LET'S STICK TOGETHER Colin Watson, technical business development managerfor Loctite UK, shows how the use of today's adhesives and sealants makes sound business sense. Photograph 1 (above), and below, Photograph 2 O ne of the major reasons why industry has been slow to adopt the use of adhesives and sealants in production is the image of how messy liquids are to use on the production line. That image is no longer true. In the UK, Loctite long ago realised the importance to its customers, and its future business, of supplying a complete service. This means supplying all the input necessary to turn a design idea into a production reality. The inputs are: 1) Advice from fully trained sales engineers in evaluating the viability, in technical and commer- cial terms, of a design concept where adhesives/ sealants are considered as alternatives to age-old joining and sealing techniques. 2) In-depth technical advice from the Loctite technical support group on both product perform- ance and production systems. 3) The design and supply of operator-paced or fully automatic equipment to ensure smooth introduc- tion of final design into production. Loctite UK also realise the growing importance of 'team work 1 with the customer. The customers' own team consisting of the all-important partnership of the design and production departments. What the designer may select is not always the most convenient to assemble on production - the production engineer plays a vital role during the value engineering stages. How has this 'systems concept' from Loctite helped British industry to maintain competitiveness in the market place? A number of examples will help to illustrate the point. Let us first of all look at the joining of plastic and rubber. Plastics Most engineering plastics may be bonded by one type of adhesive or another. Some, such as polyolefins, need careful surface preparation to achieve good strength however. A major advantage of using Loctite prism cyanoacrylate (Superglues) adhesives to join plastic components is the speed of cure (seconds to handling strength) and the fact that they can be automatically and accurately dispensed to components. Case History 1 Photograph 1 shows an operator applying cyanoacrylate using a simple dispenser to the groove of a PVC moulding to bond a flexible plastic cover in position. The assembly is an external light switch. Alternative methods would be mechanical fastening plus a sealant or the use of a solvent-based adhesive. However, the cyanoacrylate is a solvent-free, single component adhesive that can be simply dispensed, only takes seconds to cure and it seals as well as bonds - the ideal choice for production. Case History 2 Photograph 2 shows a cyanoacrylate being used to bond a number of loudspeaker components together - suspension (impregnated linen) to cone and chassis, and also rubber surround to composite cone. The components are picked up by the operator and placed onto the turntable. The turntable will then revolve and come to rest beneath the adhesive dispenser. The component part itself is then revolved below the static dispensing head. Once the adhesive is applied, the turntable moves to the next station where the other component is placed in position and the bond takes place. Previously, adhesives of a solvent-based type were used, which gave a much longer process time. Rubber Even the most sophisticated rubber such as EPDM can be bonded using cyanoacrylates, some of which are tailor-made for specific rubbers such as EPDM. An alternative method of joining is vulcanising. Today, thousands of metres of rubber are being simply bonded using cyanoacrylates. Typical applications are the bonding of mitred corners of rubber sealing strips for sealing car doors and household double glazing units and trim strip for cars to plastic mouldings. The adhesive can be automatically applied as the two sections are brought together, either as an extrusion type process, or as two faces of a mitre brought together. MANUFACTURING ENGINEER 38 MAY 1989
Transcript
LET'S STICK TOGETHER
Colin Watson, technicalbusiness development
manager for Loctite UK,
shows how the use of today'sadhesives and sealants makes
sound business sense.
Photograph 1 (above),and below, Photograph 2
One of the major reasons why industryhas been slow to adopt the use ofadhesives and sealants in productionis the image of how messy liquids are
to use on the production line. That image is nolonger true.
In the UK, Loctite long ago realised theimportance to its customers, and its future business,of supplying a complete service. This meanssupplying all the input necessary to turn a designidea into a production reality.The inputs are:1) Advice from fully trained sales engineers in
evaluating the viability, in technical and commer-cial terms, of a design concept where adhesives/sealants are considered as alternatives to age-oldjoining and sealing techniques.
2) In-depth technical advice from the Loctitetechnical support group on both product perform-ance and production systems.
3) The design and supply of operator-paced or fullyautomatic equipment to ensure smooth introduc-tion of final design into production.Loctite UK also realise the growing importance of
'team work1 with the customer. The customers' ownteam consisting of the all-important partnership of thedesign and production departments. What thedesigner may select is not always the mostconvenient to assemble on production - theproduction engineer plays a vital role during the valueengineering stages.
How has this 'systems concept' from Loctitehelped British industry to maintain competitivenessin the market place? A number of examples will helpto illustrate the point.
Let us first of all look at the joining of plastic andrubber.
PlasticsMost engineering plastics may be bonded by one
type of adhesive or another. Some, such aspolyolefins, need careful surface preparation toachieve good strength however. A major advantage ofusing Loctite prism cyanoacrylate (Superglues)adhesives to join plastic components is the speed ofcure (seconds to handling strength) and the fact thatthey can be automatically and accurately dispensedto components.
Case History 1Photograph 1 shows an operator applying
cyanoacrylate using a simple dispenser to the grooveof a PVC moulding to bond a flexible plastic cover inposition. The assembly is an external light switch.Alternative methods would be mechanical fasteningplus a sealant or the use of a solvent-based adhesive.However, the cyanoacrylate is a solvent-free, singlecomponent adhesive that can be simply dispensed,only takes seconds to cure and it seals as well asbonds - the ideal choice for production.
Case History 2Photograph 2 shows a cyanoacrylate being used
to bond a number of loudspeaker componentstogether - suspension (impregnated linen) to coneand chassis, and also rubber surround to compositecone. The components are picked up by the operatorand placed onto the turntable. The turntable will thenrevolve and come to rest beneath the adhesivedispenser. The component part itself is then revolvedbelow the static dispensing head. Once the adhesiveis applied, the turntable moves to the next stationwhere the other component is placed in position andthe bond takes place.
Previously, adhesives of a solvent-based typewere used, which gave a much longer process time.
RubberEven the most sophisticated rubber such as
EPDM can be bonded using cyanoacrylates, some ofwhich are tailor-made for specific rubbers such asEPDM. An alternative method of joining isvulcanising. Today, thousands of metres of rubberare being simply bonded using cyanoacrylates.Typical applications are the bonding of mitredcorners of rubber sealing strips for sealing car doorsand household double glazing units and trim strip forcars to plastic mouldings.
The adhesive can be automatically applied as thetwo sections are brought together, either as anextrusion type process, or as two faces of a mitrebrought together.
MANUFACTURING ENGINEER 38 MAY 1989
Photograph 3
Photograph 4
Cylindrical ComponentsProduction engineers are constantly looking at
ways of reducing machining and assembly costs -some of the best 'design' ideas come from productionengineers!
In cylindrical assemblies such as gears/pulleys toshafts, bearings into housings, and bushes/sleeves/tubes into castings, the components have to bemachined to close tolerances, keyways have to becut, holes drilled to take extra component parts suchas pins, keys, circlips and screws. The two primarycomponents, plus the extras - keys etc, have to beassembled. During some assembly operations ofcylindrical components, the outer has to bepre-heated, or the inner frozen or a press used.
If it were possible to reduce or eliminate thenumber of extras, reduce or eliminate the machiningoperation to take keys, pins, circlips, etc and to makethe final assembly easier, the production engineerwould be satisfied, and the cost reduced.
It is a well known fact between maximum fit usingthe smoothest surfaces, there still remains a 60% gapbetween cylindrical components, see Photo 3.Anaerobic adhesives (they remain liquid in air andonly harden between components when assembled)are used in many varied cylindrical assemblies toaugment mechanical fit strength and reducemachining and assembly costs.
Case History 3Cylinder liners and carburettor tubes are
assembled to castings using anaerobics which bondand seal at the same time.
Photograph 4 shows a workstation in the PerkinsEngine factory where they manufacture the world-beating Prima diesel engine. Originally, in the autoindustry, cylinder liners were lipped - the blockrecessed. The liners were heavy interference fit in theblock. Because of distortion, the bore wassubsequently honed after assembly.
The modern technique is to produce a liplesspre-machined liner. The block is positioned beneaththe Loctite equipment. The application headsautomatically advance into the three bores at thesame time and apply a metered quantity of anaerobicover the required bore length. The liner is lightlypressed (fit reduced) into the block.Material cost of liner is reduced - no lip.Press fits reduced - smaller press could be used.Post-honing operation eliminated - cost reduction.Adhesive automatically applied.
Case History 4Since 1975, Delco Products has used an
anaerobic on the commutator to the shaft of anarmature. The armature is fed to a stop beneath theadhesive application head. The head advances andapplies a precise quantity of adhesive to the shaft.The commutator is then automatically fed, from abowl feeder, onto the shaft. The armature assemblythen moves to the next workstation of the windscreenmotor assembly line.Photo 5 (over page) shows the adhesive application and
MANUFACTURING ENGINEER 39 MAY 1989
commutator/armature assembly station. The brass
bush was eliminated - main reason lor bonding to
eliminate costs. Adhesive dispensing and assembly
is automatic.
GasketingConventional gaskets are pre-tormed and made
from a multitude of materials such as paper, cork,
rubber, etc. Gaskets should effect a continuous seal
between components - but they do not in many
instances. When they fail, that is leak, as they
frequently do, the result is loss of performance, but
more important - loss of image for end-user industry.
Why do conventional gaskets leak? Research
shows that the two main reasons that this occurs
using pre-formed gaskets are:
1) Loosening of clamp bolts due to compression of
gaskets in service and
2) Micro movement of faces causing fretting of the
gasket, leading to leaks.
To overcome these problems, 'formed in place1
gaskets have been used: they can be automatically
applied - no manual picking and placing is required
as in the case of conventional gaskets.
Anaerobic gasketing product is applied to one
surface where it will remain liquid until the two faces
are mated. The two components are assembled -
metal touching metal. The anaerobic then cures. As
well as sealing, it also increases structural rigidity of
the joint by providing a solid plastic that keys into the
surface imperfections of the two mating faces.
Because there is metal to metal contact, there is
no compression set in service leading to leaks, and
because it prevents movement between faces there is
no fretting, hence no leaking. The two major
problems with the use of conventional gaskets
therefore have been overcome.
Case History 5Years ago, the engineers of Terex Equipment Ltd
decided that they had to change gasketing methods
to prevent leaks. This resulted because conventional
gaskets were used. On some occasions, two men
were taking a shift to rectify leaking axles on massive
scrapers and dump trucks. This, the engineers knew,
was costly and avoidable and also if experienced in
the field would damage the image of the company.
The leaks were caused by tiny flexing movements
between the differential flange and axle casing when
the earth moving machines were given their
pre-despatch workout. The impact, vibration and
torsion generated as the components were subjected
to tremendous torque load proved too much for a
conventional gasket.
At one stage there seemed to be no easy answer.
Different gaskets were tried, different sealants were
applied, all to no avail. It was only when the company
turned to using an anaerobic gasketing product, they
discovered they could get increased rigidity at the
