What are the issues to consider for CNC machining aluminium?
Table of Contents
Inside the CNC precision parts machining field, aluminium parts are very common. They are used in most fields because of their wide range of applications and material properties.
Aluminium metal material characteristics
Compared with other metal materials, aluminium alloy has some characteristics as follows.
1、Small density The density of aluminium and aluminium alloy is close to 2.7g, about 1/3 of iron or copper.
2、High strength Aluminum and aluminium alloy have high strength. After a certain degree of cold processing can strengthen the strength of the matrix, some grades of aluminium alloy can also be strengthened through heat treatment.
3、Good electrical and thermal conductivity Aluminum is second only to silver, copper and gold in electrical and thermal conductivity.
4, good corrosion resistance aluminium surface is easy to naturally produces a layer of thick and solid AL2O3 protective film, which can protect the substrate from corrosion. Through artificial anodic oxidation and colouring, good casting performance of cast aluminium alloy or processing plasticity of deformed aluminium alloy can be obtained.
5、Easy processing After adding certain alloying elements, good casting aluminium alloy with good casting performance or deformed aluminium alloy with good processing plasticity can be obtained.
In addition, it can be made into various decorative products by using the feature that aluminium alloy can be coloured after anodic oxidation treatment. The surface of aluminium alloy plates and profiles can be processed secondarily, such as anti-corrosion, embossing, painting and printing to make various decorative plates and profiles as decorative materials. One of his characteristics is the low cost and the fact that the same parts can be produced in large quantities using one processing process.
According to processing methods, aluminium alloys can be divided into two categories: deformed and cast aluminium alloys.
Deformed aluminium alloys can withstand pressure processing. It can be processed into various forms and specifications of aluminium alloy. It mainly manufactures aviation equipment, doors and windows for construction, etc. The deformed aluminium alloys are divided into non-heat-treated strengthened aluminium alloys, and heat treated strengthened aluminium alloys.
The non-heat treatable strengthened type cannot improve mechanical properties through heat treatment. Still, it can only be strengthened through cold working deformation, mainly high-purity aluminium, industrial high-purity aluminium, pure industrial aluminium and rustproof aluminium. Heat-treatable reinforced aluminium alloy can improve mechanical properties through heat treatment such as quenching and ageing, which can be divided into hard aluminium, forged aluminium, super hard aluminium and special aluminium alloy.
Cast aluminium alloy can be divided into aluminium-silicon alloy, aluminium-copper alloy, aluminium-magnesium alloy, aluminium-zinc alloy and aluminium-rare earth alloy according to chemical composition, among which aluminium-silicon alloy has peri-eutectic silicon aluminium alloy, eutectic silicon aluminium alloy and single eutectic silicon aluminium alloy, and cast aluminium alloy is used in the cast state.
Aluminium precision parts product characteristics
1、The material hardness is moderate, which is less abrasive to the processing equipment and CNC machining centre tools.
2、Can be processed into geometric shapes such as plane, cavity, shell, sphere, arc, anisotropy, etc.
3, not easy to stain, easy to maintain clean.
4, has good durability and is not easy to corrosion, coupled with a special treatment process, makes the parts more long service life.
5, aluminium environmental protection, can be 100% recycled and has a high recycling value.
The above five points are the material characteristics of aluminium products; aluminium is a common material in CNC processing, and its hardness is moderate, durable and not easy to corrode. Plus, the material’s own cost is appropriate. It is the material of choice for most parts product manufacturers.
CNC CNC machining aluminium, to make the processing in the size of stable, what issues to consider?
In CNC CNC home, if the processing of aluminium parts is to keep the size of the stability, then we need to consider the following two categories of factors.
I. Irresistible factors.
I. Irresistible factors.
1. The stability of the machine tool itself.
The machine tool is not brand new or has a large number of processing and no debugging; there may be the machine tool itself for reasons of dimensional deviation. And the cause of the machine tool itself deviation factors is as follows.
Mechanical aspects.
a. Loose between the servo motor and the screw.
b. Ball screw bearing or nut wear.
c. Insufficient lubrication between the screw and the nut.
Electrical aspects.
a. Servo motor failure.
b. Dirt inside the scale.
c.Servo amplifier failure.
2. Thermal expansion and contraction deformation of the workpiece.
The thermal expansion and contraction deformation of the workpiece after processing is unavoidable, so we should pay attention to the effect of cooling when processing and increase the frequency of in-machine measurement while paying attention to the deformation condition of the workpiece after cooling.
Second, avoidable factors.
1. processing technology
2. To control the processing error is inseparable from the good processing process, in addition to the process arrangement, to ensure that the basic machining process (such as milling CNC machining “first coarse, then fine, first surface after the hole, first large surface after the small surface” or the use of fixtures “to reduce the number of clamping, try to use a combination of fixtures “and other basic processing process details) of the principle of the basis, but also to minimize the aluminium chip processing errors caused by aluminium parts, we all know that aluminium parts are very soft, and the exclusion of waste chips and very easy to make aluminium parts processing errors.
3. cutting three elements: cutting speed vc, feed f, depth of cut ap and tool compensation
In this regard, it is to ensure the tool’s wear and processing quality by adjusting the cutting parameters so that the tool’s cutting performance can give full play to the highest cutting efficiency and the lowest processing costs.
In CNC lathes, elements such as tool head wear compensation need to be considered.
3. Numerical calculation of manual programming
In manual programming, it is very common to have errors in the calculation process; however, it is automatic programming now, but if you encounter manual programming, you still need to pay more attention to the situation.
4. Accurate tool setting
If the knife is not accurate is also caused by the size of the error; therefore, the edge finder tries to choose a better one. It is best to equip the machine with a laser tool setting instrument to ensure the accuracy of the knife. If there is no edge finder, there is no condition, only the simplest test cut method!
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