03.05.05 - SCT End Cap Thermal Enclosures
Work Instructions for assembly of Rear Thermal Endplate
Introduction
As a result of a series of prototyping trials carried out at RAL on a variety of test samples, these
instructions attempt to provide what is considered to be the least complex and most reliable
method for the construction of the rear thermal enclosure (RTE) thermal endplate. These should
be considered as recommendations only, based on our experiences and should be understood to
be guidelines rather than strict explicit instructions. No attempt has been made during the
prototyping phases at RAL to produce a complete RTE endplate, but the construction is very
similar to many of the other components comprising the thermal enclosure, using almost
identical methods. This should allow a more flexible approach to be taken that best suits the
preferences of those involved in producing these components. It should therefore be left to the
discretion of the team to decide on the best methods of construction.
Before starting manufacture of the endplates, it is strongly recommended to carry out a few
small test trials so as to get some confidence in the procedures. It may also be found during
these trials that alternative techniques may provide a more successful end result, which may be
dependant on the available facilities and tooling at CERN.
Materials and Tooling

AIREX® foam sheet 12mm thickness – spec R82.60 (sheet sizes 2.8m x 1.35m)

KAPTON® film 0.025mm thickness – aluminised on one surface only (supplier:
Sheldahl – description: VDM;1.0MIL,*SH*4’x115’)

Epoxy adhesive – Araldite 2011 (AW106/HV953U, 100/80pbw)

Template for cutting the foam (refer to detail drawings: TD-1012-445, to be supplied)

Precision weighing scales for measuring resin and hardener proportions.

Roller, soft bristle paint brush and/or palette knife/scraper

Neoprene rubber gloves

Cleaning agents: ethanol, isopropyl alcohol.

PFSR sealant remover (Allchem) for wiping off excess uncured epoxy.

Rolls of cotton cleaning tissue

Flat working surface tables of sufficient length and width to fully support the panels.

Scalpel blades and scalpel holder

Scissors

G-clamps or carpenters panel clamps

Linoleum or linoleum like plastic sheets, sufficient to cover working surface

Long steel rule or builder’s ‘Straight Edge’

Engineer’s square

Drill bits or cork borers up to 13mm

Hand-held vacuum cleaner
Preparation
All supplied materials must be stored in a clean, dry environment and should be left in their
containers until assembly is about to commence. The Airex® foam is particularly sensitive to
moisture penetration and this will require priority care during storage.
The assembly environment must be clean and dry; ideally with climate control to ensure the
humidity levels remain relatively low. The working environment temperature will need to be in
the region of 20º C to ensure that the epoxy cure times are not excessive. However it would be
an advantage to be able to increase the room temperature (to approximately 25º C) to reduce the
curing time of the epoxy once the Kapton films have been fixed and clamped
A template will need to be manufactured according to the dimensions on drawing TD-1012-445
(2 sheets). This is envisaged to be a flat aluminium alloy plate with a thickness of about 3mm.
The template will be used to cut the foam annulus to the correct inner and outer diameters and
for cutting the holes. Material choices and thicknesses will be left to the discretion of the
production team.
FIG. 1
The scalpel must be used with some care to ensure that the edge cut remains perpendicular to
the plane of the template surface. This can quite easily be achieved by mounting the blade on a
machined aluminium block and performing the cutting operation by maintaining face-to-face
contact between the base of the block and the surface of the template, as in FIG. 1.
All working surfaces must be kept as clean as possible and rubber gloves should always be
worn when handling foam sheets and films. Generally, gloves should be changed at regular
intervals throughout the components’ construction, especially during the bonding phases. The
working surfaces must be flat and have a smooth, non-porous finish. A covering of a few
millimetres thickness of a material like linoleum would be most suitable for this.
It is recommended that the roll of aluminised Kapton be transferred to a spindle supported at
each end by suitable stands at approximately the same level of the working surface. This makes
dispensing of the film much easier and contact with the material is therefore minimised. It also
ensures the material does not come into physical contact with any objects that may transfer
contaminants. The Kapton film when dispensed from the roll is in a satisfactorily clean
condition and will not require further treatment. Sometimes it is recommended to prepare the
Kapton surfaces using a solution of NaOH to remove any traces of grease and grime, but
experiences at RAL suggest that this is not necessary if it is dispensed straight from the roll.
However it is essential that there should be minimal handling of the Kapton side of the film (i.e.
the non-aluminised side) since this is the side that will be bonded to the foam. During any
handling procedure the film should be held at the extreme edges so that the areas that are
actually glued to the foam are never touched; the handled areas will most likely be the areas to
be trimmed off and discarded. Also, ensure that when the Kapton is not being dispensed it is
kept covered at all other times to keep it protected from accidental touching etc.
Assembly Procedure
1. Place the linoleum sheet over the working surface. Remove a single sheet of the
12mm Airex® foam and place on top of the linoleum. Position the engineer’s square
and the rule on the foam where the material is to be cut (allow sufficient excess for
the 1140.3mm outer diameter of the annulus; cutting a width of about 1200mm
should be adequate).
Ensuring that sufficient pressure is applied to the rule to stop it slipping, use a
scalpel to cut the foam, running the blade along the edge of the rule; this is best
carried out with several swipes, progressively cutting deeper and deeper through
the foam. If required, for ease of handling, the longer edge (1350mm) of the sheet
could be trimmed back to reduce it to a square sheet 1200mm x 1200mm.
Using the hand held vacuum cleaner, remove any traces of Airex dust that will have
been produced during the cutting. Go over both sides of the sheet with the vacuum
cleaner to remove any other traces of dust and debris. Remember to ensure that the
working surface is also clear of any dust and debris.
2. Place the foam back on the linoleum working surface and position the template
centrally over the foam sheet. These items must be situated on the table conveniently
close to the working surface edges so that clamps can be used to apply a sufficient
force to prevent the template from slipping
Using a scalpel, carefully cut the foam around both inner and outer edges of the
template ensuring that the cut is perpendicular to the plane of the template (perhaps
using a modified holder as shown in FIG. 1, or some other variation on it).
Remove the clamps and take off the template. Again, remove any dust that might
have accumulated from both the foam and working surface using the vacuum
cleaner.
3. The epoxy should be mixed following the manufacturer’s or supplier’s
recommendations for use. The quantities should be accurately measured using
precision scales. It has been found that due to the transparency of the epoxy, it is
difficult to judge the coverage of the glue when applied to the foam. There are
colouring agents available that can be added to the epoxy so that the glue coverage
can be seen much more clearly. A suitable colouring agent additive is carbon black.
It is recommended that 5% to 10% by weight can be added without any need to
adjust the mix ratio of resin to hardener.
Tests so far carried out at RAL on bonding Kapton® to the Airex® foam were
always done by applying the epoxy to the foam and not to the Kapton®. Our
experiences indicate an average glue layer thickness on the foam of as much as
0.45mm can result if the epoxy is applied with a palette knife or scraper. This tended
to deliver a larger quantity of adhesive to the foam compared to the paint-brush or
roller. The palette knife is by far the quickest method of applying the epoxy, but it is
easy to apply over-copious amounts.
During the tests carried out at RAL, it was the roller that ensured a minimum
thickness of glue was applied. This way, one could achieve a glue layer thickness as
low as 0.1mm, but it took a lot more time and effort to apply than using the scraper
blade. Also it was very difficult to judge if the coverage was uniform, since the glue
actually ends up (on a microscopic level) on the narrow, higher parts of the foam
material surrounding the exposed foam cavities, and this was very difficult to see,
even with the addition of a dyeing agent. From the physics point of view it would be
very desirable to limit as much as possible any excess glue and it is felt that this
should be pursued as the preferred method of application.
Tests are continuing at RAL to get a better and quantitative understanding of the
peel strength variations for each type of glue application method. It should also be
mentioned that the application of glue using a soft bristled brush also gave quite
satisfactory results, again a lot of care was required and the process took a long time
to carry out.
If the preferred or only suitable method of application turns out to be the scraper
blade, then some effort will be needed to carefully inspect the surfaces for excessive
build-up of glue and then removal of the excess. Regular cleaning of the blade after
each scraping pass has been found to be a satisfactory way of controlling the glue
thickness. Whilst it is important to try to limit the quantity of glue applied to the
foam to reduce the overall mass of glue contained within the foam’s outer cavities, it
is vital to ensure that there is sufficient coverage to obtain an optimum bond
between film and foam.
One should bear in mind that the epoxy will slowly start to cure and its viscosity
will gradually increase once the mix has been prepared. Therefore, it is important
that the epoxy is applied with minimum of delay. The viscosity of the mix can be
reduced if the component parts of the adhesive are kept at around 30º C prior to
mixing, and then applied quickly to the parts to be bonded. Also, the cure rate will
be reduced if the application to the foam is carried out at a lower room temperature
of about 18º C. Another means of extending its workability, is to transfer the epoxy
to a flat aluminium tray, so as to spread its volume over a larger surface area. This is
effective because the curing process is exothermic and a wide flat tray acts to
dissipate any heat generated within the glue, increasing the cure time.
A rough estimate of the amount of glue required to produce one thermal endplate,
based on 0.45mm thickness of epoxy on both front and rear surfaces, is approx. 800
grams. The quantities of epoxy applied should be carefully measured and recorded
during the assembly process and brought to the attention of the physicists involved
on the project (S. J. Haywood) for their ‘materials used’ records.
4. Two lengths of Kapton® film (one for each side of the sheet) should be cut from the
roll using either scissors or a scalpel. The sheets should be cut to a size sufficient to
cover all regions of the foam, mindful of the cleanliness observances discussed
earlier. Whatever method is chosen to apply the epoxy (depending on previous trials
that may have been performed), completely wet one surface of the Airex® foam
sheet with the glue, taking particular care to remove excess build-up on the inner
and outer edges of the sheet. A soft bristled brush is very effective in removing
excess glue, whilst maintaining an acceptable ‘wetness’ of the foam.
Carefully lay the aluminised Kapton® on top of the foam with the aluminised side
outermost. The Kapton® should be slightly tensioned by lightly tugging outwards at
the outer edges to remove any wrinkles. Closely inspect the surface of the Kapton®
film for any undulations, then apply firm stroking actions with a dry tissue to
eliminate any trapped air bubbles. These are often quite easily visible and when
spotted need to be coaxed toward the edges of the sheet to purge them, using the
same stroking action. It is important to take time and care to fully inspect the surface
for any blemishes. Another method that might also be effective in removing any
trapped bubbles (particularly those farthest from the edges of the foam) would be to
puncture them using a pin, then smoothing the film to drive out the trapped air
through the pin-holes formed.
Important note: Ensure that the stroking action does not cause the Kapton® film to
slide over the foam sheet by firmly holding it in place.
After careful inspection, clean the aluminised outer surfaces of the Kapton® film
with PFSR sealant remover and cotton tissue to remove any traces of epoxy that may
have been accidentally transferred to it by handling or seepage through any holes
created.
Carefully lift up the foam assembly from the working surface and place a sheet of
the ‘Armaflex’ (or equivalent) foam rubber sheet (of slightly larger dimensions to the
foam) and place on the working surface.
Invert the foam + Kapton® and place onto the foam rubber, aluminised side down
Perform exactly the same process as for the first side and after the second Kapton®
sheet has been positioned and satisfactorily purged of bubbles and wrinkles, place
another sheet of foam rubber over the top surface of the ‘Kaptonised’ foam.
APPLY PRESSURE
TEMPLATE
FOAM RUBBER
(ARMAFLEX)
KAPTON
+EPOXY
AIREX
FOAM RUBBER
(ARMAFLEX)
WORKING SURFACE
FIG. 2
Place the template over the top of the upper foam rubber sheet and apply a load to
the template. This could be a number of lead blocks or a set of clamps, but sufficient
force should be applied to be confident that an even and constant pressure is applied
over the whole of the assembly. The schematic in FIG. 2 indicates the final
appearance of the assembly whilst the epoxy is curing.
The assembly should be left undisturbed for as long as it takes to cure the epoxy. If
the room temperature can be increased this will advance the curing time. Leave the
tray of remaining epoxy nearby to judge when the epoxy has cured.
5. After the epoxy has cured, remove all the weights or clamps and take away the
template and foam rubber sheets. Inspect the surfaces to ensure the glue has
effectively bonded the Kapton® film to the foam.
Using a scalpel blade carefully cut away the residual Kapton® film from the inner
and outer edges. If a certain quantity of glue has seeped out at these regions and
accumulated at the edges, the glue may need to be carefully pared back to become
flush with the foam edges.
CORK BORER
APPLY PRESSURE
APPLY PRESSURE
TEMPLATE
KAPTON
+EPOXY
AIREX
WORKING SURFACE
LINOLEUM
FIG. 3
Alternatively the template could be replaced and carefully re-aligned over the
assembly. The inner and outer edges of the template can then be used to more
accurately guide the scalpel blade.
To cut the holes, the template will need to be re-positioned accurately over the
assembly, with the sheet of linoleum placed underneath, as shown in FIG. 3. The
cork-boring tool can then be used to cut the holes, using the holes in the template as
the guide (a photograph of one of these tools is shown in FIG. 4). It is simply a brass
tube with a sharpened end. It is a hand tool, but if the results of earlier tests aren’t
satisfactory, it would be possible to mount a similar type of tool in a bench drill, or
even attempt using a standard drill bit.
FIG. 4
The quality of the finish of some of the earlier tests carried out at RAL show that the
Kapton tends to tear at the rear surface when a cork-boring tool is used. It is
recommended that some pressure be applied close to the hole being cut; this tends to
reduce this effect. FIG. 5 shows the holes where the cutter is applied and FIG. 6
shows the back of the specimen.
FIG. 5
FIG. 6
When forming the holes, always ensure that the cutting tool or drill is carried out
from the same side. This way, the small end flanges on the inserts (item 1 in FIG. 7)
can cover over any torn or untidy hole edges.
FIG. 7
The exposed regions of foam on both inner and outer edges of the assembly need to
be covered with close-out strips as shown in FIG. 7. The same Kapton® film is used
as well as the same bonding methods as used for the Kapton® to the foam plane
surfaces. The strips will initially be cut to a width significantly wider than the edges.
After curing of the epoxy, the excess film can be removed by paring it against and
flush with each of the front and rear planes.
Alternatively, the film can be snipped at numerous intervals around the
circumference and the remaining tabs of film folded over and bonded to each of the
front and rear planes. This may offer some protection against accidental damage and
subsequent peeling of the film from the foam.