Posted on Dec. 13th, 2018 | By Kenzi, WayKen Project Manager
Using CNC to machine projects for different applications is a very common way in rapid prototyping industry, even though in this modern time we still have faster 3D printing, CNC machining is the main option for many designers. In this article, we are going to discuss machining projects by CNC in various materials. Should you be interested in how to make and improve your machining projects to be great ones? Let's move on to the following texts.
1. CNC Milling for Widely Used Plastic Projects
For CNC milling, there are always some common materials that can apply in many occasions, for example, the plastic ABS material, many products such as medical devices’ top cover & bottom cover, mobile phone covers, earphones covers, nearly every product that can be found in our living life, using ABS as the material. Therefore, to a machine, this material is not difficult, and also this is the cheapest material among plastics.
As far as I know, milling this material is very easy. Thus, in order to keep low costs to meet the intense budget of projects, manufacturers will choose to split to a machine then glue together. We use the acetone solvent for Glued. The acetone can be only used in the same or similar thermoplastic material bonding. Put the 2 parts on the fixture and make sure the position, then apply the agent on the gap surface. The agent will spread slowly into the joint surface after completely glued; the joint will become strong which will not become weaker gradually. ( strength is better than bonding agent)
Besides ABS, ABS+PC is also a very common material for plastic machining projects, and it is also as easy to machine as ABS, its material cost is only a little higher than ABS, but the milling way is nearly the same. After gluing splitting parts together, the bonding line is not very visible and can spray some paint on the surface to make it more beautiful.
2. Automotive Optical Clear Parts Machining
Automotive machining is a technology that requires continuous updates to machining equipment and cutting tools in order to maintain the highest quality machined clear plastic parts in the industry. By combining 5 axis precision milling with diamond machining technology, it can improve the ability to machine more complex shapes and optical details.
A diamond tool to machine automotive optical parts also becomes a widely milling way now, it can achieve a clearer without any post-polishing for the optical parts, many manufacturers are tending to use a smaller tool R0.1 diamond tool to apply on the milling on important optical parts such as light guides and reflectors.
The other more difficult machining way for automotive machining projects is the 5-axis linkage milling, what is the 5-axis linkage? It is a requirement to let both support base and milling tool to turn at the same time, as most of the time the optical clear parts will use PMMA as the material, and we all know that PMMA is a fragile material, thus when using the 5-axis linkage milling way to machine the parts, the risk that part gets crack is higher and easier to happen.
3. High Precision Aluminum Parts Machining
For metals, to machine aluminum parts are as common as ABS of plastic, many mechanical parts that applied on automotive machines and devices are from aluminum, except the surface roughness requirement, holes precision is super restricted with precise tolerance such as H6, h6 or even h5, these are normally the reaming holes that require carefully machining.
There is also a very important point among the high precision aluminum machining projects that designers care very much for cylinder aluminum parts, which is the surface finish. There are three different measurements (Rz – the range, Rmax & Ra) which are specified, it is the same surface finish for the whole surface, but there are three tolerance ranges for each type of measurement.
The Mean Roughness (Roughness Average Ra) is the arithmetic average of the absolute values of the roughness profile ordinates. Ra is one of the most effective surface roughness measures commonly adopted in general engineering practice. It gives a good general description of the height variations on the surface. The units of Ra are micrometers or microinches.
The Mean Roughness Depth (Rz) is the arithmetic mean value of the single roughness depths of consecutive sampling lengths.
The Maximum Roughness Depth (Rmax) is the largest single roughness depth.
(Rz = average of Rz1, Rz2, Rz3) – Rmax = the maximum of the three Rz’s so is Rz3 in this case. However, how to ensure this value? The answer is to do high polish then measure the value then polish again until the test date is correct.
4. High Hardness Steel Parts Milling
There is a difficult situation for most of the CNC manufacturers to overcome, which is to machine the steel parts. As we all know most of the tools are made from steel, as tools are steel, if parts are steel material, the hardness of the tool must need to be higher than the material, or the tool will become broken easily during machining. This character makes the steel parts are more difficult to machine compared to other metal parts, as a result, the using life of tools become shorter, it will also shorten the using life of CNC machines.
With the above disadvantages of milling steel parts, manufacturers normally only plan to use 2 machines to mill the steel parts, which makes the lead time for steel machining projects become longer.
5. 4-Axis & 5-Axis CNC Machining
Normally many parts can be finished by 3-axis CNC, however, with those parts that have details on sides or undercuts, it will need 4-axis CNC or even 5-axis CNC machine to do.
5-axis can keep the parts to a machine in one complete piece without splitting in spite of the under-cuts; this is a very modern machining machine to improve the old machining methods, many applicants such as automotive reflectors, automotive light guides will require the 5 axis CNC to mill.
At last, with all above introduction for CNC milling methods, WayKen are capable of machining it, and we can machine with cheaper cost and higher quality with the support of our well-experienced technical team.
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