Irrespective of the machine shop you choose to work with, the pricing of the cnc machine rapid prototyping parts will vary depending on various factors.  It can be simplified a little by thinking about the big three factors: Raw material, manufacturing time and ‘fixed’ or other costs. See how each element contributes to a price:

Raw material

Metals: metal costs has few surprises – steel and aluminium are abundant (Al6082 is our most common grade) and have the lowest raw material cost per kg (or pound).the more specialist aluminium and stainless steels that contain expensive alloying elements. Finally titanium, which is surprisingly abundant, but difficult to refine (which also contributes to its high price but also properties like corrosion resistance). 

Plastics: on the other hand can look quite similar, but have an even more extreme price range.

• Lower cost: Nylon (PA6), acrylic and ABS are workhorse materials; used extensively in injection moulding as well as CNC components. However, there is a material that may work out both cheaper and have better performance. Acetal (often referred to a Delrin®) is a great general purpose engineering plastic with good stability.
• Medium cost: You will pay about 50% more for glass-filled grades – the brittle but fragile properties of glass fibre, combined with the tough plastic, creates a composite. Which is stronger and harder wearing.
• higher cost: these raw materials exceed the price of titanium (can be over £100/kg) so worth checking if you can use an alternative first! Generally they are required to meet a specific need: PC (polycarbonate) is so strong it is used for bullet proof glass! PEEK – the go-to choice for F1 and aerospace, stronger than some metals, UV and flame resistant it can cope with almost any demand. PSU, PPSU, PEI are generally used in food and medical applications. Finally, POM-ESD is modified to be just conductive enough to prevent static discharge.

Manufacturing cost

• Quantity of parts 

The number of parts ordered for a machine influences the overall cost. This is because large orders are expensive, however the higher the number of parts the lower the cost of each additional unit. This means large orders increase the final cost of the part but reduce the cost per unit. The turnaround time for the parts is also important in determining cost as a part to be shipped in a number of weeks will be more affordable than that to be shipped in two to three days. 

• Part geometry 

This refers to the dimensions of a part. The larger a part is, the more material it will require to be manufactured hence the more expensive it will be. Complex and very detailed parts also increase costs significantly. This is because of the multiple processes that will be needed to be employed as compared to simpler parts. Designing unnecessarily expensive parts in the design phase of a machine is very easy and thus is advised to consult a knowledgeable manufacturer at the time to enable you to come up with a functional yet efficient part to manufacture. 

• Manufacturing equipment required 

Modern machining and manufacturing equipment vary and are extremely expensive. It is important to know whether a part can be completed using one multi-axis machine or will require multiple machines. As well as how many different machines and operations will be needed. The size and capability of the equipment needed will add to the factors that will influence of the overall cost incurred. At GT we equipped with 3, 4, 5 axis cnc machines in-house. 

• Part tolerances 

This refers to how close the physical part needs to be to the design submitted. It is usually measured in hundredths or thousandths of an inch. Unnecessarily tight tolerances on a part increase the overall cost due to its complexity and demand. Tight tolerances should be reserved for where the part interfaces with others. Our typical tolerance accuracy ranges from +/-0.02mm to 0.1mm, depending on customer’s requirement.

Other and fixed costs

The machinists involved in creating a part have to be paid for their work. If a part is difficult, more complex and requires the expertise of more highly and trained machinists the cost of production goes up. These extra skills and experience come at a cost because they are mainly obtained from on-the-job experiences and not formal education. The more labor intensive the production of a part is the higher its pricing will be. 

If your part requires additional treatments, the overall cost is bound to go higher. These treatments include heat treatments, specialized coatings, anodizing, surface finishing and specialty machine operations. These treatments should, however, be evaluated for necessity and value before carrying them out. Part surface finishing including: Painting, Anodized, Chromed, Metallizing & Chrome Sputtering, Blacking, Silk-Screen, Water Transfer. 

Inaccurate and incomplete CAD drawings may end up in becoming very costly in the production of parts. This is because incorrect information on the models may lead to manufacturing a part twice just to get exactly what it is you wanted because your drawings did not initially communicate that effectively. Consulting an experienced machinist or engineer during the design phase may add initial cost to the project but will save much more in the long run. 

“Time is money” as the saying goes, and your time is especially valuable. Whatever you are designing will make an impact, and your customers want it now. We have helped prototype and manufacture everything from better medical devices and more efficient electrical equipment to better transport solutions. 

It’s likely that spending 5% more on solid prototyping and testing will pay back with a better product, but, turning up 5% late (or say 7 days after a major product launch!) is a costly problem. 

GT provides professional CNC machining services.The above factors should be carefully considered when deciding to embark on a CNC machining project to have a clear indicator on an expected budget. Contact GT and send through the CAD files to get a project review today, to see what our CNC experts can help your project.