Brief introduction
Between the design phase and the marketing phase of a particular product or an equipment, there are several steps that we should follow. One of the key milestones of the product manufacturing process is the selection of the most appropriate process for the production of that part. At the same time, you can identify that as one of the most important steps in the overall lifecycle of the product. CNC machining and injection moulding are the two most commonly used processes for this production process. You might definitely wonder how the most suitable process can be selected for a particular method. Don’t worry. This explanation will clarify your problem. First of all, let’s have a look at the separate processes.
CNC Machining
The term CNC stands for Computer Numerical Control, and in this method, the material removal from the block of material that is used to produce the part takes place. The precision of the part is pretty high as the computer control is used to produce the part. The CNC machining method can be used to produce single components as well as be suitable for mass production.
Injection Moulding
In the Injection Moulding process, the raw materials are melted, and the molten material is injected into the mould under the application of high pressure. After that, the mould is cooled by water cooling, air cooling, or a hybrid method, and the moulded parts are ejected from the mould after it is opened. This is how one cycle is carried out, and the same procedure is repeated continuously until any planned or unplanned stoppage takes place. The injection moulding method can be used to produce either a single component at a time or a number of parts at once. However, there are both pros and cons to this method, as with any other method.
Which One is the Best Option?
According to the method of production, a material removal process takes place in the CNC machining and a cavity filling is carried out in the injection moulding. Which process should you follow to produce a part/parts if both CNC machining and injection moulding processes are provided? How can you finalise and validate your selection? We know that it is quite problematic if you do not have a deep understanding of the two separate processes and their pros and cons. So, let’s consider how the selection process can be done. For that, we have to consider a number of factors that are essential in the manufacturing processes. They are: speed, volume, material, cost, defects, surface finish, and skill requirement. However, you should keep in mind that there is no exact limit between the two processes. You have to select the process by considering the strength of the application based on the mentioned aspects.
Speed:
In injection moulding, before producing a particular product, a mould should be produced. After producing the mould, the products can be generated. The mould preparation takes the longest time because precision should be ensured while producing the mould, and after the mould is prepared, the parts can be produced very quickly because the cycle time of injection moulding is not too high. However, the cycle time for preparing the part is varied depending on the size of the product. When it comes to CNC machining, the initial step is CAD file creation. It is not a time-consuming process, and the precision of this method is higher than the precision of the mould preparation. However, when considering from the very beginning, the initial step of injection moulding, mould preparation is more time-consuming than the initial step of CNC machining. But the speed of the product preparation by injection moulding is higher than that of CNC machining. If you need to produce a large number of components, it is better to use injection moulding because of the lower cycle time.
Volume:
When considering the price per part, it will be better enough to use CNC machining if you are going to produce a small number of parts. If you are going to produce thousands of parts, you need to use injection moulding because it can provide a cost benefit. But there is a little constraint that the initial cost of mould preparation is more expensive than the CAD file creation in CNC machining. Because of that, make sure to avoid applying injection moulding for the production of a small number of parts.
Material:
CNC machining is capable of applying for a wide variety of materials such as, plastic, metal, fiberglass, wood, etc. But the application of the materials in injection moulding is limited to plastics and rubber. Therefore, before finalising the process for the production, you should identify the used material, and then the process should be selected.
Cost:
The mould preparation for injection moulding is a high-cost and time-consuming task, but the CAD file generation does not require that much time and cost as injection moulding. Because of that, based on the initial cost requirement, CNC machining is more effective than the injection moulding method.
Defects:
There is a higher possibility of having defects in the parts of injection moulding if the required working conditions are not properly arranged. But in the CNC machining, the precision is higher than in injection moulding and thus the occurrence of defects is minimum.
Surface Finish:
When considering plastic part manufacturing, both the processes are feasible to use, but when considering the applicability in terms of the surface finish, the CNC machining takes higher marks than the injection moulding process. The reason for that is that different kinds of surface imperfections can be shown by the injection moulding process, such as oil marks, burn marks, evidence of the gate and ejection, etc. If these kinds of surface imperfections are not that much considered, you can neglect this factor and select the process based on other criteria. But, if a perfect surface finish is a must, you should focus on CNC machining.
Skill Requirement:
High skill requirements and experience are musts for CNC machining, while high skill requirements and experience, are not essential for operating the injection moulding machine. However, this should not be considered as a leading contributing factor for the selection of the process and this should be kept as the final option.
Conclusion
Before finalising the most suitable process between CNC machining and injection moulding, you should undertake a comparison considering the mentioned aspects. After that, the most effective process should be applied to the particular requirement for getting the best output.
How can we help you?
ArpTech is an Australian-based company that deals in manufacturing of low to medium volume production parts. We use state of the art machinery to produce high-end plastic and metal products. So, contact us now and find out the best solution for your next project.