Waste Reduction in Engineering – A High Pressure Die Casting Process

Waste: an unwanted or undesired material or substance (Wikipedia: online encyclopedia). To an outsider, looking in at the metalcasting industry, it seems as though the substances we waste most often are time and energy – and they might well be right! At some foundries, these non-replaceable resources are squandered – not recklessly, not intentionally – but because their design and production methods are based on outdated production processes.

Past Engineering Process

In times past, paper and pencil were the most important tools a casting designer had – and the development of a casting was a process that was tedious and time consuming. A paper design was created; the blue print was introduced to the die caster – who teamed up with a toolmaker. Together, a die-casting machine was selected; the process and mold layout developed and costs estimated. Quotations were made. The bidding winner gave permission to his tool vendor to order die steel and start with mold designing. When finished, the mold was sent to the die caster for a first test. After building it into the machine, castings were made and checked for imperfections.

It was not until this point in the process that those involved got any idea about the quality of the casting. If the casting didn’t measure up to the desired standards, changes would have to be made. Different process settings and minor die corrections could be done at the die-casting machine immediately – but if the first trial showed that the mold had to be changed, steel had to be ground away and welded back in other places, and that work had to be done at the tool vendor’s facility. The mold traveled back and forth between toolmaker and die caster until an acceptable casting quality was achieved. The time between starting the casting design and shipping good castings could take weeks, months or years depending on the complexity and size.

Furthermore, mold designs could – and did – change, even after production had started, and those changes meant molds might have different designs, different ages and wearing patterns, and different casting qualities. In addition to mold changes, variations in production parameters like die casting machine pressures, pouring velocities and transitions, lubrication volumes and locations, solidification and cycle times changed throughout the casting process. The never-ending need to adjust and improve the casting ended only when the casting was not needed anymore. Working toward a better casting quality kept a huge team active with involvements of the process engineer, the machine operator, mold maintenance and toolmaker, quality office, casting designer, casting machining, even assembly and material planning and handling group.

While there was a time when this type of ‘engineering’ was necessary, the economic realities of today make it financially unfeasible to continue in this way – but even so, this “engineering” can be found in companies that are struggling their way through tough times.

“The die casting industry’s capacity in the U.S. shrunk … with the closing of plants that were not able to keep up with technology…” Daniel L. Twarog, President NADCA, Letter from the Publisher, LINKS, February 2009

Streamlining the Process Today

With the addition of computers into factories, the engineering process is continually changing and becoming more streamlined. Casting are no longer drawn on paper and tooling dimensions don’t have to be transformed to mold drawings anymore. Computer aided designs available in 3-dimensional volume models allow information to be transferred with the push of a button and be used as input directly into the steel machining equipment. Changes in models can be made quickly and easily shared with all design departments.

The great value of computerization lies in the opportunity to develop, design and build at almost the same time. These parallel working conditions decrease the development time and speeds ‘time-to-market’ to a level that was not even dreamt of years ago. Computerization within the engineering and manufacturing process have also allowed for more precise machining equipment in the tool shops, customized die steels and heat treatment processes that allow changes based factors such as: length of production run and material in direct contact to the melt or for better heat transfer and heat flow.

One of the biggest changes has been in the field of process improvement. Using MAGMASOFT(r) simulation software, the complete casting process can be simulated, changed and optimized in the short time frame available to the toolmaker. Simulations made of casting models provide information about the quality to expect during casting production – before being released. Based on the simulation results, changes to the casting, runner system, the mold or process parameters can be easily made and results quickly reviewed.

Similarly, the casting can be optimized to fill better and solidify more evenly, avoiding porosities; the runner system can be modified to reduce the amounts of entrapped air, which leads to porosity; the internal cooling layout is developed to minimize solidification times and allow faster production cycles, and simulations which include stress calculations can be used for prediction of die life, cracked castings or distortions. The consistent use of MAGMASOFT(r) during casting and process development creates good castings and stable processes from the first die trial on.

Further adjustments during casting production are on a minor scale only and should not change the mold or casting design at all. The result is one design for casting, mold and process, which can be used until castings are not needed anymore, significantly reducing design and production time and costs. Reducing the time and effort involved in the design and production areas allows the improvement team the time to concentrate on other important tasks, such as the effects of different die steel or better heat treatment to extend die life, implementation of more sophisticated equipment to increase the opportunity to cast more complex castings or save melting energy, increase automation and educate the work forces – and all this without disturbing a good production run.

Committing to these changes leads to higher competitiveness and strengthens the industry’s position in the worldwide market.

“Optimization has the potential to significantly amplify the utility of simulation and simulation results for casters.” R. Allen Miller, Computer Modeling Worldwide Literature Review, LINKS, February 2009

More Time and Energy to Save

The area least able to be improved is that of human working speed. Computer work hundreds of times faster than they did years ago, but that is a transformation that humans will never be able to duplicate. Unlike machines, however, humans are intelligent, and capable of using those software and hardware improvements to our advantage. Yes, getting out of the office, flying to a meeting, having a big lunch and staying at a nice hotel is great – but is in the most cases, it’s also inefficient and a waste of time and money. Today, with ready access to the internet, industries have the availability of e-mail, ftp, phone- or web-conferences, and those technologies are finding their way into the engineering process. Gone are the times when people had to drive hours for a brief meeting, or traveled overseas to visit foreign sources. This is not to say that the designer, die caster and tool maker should not know each other – but in a time when engineering has been reduced to a commodity and can be sourced globally, the personal, “one on one” visit will be reduced or even eliminated.

With the ever-shortening time frame allowed for engineering, developing, building and implementation, a process travel time is not feasible or economical anymore. That time is needed to work on the project. Every day on hold can jeopardize the delivery date. Sending huge digital files via the Internet can take some hours, but once transmitted, they are instantly available for a web conference. Some business, however, still require face-to-face meetings to evaluate the results, wasting time and money for almost all of the participants. But the biggest waste of time has not even discussed yet. This is the hesitation in making decisions at the buyer’s side to place the project order. Even when quotes from casting and tool vendors have been made in a timely manner, company finances or policies may mandate a second or third round of quotations in an attempt to save an additional dollar here or there.

Even when the total ‘time-to-market’ is severely limited, more than half of that time may be spent in the selection process to take as much as four months, resulting in the caster and toolmaker having insufficient time to create a process, build the die and deliver good castings. The buyer’s hesitation to determine a source cuts into the available engineering time and can add significant costs onto the process, nullifying any short-term savings with additional production costs and delays in time to market. As long as one department sees only the direct costs and does not consider the total casting cost, the project never realizes its full financial potential for the company.

Summary

Streamlining the high pressure die casting engineering process can still save a lot of time and energy which will be seen as huge money savings. With updated computer equipment and software, travel times and costs can be reduced considerably, while communication can be made faster and more effective. Making faster decisions to sources will give more time to the engineers developing more stable processes that produce better castings. By embracing the technologies available, companies can conserve their irreplaceable resources – time and energy – and while growing more efficient, and most importantly in this economy, more profitable.


Post time: 04-12-2017