Extrude To Fill rethinks the injection molding process

Erie Pa. — A low-pressure injection molding machine that can use multiple extruders that heat the melt in an electrically heated barrel, then pump the material into the mold gives low shear, lower pressure and better melt processing than standard high-pressure injection presses, according to Extrude To Fill LLC.

The preparation of the molten material is de-linked from the delivery of the melt into the mold, said Rick Fitzpatrick, chief technical officer of the company in Loveland, Colo., which goes by X2F. The machines use small extruders and thin-walled barrels designed to electrically conduct heat.

"It's a level of flexibility that you don't have with a machine that relies on a pressure-generated heat," he said.

X2F is different from conventional injection molding in many ways, Fitzpatrick said in a presentation at Penn State Erie's recent Innovation and Emerging Technologies Conference in Erie.

He said it's an output-based process that is controlled in real time using sensors. Resin viscosity is set and monitored using temperature readings and resistance to flow through motor torque data, screw back pressure and output of the extruder.

One big difference is pack and hold.

"So what we're doing, when we fill, is we build up to that final pack pressure. We begin extrusion. We build pack pressure as the mold cavity fills, and then we're able to go ahead and pack it out at whatever that set point is," he said.

Traditional injection molding uses high-velocity injection that creates a lot of shear. The machines must be large since they have to generate and contain the extreme pressures.

"You're coming in with stage one at a very high injection force. You're looking for a gate freeze-off and then you're trying to hold a second-stage pack and hold pressure," Fitzpatrick said. "And it's a difficult process to do because your pressure source is so far removed from where your pressure is actually needed, at the back of the screw."

X2F machines use much less tonnage and are lighter and cheaper than regular injection presses, he said. They can run traditional molds, but the low-pressure process also allows the use of aluminum molds.

Extrude To Fill claims its costs are more than 50 percent lower than those for conventional injection molding machines.

And the equipment is easy to use.

"Anyone in this room can be taught to run that in about 15 minutes, because the whole idea of using an output-based process means the control algorithm sets up the machine to run. You turn it on, it's going to warm up for five minutes. And it's ready to mold parts," he said at the Penn State Erie conference.

The X2F process is self-tuning, using precise controls.

"Screw speed is controlled by our machine algorithm," Fitzpatrick said. "Basically it's a self-diagnosing system where we understand material viscosity by the torsional load on the screw as well as the back pressure on the screw and other pressure sensors that we have buried in the system."

There is no gate freeze-off because X2F maintains a dynamic load at the gate, continuing to add material as it shrinks and fills the mold, he said, much like gas-assisted molding. "So it helps speed up your cooling because you're pushing it against the cavity wall so you get heat induction, but you pack out those parts," he said.

The equipment can bring material to a known viscosity without anything moving on the machine, he said.

"The whole process is based on our use of sensors, whether in the mold cavity or within the extruder," Fitzpatrick said.

The programmable logic controller handles the heater profiles so the machine can obtain the correct viscosity without overheating the material.

Extrude To Fill has received patents on the process and is starting to commercialize the machinery. Machines available include Model E30V, a vertical press with a 30-gram shot size, and a horizontal Model E150H running a 200-gram shot size.

So far, four X2F presses are running production at a medical facility and an electronic appliance maker. Production machines are available now including horizontal- and vertical-clamp machines. The company's first customer was Aurisonics Inc., which molded tips for its ear buds out of medical-grade thermoplastic elastomers.

Aurisonics makes in-ear monitors used by musicians during live performances. Fender Musical Instruments Corp. now owns Aurisonics.

Extrude To Fill is using another company in Colorado that supplies machined structural steel and aluminum components. But X2F is building the machines in Loveland, and the company will continue to be making its own extruder screws and controls — key parts of the system, he said.

"We're not dealing with heavy castings and forgings and things of that nature," Fitzpatrick said. Traditional high-pressure molding requires machinery with mass. "The pressure-dependent molding basically dictates the size of the machines, the facilities that they have to be housed in because of the power requirements, the space requirements. The concrete underneath. The talent required to run it, because it is still somewhat of a black art."

Fitzpatrick has worked in plastics for more than 30 years, with a diverse background in mold design, product design and engineering and management at Courtesy Corp., Capsonic Group and DTM Products Inc., which was sold to Flextronics International Ltd.

He then became a consultant, where he began looking at alternatives to the reciprocating screw for injection molding.

Fitzpatrick said molders have been "fighting the same issues" for years. In thinking about the process, he thought: "Plastic viscosity is always related to the temperature of the plastic. Is there a way to get it to its melt temperature, and then get it into the mold, under control, and without shear thinning?" What is the lowest-cost way to turn a pile of resin pellets into a finished part?

"Any plastic in its free form is at its lowest natural state, which is why when you look at a purge patty down on the machine bed, it's pliable, flexible. You can move it around, and you know, myself I used to wonder, how is it that the same material that seems so fluid, in a way, is so difficult to get into a mold?" he recalled.

After years of work, Fitzpatrick developed the X2F process. Then he made a connection with an old college buddy, Ronald Leach, who lived in a dorm room across the hall from Fitzpatrick freshman year at Michigan State University. They joined the same fraternity.

The friends stayed in touch until the mid-1980s, then, as often happens, lost contact with each other. Leach pursued his own plastics career, working in engineering and management roles, then getting into the private equity sector. Meanwhile, Fitzpatrick was doing consulting and signed up for a professional networking site. Someone from a private equity firm was looking for an injection molding expert.

That someone was Ron Leach.

"That's a million-to-one shot, and that's how we got reconnected," Fitzpatrick said. He filled in his old college dorm-mate on what he was doing. Leach was skeptical until he came out to Colorado. Then he got it.

Leach, who was the initial investor, is Extrude To Fill's president and CEO. Both men attended the Innovation and Emerging Technologies Conference.

Fitzpatrick said that skepticism is common and he encouraged molders to visit the company or send him molds for parts that have considered difficult or even impossible to run. He faces a selling job about the technology and its ability to greatly reduce part costs, as opposed to, he said, "What we accept today because it's always been done that way."

Fitzpatrick said the X2F process can be easily scaled up and can run a wide range of materials. The self-adjusting nature makes it possible to change between grades of material, say, a 50-melt to a 20-melt without manually adjusting the machine, he said. The process also can handle heavily filled materials, recycled plastics such as heavy plastic sheeting from construction sites, and reprocessed shopping bags and metalized snack bags.

X2F also runs metal-filled materials at high loadings, including stainless steel, carbon steel and aluminum, which he said should be a growing area over the next five or 10 years because molded aluminum can replace die-casting.

"We don't rely on pressure-generated heat, so material purity doesn't mean anything to the system," he said.

His experience with high-cavitation molds has made Fitzpatrick an advocate of running parts on a larger number of machines with smaller-cavitation molds, to reduce electricity and avoid downtime, or the need to shut off mold cavities.

Extrude To Fill also offers a patented Multiport setup that runs a cluster of extruders, each one individually controlled, that feed multicavity molds or work in tandem to fill large parts, such as car bumpers. Fitzpatrick called the configuration a type of "live hot runner system" that keeps clamping pressure and power consumption low and allows the use of smaller machines.

X2F also can run four different materials, or colors, through four different extruders, cycling at the same time. "If you got a four-part assembly, it could be a family mold where running four parts of the same material, four parts of different colors. You could be running different sized extruders for different shot sizes on each one because you can optimize these," Fitzpatrick said. "Scaling them is very easy to do.

He said you also can readily change colors, usually in three to five minutes.

Fitzpatrick remains committed to the X2F process as an alternative to the reciprocating screw, now more than 60 years old.

"Basically, we changed the entire economic picture when it comes to pricing plastic parts because you don't need the same talent, you don't need the same power, you don't need the same kind of tooling," he said. "The entire workflow from front to back changes as you also reduce your material costs because you have so many different opportunities to be flexible with materials."