January 2004

PRESSING

New year, new thinking and new presses

As the year turns, so do the options open to manufacturers. That's true in powder metallurgy just as in any other industry. For although stamping out green parts may seem to be the run-of-the-mill first stage to PM production, a US press maker has combined new thinking with new technology to get profitable results that should set the small world of press builders talking…

It's mostly how it is. You, the customer, have a need, and you go to the shop to fulfil it. Once in the shop you offer a brief description of what you want, or want to achieve and, usually, you're offered a range of options of the kit that is in stock or can be supplied. If it has to be bought in, you may have to wait. Sometimes, to save time on that wait, another option is on offer - a rebuilt and totally guaranteed item.

In this respect, the world of powder pressing is no different from any other. A rebuilt press can outperform its original specification, simply because things move on and knowledge filters down to make things better. Perhaps the first thing to realise here is that not everyone needs "ultimate" performance to produce an article. And not every customer is looking for it, either.

But it is certainly true that new presses can do things that even five years ago would not have been dreamt of. New presses employing technologies such as die-wall lubrication, warm compaction and high velocity compaction (HVC), singly or in combination, can attain densities in steel powders that would make even the most discerning engineering production manager take note.

But there are overriding considerations, and prime among those are market economics. The current, hard-nosed, economics dictate that ambitious PM manufacturers seek the elusive goal of 100 per cent density to service the ever-hungry and economically strapped automotive industry, which is where the big, repeatable and extremely profitable contracts lie.

However, that same industry is putting the onus on PM manufacturers to come up with the solutions they need at attractive (read lower) prices. This is hardball - for real. The big Tier One contractors have taken the message to heart, and you only have to read Christine Garramone's message in the December issue of Metal Powder Report to get the drift.

But reality bites. And reality says that for a given task, there is often more than one solution. So it is in powder pressing. A small New Hampshire company founded in West Lebanon by venture capitalist Alan Beane and his inventor brother, Glenn, offers a new take on the thinking that has seen generations of press builders grow and prosper over 70 years or so.

Satisfied customer. Lovejoy’s Woody Haddix with the 1000-ton Mii press system recently installed at the Downers Grove plant.

The manufacturing system developed by their company, Mii, offers a radical difference. It uses digitised technology and hydraulics to produce complex parts of high green density - allowing green machining - with lower and more uniform shrinkage, and minimal ejection/deflection cracking.

And there are economic benefits right from the start. The Mii system is compact and light, around 25 short tons for a 1000-ton press. This means that it needs a much lighter and smaller building the house it, and money is saved, quite literally, from the foundations up. For while most traditional presses require a pit beneath them to house part of the machine, this one does not. Another bonus is the comparatively short lead time on delivery of a system configured precisely to meet a customer's needs - around six months from order to production start-up.

Digital control makes possible highly accurate production and quality management, as well as remote diagnostics and troubleshooting. The system can employ die-wall lubrication and warm pressing where required.

The seminal thinking that produced the press system took apart what traditional pressing technology did, and how it did it. The result is system designs that are scaled for up to a 2100 ton capability (total press force that can be generated), yet systems at any tonnage can press at up to 100 tons per square inch depending on the surface size of the part. But the Mii approach to making high-precision, high-density parts does not rely on compaction alone. It is a function of multiple processes, including fill uniformity, weight control and independent punch control, says Glenn Beane. "If you want to press net-shape car doors or you require a 100 000-ton capability, we can engineer a manufacturing system based on today's designs, configured to meet specific economic, production and quality assurance requirements.

"Mii presses are designed to do one thing well - to press square and perpendicular every time. Deflection takes place in the piston cylinders rather than the tooling or the part."

But on the way the system also attacks entrenched thinking and high overheads by another route. Press skills are traditionally built up over years by a select pool of dedicated technicians. The Mii system, say the makers, opens the market to operators from a different skill pool made up of those people who understand information technology and its applications.

Costs take a hit from another direction too. With fewer than 30 moving parts in a 1000-ton machine, compared with hundreds in a conventional press, tooling changes take only a few hours. The system's lightness means that it can be unplugged from its electronic and hydraulic connections and moved to another part of the production line - or to another location entirely - without much fuss.

The docking system concept that allows the press to be decoupled from its hydraulics is an important factor in reducing the Mii system's size. In traditional presses where each press has its own power source the equipment needed adds greatly to the size and weight of the press.

So how is it done? Metal powder fed into the die is measured by weight, rather than volume. Once in the die, uniform distribution is ensured by a patented fluidisation process.

Once settled, the powder is compressed by up to 14 levels of computer-controlled hydraulic tools on one axis. The result is high-density green parts that exhibit lower shrinkage than normal in the sintering process. They can be green-machined but are "shipping-ready", requiring minimal finishing, if any.

PC-based computer controls monitor and oversee the whole process and self-documenting process flows preserve "recipes" to ensure repeatability. The system is essentially self-operating, requiring minimal operator intervention. In theory it can run round the clock without too much attention to traditional shift patterns, and that fact alone may force change in the pressing industry's rhythms.

However, if problems do occur when no operator is present the system can page or call an operator who may be able to diagnose and resolve matters remotely. In the last resort Mii support staff can use the same tools from its headquarters to assist with any system, anywhere.

What today is Mii Technologies LLC began life as Materials Innovation Inc in 1987, developing coated metal powders. Mii itself was founded in 1995, but after a few years in the PM, ceramic and plastics moulding markets the realisation gained ground that its real role was to supply superior manufacturing capability to parts makers. It was a profound rethink. For that is where seminal thinking wins out - right at the start of the process.

Marketing director, Holly Ripley-Boyd, said: "We supply durable manufacturing systems solutions to help parts makers realise the promise of net shape for metal, soft magnetic, ceramic and plastic components. The service includes process development and prototyping services.

"We start by looking not only at the component, but the underlying economics, physical process and production parameters that will determine success.

"Then we work backwards to integrate a manufacturing system that will meet technical requirements and achieve the business objective."

The Mii system was declared to be one of three Time Magazine "inventions of the year" in 2000. Since then, seven have been sold, including a 1000-ton unit to US PM manufacturer Lovejoy Inc (see Metal Powder Report, November 2003) and Mii currently has another nine proposals under consideration.