Troubleshooting - Thermoforming - kp Advantage

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Troubleshooting thermoforming and form/fill/seal machinery takes patience and time. Everyone wants the problem solved immediately. Rather than trying to rush to a solution, it is best to take the time and find the root cause of the problem. Time and patience will solve it.

When a problem is noticed, the operator should look at every stage of the process. First, find at which stage the problem started then find the cause. Here are some hints to help you solve a few common problems. Always remember to keep a log book with the problems and solutions. They'll be easier to solve next time around.

Don't forget to write your original settings down before you begin troubleshooting. Try one thing at a time. If it doesn't work, return to the original settings and try something else.

THERMOFORMING

Problem	Cause	Solution

Appearance of folds, webbing, or wrinkles
Appearance of folds, webbing, or wrinkles	Material too hot	Reduce heating time / intensity
	Stretch of the material too high / sagging	Reduce heating time / intensity; if moulding insufficient change material
	Big shrinkage differences over the width or excessive TD growth	Defective material
	Irregular heating	Check temperature of radiator (oven)/heating plate. Inspect for bent/damaged heaters, replace
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Material tears or blows holes when contacting the tool or during forming
Material tears or blows holes when contacting the tool or during forming	Material too hot	Reduce heating time / intensity
	Material too cold	Increase heating time / intensity
	Compressed air / vacuum too early	Adapt delay
	Tooling too cold	Increase temperature of the tool
	Edges and corners of the tool are too sharp	Change geometry of the formed part
	Tool too rough (material does not slide)	Polish tool surface
	Excessive material sag; drags tool on index	Reduce heating time or increase line speed
	Too little clearance between tooling components	Adjust tooling for greater distances between male/female
	Forming press / plug speed too fast	Adjust speed
	Material gauge insufficient for designed draw	Increase material gauge / review tooling draw ratios
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Glossy spots
Glossy spots	Material too hot	Reduce heating time / intensity
	Unequal material distribution	Add vacuum holes around this area
	Non-uniform tool surface	Bead or polish tool
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Walls too thin
Walls too thin	Cold or hot areas in heating station	Check radiators / heating plate
	Not enough space between cavities	Increase space between cavities
	Tool close or plug speed too fast	Adjust tool close or plug speed
	Material gauge insufficient for designed draw	Increase material gauge / review tooling draw ratios
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Bubbles or pit marks on surface of formed part
Bubbles or pit marks on surface of formed part	Material too hot	Reduce heating time / intensity
	Form ejected too fast	Decrease demoulding speed
	Irregular heating	Optimize heat distribution
	Heating too intensive	Reduce heating time / intensity
	Forming temperature window of material too narrow	Exchange material
	Trapped air between sheet and tool	Roughen or sand tool to assist in air escape
	Dust, dirt, or small particulate matter on tool	Clean tool
	Condensation on tooling / water dripping on sheet	Increase tooling temperature / repair leaks
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Bad transparency of the formed part; hazy or blushing
Bad transparency of the formed part; hazy or blushing	APET-film too hot (cristallisation)	Reduce film temperature
	Film temperature too low (whitebreak)	Increase film temperature
	Surface of the mould too rough	Polish surface
	Tool or plugs too cold	Increase tool or plug temperature
	Plug or tool speed too fast	Decrease plug or tool speed
	Material surface scratched or abraided	Inspect material transport through machine
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Bridges/Webs
Bridges/Webs	Material too hot	Reduce heating time / intensity
	Insufficient compressed air	Increase air pressure
	Tool too hot	Reduce tool temperature
	Sagging of material	Reduce heating time / intensity; if moulding insufficient change material
	Space between plug and mould too narrow or wide	Optimize plug and/or ring dimensions
	Tool construction	Optimize tool geometry, install technical aid
	Cycle time too long / short	Optimize cycle time
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Cloudy areas; surface distortion or marks
Cloudy areas; surface distortion or marks	Tool temperature too low	Increase tool temperature until cloudy areas disappear
Cloudy areas; surface distortion or marks	Too much silicone on surface or film defects	Exchange material
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Material tears on the bottom of the formed part or formed cavity too thin
Material tears on the bottom of the formed part or formed cavity too thin	Material too hot	Reduce heating time / intensity
	Too much pre-stretching	Decrease level of pre-stretching
	Upper plug too late / too slow	Optimize timing / speed
	Material too thin	Choose thicker material
	Uneven thickness profile over width	Check thickness profile over width
	Material has inclusions	Check material specification
	Vacuum on too early or too much pressure	Adjust vacuum timing or pressure
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White stretch (stress) marks
White stretch (stress) marks	Upper plug too early / too fast	Optimize timing / speed
	Distance between heating plate and tool too big	Decrease distance
	Material difficult to thermoform	Exchange material
	Material too cold	Increase heating time / intensity
	Ejection air pressure too low	Optimize ejection air pressure
	Tool surface too rough	Polish tool surface
	Table moves down too quickly	Reduce speed of table-movement
	Form press opens too fast	Decrease opening speed
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Bad definition at the edges of the forming area
Bad definition at the edges of the forming area	Material too cold	Increase heating time / intensity
	Ejected part too hot	Reduce temperature of tool; increase cooling time
	Downholder	Reflect downholder out
	Draught (draft) over the film	Protect machine / film against draught
	Not enough space between cavities	Increase space between cavities
	Clamping frame too narrow	Enlarge clamping frame
	Clamping frame not reflected out	Reflect frame out
	Pressure and or vacuum timing not optimized	Modify vacuum and pressure settings
	Pin chain rails cooling edges of material	Increase temperature of pin chain rails
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Folds on thermoformed part
Folds on thermoformed part	Material too hot	Reduce heating time / intensity
	In corners: compressed air / vacuum too early	Optimize delay
	On walls / bottom: compressed air / vacuum too late	Optimize delay
	Too much pre-stretching	Decrease level of pre-stretching
	No evacuation / evacuation holes plugged	Optimize mould / clean evacuation holes
	Corners or undercut of the mould too sharp	Adjust geometry of the part
	Sagging of material / material touches mould	Reduce heating time / intensity; if moulding insufficient change material; use sag bar or spread chain rails
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Formed part sticks to tool
Formed part sticks to tool	Ejection-air (missing or too low)	Check pressure of compressed air
	Edges / corners or undercut of the mould too sharp	Adjust geometry of the part
	Surface of the tool too rough (material does not slide)	Polish surface of the tool
	Bad demoulding of film/poor mould release	Exchange material / use release agent
	Tool too hot	Reduce tool temperature
	Material too hot	Reduce heating time/intensity
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Part deforms during demoulding
Part deforms during demoulding	Material ejected too hot	Increase cooling time
	Tool too hot	Reduce tool temperature (cooling)
	Ejection air too high / ejection time too long	Optimize ejection
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Parts in the corners too thin
Parts in the corners too thin	Material too hot	Reduce heating time / intensity
	Radius of the mould too small	Increase radius/use thicker material
	Tool too hot/cold	Adjust tool temperature (cooling or heating)
	Flanks too flat	Redesign part
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No demoulding of material - parts do not eject
No demoulding of material - parts do not eject	Temperatutre of tool too high	Reduce tool temperature (cooling)
	Ejection air too low	Increase pressure of ejection air
	Material too sticky	Exchange material
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Details too sharp (e.g. vacuum holes visible)
Details too sharp (e.g. vacuum holes visible)	Material too hot	Reduce heating time / intensity
	Surface of the tool too rough	Clean surface / reduce roughness of the tool
	Level of compressed air too high	Reduce pressure
	Tool too hot	Reduce tool temperature (cooling)
	Vacuum or pressure duration too long	Reduce vacuum or pressure timing
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Bad forming; no definition
Bad forming; no definition	Closing of tool not sufficient	Check / change sealing ring; check flatness of plates
	Bad timing of vacuum-/ pressureforming	Adjust timing
	Forming pressure not sufficient	Increase pressure
	Material too cold	Increase heating time / intensity
	Cycle too short	Increase cycle time
	Tool too cold	Check/optimize cooling temperature
	Vacuum not sufficient	Increase number of vacuum holes
	Vacuum not sufficient	Check vacuum system for leaks
	Trapped air between cavity and film	Check arrangement and number of vacuum holes
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Thermoformed part warped
Thermoformed part warped	Tool too hot	Reduce tool temperature (cooling)
	Clamping frame doesn't work properly	Increase closing pressure of clamping frame
	Jaws in chain not adjusted properly	Adjust jaws in chain
	Vacuum and/or air pressure not syncronized	Adjust forming air timing
	Excessive post forming material shrinkage	Mold design - consider oversized molds or re-design
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Thin areas
Thin areas	Wrong temperature of material	Optimize profile of heat distribution
	Material too thin	Use thicker material
	Vacuum too fast	Optimize vacuum speed
	Cavities too close together	Increase distance between cavities
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Tearmarks
Tearmarks	Wrong setup of pre-stretching	Use pre-stretch plug made of polished aluminium, coated Teflon® or expanded plastic
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Webs or folds in the corners when positive forming
Webs or folds in the corners when positive forming	Material too cold	Increase heating time / intensity
	Pre-stretching sequence too long	Shorten pre-stretching sequence
	Form of mould not enough conical	Design form of mould more conical
	Edges and corners too sharp	Redesign mould
	Walls too vertical/draft angle too steep	Redesign mould allowing greater draft
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No contact to the forming tool
No contact to the forming tool	Tool does not close properly	Check flatness of tool
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Lateral quench marks
Lateral quench marks	Upper plug moves too early or too quickly	Optimize time and speed
	Tool too cold	Increase tool temperature
	Surface of the tool too smooth	Sandblast surface of the tool
	Heat distribution	Optimize heat distribution profile
	Pre-stretching too low / too short	Increase pre-stretching
	Upper plug too cold	Increase temperature
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Unequal border (trim) width of the formed parts
Unequal border (trim) width of the formed parts	Material too hot	Reduce heating time / intensity
	Pre-stretching too early	Delay pre-stretching
	Forming too early	Delay forming
	Table moves too quickly	Reduce speed of table-movement
	Insufficient closure of tool	Check flatness of tool
	Material too thin	Choose thicker material
	Shrinkage of material too high	Exchange material
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Poor surface of the formed part
Poor surface of the formed part	Poor tool surface	Polish or abrasive blast tool surface
	Dirty material	Sort material out
	Heating plates dirty	Clean heating plates
	Surface of upper plug too rough	Polish plug
	Dirty mould	Clean mould with applicable cleaner
	Inclusions in the material	Check specification
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Marks on the bottom of the thermoformed part
Marks on the bottom of the thermoformed part	Material too hot	Reduce heating time / intensity
	Vacuum not sufficient	Optimize vacuum
	Pre-stretching insufficient	Optimize pre-stretching
	Vacuum holes too small / too less	Increase dimensions / number of vacuum holes
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Material accumulation in transversal direction
Material accumulation in transversal direction	Vacuum too slow	Increase vacuum speed
	Material too hot	Reduce heating time / intensity
	Tool surface too smooth	Sandblast tool surface
	Wrong position of vacuum holes	Redesign position of vacuum holes
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Air streaks on thermoformed part
Air streaks on thermoformed part	Vacuum not sufficient	Optimize vacuum
	Tool surface too smooth	Sandblast tool surface
	Insufficient closure of tool	Check flatness of tool
	Vacuum holes too small / too less	Increase dimensions / number of vacuum holes
	Material defects	Exchange material
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Blister is not (well) stackable; denesting problems
Blister is not (well) stackable; denesting problems	No antiblocking additive (PET)	Exchange material
	Film too thick	Reduce thickness
	Too little release agent between mould and material	Use release agent or silicone coated material
	Part design	Add denesting lugs, increase draft angles, or remove undercuts; redesign
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Blister is unstable
Blister is unstable	Material too thin	Change to ticker material
	No reinforcing ribs	Add reinforcements
	Part design	Add chamfeurs or redesign part
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Holes in thermoformed part
Holes in thermoformed part	Cycle time too short	Adjust cycle time
	Irregular heating	Change defect parts of heating system
	Material too cold	Increase temperature / intensity
	Material sticks to mould	Change material / use mould with Teflon® coated surface
	Vacuum holes too large	Close vacuum holes and redrill smaller holes
	Inclusions in the material	Check specification
	Ventilation does not work properly when plug moves into the cavity	Check ventilation
	Vacuum / Pressure timing not optimized	Adjust vacuum and pressure onset / duration
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Angel hair
Angel hair	Knife too blunt	Sharpen knifes, or change for new ones - replace strike plate
	Material too soft or tensile strength too high	Modify material choice
	Cutting depth too low	Increase knife penetration
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No cutting
No cutting	Knife too blunt	Sharpen knifes, or change for new ones
	Knife has no contact to cutting plate	Adjust position of knife
	Punching pressure too low	Optimize punching pressure
	Hydraulic system contains air	Close and purge hydraulic system
	Punching knife warped	Adjust / renew knife
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No continuous cut
No continuous cut	Irregular blade	Exchange cutting blade
No continuous cut	Cutting knife not installed properly	Adjust knife position
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Material sticks to knife
Material sticks to knife	Material too hot	Increase cooling
	Knife temperature too high	Reduce knife temperature
	Silicone coated side away from knife	Reverse material at the unwind
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FORM/FILL/SEAL

Problem	Cause	Solution

Base web feeding
Transport chain or feeding system does not grip or index the film	The transport chain or clipping mechanism pulls on one side only (wear)	Tighten or exchange the transport chain; replace springs or worn clips
	Bad closing tension	Revise closing tension
	Alignment of machine not horizontally	New alignment of machine
	Control cam misadjusted	Set the control cam
	Unwinding device and idler pulley are not aligned	New alignment of unwinding device and idler pulley
	Offset stacking of film	Adhere to tolerances
	Wrong width of film reel	Exchange material
	Braking power of unwinding station too high	Adapt braking power of unwinding station
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Film rips out of the transport chain or clipping mechanism	Film width is too narrow	Exchange material
	Bending of the film	Adhere to tolerances
	Bad closing tension	Revise closing tension
	Dancer stroke is misaligned to index	Adjust dancer stroke
	Excessive TD shrinkage	Exchange material
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Crinkles or folds/wrinkles	The transport chain pulls on one side only (wear)	Tighten or exchange the transport chain
	Alignment of machine not horizontally	New alignment of machine
	Control cam misadjusted	Adjust control cam
	Wrong width of film reel	Exchange material
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Heating unit
Cracknels, bubbles, or surface marks	Air inclusions between heating plate and film	As a basic principle: keep forming temperature as low as possible
		Sandblast and Teflon®-coating of heating plate
		Mask heating plate with Teflon®
		Raster heating plate with holes of 0,8-1,1 mm
		Position heating plate lower than the frame
		Reduce heat plate vacuum pressure
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Cloudy parts	Temperature of heating plates too high	Adapt temperature
	Heat plate vacuum pressure too high	Reduce heat plate vacuum pressure
	Dirty or worn heat plates	Clean or replace / recoat plates
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Cristallisation (danger with APET-films)	Temperature of heating plates too high	Adapt temperature
Cristallisation (danger with APET-films)	Index / cycle too slow	Increase index / cycle speed
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Whitebreak	Temperature of heating plates too low	Adapt temperature
Whitebreak	Index too fast	Slow index speed
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Thermoforming station
Insufficient moulding / cold forming	Forming temperature too low	Adapt temperature of heating plate
	Forming pressure too low	Adapt forming pressure
	Forming time too short	Adapt forming time
	Vacuum too low	Revise vacuum system
		Revise evacuation holes
		Revise gasket of sealing frame
		Revise sealing of forming tool
	Downward movement of the plug too slow	Regulate downward movement of the plug
	Wrong thermoforming ratio	Adapt film thickness to thermoforming depth
	Wrong thermoforming ratio	If applicable use plug
	Mold / plug temperature too cold	Warm mold / plug
	Dancer stroke is misaligned to index causing neck-in and loss of seal / vacuum	Adjust dancer stroke
	Excessive TD shrinkage causing neck-in and loss of seal / vacuum	Exchange material
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Deforming of formed part	Temperature of the forming tool too high	Pay attention to temperature of the forming tool, if applicable install cooling device for forming tool
	Cooling time too short	Optimize cycle
	Air eject pressure too high / early	Reduce pressure / adjust onset timing
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Material breaks when thermoformed	Thermoforming temperature too low / too high	Adapt thermoforming temperature
	Film thickness too low	Adapt film thickness to thermoforming form
	Thermoforming ratio too high	Adapt film thickness to thermoforming form
	Edges of the package are too sharp	Change design of the package
	Dancer stroke is misaligned to index	Adjust dancer stroke
	Plug /assist plate speed too fast	Reduce plug / assist plate speed
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PE-layer breaks when thermoformed (with a plug)	Too low tolerance of the plug/too high friction between film and plug	Adapt size of plug to the mould
	Plug (if heated)/temperature of the film too high	Reduce temperature of the plug and the mould
	Activation of plug too early	Adapt time sequence of plug
	PE layer sticks to heating plates	Reduce heating plate temperature of PE layer side
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Airmarks	Insufficient vacuum	Inspect vacuum system/increase vacuum pressure
	Tool does not seal hermetically	Revise hermetical sealing
	Fish eyes or inclusions in the film which might break open	Comply with quality specifications
	Vacuum time/vacuum level is set too low	Increase vacuum time/vacuum level
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Too much detail in thermoformed part (aluminium pits are visible)	Film temperature too high	Reduce thermoforming temperature
	Surface of the mould too rough	Polish or blast surface of the mould
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Film rips out of the transport chain / index mechanism	The temperature of the heating plate is too low which leads to a high tension on the film transport chain	Increase temperature
	Dancer stroke is misaligned to index	Adjust dancer stroke
	Excessive TD shrinkage	Exchange material
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Filling of the package
Film rips out of the film transport chain	Filling weight too high; the package is not underpinned	Adapt filling weight to the package
Film rips out of the film transport chain	Bending of the film	Adhere to tolerances
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Feeding of sealing film
Crinkles,folds, or wrinkles	Unbalanced unwinding of sealing film	Revise unwinding station, e.g. adjust web tension
	Curvature	Exchange sealing film if necessary
	Curling of sealing film in machine direction too strong	Exchange sealing film if necessary
	Wavy edges	Exchange sealing film if necessary
	Mis-alignment of roll	Adjust alignment
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Variation of dimension	Dimensional variation of repeating pattern	Revise length of repeating pattern
Variation of dimension	Dimensional variation of repeating pattern	Adjust photoelectric cell
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Sealing unit
Package leaking / poor sealing	Film inserted incorrectly	Sealing layers of sealing film and base film have to be positioned inline
	Sealing layers of sealing film and base film have to be compatible	Revise compatibility of sealing layers
	Sealing temperature too low/too high	Adapt sealing temperature
	Sealing time too low/too high	Adapt sealing time
	Sealing pressure too low	Increase sealing pressure
	Gasket of sealing tool worn	Exchange sealing gasket
	Membrane in upper part of sealing tool defective	Exchange membrane
	Sealing plate damaged	Exchange sealing plate
	Sealing plate not planar/level or flat	Revise planarity/level or flatness of sealing plate
	Sealing valve defective	Exchange sealing valve
	Heating elements defective	Exchange heating elements
	Contamination of sealing area with product	Pay attention to clean sealing areas
	Length of repeating pattern of sealing film too short, thereby high tension on heat sealed joint	Revise and maintain tolerances
	Filling level of the package too high	Reduce filling level of the package
	Speed of upper vacuum / vacuum of the valves too fast; the product is pulled onto the sealing area	Adapt vacuum speed
	Hot-tack of the film is not sufficient when applying upper valves	Apply other materials with improved hot-tack properties
		Adapt filling level of the package
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Sealing film shrinks in transversal direction	Shrinking properties of sealing film	Revise shrinking properties of sealing film, if applicable, exchange material
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Penetration of sealing film	Rapid ventilation of the package	Revise setting
	Product with sharp edges	Pay attention to right positioning of the product within the package
	Travel or position of sealing device too low	Adapt filling level of the package/adjust sealing head stroke/ position
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Defective sealing (with skin packaging)	Sealing temperature too low/high	Adjust sealing temperature
	Sealing layer contaminated with product	Pay attention to clean sealing areas
	Sealing layers of sealing film and base film are not compatible	Revise compatibility of sealing layers
	Sealing tool contaminated	Clean sealing tool
	Venting valves set up incorrectly	Revise setting
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Insufficient vacuum	Vacuum set too low	Revise setting
	Evacuation time set too short	Revise setting
	Filter of vacuum pump plugged	Exchange filter/check vacuum system
	Valve of sealing tool leaky, sealing plate pushes downward	Exchange valve of sealing tool
	Non-return valve of sealing tool defective	Exchange non-return valve
	Product temperature	For humid food products, we recommend a maximum product temperature of 4°C
	Sealing membrane defective	Exchange sealing membrane
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Airmarks	Contamination of heat-sealed joint	Clean heat-sealed joint
	Frame of sealing tool contaminated	Clean frame of sealing tool
	Sealing rubber defective	Exchange sealing rubber
	Sealing time too low	Adapt sealing time