Plastic World – Custom Fabrications
Fabrication generally refers to manufacturing processes which involve a certain amount of hand work combined with various different basic procedures. Various plastic materials can be used in the creation of custom made articles, in some cases combinations of different plastics can also be used to achieve the desired result.
Even though fabrication often relates to specialized single or small quantity items, it can easily be expanded into significant run quantities where appropriate. There are cases where quantities or technical requirements warrant the use of moulding processes such as rotational, injection, etc but here we are dealing with basic fabrication techniques.
The most common fabrications we do use either cast or extruded acrylics for anything from simple point of sale units to items such as podiums, museum covers, tanks and the like using thicker materials as required. Material thickness relates to function, cost and appearance in order to achieve the desired result. Minimising cost at the expense of functionality is unlikely to produce a proper solution.
To take flat sheet material, as well as other forms of acrylic such as rod and tube and create finished articles usually involves a number of processes, mostly quite basic but also employing sophisticated machines where applicable. Processes include sawing, drilling, bending, laser-cutting, router-cutting, machining, water-jet cutting, edge polishing, machining, solvent-bonding, gluing, annealing, mechanical joining and any others not listed here in the required sequence to achieve the best outcome. The resultant product usually has to be functional and presentable. Acrylic is mostly unforgiving and errors are punished by poor appearance or having to be re-made!
The simplest fabrication such as a box may be made by cutting the required panels and solvent-bonding them together. When setting the panel sizes, the material thickness needs to be accounted for so that the correct fit and dimensions are achieved. The next level of complexity might be to use line bending using a strip heater and then solvent-bonding cut pieces to the bent element to arrive at the required unit. As one introduces more complex processes, it can be seen that very involved articles can be produced. It is most important to follow the correct sequence of processes as back-tracking, especially with clear materials is not always possible. Join quality is either achieved by creating the smoothest possible interfaces if using solvent-bonding, or using filler adhesives such as Magmabond C2 for stronger and bubble-free joins. Bubbles in joins reduce the bonded surface area and are weaker than clean bubble-free joins. Other considerations in joining relate to crazing – this is a relief of stresses that may be introduced by processes such as laser cutting and manifest as small cracks which are both unsightly and eventually lead to weakening or total failure of the fabricated item. Annealing of elements after heat processes and before gluing can reduce the likelihood of crazing but are often not commercially viable when considering fabrication time in a production environment.
Fabrications – Other Sheet Materials
Fabrication of products is not limited to acrylics but can include associated materials such as ABS, HIPS, UHI and the like. It is also possible to create high strength units in polycarbonate using similar techniques to acrylics but with some limitations. Laser cutting is possible but not ideal with some of these materials – in some cases the gases released are unpleasant or even toxic. In such cases, water-jet cutting can offer a precision-cutting alternative when dealing with the likes of polycarbonate. HDPE and Polypropylene are also suitable for fabricated items and are usually heat welded or mechanically fixed as they are generally unlikely to be successfully glued. uPVC is also used for fabrications that require high chemical resistance. There are certain glues that can be used with this material but higher strength joins are mostly achieved with hot air welding.
There are applications which are best suited to mixing various materials to achieve the best result. Some materials by virtue of their make-up lend themselves to simple solvent-bonding with varying join strengths usually governed by the compatibility of the materials involved. The higher the percentage of commonality, the more likely the success of the join.
The materials we generally work with include:
Cast Acrylic sheet (Perspex, Plexiglass, etc), Extruded MI acrylic sheet, Extruded UHI acrylic sheet, Polycarbonate solid and twin-wall, uPVC, ABS, HIPS, Foam PVC, HDPE, Polypropylene, Nylon, PTFE (Teflon) and PETg.
The knowledge and experience accumulated over many years of hands-on application helps when trying to offer the most appropriate solution to meeting our customers’ requirements.