From specialist compression moulding to reduce the cost of metal and die casting for businesses as varied as electronics manufacturers and public transport seating makers, to injection moulding for producing large quantities of plastic parts, there are numerous benefits of compression and injection moulding for a variety of industries.

Here at Merriott Group, we want to focus on the post-mould finishing options bringing added value to not only the functionality of moulded products, which will save on total time and cost during production, as well as tried and tested methods that add personal branding touches making your product unique to your business.

Post-Mould Inserting for Rapid Assembly

Particularly useful when needing threaded fixings of either tapped holes or studs, post-mould insertion involves using a variety of mechanical techniques such as heating and ultrasonic frequencies using either brass, steel, or plated inserts.

Post-mould inserting has distinct advantages over mould-in inserts, due to not needing to clean off any flash residue, while fewer rejects tend to occur in the production process due to reduced chance of dislodging.

The end results in stronger, wear-resistant threads that can be used across many thermoplastics materials. This method is also beneficial when piecing together several parts, thereby reducing overall time and cost.

Drilling for Consistent Holes

Due to size or orientation issues, it can sometimes be difficult to mould certain diameter holes. This is where drilling post-mould can offer the level of clean consistency you’re looking for.

A technique we can apply to a range of different products and applications, this secondary operation can provide stronger products and is recommended when weld line detail is close to the part edge around a hole form.

Thread Tapping for Size Uniformity

A machine tapped or threaded form is a great solution when the precise size or thread insert can’t be specified.

Depending on the product material itself, small threads are possible using this method, while at the other end of the scale, larger threads can also be machined post-mould, which ensures consistency in form of aesthetics and specification, so as to meet required quality standards.

Screen and Pad Printing for Product Identification

We receive many requests for unique branding on our thermoplastic and thermoset injection mouldings.

Branding and product marking also serve an aesthetic purpose when it comes to post-mould finishing options, with our screen and pad printing finishes using appropriate inks to mark logos and other visual graphics using high-quality in-house equipment.

Pad printing is an ideal choice for smaller moulds when looking for a swift, cost-effective solution without compromising on the finish, while plastic parts with a larger surface area and speciality products requiring vibrant logo designs would usually benefit most from screen printing.

Ultrasonic Welding for Mass Production

This post-mould technique is highly practical when crafting a large number of parts that mirror each other to create a full product, car light assemblies, instrument casing, and smartphone casings that have identical units.

This economical and automated process involves high-frequency mechanical vibrations using suitable jigs and specific horns to weld specific joint forms/detail into solid-state welds.

Hot Staking for Custom-Part Assembly

Involving the use of heat to swage a pillar into a rivet head so as to hold the plastic or metal part in place, this is a post-mould finish that works best when trying to create detailed assembly parts.

Known for being particularly clean in nature, hot staking keeps costs down when looking for custom-crafted materials requiring fixings within the plastic part itself.

We would already have the holes ready and waiting for fixing during the injection mould process itself, before using a heat staking device, to apply heat to soften the moulded pillar form and thus create a domed rivet head.

3-Axis CNC Routing for Different Versions of a Base Mould

When looking for injection or compressed moulds offering flexibility in terms of additional features or alternative versions of a base mould, 3 axis CNC routing is a versatile post-mould finishing technique.

Examples of where this method is used include creating different size apertures for different instruments within a frame case door, or machining components to add other product options, without expensive tooling cost.

When making use of the 3 axis CNC routing technique, your business wouldn’t have to worry about heightened costs associated with tooling and inventory, as our machine heads are capable of either locking together or working independently of each other.

Electrical and Pressure/leak Testing for Compliance

If you work in an industry where electrical resistance testing is required, then we can ensure that your products are safe for purpose.

As a post-mould operation, involves making sure that there is no electrical tracking where inserts are to be moulded in or tracking weakness in thicker critical sections. This is carried out using calibrated equipment and up to 10kVA.

Valve products are both pressure and leak rested through the detailed jig and test equipment, ensuring we can easily check that the products meet all spec requirements and that the assembly takes into account the correct positioning of critical seals.

Vibration Welding as an Alternative to Ultrasonic Welding

A method used when ultrasonic welding isn’t possible for mass production of products due to product shape, size and welded length, vibration welding makes sure that more complex designs are fit for purpose.

This technique works by having one part generating friction heat to a mating part surface so as to produce heat and then pressure is applied thus creating a welded form.

Advantages of vibration welding include swift weld times, energy efficiency and compatibility with a range of thermoplastic polymers.


The product finish specification you require will largely depend on whether we’ve used injection or compression moulding during the manufacturing process itself.

Our experts here at Merriott Group will take into consideration the design process requirements, tooling and materials when deciding which post-mould finish method to apply to your product – and are always on hand to assist with your enquiries.

Please contact us today to speak to a member of the team who will guide you towards a quality finished plastic or metal product.