Manufacturing Processes

Injection Moulding:

Injection moulding is a manufacturing process used to produce complex and precise parts by injecting molten material into a mould cavity that has been shaped to match the desired final product. The material, typically plastic, metal or rubber, is heated until it becomes fluid, then forced into the cavity under high pressure. Once inside the mould, the material cools and solidifies, taking on the shape of the mould before being ejected as a finished component.

This process allows for the creation of both solid parts and intricate multi-faced shapes, depending on the mould design. The method can use a variety of materials, including thermoplastics, thermosetting polymers, and elastomers, allowing for multiple designs and applications for the same shaped part.

Over Moulding:

Over Moulding is a specialised variation of the injection moulding process, designed to create combined parts with multiple materials. Unlike injection moulding, over moulding requires a second component, often made from metal or plastic, to be placed into the mould before injecting the molten material around it. As the moulten material solidifies it forms a strong bond with the insert part. This is done to increase structural integrity or functionality.

This process is widely used in various industries to improve a products durability, grip and ergonomics. Common parts that use over moulding include bolt on plastic feet for furniture, tool handles with a rubberised grip and medical devices that require a combination of soft and ridged materials. A common everyday tool that is over moulded would be a screwdriver with a rubber grip.

Compression Moulding:

Compression Moulding is a commonly used manufacturing process that is used for shaping materials like rubber and plastic. This method starts from the raw material being placed on the lower half of a heated mould cavity. The upper half is then lowered towards the part which starts to apply high temperature and pressure. This forces the material to form into the desired shape.

Compression moulding is a valued process due to its minimal waste and high durability and strength parts. It is used most frequently to make components such as gaskets, seals, and electrical insulators.

Reaction Injection Moulding (RIM):

Reaction Injection Moulding is a manufacturing process used to create complex plastic components. It involves mixing two or more reactive monomers before injecting the mixture into the mould. Once the mixture is within the mould a chemical reaction takes place and begins the polymerization which solidifies the plastic mixture into the desired shape.

RIM shares similarities with injection moulding however, the key differences are based in the temperatures and pressure applied to the part with RIM requiring less pressure and lower temperatures. This makes the process suitable for producing large lightweight parts. A drawback of RIM is the fact that the process takes more time than compared with injection moulding due to the time taken for polymerisation to take place.

Vacuum Form:

Vacuum moulding is done by placing a thermoplastic sheet over a mould and heating it until it becomes pliable. Once the sheet is softened it is pressed down over the mould and then a vacuum is applied to remove the air between the mould and the sheet. The external pressure from the atmosphere causes the plastic to form more accurately over the mould creating the desired shape. The part is then cut out of the sheet using a stamp press, this can be done on the same tool or, more commonly, it is done on a separate tool.

Thermoforming:

Thermoforming is a versatile forming method, similar to vacuum forming, that  starts by heating a sheet of thermoplastic until it is soft and then placing it over a mould. Thermoforming uses several different forms of pressure in order to make the part including compressed air and mechanical forces to ensure that the parts details are clear and to improve the structural integrity. 

Extrusion Moulding:

Extrusion moulding is done by forcing molten material through a pre-defined shape which produces materials with a tubular or rod like profile. This is like injection moulding but does not use a cavity to mould the part but instead uses a die to create a continues profile with a consistent cross-section. This material is continuously extruded and cut to length after being extruded.

Tape Manufacturing:

Tape manufacturing has several steps. These steps remain mostly the same no matter what type of tape is being produced. The first thing to be produced is a substrate (Base part of tape) which is extruded out. While the substrate is being extruded the adhesive is made simultaneously, the adhesive is then layered onto the substrate sheet and rolled onto a core. These cores are a large in length but are cut down to size after the tape is attached. The materials used within the substrate and adhesive are changed depending on the material properties that are desired. 

FDM (Fused Deposition Modelling):

FDM 3D printing is a widely used 3D printing method that builds a part by layering heated thermoplastic filament according to G code that has been programmed from a slicing software. The software is used to alter settings such as layer height, wall thickness and infill percentage. The process begins with a reel of thermoplastics, such as PLA, ABS, or PETG, being fed into the printer head through boden tubes. Within the print head the filament is heated to a precise temperature (this is decided within the slicing software or can be left default) to melt it before being extruded through the nozzle, this ensures a controlled deposition of material. The print head moves in accordance with the file that has been uploaded this allows the print head to bond the new layers to the older one. As the material is deposited, it begins to cool down quickly until it has solidified. This ensures that the part can maintain structural integrity while being printed. Once the print has been completed, extra steps such as removing supports or smoothing the part may be necessary to refine the part.

FDM printing has a wide variety of materials that can be used each with their own material properties. This includes flexibility, strength, or heat resistance. The technology is also rapidly improving allowing for better quality prints and more material options.

SLA (Stereolithography):

SLA printing is a modern and precise process for fabricating objects using resin. This method uses lasers or UV light to selectively cure the liquid resin layer by layer into the part. There are many different resin types each with different material properties such as, tough, and impact-resistant to flexible or clear resin options.

After printing the part, it must go through the post processing stage. This is where the print is first removed from the printer and placed into an IPA (Isopropyl Alcohol) solution wash. This process is done to remove any uncured resin that may still be on the surface of the part. This process can vary depending on the printer that is owned as some come with a wash where the whole print bed is placed into it, whereas others require the part to be removed from the print bed and placed into the wash separately. This step is done to ensure that the finish, dimensional accuracy, and details are kept when curing the part. 

The next process is placing the washed part into a UV oven where the part is exposed to intense UV radiation and elevated temperature to increase the rate at which the resin is fully cured. While the resin would have been partially cured during the printed process the final stage in the oven is where the final curing takes place and increases the parts strength and durability. An alternative option for curing a part but not hugely recommended is leaving the part in direct sunlight for an extended period of time. Although his will cause the resin to fully cure it can also lead to warping or deformation due to the uncontrolled temperature fluctuations and uneven exposure to UV.

SLS (Selective Laser Sintering):

SLS printing is an advanced manufacturing process that uses high-powered lasers to fuse powdered polymer into a solid part. This technique is one that uses powder bed fusion, where material is deposited layer by layer and fused into the desired part using the high-power laser.

The main advantage to SLS printing over traditional printing is that there is not a need to add printed supports. Instead of printing supports the excess powder acts as a natural support to the part. This allows the printer to produce highly detailed parts with moving components in a single print.

The most common materials used in SLS printing is Nylon 12 and Nylon 11. This is due to the material properties that these types of nylon offer including, flexibility, durability, and Impact resistance. Although nylon is the most common material used SLS supports other thermoplastics such as thermoplastic polyurethane (TPU), which has different material properties to nylon which is why it is used. TPU offers elastic and rubber-like properties making it the choice for flexible parts like gaskets and seals. 

Once a print is completed you must clear away the excess powder that is around the part this should be done using a brush or compressed air. After cleaning the part, the part needs to go through a post-processing technique which varies depending on which aspect of the material properties are desired. The most common technique is heating treatment which is used to improve the bond between the material even after the laser sintering. Another technique which is done to improve the finish of the part is to use techniques like sanding, tumbling or chemical smoothing to remove rough textures and create a uniformed finish.

MJF (Multi Jet Fusion):

MJF primarily uses thermoplastic powders with Nylon 12 being the most common material, but other thermoplastics are also used such as TPU. MJF is a printing process that uses an inkjet printhead to deposit, fusing and detailing materials onto a layer of nylon powder. A heated bed is used to initiate the fusing of the materials.

The most recognised advantage of MJF printing is the surface finish of the parts that are produced. The printing process ensures that the components produced also have functional strength and are able to with stand stress while being used.

After a print is produced the post-processing of the print must take place. The first step is to remove any excess powder that may be on the part. This can be done using a brush or compressed air. While MJF is a quick process the surface finish of the parts is quite rough, this can be resolved using solutions like sanding, tumbling and chemical smoothing. Machining can also be used to ensure that the part is within specified tolerances. 

Water Jet Cutting (CNC)

Waterjet cutting uses a high-pressure stream of water, sometimes mixed with abrasive particles like garnet, to precisely cut through various materials, from soft foam to tough metals and stone. The water is forced through a fine nozzle, increasing accuracy and cutting speed. Unlike other cutting methods, it does not generate heat, eliminating material distortion or structural changes. This makes waterjet cutting ideal for industries like aerospace, automotive, and manufacturing, where precision and material integrity are crucial. Additionally, it can manage intricate designs and complex shapes, offering versatility for applications ranging from art and architecture to industrial engineering.