Decision-making, change and progress within an established manufacturing company usually makes financial sense. However, there is always the human factor. Even with overwhelming evidence for progressive improvement, resistance to change has to be expected, and the reasons for it understood. Technical Editor Mike McDonagh takes us through one such example.
This is a case history based in a lead-acid battery factory, dating back to the 1980s. There were still hangovers from the ’70s with entrenched attitudes that were seen by progressives as an anathema to financial and technical improvements. Beneficial reforms were often opposed by senior employees, mostly under the guise of “uncertainty of outcome”.
However, there was almost always an element of a personal stake in the outcome. To put this true-life fable into context, the lead-acid battery industry in the ’80s was severely rocked by massive large-scale failures related to new, cheaper separator materials. Very fresh memories of adopted changes that led to disaster for some battery manufacturers still lingered in almost every manufacturer’s consciousness.
So, to make any changes in this area, you really did need to know what you were doing. It was against this backdrop that a new MD of an established lead-acid battery manufacturer had appointed a new technical director whose first significant act was to radically change the company’s separator material and design.
Make this company profitable
The new MD, David, had the brief to turn this subsidiary company from loss-making into profit. As a first stage, he ordered each department to provide a review and breakdown of their costs, and then to make proposals for reducing those costs without reducing competitiveness. The usual proposals were made, each department wanting other departments to take the brunt of the cuts.
On the third re-run of the brief there were some decent proposals on the boardroom table. Some capital inputs by production were accepted as they clearly would reduce manpower and improve productivity; less travel and lower expenses by sales were reluctantly negotiated, and some supplier changes to obtain cheaper substitute materials, proposed by finance, were deemed acceptable.
However, the most controversial proposal came from the new technical director, Anthony. His proposal was to radically change the separation system used in the entire 2V traction cell range.
The original design was a belt and braces solution that no-one else in the industry had adopted, or even attempted to replicate. To explain: separators are necessary in electrochemical storage cells to prevent contact (short-circuits) between positive and negative plates. This can happen by plates physically touching, or lead dendrites growing from one plate to another.
Also, active material shedding from plates can cause a conducting bridge around the edges and bottom of plates. The company’s separator solution was to make a protective envelope for the plate, from two porous PVC sheets, with a PVC edge strip ultrasonically welded together to form a pocket.
The positive flat plate electrode was wrapped in a folding glass mat sheet, then manually inserted into this PVC envelope, whilst the tubular positive plate was inserted directly, without glass mat. However, this porous PVC material was of a large pore size. This meant it was not proof against small lead dendrites growing through the pores, causing a short circuit. To prevent this, a second separator – a rubber-based sheet with standard separator characteristics – was inserted between the positive enveloped plate and the negative electrode.
Expensive and time-consuming
It was an expensive, time-consuming and labour-intensive process. The cost was further increased by the fact that the rubber-based separator had to be very thin in order to fit into a normal separator pitch (fixed space between the plates) along with the PVC separator. The rubber separator was supplied by a separator manufacturer, but was well outside of the standard thickness range within the rest of the industry.
This made it an expensive item which had to be bought in large quantities to get an efficient production run. Then it had to be cut to size before shipping, and there were 23 sizes between the BS and DIN standard cells. This made stock control something of a nightmare due to the relatively flat sales distribution curve for the range of product types.
The proposal from Anthony was to remove the PVC envelope with associated production and material costs and to replace the bespoke rubber separator with an industry standard polyethylene separator.
He had his reasons. The whole separator assembly and its manufacture were very expensive. It employed four people and was a very skilled job that not many people were able to master. On top of that, it used ultrasonic welding, which at that time was not entirely reliable.
This resulted in excessive maintenance and frequent line breakdowns. Added to that was the bespoke nature of the additional sintered rubber separator. In fact, it was thinner than that purchased by any other lead-acid battery manufacturing company. This adversely affected not only its price, but also its availability, often resulting in long lead times.
Damage to the rubber separator
However, the killer fact, presented by Anthony, was that the quality records showed that the largest source of warranty returns was caused by damage to the rubber separator. In fact, 60% of first year warranty claims were due to this.
Anthony had researched the reason for the separator damage and found it to be due to the manual cassette cell manufacturing method used in the production process. It was a two-person operation; one was a loader (of plates and separator) and the other was the plate group welder.
The loader would take a negative plate and place it upright into a purpose made jig. This would be followed by taking a rubber separator from a stack to one side of the cassette, then, holding it at the top, it would be flicked vertically into the jig to rest against the negative plate. Then the positive enveloped plate would be added, followed by another separator, the next negative and so on until the jig had been filled with the correct plate count.
This flicking action for the separator placed a great mechanical stress on the separator, which was very brittle. The net result was a very high probability of inducing unseen microcracks in the separator backweb.
Key source of separator failure
It was this that Anthony had identified as the key source of the separator failure found in first year warranty returns. Based on these factors, he proposed to replace the current, double separation construction by a single polyethylene separator fabricated into an envelope. He finished by comparing the present separator cost to the company with that of the proposed new material.
The current manufacturing and material costs included the production of the PVC envelope line (manning, amortisation, energy, maintenance and materials), the production interruptions related to poor supply of the bespoke sintered rubber separator, and the first-year warranty returns arising from the separator damage in production.
After listening to the arguments, the MD, David, regarded the separator materials and design change to be a clear no-brainer. Furthermore, provided Anthony had got his facts and sums correct, then this should be adopted as soon as possible. Unfortunately, as Anthony sat down from his presentation, the meeting erupted into a furore. David called for order and asked each department head in turn to state their objections.
For the sales director Brendan, the present double separator was a USP that could be used to justify the extra cost. It also enabled the sales team to offer longer warranties. He also mentioned the replacement of cells under warranty.
These would be a different design with lower IR and higher on-charge voltages. That would cause an imbalance within a battery with replacement warranty cells, and lead to battery damage. He also thought that the risk of putting out a totally new and untested design and material into the market was too great.
Fierce defence from technical
The technical department fiercely defended it as providing a longer life due to preventing short-circuits from separator failure. Geoff the technical manager pointed to the testimonies of some customers who had batteries last several years longer than the competition. He then pointed out the risk of separator shrinkage with heat. Polyethylene is more prone to that than rubber; it may push up warranties especially for the taller cells.
Against this, however, were the financial advantages, the clear-cut evidence of the QA records, the removal of a production bottleneck and the fact that polyethylene separators from the same supplier were used by many larger prestigious companies with no problems; and of course they enjoyed a higher profitability.
Regarding the warranty cell replacements, Anthony agreed there would be an electrical difference. These cells would have a higher voltage and a lower resistance than the old design. But this had always been a problem with cell replacements. Even with the old design, new cells would have a higher on-charge voltage and lower IR than the older used cells.
Better that cells don’t fail
The more the age difference the worse it would be. However, it is better not to have cells fail, thereby removing the problem, rather than soften the impact of the different design on already failing batteries.
When the objections were finished, David once again addressed the meeting, and quizzed Anthony about the timescale and tests required to verify the performance and life expectancy of the new design cells. Some tests had already been done.
It turned out (not unexpectedly) that the electrical performance was improved. The reason was the lower IR and greater acid volume due to the removal of the PVC separator leaves and the dormant edge strip in the envelope construction. Life tests, even accelerated versions, had not yet been completed due to the timescale.
But these would not pick up the main source of failure, broken separators, as the samples were small and usually carefully manufactured without defects, specifically for the tests. Anthony further argued that these changes were not life-critical as the new material was a standard in the industry. Besides, competitors’ batteries performed better, as documented by their own product testing. Curiously, those results had never seen the light of day.
It was important to make accurate evaluations of all these factors. After further reflection and discussions, David quietened the meeting, gained everyone’s attention and announced the following measures:
The first was to take the product cell range which had the highest warranty return rate, the DFP 720 (the tallest cell type), and replace those with the new design. Since those cells failing due to broken separators are usually returned within six months, there should be a reduction in warranties within six months.
In the unlikely event of the warranties increasing, the materials and manufacturing cost savings alone will outweigh any financial disadvantages. Should the warranty levels stay the same, we will have lost nothing and gained a whole lot more. That will be our product life testing.
Regarding the investment in the old construction, it would be better to cut our losses and put in an improved design which should reduce warranty returns and their associated costs. If the warranty rate for older batteries were to increase, then the higher profitability alone would swamp these lower cost replacements (age pro-rata warranty agreement).
The programme to change the design began with ordering material and setting up a new production line. There were few difficulties and the polyethylene material proved to be heat and pressure weldable, which both simplified and reduced the cost of the entire cell assembly. It also removed the tyranny of requiring a high skill level. This, however, was a minor hiccough compared with the resistance from some quarters in the management team.
The engineering manager, Ted, who had designed the equipment and the process for the PVC envelope, spent the first three weeks criticising and undermining the designing and installation of the simplified heat-sealing equipment. He found fault with every aspect of the principle and the installation integrity. In order to finish it, Anthony resorted to working four hours overtime each day, two hours in the morning and two in the evening in order to avoid Ted’s interruptions.
Resentful of newcomer’s dismissiveness
Ted had in fact, spent a year of his early career in the company, designing and constructing the existing PVC enveloping line. Due to the inherent difficulty of the materials processing, he had to devise very clever solutions to the problems of achieving a reliable, good quality weld as well as achieving a suitable production rate. In fact, he was deeply resentful of a newcomer dismissing this achievement as an extra cost burden.
The sales director, Brendan, had spent years convincing his customers of the benefits of this USP to extend their battery life. He would look very foolish now trying to reverse his previous sales pitch. In his opinion it would also break the trust that he alone had built with his loyal customer base. It appeared to David that he threatened the board at least twice weekly with his resignation (usually after every customer call).
The incumbent technical director, Stuart, was glad to be retiring. He was a belt and braces person; he had always designed lead-acid cells like battle tanks, rather than high performance sports cars. Sadly, his battle tanks were less reliable than the sports cars, as well as being outperformed by them. He also gave voice to occasional objections and dire warnings of future disasters due to relying on a single instead of a double protection from the separator system.
This all created a deeper mud in the working environment. This meant that Anthony needed to make extra effort to wade through the objections and problems thrown at him. However, he had been prepared for this resistance and was acutely aware of the pitfalls of making changes to established designs and practices for a mature product.
He was keenly sensitive to the reasons for the resentment from established staff, who continued to cast doubt on his judgement. However, he did find some allies, particularly in the lab manager, Dennis, and production supervisor, George, who helped him to obtain the QA records and arrange manufacture of samples to do the testing.
These two in fact had already become allies as they had previously been ostracised for raising concerns about the warranty returns and the difficulty and skill level of the existing process. Some junior fitters and purchasing staff who had to deal with the maintenance and material price and delivery issues were very keen to progress this advancement. These staff proved critical in enabling fast progress in setting up the plate enveloping line. Within a month the company was selling the DFP 720 range with the new separator arrangement.
200% increase in productivity
The labour saving and productivity proved to be better than anticipated. As a bonus, the new supplier for polyethylene material agreed to a further 2% discount due to the company accepting one of their standard designs. After six months of supply, the warranty results for the DFP 720 were presented by Dennis, the lab manager. These showed zero warranty returns for these cell types but normal returns for the rest of the range. George, now the production manager due to Ted leaving, reported a 200% increase in productivity for the new line at less than a third of the cost. There was also a substantial reduction in maintenance and downtime for the new line.
Based on these results, David ordered the complete changeover to 100% usage of the new separator construction. Because of the higher productivity, there was no need to have more than one additional line. This meant the complete transition could be achieved rapidly, without the need for a large capital outlay in additional lines.
These two replaced the four original and very expensive lines. This was good news for the company, but the consequences for staff members, and the overall factory morale were far-reaching. David was keenly aware that he now had a difficult job ahead of him, to restructure and rebuild the human organisation and morale, in addition to the factory machinery, in order to achieve the full potential of this manufacturing unit.