be changed quickly.
- The machine can accept a new product for production again.
The advantage of using high-speed machines in a high-mix environment is straightforward, i.e., once machine setup is completed, less time is required to finish one production run and begin the next. To be sure, if the run is only a couple of boards, the benefits are minimal. However, many production runs once considered low volume, e.g., 150, 100, 50 or 20 boards, now can benefit from high-speed equipment.
For example, if the actual run time can be reduced by 33 percent, the number of jobs completed in a workday can be increased significantly enough, perhaps, to reduce production from two shifts to one or to eliminate additional production lines. In such accounting, all elements of production must be considered: the costs of floorspace, equipment, power, compressed air, heating, cooling, lighting, cleaning and labor. These can be combined and examined to justify high-speed machines in high-mix environments. In fact, with these elements in the equipment equation, the likelihood is that high-speed solutions in high-mix production settings will be the norm not the exception.
Loading/Changeover Times NeutralizedBased on current and projected demand, new PCB assembly lines should be equipped with gang feeder replacement systems for both high-speed and flexible placement equipment. By enabling the new lines to change from one product to another in minutes, the systems can eliminate loading and changeover times effectively as an equipment issue. With production time, the operative evaluative parameter, high-speed technology can be leveraged to full advantage through higher throughput.
Planning and preparation are key to high usage and efficiency in a high-mix, low-volume environment. Floor supervision is paramount to direct which jobs are next and to ensure that the following two to three setups are being prepared off-line. To avoid last minute delays, kits must be completed and verified before their introduction to the production floor. While gang feeder replacement systems work well, they must be used properly, i.e., set up in advance and served by additional pallets and feeders a cost, however, that can be recovered via the higher efficiencies through high-speed lines.
The product mix listed in Table 1 is typical of a high-mix, low-volume environment, i.e., all jobs are from parameters observed at CM sites. If it were run within traditional high-mix and high-speed production lines, the differences in production time would be dramatic. This analysis is made using the following assumptions:
1. A traditional high-mix line assumes the presence of a stencil printer, a chip placer with a rated speed of 22,000 cph and an actual speed of 15,000 cph; a flexible placer with a rated speed of 4,000 cph and an actual speed of 2,000 cph; and a reflow oven.
2. A high-speed, high-mix line also includes a stencil printer; a chip placer with a rated speed of 54,000 cph and an actual speed of 35,000 cph; and a flexible placer with a rated speed of 7,200 cph and an actual speed of 4,000 cph.
3. Both lines are calculated using a changeover time of 15 minutes.
4. All set-up kits are complete and verified.
Conclusions:
- If both lines begin placements at 7 a.m. on a typical workday, the high-speed line is finished at 3:45 p.m. In contrast, the traditional high-mix line does not catch up until 11:20 p.m.; the labor savings alone is significant.
- Assuming that each line requires two operators per shift at $25/hour/operator plus one supervisor each line per shift at $35/hour/supervisor, this would contrast with the traditional high-mix line that would require two shifts x two operators = four operators = $200,000/year. The latter also would require two shifts x one supervisor = two supervisors = $140,000/year; annual labor cost = $340,000.
- The high-speed line, using just a single shift, cuts the annual costs in half to $170,000/year. Thus, when multiplied across a five-year machine life, a savings of $850,000 can be figured.
The two job factors that serve to maximize labor savings with the high-speed alternatives are number of placements per board and number of boards per lot. As these numbers increase, so do the gains accrued over traditional machines. Similarly, an additional cost savings potential may be realized with factories using multiple production lines. By reducing the number of lines needed to produce a given quantity of work, high-speed lines effectively reduce the floor space required together with fewer ovens, stencil printers and conveyors necessary for additional lines.
How to Know WhenTo assess whether high-speed or traditional lines are indicated in a high-mix, low-volume environment, the following questions should be thoroughly examined:
- What is the average number of placements per panel?
- What is the average number of panels per job?
- What is the maximum number of feeder positions needed to complete the most complicated project?
- How many components per hour must the facility place to meet production requirements?
- How many daily changeovers are anticipated?
Once these are answered, calculations must be made to determine the time needed to run products in an average production environment. Companies that have one or two low-volume lines and are considering adding another should consider the cost vs. replacing the old equipment with a single, new high-speed system. An incentive: By using the existing stencil printer and reflow oven and eliminating the need for additional floor space and labor requirements, significant value can be realized immediately.
Companies also must reassess their perceptions. Today's high-speed SMT placement machines are ahead of those produced a decade ago, particularly in the flexibility they offer the high-mix CM. Many standard features relating to programming, setup and changeover make them easier to operate than before, despite achieving a higher level of technological sophistication. For example, high-speed machines generally require no operators to teach component pick positions, where with many entry-level machines such instruction is vital as part of the setup process.
The basic technical elements for high-speed machine operation in high-mix environments split-D axis function, high-speed board loading and gang feeder change units for rapid changeover have been in place for years. Today's new market conditions are providing the incentive for equipment providers and electronics manufacturers alike to bring these high-speed solutions into a production environment in which speed is an increasingly compelling competitive advantage.
Scott Wischoffer may be contacted at Fuji America Corp., 171 Corporate Woods Pkwy., Vernon Hills, IL 60061; (847) 821-2405; Fax: (847) 913-9805; E-mail: scottw@fujiamerica.com.