In traditional manufacturing, such as CNC machining, Metal stamping or Injection moulding, a large percentage of the price can be the initial set-up time and tooling cost. It is normal to have high prices for short production runs, with prices getting ever cheaper per unit, as the volumes increase. This is ideal when producing high production numbers, but can be costly when production numbers are limited.
3D Printing or Additive Manufacturing (AM), have very different costs, and depending on the technology, can be somewhat confusing to understand. We’ll list and explain the costs with the most commonly used technologies for industry.
With all AM technologies, a 3D file is required (usually STL) of the component that is to be built. Time will be taken to inspect the file, check resolution, wall thickness and buildability. Then, using experience, suitable orientations will be carefully chosen, taking into account surface finish, strength and accuracy requirements. Apart from SLM, the complexity of a component does not normally increase the price.
SLS (Selective Laser Sintering)
When the nylon powder is processed through a build cycle, it is taken very close to its melting point. This degrades the powder and so not all of it can be recycled for the next build. Therefore, the bounding box (the dimensions required to encompass the entire part in a box) of a component is typically more relevant to calculate material cost and the space it takes up in a machine. The part volume is less important but does have some influence on the build time, as the single spot laser draws the component. Surface area is also used to calculate the expected finishing time, as all parts need to be thoroughly cleaned of powder prior to inspection. Preparing a machine for a build with cleaning and maintenance takes several hours, as does the powder management and quality controls. This adds to the costs associated with producing a part.
As material cost is so high with SLS, it is tempting for some companies to re-use old material in the machine at higher ratios than recommended. This does reduce cost, but at the expense of mechanical properties, surface finish and repeatable accuracy.
SLM (Selective Laser Melting)
Printing in metals is very challenging and care needs to be taken to ensure the component has been designed for the process. Removing the metal supports and finishing the component also needs to be considered and this post-processing takes time. The way SLM parts are costed is therefore similar to CNC machining, with the first part costing the most, but ordering a batch of 10 or more can significantly reduce the unit price. Raw material prices and machine running times are much higher with SLM compared with CNC. SLM has an advantage over CNC in its geometry, which would be very difficult – or impossible – to machine. Part volume and the bounding box will have the largest influence on price due to material prices and machine run time. The complexity of the component will also influence the price, if it presents additional challenges in post-processing.
SLA (Stereolithography Apparatus)
SLA was the very first 3D Printing technology developed, and produces parts with a photocurable resin. There is some nominal time required designing and removing supports, taking care not to have supports on critical features. The time to set up and start a machine is minimal, but cleaning the parts takes longer than it does with SLS or MJF. There is very little wastage of material, but most of the cost is still in the raw material and machine running time. A large part can take up to a week to ‘grow’ in the machine and costs thousands of pounds in material. Pricing for SLA parts will typically be weighted towards the total volume of the part, as this influences the material used and time it takes for the laser to draw the component. The surface area of the part will also influence the price, as this determines the washing and finishing time. The total bounding box of the part is used to calculate how much room it will take up in a machine, but contributes less to the total cost.
MJF (Multi Jet Fusion)
Unlike SLS, the majority of the powder in MJF is recycled, but there is also a binding agent used to fuse the parts together. Surface area is used to calculate finishing time and detailing agent costs. The result is costing more akin to SLA, where the material cost accounts for a large percentage of the price. Lastly, bounding box is used to calculate the machine space it will take up. MJF is one of the few technologies where the volume of the parts does not change the build time. This is what makes it very competitive in scaling up production quantity.
FDM (Fused Deposition Modelling)
This is one of the easier technologies to price for. Building time is directly proportional to the material used. The volume of the component will have the biggest influence on the price, with some consideration given to the support structures needed and any additional finishing required. Surface area is also used, as the border of a part is drawn slower than the infill.
With the exception of SLM, all of these technologies do not require any tooling costs and only have minimal setting up costs. Most of the costs associated are in the material, machine and finishing time. That is why there is no real cost savings to be had when increasing the quantity of parts.
As you can see, each technology has different costs associated with it. This makes it difficult to say that one technology will be more or less expensive than another. It depends on the geometry.
However, there are some efficiencies to be gained by ensuring machines are fully utilised. This is why we offer discounted prices for longer lead time production work. It helps to keep machine utilisation up and helps reduce the hourly cost of the machines. This is a cost reduction we can pass on to our clients.
