Insert Technology For Plastics, Composites And Metal Alloys

The Tappex Multisert range of inserts for plastics has been developed to be a multi-purpose insert for various environments and application criteria. It includes four primary designs – Unheaded, Single Thickness Headed (at standard & reduced diameters), Double Thickness Head (at standard & reduced diameters) and Microbarb.

Unheaded - Product Features

The most significant feature of the Mulitisert is its Barb Form that makes the insert suitable for different installation methods. The designer can therefore increase pull-out performance using the same insert by changing from press-fitting cold to heat or ultrasonic insertion.

External Barb form gives good flow characteristics and high pull-out performance.

Plain top ring gives a good bearing surface for mating components and traps any molten plastic forced upwards during insertion providing a clean flush fit (correct hole size must be used).

Free running internal thread – the insert is set in the plastic independently from the expansion action of the mating screw. This prevents rotation or screw breakage during assembly.

Plain location spigot and pilot barb ensures that the insert locates squarely in the drilled or moulded hole prior to assembly.

Unheaded - Design Aids

• It should be specified for press-in applications in flexible thermoplastics, installation can be at the moulding machine to make use of operator time.
• It can be installed into most thermoplastics by heat or ultrasonics to give higher resistance to pull out loads.
• It should be specified for small or medium volume usage where there are a limited number of inserts per moulding.
• It should be specified for high volume, single insert applications in small mouldings.
• It is available in two standard lengths to maximise choice, the barb form design makes it possible to manufacture non-standard lengths if customer applications cannot accommodate standard lengths.
• To obtain maximum performance from the insert, the hole diameter in the mating part should be clearance for the screw thread. The mating part will then seat on the top face of the insert significantly reducing the possibility of rotation or jack-out during clamping.
• It can be used as a pull-through insert where access to the rear of the plastic component is possible. This is only recommended where a stepped hole design is used as illustrated.

Single Thickness Head - Product Features

The Single Thickness Headed version of the Multisert incorporates all the standard features of the unheaded version but provides the designer and production engineer with three standard options to match product availability to common assembly situations not suitable to an unheaded insert.

Large Diameter Head prevents jack out in applications where elongated slots or larger than standard clearance holes are necessary in the mating component. It has a larger bearing surface that is required in high torque applications. Two standard head diameters are available to provide for both performance and cost priorities.

Single Thickness Head - Design Aids

• It should be specified in applications where increased resistance to rotation is required. The insert can be installed by press-in or heat insertion. It is not recommended for ultrasonic insertion without consultation.
• It also provides an excellent conductive surface for electrical contacts, ring connectors or eyelets.

Double Thickness Head - Product Features

The Double Thickness Headed version of the Multisert incorporates all the standard features of the unheaded insert but provides the designer and production engineer with a higher performance press-in insert for applications with through holes where access to the back of the component is possible.

Double Thickness Head can be used as a stand off or heat sink; it is possible to increase the head thickness still further, subject to quantities required.

Large Diameter Head for use in very soft materials where a smaller head diameter would pull through due to the flexing of the plastic.

Double Thickness Head - Design Aids

• The reduced head diameter short length versions (part Nos.072 & 073) should normally be specified in compact plastic materials as they have the lowest unit cost but in most rigid materials give very high performance. Use of a stepped hole similar to that when using unheaded inserts in pull-through applications will, where space allows, increase performance.
• The regular length insert body (part No.005) should only be specified where there is a high push-out force prior to engagement of the screw.
• Normally press-fit insertion is acceptable except when the assembly is subject to heat, vibration, drop tests or the plastic is stress prone and unfilled.

Microbarb Product features

The Microbarb version of the Multisert incorporates all the standard features of the other insert but provides the designer and production engineer with an insert suitable for applications in thin section materials.

Larger head and barb diameter to provide increased bearing surfaces, for larger thread sizes the back of the head is chamfered to reduce the apparent projection.

Maximum thread engagement is achieved due to the reduced thread length only being countersunk at the one end.

Microbarb - Design Aids

• Ideal for use in vacuum formed, rotational moulded and fabricated components.
• It is designed for use in thermoplastic and thermosetting plastic materials with a tensile strength less than 100Mpa and some degree of resilience.
• The under-head insert length should be slightly less than the material section thickness, to ensure that, after material compression, the insert is rigidly clamped. Insert creep is then eliminated by both contact of the mating part with the front face of the insert, and the underside of the insert head with the parent material.

Installation details

The Tappex Multiserts can be press fitted cold, hot or with Ultrasonics, depending on the material it is being installed into.