Design & Manufacture of Low Pressure Moulding Mould Sets & Tooling

Mould sets and tooling for Low Pressure Overmoulding

Mould sets for low pressure overmoulding are normally manufactured from aluminium and precision-machined to form the features of the desired part. Aluminium is well suited for mould-set manufacturing due to its excellent heat transfer properties (i.e. short cycle times) and is economical from a cost and time perspective.

Aluminium mould-sets are relatively soft and care must be taken not to damage the cavity surface. If the component to be over-moulded has steel or hard glass filled components, it is recommended to have steel inserts in the mould cavity to reduce any wear on key tool components. This is generally required when moulding connectors. Mould-sets can also be manufactured from tool steel such as P-20. It may be required to cross drill steel mould-sets to ensure sufficient cavity cooling.

When using non-abrasive Polyamide moulding materials such as Technomelt from Henkel, combined with the low injection pressure, there is negligible wear on the mould-set resulting in a long and cost-effective operational life manufacturing tens to hundreds of thousands of parts.

Multi cavity moulds are normally used for all production moulding. With 1 ton of clamping force and packing pressures rarely exceeding 10 bar (145 psig) this will normally allow for cavity cross sectional area of at least 80 square cm (12 square inches).

Ejector systems

Most production mould sets utilise ejector systems. Guide-pins and ejector-pins are sandwiched in between a base plate and a retainer plate. This sandwiched arrangement slides on shoulder bolts with return springs. Typical ejector stroke ranges from 3 to 10 mm depending on the application.

Release agent

Release agent may sometimes be required for mould sets. A new mould set may require application of this release agent several times daily. Considerable research has gone into selecting the optimum release agent for this technology. After extensive testing of a wide range of mould release agents, here at Overmould we have concluded that one particular product demonstrates superior performance: Mono-Coat E-255 from Chem-Trend Incorporated. We do not recommend the use of Silicone based release agents when over-moulding electronic components. Silicone can migrate over time resulting in partial electrical insulation degradation and non-functional components.

Low pressure moulding machines from Overmould are specifically designed to accommodate various mould tool sizes, and a typical tool change only takes a matter of minutes.

The HB500 Docking mould set offers cost effective interchangeable tooling, so only one dock is required and you can have limitless numbers of inserts for multiple applications.

Any mould-set from us will be documented including a pre-determined moulding profile so that all moulding parameters can be entered directly. Some minor fine-tuning may be required as a result of different ambient conditions.

Delivery time for mould-sets is typically 15 – 20 working days.

Overmould provides manufacturers across a host of industry sectors with a low pressure moulding service complete with machine, aluminium mould tools and Henkel’s Technomelt.

Overmoulding for Strain Relief

Strain reliefA strain relief is a standard feature in cables for relieving the stress and tensions between the rigid connector or device and the flexible cable. The point at which a cable exits a connector body or other component can be a critical failure point because of repeated flexing therefore a well-designed strain relief is vital for the mechanical and electrical integrity, optimum lifespan and general performance of all types of cables.

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Low Pressure Overmoulding versus Potting or Encapsulation

Overmoulding protects electronic products from the environmentIn electronics, encapsulation or potting is the process of pouring liquid resin over electrical and electronic components, circuit boards and completed electronic assemblies for electrical insulation and to protect the product against thermal shock, vibration, moisture and corrosive substances.

The process typically consists of 7 -8 steps including a curing period. Depending on the product, higher temperatures can be used to reduce cure times; but this increases the risk of thermal damage. Potting compounds cure exothermically, and these cure reactions can generate heat to damage electronic components. It’s not uncommon, for example, for potting compounds to heat up by 200°C or higher, as they cure.

Aside from this risk of damage to components, potting can be a messy process that can have many other problems associated with it, not least of which is wastage!

A fast, cleaner and lower cost alternative to encapsulation or potting  is Low Pressure Overmoulding.

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Low Pressure Overmoulding Materials & Process Overview – Henkel Technomelt

MacromeltUnprotected electronics and PCBs are vulnerable to moisture, dust vibration and damage. Overmoulding allows you to protect, strengthen and seal electronic components and parts without damaging them. Specifically, low-pressure moulding is the process that lies between injection moulding and potting. It is basically injection moulding at very low pressures with hotmelt adhesives.  The process is fast, with products finished in seconds. Continue reading