P & P Precision Designs Limited

foam welding and laminating machines

Foam Laminator » Operating Instructions

OPERATING INSTRUCTIONS
Issue 1 August 2003

P&P Precision Designs Ltd
Laminator Mk 7 (1250 49”)

CONTENTS

Part 1 Part 2 Part 3 3.1 3.2 3.3 3.4 3.5 3.6 Part 4

INTRODUCTION CAPABILITIES OF THE MK 7 LAMINATOR MACHINE OPERATION Introduction and General Operation Blade temperature Roller speed Roller and heater blade positions Laminating dissimilar materials together Failure Modes HEALTH AND SAFETY

APPENDICES

Appendix 1  All LD and MP based products
Appendix 2  All EV and VA based products
Appendix 3  All HD and HL based products
Appendix 4  All PPA based products
Appendix 5  All Conductive and Static Dissipative products
Appendix 6  Laminating materials of individual thicknesses less than 10mm
Appendix 7  Optimising blade and roller Positions
Appendix 8  Glossary of Terms

PART 1 INTRODUCTION

Lamination is the process of bringing two surfaces together by heat or by adhesion to form a thicker block with a laminated bond equivalent in strength to that of the individual sheets. The MK7 machine uses an electrically heated blade to melt the sheet surfaces. The thickness of the melted material is commonly known as 'melt back' and is dependent upon several factors :

i) Density: High density grades require more heat to melt an equivalent surface area.

ii) Grade: Amount of heat required to melt a sheet surface depends upon the melt properties of the base polymer ; e.g. HDPE has a higher melting temperature range than LDPE.

iii) Contact: Amount of material in contact with the blade, which depends upon the blade and roller positions (refer to Part 3.4)

CONTENTS PART 2 CAPABILITIES OF THE MK 7 LAMINATOR

2.1 Use of Laminator
The machine is designed to laminate Plastazote, Evazote and Supazote foam grades produced by Zotefoams.

2.2 Width
The heater blade is clamped at both ends leaving an available heated surface width of 1550mm.

The blade temperature across the middle 1400mm is very constant. For most materials 1300mm is the maximum sheet width possible to achieve a satisfactory bond across the entire sheet.

However there are other factors which affect the laminated width achievable which are not related to the design of the laminator. The maximum width achievable depends upon the flatness of the sheets at the edges and the alignment of the sides as they are being fed-in. The latter factor becomes more important when building up thick block as continuing misalignment means a decrease in the total laminated block width.

2.3 Functions of the Laminator
The height of the heater blade and the position of the top drive rollers are adjusted by two hand-wheels located on the side of the machine above the Control Console (Figure1). A small upper guide roller with an adjustable height relative to the upper drive roller is located above the heater blade. A hand-wheel to adjust this is located on the front face of the machine above the feed-in tunnel. The function of this roller is more critical when laminating thin materials (Part 3.1.4).

2.4 Laminated Block Thickness
The maximum distance possible between the drive rollers (R3 & R4) is approx. 300mm (Refer to Figure 2)

The maximum travel of the heater blade is approx 250mm. (Gap A)

The maximum travel of the top drive roller from the heater blade is approx. 100mm. (Gap B)

2.5 Thin Laminations
Laminations with individual sheet thicknesses of 5mm are possible but greater care must be taken when feeding material in. For a total laminated thickness of less than 20mm the material to be laminated should be prepared in roll form to minimise the difficulty of feeding in thin sheets (see Part 3.1.4).

2.6 Rate of Lamination
This is controlled by the speed of the drive rollers R3 & R4. The speeds are indicated for both rollers as either feet per minute or metres per second. The relative speeds of the top and bottom drive rollers can be varied to make either one faster or slower than the other.

2.7 Lamination Temperatures
Temperature can be set in 1°C increments up to a maximum of 550°C. The highest setting necessary for current Zotefoam products is 540°C.

CONTENTS PART 3 MACHINE OPERATION

3.1 Introduction to Operation
The Laminator operates by passing two sheets either side of the electrically heated blade. The surfaces are then brought into contact by feeding the sheets through the gap between the drive rollers. These rollers then proceed to pull the sheets across the blade at a rate to achieve the required heat transfer. The adjustable spacing between these drive rollers controls the amount of pressure exerted on the sheets to bring the surfaces into contact. These surfaces are melted and then forced together by the drive rollers where solidification takes place.

3.1.1 General Operation
Before attempting to operate the laminator the user must be fully conversant with the Health and Safety Section (Part 4) of these instructions as well as being fully familiar with the locations of the five Emergency Stop buttons and all the operational buttons and switches.

All Emergency Stop buttons isolate power to the drive rollers and the heater blade. They are located as follows :

On the top of the Control Console.

Left and right at front edges of the feed-in tunnel

Left and right at back edges of the take-off tunnel

Before attempting to start ensure all Emergency Stop Buttons are pulled out.
 
Figure 1: Control Panel

3.1.2 Sequence of Operation

	ACTION	KEY POINTS
1	Switch power on at main isolator switch.	Fault light flashes every 10 seconds.
2	Depress 'Control On' button.	White 'Control On' light illuminates indicating control supply is available and machine is ready to start. Temperatures will be displayed on the Temperature control unit, but the power to the heater elements will remain off until the rollers are started.
3	Depress 'Run' button.	Green 'Run' light will be illuminated. Rollers will start running at the speeds indicated for 'Upper Roller Speed' and 'Lower Roller Speed'. Power will now be on to the heater elements and the actual displayed temperature will increase.
4	Set temperature control unit to lamination temperature required as described in Part 3.2.	Allow actual displayed temperature to control at set temperature for at least 15 minutes. See Appendices for material conditions.
5	Adjust 'Roller Speed' as described in Part 3.3.	See Appendices for material conditions.
6	Switch on 'Roll Pause' if required as described in Part 3.1.5.	See Appendices for material conditions.
7	Adjust blade and roller positions as described in Part 3.4.	See Appendix 7 for optimising positions.

3.1.3 Sheet Feeding
A glass support plate is fitted to the blade such that any movement of the blade will also move the plate. The top surface of the glass divider and that of the blade are level to ease feeding the sheet over the blade without any obstructions.

Ensure that the front and the sides of the top and bottom sheets are lined up with respect to each other.

Sheets must be positioned centrally across the blade to achieve a uniform bond without any weak areas due to passing over the cooler extreme ends of the blade. The operator will have more control by standing by the side of the sheets rather than behind them. One hand can be used to line up the front and edges and guide the front over the glass. The other hand is used to feed the material into the machine.

Until the front of the sheets have passed over the blade and into the drive rollers the rate of heat transfer from the blade is totally dependant upon the operator feed rate. This represents the first 95mm of the sheets and may affect the quality of the bond; too slow a feed rate will result in overheating and charring, too fast will result in a weak bond or even a gap.

The correct feed rate can only be established by passing the sheets over the blade at a speed equal to the roller speed such that when the front of the sheets touch the drive rollers no hesitation occurs. Hesitation causes a burn line or hole across the width of the laminate.

3.1.4 Producing Thick Blocks
Any successful lamination relies upon the contact surface maintaining even heat transfer. The heat transfer from the blade depends upon :

i) Density High density grades (more material per volume) require more heat to melt the surface.

ii) Grade Heat required to melt sufficient of the material surface depends upon the melt characteristics of the grade.

iii) Contact Surface area in contact with the blade depends upon the Gap Settings (Part 3.4) and the mass of the top component, both of which contribute to the amount of pressure exerted on the blade.

To control heat transferred from the blade when producing laminated blocks which consist of more than three sheets, the block must be built up by adding a single sheet on top to gradually increase the thickness. By using this method every join will be of equivalent strength and appearance.

3.1.5 Laminating with Thin Sheets
For any lamination using individual sheet thicknesses less than 10mm it is recommended that they are prepared as roll feed to assist the lamination. With flexible materials problems are greater due to the lack of rigidity of sheets of this thickness; feeding in becomes difficult to control as the front of the material tends to flex rather than lie flat. The material may not slide easily across the blade and tends to stick more readily. Feeding of thin material can be eased by cutting a V-shape at the front edge. This will result in minimal wastage when using roll feed but is not a practical solution for single laminations.

The small pressure roller above the blade has a 20mm adjustment relative to the upper drive roller. Adjustment is made by a hand-wheel located on the front face of the guard above the feed-in tunnel.


Difficulty may arise when feeding the bottom thin sheet under the blade. This may be overcome by raising the heater blade an extra 1 - 2mm whilst maintaining the correct amount of pinch pressure. The blade can then be moved back to get better surface contact if necessary. Tension must be kept on the laminated product as it comes out of the drive rollers.

3.1.6 Roll Pause
A photo-sensitive cell is used to stop the drive rollers for a pre-determined time to ensure the end of the laminated block is successfully bonded. This operates by sensing the end of the sheets and temporarily stops the rollers which hold the back of the lamination together so as to achieve a better weld. The 'Roll Pause' is operated by a switch on the control console and is used for laminations as specified in the Appendices.

CONTENTS 3.2 Blade temperature

3.2.1 Adjusting the Temperature Controller
The set temperature is controlled and adjusted by a Temperature control unit.

With power on, the actual blade temperature is continuously displayed.

The 'Desired Temperature' is adjusted by depressing either the up or down buttons whichwill change the set point value. Short presses change the set point by single units. Long presses accelerate the set point for large adjustments.

3.2.2 Setting the Correct Lamination Temperature
i) Temperatures must first be set up as specified in the Appendix for the specific grade and thickness.

ii) After start-up from cold allow heated blade to maintain set temperature for at least 15 minutes before beginning any laminations.

iii) During production do NOT start a lamination until displayed temperature is above the 'Lower Limit Starting Temperature'.

iv) Do NOT allow the displayed temperature to fall below the 'Critical Blade Temperature' during lamination.

v) Rate of throughput must be limited in order to comply with iii) and iv) above, especially on higher density and thicker block laminations.

3.2.3 Using Temperatures Higher than the Operating Temperatures
Setting the temperature slightly higher than indicated in Appendix 1 - 6 may improve weld when sheets are uneven. However, in excess of 20°C - 68°F higher may result in unsatisfactory weld quality.

i) The lamination temperature should be kept as low as possible. In the event of the foam becoming trapped while in contact with the blade, the higher the temperature the greater the risk of fire.

ii) Unnecessary over-heating of material may give a thicker, darker, more prominent join.

iii) Material will be more prone to sticking to the blade and uneven melt-back will be more likely to occur; i.e., gaps and solid lumps giving very poor quality weld.

iv) Over-heating and material sticking to the blade will result in the emission of excess smoke and fumes.

v) Higher density or more rigid materials will come apart if the temperature after passing over the blade and through the pinch gap is still much higher than the melt temperature of that grade.

CONTENTS 3.3 Roller speeds

3.3.1 Adjusting the Roller Speeds
There are two thumb-wheels to control the speeds of the top and bottom drive rollers.
The roller speeds are indicated by a digital display.

3.3.2 Setting Roller Speeds
i) Roller speeds must first be set up as specified in the Appendices for the specific grade to be used.

ii) For lamination of 2 sheets of equivalent thickness top and bottom, then the Upper Roller Speed and the 'Lower Roller Speed' should be the same in order to achieve a flat laminated block. The flatness of these laminations can be controlled by adjusting the 'Roller Balance'.

iii) For laminating dissimilar thicknesses, e.g., thin on thick, an adjustment of the Roller Balance is required. With a thinner sheet on top then the Upper Roller Speed should be at a relatively faster speed than the Lower Roller Speed.

Adjust the 'Roller Balance' until bowing is eliminated and a flat block is achieved.

CONTENTS 3.4 Roller and heater blade positions

3.4.1 Adjusting Positions
There are two hand-wheels which are manually adjusted. Both have a digital read-out incorporated within the wheels which relate to actual distances.

The Right Hand Wheel displays the distance between the bottom drive roller and the centre of the heater blade,
(Bottom Gap = Gap A in Figure 2).

The Left Hand Wheel displays the distance between the centre of the blade to the lower-most surface of the top drive roller, ('Top Gap' = Gap B in Figure 2).

The 'Total Gap' between the top and bottom drive rollers is equal to the 'Bottom Gap' added to the 'Top Gap'.

3.4.2 Setting Blade Position ('Bottom Gap')
i) For a block comprising only 2 sheets setting is very straight-forward:

Measure thickness of bottom sheet across width and set 'Bottom Gap' to the maximum measured thickness.

This equals 'Bottom Gap Setting'

ii) For a block comprising more than 2 sheets :

Thickness across the width of bottom component must be known. If this cannot be accurately measured then use the individual measurements and subtract 0.5mm per laminated join. Set 'Bottom Gap' to maximum thickness found/measured.

This equals 'Bottom Gap Setting'

Notes: Position of blade can be further optimised, to take account of thickness variation, by sliding the front of the bottom sheet rapidly under the blade then retracting it. If this feels relatively tight then the gap should be increased in 0.5mm steps until the sheet can be fed in with ease whilst maintaining light contact on the blade. Feeding in can also feel tight due to the temperature of the blade being too low, hence check correct conditions are being used.

3.4.3 Setting Roller Position ('Top Gap')
Determine the minimum combined thickness of the top and bottom sheets (Tmin).

Subtract the 'Bottom Gap Setting' plus 3mm from 'Tmin' to give 'Top Gap Setting'

3mm is a general guide for most materials at most thicknesses to ensure there is sufficient compression to bring the surfaces in contact and to pull the block over the blade. This gap can then be optimised as described in Part 3.4.4.


'Top Gap Setting' = 'Tmin' - (Bottom Gap Setting + 3mm)
Gap B in Figure 2

3.4.4 Optimising Positions
The amount of compression exerted on two sheets between the top and bottom drive rollers is defined by the total thickness of the laminated block less the Total Gap. Therefore the thickness of the sheets to be laminated must be measured across the total width in order to control the amount of force exerted on the weld line. This compression also affects the amount of contact the surfaces of the sheets have on the heated blade, i.e. how much material is melted. Contact occurs on the top and bottom curved surfaces of the blade only. Refer to Appendix 7 for further information.

Figure 2
Schematic Diagram Of Laminator

CONTENTS 3.5 Lamination conditions for joining sheets of dissimilar grades

Step 1 Determine the lamination conditions from the specific table in the Appendices for each grade; i.e., temperature, speed.

Step 2 Set the blade temperature to the 'Set Temp' of the grade which requires the higher temperature.

Step 3 Set the roller speeds to that of the grade which requires the slowest speed. (Also limit the rate of sheet throughput to that of this grade)

Step 4 Switch photo-eye OFF if conditions for either grade specify this.

Notes Due to grades exhibiting different characteristics during lamination then the normal rules for adjusting the 'Roller Balance' for thick to thin laminations may not apply.

Materials of the same base polymer but of different densities behave similarly. If they are at opposite ends of the density range then the speed of the roller in contact with the lower density component must be decreased.

As a general guideline the relative roller speed of a higher density or a more rigid grade must be faster than that of a lower density or softer more compressible grade.

CONTENTS 3.6 Failure Modes

When the isolator is first turned on the fault light will flash every 10 seconds,
Depress the control on button and the light will go off.

There are three main faults that can occur on the machine and are as follows.

Fault	Indication	Possible Causes For Failure	Comments	Actions
1.Upper or Lower roller drive Failure.	Fault light flashes every 10 seconds. Faulty roller will stop running.	• Inverter fault (check manual for trip codes) • Roller over-temperature • Circuit breaker tripped	Heating disabled automatically.	Reset by depressing stop then start button roller will start if the fault light is off.
2. Heating Blade Over-temperature.	Fault light permanently on. Blade temperature starts to fall.	• Trip amp faulty • Thermocouple failure • Blade temp above 600°C	Heating disabled automatically.	Reset by depressing start button, blade temperature will start to increase if the fault light is off.
3. Heating blade element failure.	Fault light flashes every 5 seconds. Possible fall in blade temperature.	• Heating element open circuit • Circuit breaker tripped • Fuse blown	Machine will still run as normal but blade temperature may be slow to achieve set point.	Test heating element for resistance approx. 29 ohms each (15 ohms per pair), current approx. 7.5 amps each (15 amps per pair). Replace element if faulty or fuse if blown.

If the fault cannot be identified or reset assistance maybe required from an engineer.

CONTENTSPART 4 HEALTH AND SAFETY

Any machine can be dangerous if improperly used.

Safe working practice is the responsibility of the user.

Note that this machine contains drive rollers and a hot blade that must not be touched.

1 This machine must be properly and safely installed on a firm and level base.

2 Operators must be fully trained in the safe use of this machine.

3 This machine must only be used for the purpose it is intended.

4 This machine incorporates fixed guards which must not be removed.

5 All users must be fully aware of the location of all five Emergency Stop buttons. (Main control console, front edges of feed-in tunnel and back edges of take-off tunnel).

6 The machine must be electrically isolated before obtaining access to any part of the machine.

7 It is recommended that an Extraction Hood be fitted over the machine to duct away any fumes.

8 Under no circumstances should anybody reach inside the tunnel guard or attempt to access the machine from above or beneath.

9 In the event of the machine stopping during lamination and cannot be restarted normally, no attempt should be made to clear the obstruction until it is cooled. In the unlikely event of a fire, suitable fire extinguishers must readily available.

10 Operators must not wear loose clothing or items that may become trapped in the moving parts.

11 In addition to the above requirements local regulations on health, safety and welfare in the workplace must be followed.

Safety Handover Certificate, P&P Precision Designs Ltd, Mk7 Laminating Machine

1. The machine must be properly and safely installed on a firm and level base.
2. Operators must be fully trained in the safe use of the machine.
3. The machine must only be used for the purpose for which it is intended.
4. The machine incorporates fixed guards which must not be removed.
5. All users must be aware of the location of the five Emergency Stop buttons.
6. Electrically isolate from supply before obtaining access to any part of the machine.
7. Fitting of an Extraction Hood to the machine is recommended.
8. Under no circumstances should persons reach inside the tunnel guards or attempt to access the machine from above or beneath.
9. Should the machine fail during operation no attempt should be made to remove partly laminated work until the machine blade has cooled. In the unlikely event of a fire, suitable fire extinguishers must be readily available.
10. Loose clothing or items that may become trapped in moving parts must not be worn.
11. In addition to the above requirements local regulations on Health, Safety and Welfare in the workplace must be followed.

General Notes:
Any machine can be dangerous if improperly used.
Safe working practice is the responsibility of the user.
This machine contains pinch rollers and a hot blade which must not be touched.

CONTENTS APPENDIX 1

TABLE 1.1 : Lamination Conditions for LD and MP based products

For laminated thickness greater than 20mm.

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature °C	Nominal Roller Speed (*) m/min	Nominal Roller Speed (*) ft/min	Critical Blade Temperature °C	Roll Pause ON/OFF
LD15	380	360	8.4	27.6	350	ON
LD18	380	360	8.4	27.6	350	ON
LD24	380	360	8.4	27.6	350	ON
LD24 LC	380	370	8.4	27.6	350	ON
LD29	390	375	8.4	27.6	360	ON
LD33	390	375	8.4	27.6	360	ON
LD33 LC	400	380	8.4	27.6	360	ON
LD45	400	380	8.4	27.6	370	ON
LD60	430	410	8.4	27.6	390	ON
LD70	440	420	8.4	27.6	400	ON
MP15	360	340	8.4	27.6	330	ON
MP24	360	340	8.4	27.6	330	ON
MP33	370	360	8.4	27.6	350	ON
MP45	380	360	8.4	27.6	350	ON

Adjust roller speeds as necessary, according to method described in 3.3.

CONTENTS APPENDIX 2

TABLE 2.1 : Lamination Conditions for EV & VA based products

For laminated thickness greater than 20mm.

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature °C	Nominal Roller Speed (*) m/min	Nominal Roller Speed (*) ft/min	Critical Blade Temperature °C	Roll Pause ON/OFF
VA25	390	370	8.4	27.6	350	ON
VA35	400	380	8.4	27.6	370	ON
VA65	440	430	8.4	27.6	420	ON
VA80	540	520	8.4	27.6	510	ON
EV30	410	390	8.4	27.6	380	ON
EV50	440	420	8.4	27.6	390	ON
EM26	300	270	8.4	27.6	250	OFF
EM45	300	270	8.4	27.6	250	OFF

Adjust roller speeds as necessary, according to method described in 3.3.

CONTENTS APPENDIX 3

TABLE 3.1 : Lamination Conditions for HD and HL based products

For laminated thickness greater than 20mm.

A smaller roller pressure should be used for very stiff materials, the top roller gap ‘B’ is best set to 1.5 mm less than the sheet thickness.

Top Gap Setting = Tmin - (Bottom Gap setting + 1.5 mm).

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature °C	Nominal Roller Speed (*) m/min	Nominal Roller Speed (*) ft/min	Critical Blade Temperature °C	Roll Pause ON/OFF
HD30	440	420	8.4	27.6	390	ON
HD60	400	380	4.2	13.8	360	OFF
HD80	430	420	4.2	13.8	380	OFF
HD115(1)	500	480	4.2	13.8	470	OFF
HL34	420	390	8.4	27.6	375	ON
HL47	440	430	8.4	27.6	400	ON
HL79	475	470	4.2	13.8	425	OFF

Adjust roller speeds as necessary, according to method described in 3.3.

(1) These conditions will not give a lamination joint stronger than the foam, but will enable thicker sections to be made when the strength of the join is not critical. 

CONTENTS APPENDIX 4

TABLE 3.1 : Lamination Conditions for PPA based products

For laminated thickness greater than 20mm

A smaller roller pressure should be used for very stiff materials, the top roller gap ‘B’ is best set to 1.5 mm less than the sheet thickness.

Top Gap Setting = Tmin - (Bottom Gap setting + 1.5 mm)

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature ° C	Nominal Roller Speed (*) m/min	Nominal Roller Speed (*) ft/min	Critical Blade Temperature ° C	Roll Pause ON/OFF
PPA30	330	325	8.4	27.6	300	ON
PPA35	330	325	8.4	27.6	300	ON

Adjust roller speeds as necessary, according to method described in 3.3.

CONTENTS APPENDIX 5

Table 4.1 : Lamination Conditions for Static Dissipative and Conductive Foams

For laminated thickness greater than 20mm

During lamination of the conductive foams, the temperature of the blade drops significantly.

The blade temperature stated is an optimum value; increasing the temperature results in poorer adhesion.

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature °C	Nominal Roller Speed (*) m/min(2)	Nominal Roller Speed (*) ft/min (2)	Critical Blade Temperature °C	Roll Pause ON/OFF
LD30SD	400	390	8.4	27.6	380	ON
LD32CN	450	440	8.4	27.6	430	ON
LD50CN	440	420	8.4	27.6	400	ON
EV45CN	480	460	8.4	27.6	430	ON
EV70CN	510	500	8.4	27.6	490	ON
EV120CN(1)	540	530	8.4	27.6	510	ON

(1) These conditions will not give a lamination joint stronger than the foam, but will enable thicker sections to be made when the strength of the join is not critical.

(2) The roller speed should not be reduced. The conductive foams conduct heat. As the roller speed is reduced, heat is conducted away from the heated surface resulting in a poor bond.

CONTENTS APPENDIX 6

TABLE 4.1 : Lamination Conditions for individual sheet thicknesses less than 10mm.

Roll feed must be used to overcome feed-in difficulties with single sheets thereby minimising wastage.

Product Grade	Optimum Operating Temperature (SET TEMP) °C	Lower Limit Starting Temperature °C	Nominal Roller Speed (*) m/min	Nominal Roller Speed (*) ft/min	Critical Blade Temperature °C	Roll Pause ON/OFF
VA25	430	410	4.2	13.8	400	OFF
VA35	460	440	4.2	13.8	430	OFF
EV50	490	470	4.2	13.8	450	OFF
LD24	420	400	4.2	13.8	390	OFF
LD29	450	430	4.2	13.8	430	OFF
LD33	450	430	4.2	13.8	430	OFF
LD45	470	450	4.2	13.8	440	OFF
LD60	490	470	4.2	13.8	460	OFF

Adjust roller speeds as necessary, according to method described in 3.3.

CONTENTS APPENDIX 7

The amount of compression exerted on two sheets between the top and bottom drive rollers is defined by the total thickness of the laminated block less the Total Gap.

Therefore the thickness of the sheets to be laminated must be measured across the total width in order to control the amount of force exerted on the weld line. This compression also affects the amount of contact the surfaces of the sheets have on the heated blade, ie. how much material is melted. Contact occurs on the top and bottom curved surfaces as shown below:

Ideal Contact
A thin even layer of material melts which result in a consistent good quality weld.

Excessive Contact

i) Due to excessive pressure

Material sticking to the blade causes a build-up forming solid lumps followed by small gaps where material has been rubbed away. This uneven melt-back effect occurs through using non-optimal settings. (similar melt-back occurs with excessive blade temperatures where material tends to stick to the blade.

ii) Due to blade not in correct position

With blade too high the lower sheet will not make contact with the blade and the upper sheet will be forced around the blade causing melt-back as in i).

CONTENTS APPENDIX 8

GLOSSARY OF TERMS

Optimum Operating Temperature	Temperature at which to set the Temperature Control Unit for specific grades is referred to as 'Set Temperature'. This temperature has been found to give the best quality weld for that grade.
Lower Limit Starting Temperature	If indicated temperature is lower than this before sheets are fed in then in an unsuccessful weld will result. Do not start lamination until display is equal to or higher than this.
Critical Blade Temperature	If displayed temperature drops below this during lamination then the quality of the weld will be affected. i.e. Probable unstuck patches.
Nominal Roller Speed	Guide to where to set the Roller Speeds, which need adjusting as necessary according to method described in Part 3.3.
Upper Roller Speed (URS)	As indicated (see Figure 1).
Lower Roller Speed (LRS)	As indicated (see Figure 1).
Roller Speed	Thumb-wheel adjusts speed of both URS and LRS (see Figure 1)
Roller Balance	Relative speed between URS and LRS.
Roll Paus e	Photo-sensitive cell operated by a roll pause switch on the Control Console (see Fig. 1).
Bottom Gap	Gap between center of heater blade and the top surface of the bottom drive roller. Gap A in Fig. 1.'Bottom Gap Setting' = Max. Thick. of Bottom Component.
Top Gap	Distance from centre of blade to bottom surface of top drive roller. Gap B in Fig.1'Top Gap Setting' = 'Tmin' - (Bottom Gap Setting + 3mm).

CONTENTSTRADEMARKS
PLASTAZOTE, EVAZOTE and SUPAZOTE are registered trademarks of Zotefoams plc.

 

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