The 5 M’s of Molding—Part 5: Method

Once a molding problem has been identified, use “method” to determine whether the issue is with Man, Mold, Machine or Material.

The final M in the 5M equation refers to “Method”. Method is a very broad category that directly applies to man, mold, machine and material. Method also considers all internal and external contributors that affect the key measurable of a lean production operation.

Key measurables in plastic injection consist of production efficiency, scrap and downtime. The primary goal of lean manufacturing is 100% efficiency, 0% scrap and down time that is planned, not unplanned. These goals can sometimes seem to be challenging to achieve, but with proper analysis and approach the end result can be successful and profitable.

As measurables are recorded, a part history is developed. It is this historical data that we use to identify repeating and/or poorly performing variables. It also helps us to scrutinize what areas of production need improvement.

Once clear identification of a problem has been accomplished, it is then time to ask the question, “is this problem directly associated with Man, Mold, Machine or Material?” In some situations, only one of these will require change. In others, it could be all four that need correction. By establishing which of these categories need to be addressed, it becomes easier to develop solutions that will improve our “method”.

Here is an example of the 5 M method in use:

A Japanese headlight manufacturer determined through scrap data that a significant amount of scratches was appearing on parts already assembled. The cost of this sort of rework is quite costly… parts already assembled would need to be tore down, replacement lenses molded and then a second assembly performed to refurbish the part to an acceptable quality level.

man, mold, machine and material were all considered to determine when and how the scratches were occurring. After review of the entire production process from in-mold to assembly, the cause of the scratches was tracked to two separate problems, both of which were directly related to “man”. The problems were:

Parts produced were packed into cardboard for storage. Some scratches were due to operator handling as they were packed. The boxes were stacked on skids and then transported into warehouse racking.

When parts were needed, they were pulled from warehouse and then transported to the assembly area. Some scratches resulted directly from parts jostling as they were handled by warehouse personnel.

To eliminate the problem, special carts were developed made of a soft cloth that allowed for the parts to be packed, stored and transported to assembly without the threat of scratched product from packing and transport. What had been a very large problem became non-existent through proper analysis and methodical approach.

The 5M approach to molding is an excellent way to clearly identify problems, which is the foundation to any problem solving event. Full understanding of any problem helps to develop the most credible solution to the problems presented. Develop, maintain and regularly review recordable data for measuring production, scrap and downtime efficiencies. As the level of historical data increases, factors that improve production are discovered and implemented. That same data also offers insight into what problems exist. Clearly define the problem, and then review whether it is directly related to man, mold, machine or material. Remember that it could be one, several or all four contributing to the situation.

Develop a solid list of all areas contributing to the problem, and then systematically define solutions to those issues. Effective solutions require a complete understanding of the problems being addressed. Utilize all personnel directly related to the problem to best develop understanding and methods for correction. Effectively defining problems and solutions is dependent upon the complete knowledge base of your entire team. As their ability to create and adapt to change is refined, continuous improvement becomes more enjoyable. Clearly defined solutions add to the strength of your organization, bringing it one step closer to world-class manufacturing.

The 5 M’s of Molding—Part 4: Machine

Machinery/Auxiliary Equipment: The molding standard you set is highly dependent upon the machinery and auxiliary equipment you have available to you. Failure to properly assess the capabilities of your equipment will result in a poorly functioning production system. The following components strongly affect a facility’s scrap, downtime and productivity:

1.     Press: Molding machine capabilities are crucial to the design of any manufacturing system. Press tonnage and screw design (such as general purpose vs. nylon) are key factors in process consistency. Match your mold and material to the press to assure that your process control is not limited due to poorly functioning machinery. Also utilize your process data to further assess process control and machine problems.

2.     Robot: Robotics systems are a valuable asset for establishing production and quality systems. When evaluating the production system, always review potential fixes through robot improvements, end of arm tooling or programming changes.

3.     Automation: Other sources of automation should also be reviewed. For instance, if a quality concern keeps repeating itself, look for solutions through automation development. Involve everyone on your production team to fully assess what failures exist within the production system and utilize your engineers to develop working solutions. Better equip your operators and personnel to remove problematic conditions from the production equation.

Preventative maintenance is a key measurable in the Machinery/Equipment category. Unscheduled downtime seriously impedes production efficiencies due to the nature of unexpected system failures and the resulting unprepared approach towards resolution. Scheduled maintenance events are by far the best way to prevent poor performance. Here are some of the areas where preventative maintenance can prevent unscheduled break downs. Each of these components should have their own maintenance log to help establish what concerns are and what frequency of inspection needs to be:

1.     Molding machine: Press breakdowns can be avoided with a regular inspection system in place. Here are some of the primary inspections and a recommended frequency for performing them:

§  Hydraulic Fluid- Quarterly: Fluid samples should be taken and sent to a screener to evaluate metal content and viscosity break down.

§  Hoses- Weekly: Inspect hoses for signs of wear, rubbing or blistering.

§  Screw- Bi-Annually: Remove screw for inspection. Measure flights and shank to determine whether wear is becoming an issue. Also measure the metering zone of the barrel to verify condition.

§  Electrical-Weekly: Look for unsafe conditions and integrity of connectors.

§  Heater Bands- Monthly: Verify that all bands are in working condition

2.     Tooling- It is important to note that a simple 10-minute inspection of every mold per shift can identify problems and prevent hours of down time due to dry slides, pins, etc. Keep detailed records of mold repairs and use them to develop preventative maintenance events and timing. In a short-run shop, simple teardown and cleaning should occur after every run. In cases where molds run for extended periods of time, regular inspection should occur and molds should be torn down and cleaned bi-weekly. In all cases, cleaning frequencies should be developed based on mold history to prevent breakage through intervention and care.