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A second benefit is the way the system sterilizes the PS sheet and foil lidding materials. After sterilization in the H2O2 solution in a sterile bath chamber the materals are not directly fed into the aseptic filling chamber. Instead H2O2 residues evaporate in a special sterile heating section-entirely separate from the multi-zone contact heater that heats the thermoforming material.
This separate heating section allows Illig to guarantee a peroxide residue in the cups during filling of less than 0.1 ppm. The manufacturer also guarantees a sterility level of 1:10 meaning that fewer than 1 in 10 cups will be unsterile. In actuality Illig says sterility levels are much higher 1:100 or better.
Minimizing waste
Another special feature of the machine is automatic positioning of the sealing and die-cutting station. That eliminates waste during starts stops and restarts. It relies on fiber-optic sensors to detect cup position. If the material has shrunk during a long stop or if the cups are somehow not in the correct position the sensors signal the PLC which in turn signals the sealing and/or die-cutting stations to automatically reposition themselves to be centrally located over the cups.
While providing accurate sealing and cutting it also means there's never a loss of material after a machine stop nor are cups accidentally squeezed in the sealing or die-cutting station according to Herbert Schex plant manager at Ehrmann's Freiberg plant. Also minimizing material usage is the multiple gripper transport system which requires only a 10-mm margin of material on both sides of the web.
Packaging starts out as 51-mil PS sheet from several suppliers unwinds from rollstock. The material enters the sterile bath chamber and is exposed to the hydrogen peroxide solution of water that's 35% H2O2 at a temperature of 60°C (140°F).
The aseptic module that controls the sterile baths for the container and lidding in each of the hermetically sealed chambers is supplied by MTS Milchtechnik AG (Speicher Switzerland). The same unit also generates the sterile air and controls the aseptic atmosphere within the machine during production. Finally it controls the CIP/SIP cleaning functions.
From the sterile bath the cup material then enters the sterile heater section-separate from the standard material pre-heating section-allowing the H2O2 residues to evaporate at a temperature of 80°C (176°F). That's when the material is ready to enter the preheat section of the thermoformer located in the f/f/s area.
Four-zone heating
Inside the form/fill/seal area a steady overpressure of sterile air supplied by the external aseptic module maintains sterility during packaging. The material is pre-heated prior to thermoforming by four separate heating zones set at progressively higher temperatures. Each zone is the length of one index of 24 cups (six across and four in the machine direction). When heated to forming temperature the material indexes out of the last zone and into the forming station. Forming consists of a pre-stretching phase by plug assist followed by final forming via sterile pressurized air. Uninterrupted material gripper rails hold onto the material at all times for maximum control during heating. The benefit: no random shrinkage of material. The web of cups then indexes into the filling station.
There are actually two 24-head filling units positioned in sequence. They are used simultaneously when Ehrmann fills a product requiring a different bottom or top layer. Only one of the filling units is used when layers aren't called for.
For compatibility with the aseptic packaging environment the filler relies on ceramic pistons and non-wearing seals that are resistant to germ contamination. It is a piston dosing unit that drains product from a funnel in a vertical operation and then pushes out the product via a series of valves that fill 24 cups per cycle. Filling accuracy is ±1% according to Ehrmann. Though it can operate as fast as 36 cups/hr Erhmann typically runs it in the range of 28 to 30 cups/hr.
After filling the web of cups indexes into the sealing station. By this time lidding material which has gone through its own H2O2 sterile bath is sealed onto the cups via heat and pressure. Lidding also from several suppliers is a 1.6-mil structure consisting of aluminum foil with a heat-sealing lacquer and is gravure-printed in three to eight colors depending on the product.
Finally the cups are die-cut into four-packs with a flat die. The multipacks exit the thermoformer and are conveyed to a Krones (Franklin WI) wipe-on labeler that applies two front labels to the front two cups and separate rear labels to the back two cups. The paper labels are applied with cold glue adhesive.
The four-packs are conveyed into an automatic wraparound case-packer sourced locally that loads the desired number of multipacks and seals the case with hot melt adhesive. Cases are automatically palletized and stretch wrapped for distribution. The entire line controlled by a Siemens (Alpharetta GA) Model S5 115U PLC features fully automatic operation and usually requires only one operator per line-from forming through labeling-to restock materials.
Automatic CIP/SIP
Since each of the two lines is dedicated to a particular product clean-in-place only needs to be conducted once per week which takes about 31/2 hr according to Schex. Sterilize-in-place takes an additional 31/2 hr. Flavor changes which are done more frequently require only a 1-hr CIP procedure.
"The cleaning can be selected by a special program for the product change and runs automatically" explains Schex. "For the time being manual action is necessary for cleaning the funnels though this will be automatic on the new machine [on order]."
Schex says that uptime efficiency on the equipment is in the 92% to 95% range a figure with which Ehrmann is pleased. "Illig machines were purchased because a cooperation has developed for many years which is successful and satisfying for both parties" comments Schex. "Illig met all our demands with respect to machine technology."
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