Views: 1 Author: Site Editor Publish Time: 2023-03-20 Origin: Site Inquire
Polishing is a common process of part finishing in mechanical design. It is the process of completing a pre-treatment such as cutting or grinding to provide a smooth surface. It can improve the accuracy of geometry such as surface texture (surface roughness), dimensional accuracy, flatness and roundness.
There are two main types of sheet metal processing polishing methods.
One is the "fixed grit method" in which a hard, fine grinding wheel is fixed to the metal, and the other is the "free grit method" in which the grit is mixed with a liquid.
The following is a brief introduction of the two processing methods by a professional sheet metal processing manufacturer.
First: Fixed Grain Processing Method
The fixed grinding method uses abrasive particles that are fixed to the metal by bonding to polish the projections on the surface of the component. Machining methods such as honing and superfinishing exist, which are characterized by shorter polishing times than the free-grinding machining method.
Second: Free Abrasive Grain Processing Method
In the free-grinding method, abrasive particles are mixed with a liquid and used for grinding and polishing. The surface is scraped by holding the part from the top and bottom and rolling the slurry (the liquid containing the abrasive grains) over the surface. There are processing methods such as grinding and polishing that have a surface finish superior to that of the fixed abrasive processing method.
The main types of sheet metal processing polishing are as follows.
Honing is the polishing of the inner diameter of the parts, it is usually used to polish the inner diameter of the engine block and other parts. The cylindrical rotary tool has several grinding stones (oil stones) attached to the side.
Polishing is performed by rotating and reciprocating motion while pressing it against the inner surface by the force of a spring, thus achieving a glossy mirror finish. Since polishing is performed by rotating and reciprocating movements, web-like lines called cross-shadow lines are formed on the machined surface. In parts that slide like the relationship between engine cylinders and pistons, these reticulated lines act as lubrication grooves, allowing for low friction.
2. Electrolytic polishing
Electropolishing is a polishing method in which the object (metal) to be polished is immersed in an electrolytic solution and an electric current is applied to chemically melt the convex part in order to mirror polish the surface. The object to be polished is connected to the anode (+) and generally the lead plate is connected to the cathode (-). The current is then allowed to flow through the electrolyte to smooth the metal protrusions.
The metal is dissolved into the electrolyte through the slime layer. Since the slime layer is thin at the protrusions, the protrusions on the surface of the metal flow easily through the current and are dissolved first, thus becoming smooth.
In recent years, the precision of machinery and equipment has increased and requires, for example, polished high-precision parts that need to be polished. Super finishing is similar to grinding finishing, but it can improve the accuracy of surface texture and geometry than grinding finishing. It is mainly used for finishing the inner and outer rings of shafts and bearings, as well as the outer rings of engine camshafts. The machines that perform superfinishing are called "superfinishing machines," and there are special machines for bearings and shafts.
For example, as shown in the figure below, when finishing cylindrical surfaces such as bearings, a grinding wheel is pressed against the workpiece at low pressure while vibration (vibration) of about 1040Hz is applied and smooth machining is performed.
To perform grinding, place the object to be processed on the grinder and apply pressure from above. Then a slurry (abrasive grain) is injected between the object to be processed and the grinder, and grinding is performed while polishing, rotating while injecting the abrasive grain. The surface quality (surface roughness) and thickness of the precision can be controlled. The grinder can generally polish both sides at the same time, or polish one side of the top or bottom.
5. Fluid polishing.
Fluid polishing is driven by hydraulic pressure, is the abrasive grain with the liquid high-speed reciprocating through the surface of the workpiece, the workpiece contact surface processing, to achieve polishing effect. Commonly used fluid polishing methods are: abrasive jet processing, liquid jet processing, hydrodynamic grinding, etc.
6. Vibration polishing.
There are many kinds of vibration polishing, the first is said to be roller polishing. Will be "abrasive" and "processed object" into the drum, the drum rotates and moves up and down to polish the processed object. It is mainly used for many very small objects to be processed, such as steel balls, and is suitable for polishing several objects at once. It can also be used to remove burrs and sharp edges that appear on parts during the cutting and production process.
Similarly there is ultrasonic polishing, which is similar in principle to roller polishing. The workpiece is put into the abrasive suspension and placed together in the ultrasonic field, relying on the ultrasonic oscillation effect, so that the abrasive on the surface of the workpiece grinding polishing. Ultrasonic processing force is small, will not cause deformation of the workpiece, in addition can also be combined with chemical methods.