Feature

Injection Molding: Finding hidden profits

Hidden in the nooks and crannies of your injection molding plant, in the arcane and outdated procedures, in the fine print of the latest quality report, are opportunities for savings that will go directly to your bottom line.


Print this page

November 1, 2002 by Cindy Macdonald, associate editor

The time needed to prove out a work cell integration prior to putting the system into production cannot be compromised, advises Bruce Catoen of Husky Injection Molding Systems Ltd.
The time needed to prove out a work cell integration prior to putting the system into production cannot be compromised, advises Bruce Catoen of Husky Injection Molding Systems Ltd.

The quick fixes you’ve already found. The following examples are deeper, more fundamental changes that may take a while to implement, but which will pay off in the long run.

Self-evaluation is a necessary first step. The factory planning group at Husky Injection Molding Systems Ltd. estimates that plant audits generally reveal savings of at least 10% of total operating costs. Activities of an audit performed by Husky can range from itemizing fixed and variable expenses to reviewing work cell integration. The audit report generally includes:

a breakdown of hourly plant operating costs;

specific opportunities to reduce costs, ranging from energy consumption to standardizing work cells;

a benchmark ranking based on industry standards;

estimates of potential annual cost savings.

An injection molding company in southern Ohio asked Concentric Custom Services Inc. for a complete benchmarking survey of its factory floor and front office operations. Concentric is a plastics-industry specific consulting company that offers contract services for non-core functions.

The subsequent Gap Analysis revealed the true cost of employee turnover (US$175,000 per year), actual production rates compared with industry norms, mold change bottlenecks, and even their accountant’s failure to take advantage of a possible US$75,000 tax credit for R&D.

“Most processors have a good infrastructure, but may not have the resources to maximize its potential,” says Conan Miller, director business development, Concentric. “Each incremental improvement in these areas goes straight to the bottom line.”

Project: Lean manufacturing Result: Productivity increased 138%

Reduced costs, decreased time-to-market, decreased manufacturing cycle times, and increased productivity were the results of a lean manufacturing initiative undertaken at United Plastics Group Inc. (UPG) during 2001 and 2002.

UPG is a full-service injection molder serving industrial, automotive, electronics, medical and consumer markets from 11 facilites worldwide.

In contrast with traditional manufacturing processes, UPG’s lean manufacturing uses multi-skilled teams to reduce product flows and reduce set-up times while eliminating waste from conveyance, over-production and mis-processing.

“Our early results have shown that by balancing operator work load and maximizing efficiencies, a productivity increase of up to 138% can be achieved. Our customers are already benefiting from the flexibility of our lean manufacturing with lowered costs and decreased time to market,” says Chuck Villa, UPG’s executive vice-president, business development.

The molder’s lean manufacturing practices incorporate quick changeover techniques to reduce equipment set-up time, cellular manufacturing to facilitate continuous flow production and just-in-time materials management that reduces cycle times and improves throughput.

Project: Professional system integration of a work cell Result: Faster completion and lower cycle time; three-month payback

Husky Injection Molding Systems Ltd. was involved with a project that required system integration of a 600-tonne machine with a 2×16 stack mold and a side-entry robot producing HIPS dairy containers.

The primary objective of the project was to prove function and performance of the unit as a complete unit. The target cycle time was to be less than 5.2 seconds at 95% uptime over 24 hours.

The initial cycle time was 4.9 sec., however it was felt the system could be improved. The machine software was upgraded to start mold-close before the ejectors were fully retracted. The ejector logic was changed to check ejector positions a few millimetres before the mold was fully closed. Larger hydraulic hoses for ejectors were added on the stationary side. Cycle time was reduced to 4.5 sec.

The integration was completed in three weeks.

Given the reduction in cycle time, the savings in time to reach full production, and a savings in scrap from developing a robust operating window, the customer received a three-month payback on the fee for system integration.

Bruce Catoen, vice-president automated systems, Husky Injection Molding Systems Ltd., suggests that a successful integration must have a commitment from management not to release the system to production until it is proven. He says a system can only be considered proven after it has experienced all the variables the external environment can produce. “This takes time that cannot be compromised.” Problems in the initial integration can show up as slow cycles, high maintenance/wear, narrow operating window, high scrap rates, prolonged and frequent downtime and frequent QA checks.

Catoen also suggests a Design of Experiment should be used to determine the breadth of the operating window: “A system running on the thin edge will not run consistently over time.”

A successful integration of machine, mold and automation must deliver the injection molding cell on time, on budget and achieve the required performance. This can be the difference between profitability or unprofitability of that particular cell.

Project: Optimize your plasticating system Results: Price per part dropped from $2.21 to $1.81

Injection molders may be able to save thousands of dollars a month in production costs by optimizing the performance of the machine’s plasticating unit, according to Spirex Corp. Spirex has developed a process optimizer that improves bottom line performance by helping molders focus on the plasticating unit — the screw, valve, barrel, nozzle and nozzle tip — as a system.

At one automotive parts molder, Spirex implemented process optimization analysis and replaced the existing screw and barrel with a Spirex Z-Mixer screw and other components that were recommended based on the molder’s application and resin.

Cycle time was improved by almost 15%, scrap dropped to 1% from 7%, and price per part dropped to US$1.81 from US$2.21.

The difference in cost for the replacement components was paid for in just seven days.

“We would like every CEO of every plastics company out there to understand that on virtually any machine, new or old, by improving the performance of the plasticating unit, tremendous savings are possible,” says Paul T. Colby, president of Spirex. “But they have to think in terms of systems, not parts. Then, make an initial investment for the best system for their particular process. It will pay for itself quickly, and lead to a highly favorable influence on the bottom line.”

The optimization process developed by Spirex places production emphasis on making the highest quality part, at the fastest interval of speed, with the lowest percentage of scrap, using the least amount of power, for the lowest aggregate cost.

Project: Outsourcing Results: Variable

What are the biggest headaches in your day? Staff turnover, production bottlenecks, outside contractors, resin prices? There are times when it’s worthwhile to seek the advice of experts. Outsourcing certain functions or projects can reduce costs, reduce mistakes, improve quality, and take one more headache off your hands.

Conan Miller of Concentric told participants at the SPI Midwest Conference last month there is a trend to lowering fixed overhead costs by outsourcing non-core services and thus increaseing the output per square foot in manufacturing operations. Increased asset utilization is encouraged by lean manufacturing techniques, six sigma requirements and increased productivity/time/profitability per machine.

If you think you don’t need professional services, Miller asks:

Have you really measured the cost of your staff’s time?

Do they really have the skills and up-to-date knowledge?

What is a better use of your/their time?

Miller identifies these as potential outsourced services: training, health/safety environmental surveys, information technology, computerized maintenance management, financial services, part/mold design and facility services.

Consider maintenance management: According to Miller, the average annual operating expense for a plastics processing machine is 13 times the annual cost of
the machine itself. Contributing to these costs are troubleshooting, technicians/operators, energy, scheduling/monitoring uptime, freight/rigging, training, maintenance/parts.

Preventative maintenance, says Miller, drives higher asset utilization.

One injection molding company in southwestern Ohio has about 15 separate facilities-related contracts for each of its five plants. This company has now hired Concentric, and will turn over the evaluation and stabilization of their molding machines to Concentric project engineers. As well, Concentric will be implementing a Predictive Preventative Maintenance Program (PPMP), which requires no IT purchase on the client’s part. The result, says Miller, will be significant savings and reduced relationship management requirements for each of the facilities.

“Primary equipment is mission critical in plastics processing, and improved maintenance and troubleshooting practices result in measurable gains in the bottom line,” says Miller. “By delivering the latest in predictive/preventive maintenance and computerized maintenance monitoring software, we can deliver improvements in uptime, good-part production, and income for our clients.”

Measuring Your System

One way to measure system integration, suggested by Bruce Catoen, vice-president automated systems, Husky Injection Molding Systems Ltd., is Total Equipment Productivity (TEP). This method considers three variables: reliability, cycle time and quality.

TEP = cycle time x part quality x reliability Quality is the prime products produced (%) A TEP of 95% is considered world class.

Reliability is defined as hours run/hours available (%)

Cycle time is the rate of production performance as a percentage or a target

The robustness of the equipment determines availability. Performance is equated to production since both represent how much the system produces. Quality determines the yield. If fewer parts are scrapped, then yield goes up.