Pultruders need some self-control

At the recent JEC show in Paris, I noted the numerous stands displaying pultruded products. Most of the exhibits included standard structural shapes, gratings, handrails, cable trays, etc. — products now considered to be commodity profiles with differentiation based primarily on price. As established pultruders have watched production of ladders, tool handles and tent poles (to list a few) move to newer pultrusion businesses established in emerging economies, there has been a great deal of concern about further market decline due to low-priced competition. We tell our customers that they cannot possibly produce the same level of quality or service that we can in the States. Some suggest that we who are more experienced should simply abdicate commodity production and focus on more complex pultruded products where we currently have a degree of technical protection. Guess what? “They” are improving in technical capability and quality at a very fast rate. I contend that our concentration has to be on manufacturing cost control and productivity to retain our competitive edge.

Our ability to effectively design composition is the first opportunity to control cost. Raw material cost is usually 50 percent or more of the selling price. Knowing when to choose a polyester resin vs. a vinyl ester, epoxy or polyurethane is essential. Likewise, designing fiber architecture with the most cost-effective materials is the second chance to influence baseline cost.

Assuming the material composition of a profile satisfies the end-use requirements without giving away excess performance, the raw material cost is what it is. As it increases, we can only hope that we can pass the material cost along to the customer periodically with price increases.

We have greater potential for cost control, however, when it comes to processing. The primary opportunity to influence the processing cost and quality of a pultruded profile exists where the greatest number of things can — and often do — go wrong: before the materials enter the pultrusion die. When the product exits the die, its quality, good or bad, is fixed. Because these pre-die problems are all avoidable, a focus on prevention can have a huge payoff. Before startup, ensure that each batch of resin is formulated correctly, each roll of mat, fabric or veil is slit to precise width, and each setup is executed per specifications. Confirm that initial fiber input — the number of rovings, mats, fabrics and veils — conforms to the fiber architecture recipe, with placement defined by setup drawings. These steps are easy. When production begins, however, control is more difficult. Can the machine operator confirm without a physical count that the prescribed number of rovings and mat are present? This is not too difficult for mats and fabrics that are limited in number. But hundreds of rovings may be guided from the creel through the guides into the final preformers for large profiles or multiple stream setups. Reintroduction of rovings and mats that break out periodically is often not easy in some impregnation systems. Running below the spec levels of fiber content can affect mechanical properties to some degree, and surface cosmetics to an even greater degree.

Many defects are cosmetic, and a product may be rejected due to appearance issues only. Examples are incomplete veil coverage, surface scaling and resin shrinkage marks. Other defects are dimensional, such as a loss of a specific profile detail. Some defects, such as an inclusion of foreign material, can occur instantly and sporadically while some take time to develop, such as surface scaling that gets progressively worse as a run progresses. Machine operators have numerous tasks during the production period that prevent them from standing and watching a slowly moving pultruded part. In any case, full-perimeter visual inspection of the profile usually cannot be made until the operator removes the cut part to stack it for shipment. Because there is a considerable distance from the die exit to the cut-off saw, as much as 50 ft/15.2m of substandard product can be produced before the problem is spotted. If the problem is caught early enough, a correction to the material input or a process parameter might resolve it without process interruption. In the case of serious defects, machine downtime may result.

Given this situation, early detection of defects should receive significant attention from process engineers. There is currently no method or apparatus that automatically and continuously monitors the quality of a pultruded profile as it is being produced. Even a state-of-cure measurement wouldn’t guarantee maximum mechanical performance because it cannot quantify fiber content or fiber placement accuracy. In other industries, however, vision systems that monitor product dimensions and cosmetics and sound an alarm when defects are detected in high-speed, automated processes are commonplace. Surely, if inspecting components at 100 ft/min (30.48 m/min) is possible, then inspecting a pultruded profile at 3 ft/min (0.91 m/min) is possible as well, with a properly applied off-the-shelf technology.

An automatic detection system that can alarm the operator so he may take corrective action, however, may not be enough, because alarms are often ignored. In fact, a provision that permits an operator to silence an alarm without correcting the cause is standard on many machine controls. (I have observed many cases where audible alarms were disabled because they were an irritation to the operator!). This is where machine control features should take over. Instead of continuing to produce substandard material while waiting for attention, the machine — after an elapse of time or when a critical process threshold is crossed, such as a parameter low-limit value — could be placed in Stop or Pause mode, limiting the further loss of revenue. Simultaneously, with today’s connectivity options, which include Ethernet or wireless data transmission, event notification could be broadcast to the supervisor’s office and logged for review by production management.

Here’s some important math for pultruders to frame this discussion:

• Every 1 inch/min (25.4 mm/min) of lost production speed equals 30,000 ft/yr (9,144 m/yr) based on a 24-hours/day, 250-days/yr schedule. In a five-machine operation, 150,000 ft (45,720m) of productivity would be forfeited. The more product produced and billed each month, the more favorable are the financial statements for the shareholders, the bank and the employees who depend on a strong company to attract new business and secure their jobs.
• Here’s another measure: A machine running a single product weighing 1 lb/ft (1.5 kg/m) at 36 inches/min (0.91 m/min) would output 180 lb/82 kg per hour. With the same scheduled capacity, each machine could produce 1,080,000 lb (490 metric tonnes) of product per year. Every 1 percent of scrap produced results in a loss of 10,800 lb of fully valued product i.e., raw material cost, direct labor, manufacturing burden, SG&A and profit margin. In addition, the cost of handling and disposal of scrap is substantial. At an average market price of $2.50/lb, each 1 percent reduction in scrap can yield a savings of approximately $27,000 (USD) per machine per year, or $135,000 per year for a five-machine facility. And isn’t customer goodwill for on-time delivery with fewer returns worth something substantial as well?

In today’s competitive global marketplace, pultruders can no longer afford to overprice their products to compensate for process and supervision inefficiency — don’t complain about eroding margins and global competition if you are not willing to invest in technology to be as good as you can be! Place the onus on the operator to prevent scrap through diligent execution of daily tasks. But then provide them with the training and the tools necessary to do a better job. Management must put the burden on engineering to identify and apply prevention, detection, alarm and control technology to reduce scrap and boost productivity.