Ultrasonic machining is a special processing that uses ultrasonic frequency as a tool for small amplitude vibration and slamming the surface of the workpiece by the slamming action of the abrasive which is free from the liquid between the workpiece, which is abbreviated as USM.
Ultrasonic machining is commonly used for piercing, cutting, welding, nesting and polishing.
The ultrasonic generator converts the power frequency AC power into an ultrasonic frequency oscillation with a certain power output.
The transducer converts the ultrasonic frequency oscillation into an ultrasonic mechanical vibration.
The vibration of the tool fixed to the end of the horn is ultrasonically vibrated by the amplitude amplifying rod (horn), forcing the abrasive suspension to continuously hit at high speed and polishing the surface to form the workpiece.
Ultrasonic processing of plastic materials with corundum abrasives, brittle materials with silicon carbide abrasives, machining of carbides with boron carbide abrasives, processing of diamonds with diamond powder abrasives.
Main features of ultrasonic machining
Not limited by whether the material is electrically conductive;
The tool has small macro force and small heat influence on the workpiece, so that thin wall, narrow slit and sheet workpiece can be processed;
The greater the brittleness of the material to be processed, the easier it is to process.
The harder the material or the greater the strength and toughness, the more difficult it is to process.
Since the scraping of the workpiece material mainly depends on the action of the abrasive, the hardness of the abrasive should be higher than the hardness of the material to be processed, and the hardness of the tool can be lower than the workpiece material;
Can be combined with a variety of other processing methods, such as ultrasonic vibration cutting, ultrasonic EDM and ultrasonic electrolysis.
Ultrasonic processing is mainly used for perforating (including round, special and curved holes, etc.), cutting and slotting of various hard and brittle materials such as glass, quartz, ceramic, silicon, germanium, ferrite, gemstone and jade , nesting, engraving, batch deburring of small parts, surface polishing of the mold and dressing of the grinding wheel.
The aperture of the ultrasonic perforation ranges from 0.1~90 mm, the processing depth can reach more than 100 mm, and the precision of the hole can reach 0.02~0.05 mm.
The surface roughness can reach 1.25~0.66 μm when processing glass with W40 boron carbide abrasive, and 0.63~0.32 μm when processing cemented carbide.
Ultrasonic processing machines generally consist of three parts: power source (ie, an ultrasonic generator), vibration system (including ultrasonic transducer and horn), and machine body.
The ultrasonic generator converts the alternating current into ultrasonic frequency power output with power ranging from a few watts to several kilowatts and a maximum of 10 kilowatts.
Ultrasonic transducers commonly used are of the magnetostrictive and electrostrictive types.
Magnetostrictive transducers are available in both metal and ferrite.
High-power ultrasonic processing machines for metals that are typically used above kilowatts;
Ferrites are commonly used in low power ultrasonic machines below kilowatts.
The electrostrictive transducer is made of piezoelectric ceramics and is mainly used in low-power ultrasonic processing machines.
The horn acts as amplifying amplitude and energy.
According to the variation of the sectional area, there are cone shape, cosine line shape, exponential curve shape, catenary line shape, step shape etc.
The machine body is generally available in both vertical and horizontal types.
The ultrasonic vibration system is placed vertically and horizontally accordingly.
Ultrasonic machining application method
1) Welding method:
The welding head vibrating at ultra-high frequency of ultrasonic waves under a moderate pressure causes the frictional heat of the joint surfaces of the two plastics to be instantaneously melted and joined.
Welding strength is comparable to the body.
With suitable workpieces and reasonable interface design, watertight and airtight can be achieved, and the inconvenience caused by the use of auxiliary products can be eliminated, and efficient and clean welding can be realized.
2) Rivet welding method:
The ultrasonic welding head of the ultra-high frequency vibration is pressed against the protruding tip of the plastic product, so that the instant heat is melted into a rivet shape, and the materials of different materials are mechanically riveted together.
By means of the trajectory of the welding head and appropriate pressure, metal parts (such as nuts, screws, etc.) are squeezed into the plastic hole and fixed at a certain depth.
After completion, the tension and torque can be compared with the strength of the traditional mold, which can avoid the shortcomings of the injection mold damage and slow injection.
This method is similar to the rivet welding method.
The concave welding head is pressed against the outer ring of the plastic product, and the ultrasonic wave is super-high-frequency vibration of the welding head, and the plastic is melted and formed to be coated on the metal object to be fixed, and the appearance is smooth and beautiful.
This method is often used in the fixed molding of electronic devices and horns, and the fixing of lenses for cosmetics.
5) Spot welding:
- Weld the two plastic points without pre-designing the welding wire to achieve the purpose of welding.
- For larger workpieces, it is not easy to design the workpiece of the welding wire to perform point welding, and to achieve the welding effect, multiple points can be spot welded at the same time.
6) Cutting seal:
Using the ultrasonic vibration working principle of the ultrasonic wave to cut the chemical fiber fabric, the advantages of the slit are smooth and not cracked or drawn.