An Introduction to iMFLUX Technology: Welcome to the Green Curve
By: Jason Travitz, Sr. Processing Instructor, AIM
iMFLUX’s process control technology is becoming more widely recognized. The organization, a wholly owned subsidiary of Procter & Gamble, has installed their process control technology on an increasingly large number of machines, and we are receiving more and more questions regarding the technology and how it can be beneficial. This article takes a high-level look at iMFLUX process controls and answers just a few of the most common questions we receive regarding the industry’s latest advancement.
Conventional Scientific Molding or 2-Stage Processing (the Blue curve) has been state of the industry for quite some time. Every so often, some “thing” comes along to shake things up a bit.
iMFLUX (the Green curve) is one of those things.
As is typical with learning about innovations in our industry, I was skeptical at first. My first thought when I heard about iMFLUX was it is simply a pressure limited process, and that has been taught as taboo in this industry for a long time due to problems with viscosity shifts (among others). If that’s all it is, then it is nothing new. I can set up a pressure limited molding process and do the same thing on any of the molding machines in the lab.
But, as any good instructor and researcher would do, I decided to dig a little deeper. Here is what I learned.
To better understand what iMFLUX is and does, you first need to understand what it is not and does not do:
iMFLUX IS/DOES NOT:
- iMFLUX is not simply running a molding machine with an Injection Pressure Limit set
- iMFLUX does not fill a mold at a constant velocity
- iMFLUX does not have a conventional Transfer Position where the machine switches over from velocity-controlled Fill to pressure-controlled Pack/Hold
iMFLUX IS/DOES:
- iMFLUX is filling and packing parts at a constant melt pressure
- iMFLUX does vary the injection rate as necessary to maintain the set melt pressure
- iMFLUX does reduce hesitation in the melt front during the transition from filling and packing
- iMFLUX does allow more control over the molding machine and resulting process conditions
Conventional molding typically relies on fast filling (requiring high injection pressures) to attenuate for viscosity shifts. With iMFLUX, the plastic is initially injected into the cavity “fast” until it reaches the melt pressure setpoint, and it then it continues to adjust the screw velocity to maintain the set melt pressure.
The drive to melt pressure setpoint, the melt pressure setpoint, and step time can each be controlled as necessary to produce the desired part.
The iMFLUX system consists of a Melt Pressure Sensor in the molding machine nozzle and a control box that is interfaced to the molding machine. The system receives an OK TO CONTROL signal from the molding machine and then takes control in the machines injection forward movement by controlling the inject signal.
iMFLUX fills and packs the part by using one or more step times at set step pressures with a negative or positive Process Factor A (PFA) applied in response to the real or virtual pressure inside the mold cavity. Automatic Viscosity Adjust reacts to changes in material viscosity over time. This can all be done with precise shot control through the use of Melt Travel.
That was probably a lot of new terms for most of the people reading this, so let’s unpack this a bit more. iMFLUX achieves and maintains the set melt pressure (Step Pressure) over a set time (Step Time). Simply put, iMFLUX increases or decreases the injection speed to increase or decrease the melt pressure in the nozzle of the molding machine.
PFA is a decrease or increase in melt pressure when the melt reaches the desired position or pressure in the mold. It may be easier to think of PFA as a packing profile that can be shaped to follow the cavity pressure or any shape created as a virtual curve. You now have the ability to control the filling and packing of the mold cavity in way that couldn’t be done previously.
In regards to how iMFLUX would handle viscosity shifts, previous published ANTEC research shows that filling parts slower produces “better” parts as long as the viscosity doesn’t change. However, as soon as the viscosity shifts, more part variation typically results.
iMFLUX fills and packs the part at the injection speed required to maintain the set Melt Pressure. The required Melt Pressure to fill and pack a part will change as viscosity shifts. Automatic Viscosity Adjust monitors time to Melt Travel or time to Cavity Pressure and adjusts the Melt Pressure on subsequent shots to adjust for material viscosity changes until the process is walked back to the point where the time to real or virtual cavity pressure now match again.
In short, iMFLUX is a completely different way of injection molding a plastic part. As with any new technology or methodology it is a different way of thinking, and there is a learning curve.
We are continuing to research iMFLUX process development while evaluating how iMFLUX influences molded part dimensions and properties, and we will keep the industry updated on our research.
