Aluminum is a basic element in any wholesale cnc machining aluminum parts factory. It is one of the most commonly machined metals and can be machined quickly and efficiently. Since aluminum is cut by everyone, its processing is a really require professional approach. This is especially true for production processing. In this article, I will cover everything you need to know to get started so you can get good jobs and handle them like a pro.
CNC machining is the activity of creating finished products according to the desired size and shape through CNC machines. All these activities are carried out according to the methodical process.
Also Read: What is surface finishing in manufacturing?
The aluminum machining process
The aluminum machining process on a conventional CNC machine is performed according to the following steps:
Step1: Research detailed processing technology
- Read detailed drawings: First you need to read the parameters of shape, accuracy, gloss and materials.
- Select the workpiece, select the machine and the mounting method.
- Choose a reasonable technological process.
- Select the tool type and define the machining for each step.
Step2: Design the cutting trajectory for the material
Generally, we recommend buying aluminum parts from wholesale cnc machining aluminum parts factory
- Detailed, precise and logical tool trajectories to ensure correct cutting.
- Calculate the coordinates of the transition points on the tool’s trajectory.
- The movement trajectory of the milling cutter is the motion trajectory of the center point and the face of the milling cutter. In the case of complex profiles, the programmer can take the edge of the part to make the tool’s trajectory. However, it is necessary to calibrate the milling cutter radius to the correct position.
- When the program is active, it will direct the tool to the transition points on the cutting edge of the workpiece. To determine the position of the tool gauge, the operator can use the tool gauge once installed.
Step3: Programming CNC control in CNC machining process
This is the most important step in using aluminum CNC machining technology. The two most common programming methods are:
① Manual programming method
- As a programming method that has no connection with the computer, with this method the programmer can compile NC programs by himself based on the identification of the tool path coordinates.
- The ability to program manually is the most basic requirement for NC programmers. Because of this programming skill, only the programmer understands and can read the program. Or modify when there is an error during CNC machine operation.
- Most NC programming software is the product of its manufacturer. The programming capabilities of these software are very limited. It is only capable of programming for simple cuts.
② Automatic programming method
- This is a computer-aided programming method.
- This programming method is in a geometry processing language or CAD/CAM software.
- CAD/CAM software is now widely used and very effective in this automatic programming method.
Step4: Next is to check the control program of CNC
After editing, the program needs to be checked and re-calibrated to ensure accuracy. This is also an important step before proceeding with the aluminum CNC machining process. There are two simple ways to check:
- Manual inspection:Visually scan the program and draw out the work piece by hand.
- Check by computer:The editing program will be entered into the computer software. Based on the trajectory of the tool movement and the shape of the part, modify the program or cutter for the best fit.
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WHY ALUMINUM PROCESSING CAN BE DIFFICULT?
The very first thing is to contact a professional wholesale cnc machining aluminum parts factory. Second, figure out what you are facing. If you’re making a farmer’s bracket, it doesn’t matter how efficient you are at removing material. But if you’re making 10,000 brackets a week to sell to other businesses, you need to get the job done right.
The main problem with efficient machining of aluminum is simply to achieve the maximum material removal rate without destroying the tool. Aluminum can melt and stick to the tool when heated too much. So even if it cuts like butter, it won’t last long, if the aluminum sticks to the tool, you end up doing friction welding instead of machining.
In addition to keeping friction to a minimum, rattling can be horrendous when you hit the machine. This is especially problematic when you are trying to machine clean cuts. Okay, stop whining. Let’s move on to how you can deal with it.
Aluminum machining from wholesale cnc machining aluminum parts factory
Compared to other structural materials, aluminum and its alloys are relatively easy to machine.
Machinability
Machining usually includes all cutting processes: turning, milling, planing, drilling, sawing, etc. Since there are quite a lot of different aluminum alloys, they can have different machinability characteristics.
The term machinability includes all properties that are relevant to the machining process:
- cutting tool wear;
- required cutting force;
- chip shape;
- Surface quality after machining.
Machinability is not a material property that can be defined by a single characteristic parameter. It is a complex technological term. Machinability depends both on the physical and chemical properties of the aluminum or aluminum alloy and on the manufacturing process that was used in the manufacture of the aluminum semi-finished product or product.
Machining parameters of wholesale cnc machining aluminum parts factory
The kinematic interaction between tool and workpiece is a decisive criterion for the machining process. Strictly speaking, the term machinability must be defined separately for each individual machining process (turning, drilling, etc.). Usually, due to the well-defined interaction of tools and parts, the term “machinability” refers to the turning process.
Each technology that is used in machining depends on several independent parameters:
- cutting parameters and tool geometry;
- the equipment used;
- cutting tool material.
Aluminum machining shavings
Chip shape is an important criterion for aluminum machining. Generally, short cylindrical strands, spiral strands, or simply spiral strands are sought.
There are quite a few different types of aluminum shavings as it can vary according to wholesale cnc machining aluminum parts factory. With a wide variety of aluminum alloys, they can produce almost all known chip shapes. The following pattern is usually observed: the harder and stronger the aluminum alloy, the shorter its chips. The following general rules follow from it:
- Pure aluminum and soft wrought aluminum produce very long chips, requiring special corrective measures such as special chip breaking devices.
- High-strength aluminum alloys (eg AlMg5, AlMgSi1.0) present no chip shape problems;
- Hypoeutectic cast aluminum alloys (AlSi8Cu3, AlSi10Mg, etc.) give short chips of annular and spiral shape, which are easily removed.
- Eutectic cast aluminum alloys (AlSi12) tend to form long chips;
- Hypereutectic cast aluminum alloys always form short, fragmented chips that are often difficult to remove.
Machinability of Aluminum Alloys
Enhanced machinability aluminum alloys contain low-melting soft metals that promote short chips. Usually these are alloys with additions of lead or bismuth.
One of the technological parameters that influence the chip shape is the tooth geometry of the cutting tool. So, with a lower rake angle, shorter chips are formed in those alloys that are usually characterized by long chips. This is due to chip compression.
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Surface quality in machining
In general, the quality of the surface that is formed during the machining of aluminum and aluminum alloys depend on three independent parameters:
- Kinematic Roughness: The theoretical depth of roughness (from bottom to top) that is calculated from the relative motion of the cutting tool and workpiece.
- Roughness of a machined surface: the characteristic behavior of a material during its mechanical separation, associated with the features of its microstructure;
- External influences: parameters such as the stability of the system, the condition of the cutting edges, etc.; these parameters are especially important when machining aluminum with a high cutting speed.
In general, the influence of the material on the degree of surface roughness of the part after machining, that is, on the quality of the machined surface, depends on the same factors as the shape of the chips. Basically you can ask your wholesale cnc machining aluminum parts factory for product roughness.
With regard to wrought aluminum alloys, this pattern looks like this:
The higher the strength and hardness of the aluminum alloy that is machined, the smoother the surface can be obtained on it.
As for cast aluminum alloys, their microstructure has a certain influence on their machined surface. Hard particles that are embedded in a soft matrix can be ejected to form a rough surface. However, in general, the surface quality of the machined surface of cast alloys can also be considered good and often very good.
Aluminum Sheet Annealing Methods
Annealing of aluminum alloys is optional. But in some cases, without this method of heat treatment, it is impossible to achieve the desired characteristics of the material.
The reason for the use of annealing can be a special state of the alloy, which can be expressed in a decrease in the plasticity of the material.
The use of annealing is recommended when observing three types of conditions:
- The non-equilibrium state inherent in cast products is associated with the difference in temperature regimes. The cooling rate of cast products significantly exceeds the recommended one, at which the effect of equilibrium crystallization is achieved.
- Plastic deformation. This state can be caused by technological requirements for the characteristics and shape of the finished product.
- Inhomogeneous material structure caused by other heat treatment methods, including quenching and aging. In this case, one of the alloying components is released into the intermetallic phase, accompanied by supersaturation of the components.
The above problems can be eliminated by annealing. Normalization of the structure and state of the aluminum alloy is accompanied by an increase in plasticity. Depending on the type of nonequilibrium state, various annealing methods are selected.
To date, there are three annealing modes:
Homogenization
Designed for processing cast ingots: in the process of heat treatment of ingots at high temperatures, a uniform structure is achieved. This makes it possible to simplify the rolling process with a reduction in production costs. In some cases, it can be used to improve the quality of deformed products. The annealing temperature is maintained within 500 degrees, followed by holding. Cooling can be done in several ways.
Recrystallization
It is used to restore deformed parts. This requires pre-treatment with a press. The annealing temperature varies from 350 to 500 degrees. The exposure time does not exceed 2 hours. The speed and method of cooling has no special framework.
Heterogenization
Additional annealing after other heat treatment methods. This method is necessary for the softening of aluminum alloys. This processing method allows reducing the degree of strength with a simultaneous increase in the level of plasticity.
Annealing is carried out at approximately 400 degrees Celsius. Exposure is usually 1-2 hours. This type of annealing greatly improves the performance of the metal and increases the degree of corrosion resistance.
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Hardening of aluminum castings
Hardening is not suitable for all types of aluminum alloys. For a successful structural change, the alloy must contain components such as copper, magnesium, zinc, silicon, or lithium. It is these substances that are able to fully dissolve in the composition of aluminum, creating a structure that has properties different from aluminum.
This type of heat treatment is carried out with intense heating, allowing the constituent elements to dissolve in the alloy, with further intensive cooling to the usual state.
Chemical Treatment in Aluminum processing
Chemical treatment appeared later than electrical treatment and is now widely replacing it. The main advantage of these processes is the much lower cost, not only for electricity, but also for tanks and fixtures. Due to the fact that in this case no electric current and a movable anode rod are required, work can be carried out in baskets and with simple clamps.
Basically, the principle of chemical processing is similar to that of galvanic processing. However, chemical oxidizing agents are used instead of electric current. The driving force of chemical treatment is the difference in electrochemical potentials between the anodic and cathodic areas of the surface.
The specular reflection coefficient of smooth rolled aluminum drops noticeably during anodization if it is not subjected to chemical or electrical treatment for a short period of time beforehand.
A similar decrease in the specular reflection coefficient is also observed in the initial stages of chemical treatment, but then an increase in the specular reflection coefficient follows, which can reach 90% (the maximum possible coefficient for aluminum), subject to all conditions of chemical processing.
The same process is observed during galvanic treatment
When anodized, the specular reflection coefficient of aluminum subjected to electrical or chemical treatment remains high (although there is a slight decrease in its value with increasing time spent in the anodizing bath, caused by slow dissolution and slight roughness of the outer surface of the anode film).
Therefore, the industrial anodizing polishing process usually involves a chemical treatment immediately prior to anodizing.
Cutting force for aluminum machining
To assess the effect of the material on the cutting conditions, the so-called specific cutting force is used. This specific cutting force is correlated with cutting force, material and chip sizes. In general, the following provisions apply:
- Different aluminum alloys have differences in specific cutting forces, but relatively small.
- It is usually assumed that the specific cutting force for aluminum and aluminum alloys is 30% of that for steel.
- The magnitude of the specific cutting force of an aluminum alloy cannot be derived from its chemical composition or physical properties.
- The specific cutting force must be determined experimentally for each individual case.
The required cutting force depends not only on the size of the chips, but also on the cutting fluid and the design of the cutting tool:
- Lubricant-cooling emulsion has two opposite effects. On the one hand, cooling reduces the temperature in the cutting zone and thus increases the amount of required cutting force. On the other hand, lubrication facilitates chip movement and reduces the amount of cutting force required.
- The geometry of the cutting tool affects the cutting force through the rake angle γ. The larger this angle, the less chip compression and the lower the cutting force.
- The degree of wear of the cutting edge has a relatively large influence. Therefore, during long-term machining, the magnitude of the cutting force increases.
Anodizing aluminum
Anodizing is a process, also known as folk oxidation, which results in an oxide coating on the surface of a billet of aluminum. In this case, aluminum is oxidized, but an oxide film protects it from oxidative processes.
Such processing has a number of undeniable advantages:
- increases the protective and decorative properties of the metal;
- provides the surface with dullness and uniformity;
- eliminates mechanical damage such as chips, scratches, cracks;
- increases the thickness of the protective layer.
Processing aluminum blanks by anodizing has several varieties.
- Thermal anodizing is quite simple technology, carried out at room temperature and allows you to get a beautiful color coating. In this case, only organic dyes are used. With a skilled specialist, the same part can receive several color solutions. Of the shortcomings, it should be noted that a high degree of protection against corrosion cannot be achieved.
- Cold anodizing of aluminum blanks is distinguished by the strength and hardness of the anode layer, excellent wear resistance, and high quality. Each part used in this technology must be well cooled. This treatment has the only drawback – it is impossible to use organic dyes in the cold anodizing process.
- Sufficiently strong and hard film can be obtained by hard anodizing. A feature of the technology is the use of one of several electrolytes: in addition to sulfuric acid, oxalic, acetic, tartaric or boric acid is also used. During the process, the current density increases and, accordingly, the increased density film also increases.
For the anodizing process, several aluminum baths of different diameters are used (plastic or polypropylene can also be used). The main condition is compliance with the thermal insulation properties of the bath.
Machining aluminum: what problems can be encountered?
Soft and ductile aluminum lends itself well to machining, but sometimes you can encounter negative effects. Some alloys have a high viscosity. In this case, when milling or drilling, long chips can form, which will wind around the working tool, leading to breakage.
To minimize the risk of such a nuisance, aluminum alloy machining tools should be chosen with large flutes – although this will limit the maximum number of teeth on the cutter, it will facilitate the movement of the chips, partially solving the problem.
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Therefore you need a reliable wholesale cnc machining aluminum parts factory like Madearia. It comes with ith 3, 4, and 5-axis CNC machining capability.
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