Troubleshooting Thermoformable Packaging Optimizing the thermoforming process with differing materials. TEKNI-FILMS A A Division of Company
Defining the Manufacturing Process All processes contain variables of three differing types: Design Variables Production Variables Manpower Variables -Films Troubleshooting Guide will address the design and production variables.
Part I - Design Variables Variables determined when purchasing blister thermoforming machinery
Blister Machine Process Schematic Film Heating Blister Cavity Filling To Cartoning Lidstock Sealing Blister Cavity Formation Film Roll Unwind
Types of Machines and Sealing Devices Platen, indexed web movement Cam, IMA, Klockner, Noack,, and Uhlmann produce indexing machinery. Bosch, IMA produce rotary thermoformers Rotary, continuous web movement
More Machinery Variables Film Heating - The number and location of controlled heating zones allows for more controlled and consistent web heating. Ideally the heating plates are 3 indexes long. Blister Cavities can be filled either by flooding the fill zone with pills, or by dedicated filling manifolds. Cooling plates after forming and sealing to be present.
Thermoforming Mold Variables Molds may be coated with special releasing materials to aid in blister separation from the tooling. Different coatings may aid in separating one type of film, but may enhance the bond to another. Plug assisted cavities physically push the material prior to it s s final pressurized air forming.
Part II- Production Variables Controlling the process to yield optimal results.
Film Heating Station General Suggestions: Use the lowest setting possible to minimize film shrinkage and curl, while still forming complete cavities. Make sure platens are flat, parallel in alignment and gap. Adjust temperature in 5 O increments. Heating plate length: 3 indexes. T1 T2 T3 T4 T5 T6
Film Heating Station PVC - Upper and lower platens set to the same temperature, zones need not be increased for best thermoforming results. PCTFE or PVdC coating - Platen facing PCTFE or PVdC coating should be lower than that facing PVC. Incremental rise in temperature zones is generally desirable. T1 T2 T3 T4 T5 T6 Typical Temperature Setting: T 1 : 130 O C T 2 : 135 O C T 3 : 140 O C T 4 : 125 O C T 5 : 130 O C T 6 : 135 O C
Blister Cavity Formation General Suggestions: Always activate plug assist to at least 50% when available (up to 75% ). Plug assist aids in more uniform cavity thickness distribution, and usually results in lower platen heat settings. Air forming pressure of 60-120 PSI (4-8 bar) is optimal. Use matched tooling. P1
Blister Cavity Formation PVC - Almost any cooling conditions and coatings will form cavities. PVdC coatings - Require Teflon coated cavities to lengthen tool life. Cold tools are discouraged to reduce PVdC cracking. P1 PCTFE - These materials may bond with Teflon coatings. Mold temperatures should be room temperature. Plug assist is recommended.
Blister Cavity Filling General Suggestions: Always insure improperly oriented solid dosage forms and crushed product are removed prior to the lidstock lamination. A change in film gage will affect product fit into the blister cavity. Incompletely formed cavities will negatively affect filling performance
TEKNIFLEX Laminations - Winding PCTFE Lamination Blister Package PVC Alu Foil Lidding ALWAYS SEALS TO THE PVC SIDE Adhesive PCTFE Film PCTFE on outside of blister You must specify the winding of the PCTFE side OUT or IN for the slit roll depending on the machine configuration Winding PCTFE OUT Winding PCTFE IN
Lidstock Sealing General Suggestions: Lidstocks generally seal very well to PVC, adequately to PVdC, and poorly to PCTFE layers. Novel lidstocks seal to PCTFE. Sealing Temperatures between 170-220 O C are used for most PVC coated lidstocks. Universal and Polyolefin lidstocks can be run at 140-200 O C. T1 Note: Curling may occur with PCTFE films at higher sealing temperatures.
Part III - Troubleshooting Solutions Identifying and correcting common industry problems.
Types of Problems Film shrinkage Film curl Film sticking Film delamination Incomplete blister cavities Poor lidstock sealing Blister card curl
Film Shrinkage Most Thermoforming films shrink somewhat during the thermoforming process. Concern is placed particularly on those films which shrink in an erratic manner. PCTFE films shrink more than PVC in the trans-machine direction (TD). This shrinking both narrows the web and curls the film. Properly processed film may shrink 3-5% for copolymer and 1-3% for homopolymer PCTFE films. Note: With all films, tension in the machine direction will result in loss of web width. Lessening the heat or increasing lines speeds will reduce the TD shrinkage in most films.
Film Curl Film Curl occurs when two or more films have different shrinkage rates. This most commonly occurs with PCTFE films that are laminated to PVC with a PE tie layer. Typical solutions to this difficulty are identical to reducing film shrinkage. Curl can also be reduced by duplex laminations and conversion to homopolymer materials.
Film Sticking May occur between the heating platens and/or to the forming mold. Most common with PVdC/PVC materials (PVdC-coating relatively tacky). Cleanliness & condition of heating platen surfaces important. Gap between platens should be uniform over entire area. Platens should be replaced or reconditioned periodically with a non-stick (e.g., Teflon) surface. Additional mold-cooling recommended for PVdC/PVC, but not for PCTFE laminations. Sticking may cause MD-stretching and web shrinkage.
Film Delamination PVC/PE/PCTFE - Adhesive is semi-activated during lamination, and is fully-activated upon application of heat during thermoforming. Adhesion strength increases remarkably during thermoforming.
Incomplete Blister Cavities Normally indicates insufficient heat to film. Is sometimes accompanied by milky-white areas within cavities. Is also seen with loss of forming air pressure (audible venting). Cavity formation may usually be improved by using more heat (higher temperatures and/or slower cycle speeds). Striations may be caused by excessive heat used on PCTFE laminations. The actual temperature of the heating plates needs to be calibrated against the read-out on the controller.
Poor Lidstock Sealing Sealing temperature indicates heat applied to coating on aluminum foil-based lidstock. Sealing temperature normally identical for PVC, PVdC/PVC and PCTFE /(PE)/PVC (PVC is generally product & lidstock contact layer). Sealing to correct side? Minimum heat-seal activation temperature. Sealing pressure. Cleanliness, condition, and pattern of sealing platens is important. Alignment and flatness of platens is important.
Blister Card Curl Most common with PCTFE laminations (card curls toward PCTFE side). Same phenomenon as film curl. Same cause as TD web shrinkage: higher TD shrinkage rate of raw PCTFE film compared to PVC and PE films. Curl normally may be decreased by using less heat at heating-platen station (lower temperatures and/or faster cycle speeds). Curl may also be decreased by utilizing duplex PVC/PCTFE construction.
Control of production variables is the key to reducing or eliminating faulty packaging. Flexible thinking, clear answers.