Research On Two Additive Manufacturing Processes: Fusion Filament Fabrication And Material Jetting
I will be examining the technology and characteristics for both of these two processes, as well as giving an overview into Health and Safety whilst linking it to how it can be used within additive manufacturing.
Fusion Filament Fabrication uses a polymer that is heated and added layer by layer onto a platform or print bed. When a layer is dispensed onto the bed it solidifies and another layer is added, producing a model. From a nozzle the material is deposited, this nozzle moves horizontally across the x-axes and z-axes along the build platform. The machines vary in intricacy and the complexity of the methods for controlling the placement of the materials vary too.
The pro of fusion filament fabrication is that it produces a small amount of waste products due to it having a high accuracy when depositing the melted thermoplastic. The negative of this type of additive manufacturing is that support material is needed and that only thermoplastics can be used making materials limited. For making prototypes/models, fusion filament fabrication is ideal. The Ultimaker 2+ is one example of a machine that uses fusion filament fabrication and can use any of the following materials; PLA, ABS, CPE, CPE+, PC, Nylon and TPU 95A which are all easy to acquire. It also has a build speed of up to 24mm³/s and travel speed of up to 300mm/s which is relatively fast for building a prototype compared to the time it takes for traditional, manual manufacturing. The resolution of the Ultimaker 2+ is from 600 microns up to 20 microns and it has a build volume of 223 x 223 x 205 mm allowing an accurate, precise finish prototype to be produced quickly, with the ability to correct any flaws and create another design multiple times with little waste.
The cost of this machine is much cheaper than the Stratasys Objet24 which is a machine that uses material jetting, material jetting uses a powder and a resin which are expensive products compared to the fusion filament fabrication materials and use a higher quality, more technically built machine. The cost however affects the production quality of the product with a much smaller resolution than the Objet24 meaning the accuracy of the finished component is less than the Objet24. However, this machine uses many common and easily acquired polymers, reducing material costs and making the machine more sustainable.
Material Jetting uses a powder based material and a binder, between the layers acts as an adhesive to ensure the powder is bonded. By using an ultraviolet light, the resin hardens and the product solidifies into shape. Along the x-axes and y-axes a print head travels horizontally depositing alternating layers of the binding material and building material, the print bed moves downwards after each layer is deposited. Components that are made by the process of material jetting can be made with a range of different colours and a variation of different materials including metals and polymers. The two material method also allows a large number of powder and binder combinations which allows the process to produce products with various different properties. However, this process is less suitable for structural parts. This is due to the fact a significant amount of time can be added to the production due to post processing and the use of binders.
Material jetting can produce highly accurate presentation models/prototypes, small components with complex features, different medical devices and components as well as electronic housings. The Objet24 can also be used in a wide range of industries. The Stratasys printer uses VeroWhitePlus which is their own material, and the only material that can be used and uses the support material; FullCure® 705 which is a non-toxic gel-like photopolymer. The Objet24’s resolution is 28 microns per layer which is greater than that of the Ultimaker2+’s resolution allowing the Stratasys machine to produce a more accurate representation of the model and has a build volume of 234 x 192 x 148. 6 mm. However, this build volume is considerably small than the Ultimaker volume so the Objet24 can only produce smaller scale versions of the product. The cost of this machine is high, however this is because of the resolution at which the final is produced in. There are more applications for this machine because the quality is greater the products that are produced can be used practically and produce moving parts instead of only prototypes/models, although this machine can also be used for this. On the other hand, the lack of choice for materials with this machine can also increase the cost.
The Health and Safety at Work Act 1974 is responsible for “securing the health, safety and welfare of persons at work”. It was introduced into the work place to ensure that the number of traumas are reduced, however it wasn’t just for the employees and employers but the members of the public too, and who could have had issues arise due to health and safety risks caused by the actions of these workers. Companies must decide through a risk assessment what harm could be done to someone when doing their job and utilising equipment and what precautions can be put in place to prevent this, as well as explaining to this person how these risks will be controlled in understandable way and who is responsible for the controlling of these risks. The company must provide you with health and safety training alongside working with healthy and safety representatives to ensure that the regulations are up to date within the workplaces to lower the risk of potential harm.
Additive manufacturing equipment must be risk assessed by the company producing the machine to ensure all possible risks that could be harmful to the person using the product or the surrounding people are accounted for when symbolising this risks on the products as well as instructions and training on the equipment being provided. When using additive manufacturing processes such as fusion filament fabrication and material jetting, it is important for the manufacturer of the machinery states all possible risks with a symbol and informs users of what PPE (Personal Protective Equipment) should be used. Personal Protective Equipment at Work Regulations 1992 provides us with the all the requirements we need to know for what PPE is required for each symbolisation on a product. PPE was instated to protect one or more employees from any health and safety risks which could cause injury, the equipment includes items such as respirators, steel toe cap boots, etc. If workers are operating under the PPE requirement conditions then the equipment must be worn until they are no longer within the operating conditions.
When using equipment in additive manufacturing there are many different items that can be worn as PPE, however the items worn when using different methods depend on the risks of the machine. For most machinery, it would be ideal to use respiratory masks, especially if the material in use is hazardous to health, and gloves to protect from any high temperature components. Furthermore, if the structural supports of the finished product have to be removed by hand it would be recommended to use safety goggles to remove the material as it could have small shards snap off and cause an injury in or around the eyes. PPE is used to protect employees from any shards of material, any vapours that are harmful to health and from anything else that can harm the person using the machine and the surrounding people. PPE also has to be assessed to make sure it is fit for purpose, this means the PPE must be stored and maintained properly with instructions to inform employees or users on how to use the product correctly and safely.
Material Jetting uses an ultraviolet light making it important that the user wears tinted goggles or a tinted screen to protect their eyes, as well as possibly using a respiratory mask to protect the user from any toxic fumes or harmful powders. However, fusion filament fabrication would require safety goggles in post processing (removal of scaffolding) to protect the eyes from any shards of plastic. Gloves should also be worn when changing the nozzle of the machine as components can be hot touch meaning they could lead to burns if they are touched without PPE.
Gases, biological agents, chemicals, fumes, mists, gases (non-asphyxiating and asphyxiating), vapours, and dusts which are produced by most machines are what influenced the Control of Substances Hazardous to Health Regulations that were introduced in 1988 but have been recently updated in 2002. COSHH states “employers need to either prevent or reduce their workers’ exposure to substances that are hazardous to their health”. Ventilation, extraction and respiratory systems are used to reduce the risk of these substances harming workers. Lots of ventilation within a building and around the machinery lower the risk of employees inhaling any toxic fumes, powders or chemicals from materials, etc. as well as respiratory systems lowering the risk of harm to an employee. It is also important that a data sheet, presenting all the hazards and precautions for a material is given with the hazardous product, and that any measures that can be put in place be put in place. When using binder jetting it is vital that ventilation or respiratory systems are provided due to the use of fine powder materials and resins because fumes that could come from these products could be toxic to humans. It also applies to fusion filament fabrication for the material ABS as it produces fumes that could be harmful to humans so ventilation is required.
The overall sustainability of additive manufacturing is greater than that of traditional manufacturing, due to additive manufacturing using less energy and producing less waste. Fusion filament fabrication using easily acquirable products, as well some polymers that can be recycled and reused. Furthermore, it uses a thermoplastic called PLA which is a biodegradable and bioactive polymer made from plants, such as sugarcane and corn starch. Plants are a renewable resource so the sustainability of fusion filament fabrication is increased if this is the material in use the most due to the other polymers being made from oils they are less sustainable, although they are still more sustainable than traditional manufacturing because less waste product is produced. Less waste product being produced is a sustainable factor for all additive manufacturing and more specifically, fusion filament fabrication and material jetting because the material is being added highly accurately layer by layer rather than removing material manually which can cause inaccuracies.
