Take a practice swing
When buying a new baseball bat, tennis racquet or golf club, people select the one that fits their strength, size and swing. Similarly, cleaning machines come in all different sizes and with varying features. It is important to select the cleaning system that best fits the company’s cleaning application. This requires a four-step process.
Size. The first parameter is size. If a system is too small, there will be a backlog. If the system is too large, it will be sitting idle, which is money wasted. The ‘fit’ of a cleaning system is judged by its throughput, measured in boards-per-hour.
As an example—a batch aqueous machine that cleans 20 boards in 40 minutes has an average throughput of one board every two minutes, which means about 30 boards per hour. A batch vapour degreaser that cleans only five boards at a time but cleans them in five minutes, will have a throughput of 60 boards per hour.
Throughput affects operating expenses dramatically, especially as cleaning systems reach their operational limits. For example, a small, latest vapour degreaser should have solvent losses that do not exceed about 20 grams per hour. In standby mode, this drops to about 4 grams per hour. To compute total cleaning costs, engineers will need to estimate how many hours each day the system will be cleaning and how many hours the system will be idle.
Many factors affect throughput. For example, systems that need to pause while warming up will have longer cycles. Complex loading and unloading processes also delay the cycle. Drying times may delay cleaning cycles. Water-based machines often cycle quickly when cleaning large, simple shapes; vapour systems are faster when cleaning tight spaces or components with many voids.
[stextbox id=”info” caption=”Checklist of cleaning costs”]
1. Labour: Operator cost per hour (fully-loaded labour rate)
3. Water, solvents or saponifiers
4. Consumables (filters, etc)
5. Water-treatment system consumables
6. Waste disposal
Indirect operating costs
1. Labour: System maintenance cost per hour
2. Floor space cost per square metre
3. Training of operators
4. Supervisory staff
5. Lighting, ventilation and other services
One-time capital costs
1. Cost of buying the cleaning system
2. Freight, duties, customs fees and insurance to get it delivered
3. Site engineering and architectural planning costs
4. On-site construction
5. Electrical changes
6. Water/plumbing changes
7. Ventilation changes
8. System setup and configuration (delivery)
9. Cost of capital
Performance. Engineers should explicitly define the level of cleanliness required and then ensure each system can achieve that requirement. Simple visual inspection may be sufficient in many instances; surface insulation testing may be essential for more demanding applications. Whatever the standard is, define it before the testing stage.
Convenience. Engineers must consider where the cleaning will occur. For example, benchtop machines are slow, small and cheap, so it’s easy to have them conveniently scattered around the plant. Centralised high-volume systems are larger, more capable, more efficient and more expensive, but technicians waste time taking PCBs over to the centralised cleaning system. Convenience is complex.
Test and verify. Lastly, it is essential to conduct real-world tests of the systems. Prepare a batch of products with typical contamination loads. Have each system manufacturer run them through their cleaning systems. Double-check to ensure that cleaning did not degrade components or leave residues in hard-to-reach locations. Each equipment manufacturer should be able to produce a brief written report describing the process, results, fluids, temperatures and times. Disqualify any system that cannot clean successfully.
At this point in your equipment search, the above four criteria should produce a short list of cleaning systems that fit your company’s requirements. Now comes the hard part: determining which system will produce clean parts at the lowest total cost.
Three types of costs
Once the throughput has been defined, the engineer must research the direct operating costs, the indirect operating costs and the fixed costs for each alternative. Direct operating costs include the cost of consumables and labour required by the cleaning system when it is operating. Importantly, when the machine stops, so do the costs. Direct costs are directly proportional to throughput.
Indirect costs are those costs that occur even when the machine is not cleaning, such as rent and training.
Fixed costs are usually one-time installation capital costs.
Let’s take a look at each of these costs:
[stextbox id=”info” caption=”Cleaning scoreboards”]
There are many different types of sports scoreboards, but they all summarise the performance of the players and indicate who performed the best on that particular day. Engineers also need a scoreboard, to help compare the different types of cleaning systems.
There are four main types of cleaning systems used in electronics assembly—aqueous systems, semi-aqueous systems, hydrocarbon systems and vapour degreasing systems—and they vary widely in size, performance, operating costs, labour costs and more. A clever cleaning scoreboard helps engineers decipher these complexities and make apple-to-apple comparisons of very different types of machines.