Time is money, and when it takes thousands of hours to cut plastics injection molds from steel, every second that can be saved counts. “An entire mold like an eight-cavity mold – if it’s not too complex – may run about 1,200 to 1,400 man-hours to build,” estimates Len Graham, Rexam Mold Manufacturing business unit leader. “A mold that is larger – like a 128-cavity, two-face mold – that can take 6,000 to 7,000 man-hours. You’ll mess around with those things for months.
“Any mold shop will tell you that time is the enemy and that cost is the driver of everything,” Graham emphasizes. “Once the setups are done, all shops are fairly equal. It’s how long it takes to get going in each process – that’s the one thing we’ve concentrated on and done extremely well. Along with first-article inspection, we perform in-process checks and verifications of components as they are manufactured, not afterward, which is highly unusual.”
This time-saving method means Rexam Mold Manufacturing’s new Mega-Cell uses a robot to check the accuracy of a finished component while the operator is setting up the next one instead of having the operator check it.
Rexam Mold Manufacturing has been designing and building precision injection molding systems for more than 35 years for its own companies to use and for others outside the company. Its molds – which range in size from a couple of hundred pounds to 24,000 pounds – produce parts for the healthcare, home and personal care products, caps and closures, packaging and technology industries.
“We will get involved with sizing the proper injection molding machine for these tools, as well as post-molding automation,” Sales General Manager Jeffrey Barhoff explains. “Our primary focus is on the injection mold itself, and then we adapt or will create those systems around it depending on what the needs of the customer are. What really sets us apart is our size. We have a 90-plus-man state-of-the-art manufacturing facility covering almost 100,000 square feet – which is one of the largest in North America – and we are working towards becoming fully automated.”
Graham – who joined Rexam Mold Manufacturing last year – has been working on automated mold manufacturing for years. “What we’re building is a completely automated system for both mold inserts and the mold bases that go along with them,” Graham declares. “It is quite a long project. It will be five years before it is actually completed, but right now we’re in the beginning stages. What we’re doing here will be the most advanced in the world that I know of.”
Rexam Mold Manufacturing’s method of reducing setup time requires teamwork. “To make this work properly, we have to do things in a very consistent fashion,” Graham cautions. “The reason a lot of mold shops aren’t successful to any great degree is that flies in the face of how mold shops work. They may have palletizing and even robots, but many still work primarily in a mold-making environment – one man, one mold – and the quality stamp is on that mold based on which mold maker is on it.
“Most mold shops don’t put their mold makers together,” Graham maintains. “We organize our mold makers and specialty-machining technicians into teams. Each of those teams meets weekly to build standards and procedures on everything they do. If a mold shop has 10 mold makers and gives them something to do, you’ll get 10 different ways. It works, but the consistency is what is lacking.”
One of the most time-consuming operations in machining to tolerances that are ten-thousandths of an inch – a human hair is 30 ten-thousandths of an inch thick – is ensuring the tools and machined components are in the right position relative to one another. That is where Rexam Mold Manufacturing uses its unique stainless steel, pallet-mounted sphere or gauge ball. It is precisely produced and placed on a holder with an accuracy of one ten-thousandth of an inch of true position in all three directions. The sphere aligns machine tools with mold components and electrodes for each of the many different machining operations the mold undergoes on many different types of machines.
“That allows us to go in all departments and get consistent readings against one standardized, proven-out baseline,” Graham explains. “We all pick up that ball first and find out where it is before any tool is set in position. That’s how we are able to get things so accurate. So there’s no guessing about where we are. From one machining operation to another, that baseline is the same.”
The ball is represented virtually in the three-dimensional machining database relative to the part so the computer can associate that position to any and all cutting, measuring and dimensional recording required to complete that part. There is no need for double-checking the position before the cut is started. Subsequent like parts will be cut without the need to re-check the gauge ball position.
“A setup can take several hours if you do it in a normal fashion,” Graham maintains. “We can do a 5-minute setup real easily. It’s hard to explain, but it’s really cool when you see it work.”
Barhoff estimates a plastics injection mold designed and manufactured by Rexam Mold Manufacturing can run up to 15 percent faster than competitors’ molds because of the way it is designed and built, incorporating the latest technologies in hot runner systems and mold cooling. “We like to get into the small, critical details we build into the tools that have a big impact on the performance of the mold, such as faster cycle time and less maintenance,” Barhoff asserts.
Typically, the company’s molds are guaranteed for 3 million cycles including workmanship, materials and premature wear, and many have run 20 to 30 million cycles when well-maintained, Graham insists. Some have run for 20 years. “These tools really are dependent upon the maintenance program and the design of the tool – which we take pride in – and the precision with which it is built,” Graham concludes.