There are many advantages to using copper for machining parts. Copper is one of the most widely used metals in the world, with high corrosion resistance and good conductivity and thermal conductivity. In this article, we will discuss the processing methods, design considerations and processing requirements of copper and copper alloys, which are not only aesthetic benefits.
Copper processing technology
Pure copper is difficult to process because of its high ductility, plasticity and toughness. Alloyed copper improves its machinability, and even makes copper alloys easier to machine than most other metal materials. Most machined copper parts are made of copper and zinc, tin, aluminum, silicon, and/or nickel alloys. These alloys require much less cutting force than machined steel or aluminum alloys of equal strength.
CNC milling
Copper alloys can be processed by various technologies. CNC milling is an automatic machining process, which uses computer control to manage the movement and operation of multi-point rotary cutting tools. As the tools rotate and move on the workpiece surface, they slowly remove excess material to achieve the desired shape and size. Milling can be used to create different design features, such as grooves, notches, grooves, holes, grooves, profiles, and planes.
The following are some guidelines for CNC milling of copper or copper alloys:
Common cutting materials are carbide application groups, such as N10 and N20, and HSS grades
You can reduce the cutting speed by 10% to extend the tool life
When milling copper casting alloy with casting skin, reduce the cutting speed by 15% for cemented carbide group tools and 20% for HSS class tools
CNC turning
Another technique for machining copper is CNC turning, where the tool remains stationary while the workpiece moves to produce the desired shape. CNC turning is a processing system which is suitable for manufacturing many electronic and mechanical parts.
There are many benefits to using CNC turning, including cost-effectiveness, accuracy, and increased manufacturing speed. When rotating copper workpieces, it is particularly important to carefully consider the speed, because copper is an excellent heat conductor, which generates more heat than other materials, which will increase tool wear over time.
Here are some tips for CNC turning copper or copper alloys:
Set the tool edge angle between 70 ° and 95 °
Soft copper which is easy to be coated needs about 90 ˚ Tool edge angle of
Constant cutting depth and reduced tool edge angle can reduce the stress on the tool, and improve tool life and cutting speed
Increasing the angle between the main cutting edge and the auxiliary cutting edge (tool angle) can make the tool bear higher mechanical load and lead to lower thermal stress
Design considerations
Many factors need to be considered when designing parts machined with copper. In general, you should only use copper when necessary, because copper is expensive and usually does not require copper to produce the entire part. A good design can utilize a small amount of copper to maximize its unusual properties.
The following are some common reasons for choosing copper or copper alloy parts:
High corrosion resistance
High conductivity and thermal conductivity, easy to weld
High Extensibility
Highly machinable alloy
Select the correct material grade
During the design phase, it is important to select the correct grade of copper for your application. For example, using pure copper for complete machine parts is not only difficult but also uneconomical. C101 (pure copper) has higher conductivity due to its purity (99.99% copper), but poor processability. C110 is usually easier to process, so it is more cost-effective. Therefore, selecting the correct material grade depends on the characteristics that are critical to the design function.
Design for manufacturability
No matter what materials you use, DFM should always come first. At Fictiv, we recommend that you relax the tolerance as much as possible while retaining the functions required by the application. In addition, it is better to limit dimensional inspection, avoid deep recesses with small radii, and limit the number of parts set.
No matter what materials you use, DFM should always be your first choice. We recommend that you broaden the tolerance as much as possible while retaining the functionality required by the application. In addition, it is better to limit dimensional inspection, avoid deep grooves with small radii, and limit the number of parts set.
In particular, when designing copper parts, here are some specific best practices:
Maintain a minimum wall thickness of 0.5 mm
The maximum part size for CNC milling is 1200 * 500 * 152mm, and the maximum part size for CNC turning is 152 * 394mm
For undercuts, maintain a square, full radius, or dovetail profile
Finishing copper
After processing, there are many factors to consider when deciding which process best suits your needs. The first step of surface finish control is in the CNC machining process. Some CNC machining parameters can be controlled to change the surface quality of the machined part, such as the tool tip radius or the tool corner radius.
For soft copper alloys and pure copper, the quality of the finish directly and seriously depends on the head radius. The head radius should be minimized to prevent the application of softer metal and reduce the surface roughness. This creates a higher quality cut surface because a smaller tip radius reduces the feed trace. The wiper inserts are the preferred tool compared to traditional tool tip radius tools because they can improve the surface finish without changing the feed speed.
You can also meet the part finish requirements through post-processing:
Manual polishing – although labor-intensive, polishing will produce an attractive surface luster
Medium blasting – this produces a uniform matte surface and hides small imperfections.
Electrolytic polishing – due to its incredible conductivity, it makes copper bright and is the best choice for finishing copper.