With the continuous increase in the output and consumption of plastics, the subsequent problems of the uprising amount of waste plastics occur. The recycling of plastics has become a research hotspot. We designed a thin-film plastic crusher based on the shearing principle, including a pressing mechanism, a crushing mechanism, and a motor power device. This design can efficiently solve the difficulty of pulverizing thin-film plastics with high malleability.
The design of the Plastic Crusher has significant practical value for the recycling of highly malleable waste film plastics. The following explains and analyzes the working principle of Plastic Crusher, the 3D model, the assembly connection between each functional mechanism, the structure of the core components, and the designed hydraulic system operation plan.
Traditional crushing methods are challenging to crush Film plastic with a soft texture. The Plastic Crusher needs to quickly cut the extruded and dense film plastic block with a high-speed rotating blade. And effectively cut the plastic crumb before the plastic is wrapped around the tool. Plastic Crusher mainly includes material pressing structure, crushing mechanism, and motor power unit, etc. The mechanism principle of the whole machine is shown in Figure 1.
First, check the ambient conditions of the machine and whether the parts of the machine body are correctly installed. After ensuring safety, power on the electric motor and turn on the hydraulic station to make the power system operate reliably. At this time, the blade and sieve that perform the primary function of crushing rotate clockwise at high speed and counterclockwise at low speed. Then, put the material into the storage barrel through the upper part. After the material is filled, open the valve. The hydraulic motor drives the hydraulic oil to enter the hydraulic cylinder. It causes a considerable impact on the piston rod. With the driving force, the squeezing piston slowly moves inward to compact the plastic. On the side of the sieve plate of the storage cylinder, the compacted material will pass through the holes of different sizes in the sieve plate. At this time, the shearing action formed by the rotating movement between the sieve plate and the blade will penetrate the plane of the sieve plate. The plastic is cut and separated, thus completing the crushing process of the film plastic. With the continuous forward movement of the pressing piston, the material in the storage cylinder is gradually crushed. The crushed plastic scraps fall into the hopper under the fixed support frame under the restriction of the discharge port shell to complete the collection of the plastic wastes.
The 3D digital design of the product includes the digital design of mechanical parts and structural components. Most mechanical parts are outsourcing parts and standard parts. In contrast, the structural parts rely on parameter-driven design methods of repeated adjustments to obtain a product model that meets the requirements. For the solid assembly of a general mechanical system, first, need to construct all the relevant three-dimensional entities of the parts and then complete according to the positional constraint connections between the components.
In the design of the film Plastic Crusher Machine, after resolving the functional principle scheme, use software to perform 3D modeling of the components of the Plastic Crusher Machine. The bottom-up design method is adopted. First, draw the three-dimensional model of the main functional features, perform the component constraint coordination and layout optimization in the virtual assembly environment. So that the Plastic Crusher occupy a small working space with a simple structure and is easy to land and fix. Finally, design and add auxiliary functional components to the Plastic Crusher. Ensure the machine has no safety hazards to the operator during the work process and ensure the normal execution and long life of the various functional mechanisms of the device. The final 3D model of Plastic Crusher is shown in Figure 2.
The crushing mechanism of Plastic Crusher is mainly composed of blades and sieve plates, as shown in Figure 3. The screen plate is fixed on the side end surface of the large spur gear by bolt connection and is located at the inner end of the storage cylinder. The large spur gear with a hollow structure is sleeved on the outside of the storage cylinder, which can rotate freely and smoothly contact the storage cylinder.
The inner surface of the large spur gear is supported on the thrust bearing seat by a one-way thrust ball bearing. The thrust bearing seat is fixedly connected with the external fixed support frame. In this way, The material in the storage cylinder on the screen plate is being squeezed. The thrust generated acts on the thrust bearing seat via giant spur gears and one-way thrust ball bearings. Thereby preventing the axial deviation of the screen plate after being stressed. Both ends of the large pulley shaft are supported by deep groove ball bearings on the bearing housing hole and the small bearing seat of the storage cylinder. The small spur gear and the large pulley are fixedly installed on the pulley shaft through a critical connection. The small spur gear and the sizeable straight gear meshes. The large belt pulley forms transmission cooperation with the small belt pulley installed on the tool spindle through the V-belt. The small bearing seat is fixed on the upper part of the extended support frame by hexagon head bolts. The bottom of the elongate support frame is specified on the fixed support frame under the Plastic Crusher.
Two deep groove ball bearings support the tool spindle on the spindle bearing seat symmetrically arranged about the small pulley. At the inner end of the spindle of the tool is the blade mounting assembly. The blade fixing ring securely clamps the edge on the blade fixing seat. The blade fixing seat is matched with the tool spindle through a critical connection. The outer end of the tool spindle is connected with the motor power device through a coupling. The discharge port shell to prevent the plastic from splashing around after crushing is fixed to the side end surface of the thrust bearing seat through-bolt connection.
The primary function of the Plastic Crusher mechanism is to shear and crush the tightly compacted film and plastic blocks. The core components are blades and sieve plates, as shown in Figure 4. The blade is designed in the shape of a slender flat triangular pyramid. The cutting surface gradually increases from the tip to the tail of the knife. This shape ensures uniform and appropriate stress throughout the knife body during the cutting process. It avoids bending and fractures of the tool due to excessive local stress. The material of the blade should have high strength, rigidity, and wear resistance. The outer surface of the sieve plate should be flat and smooth, with a small distance from the blade. This can prevent serious wear problems caused by the contact and sliding of the blade and the sieve plate. The blade and the sieve plate produce sound shearing effects in the high-speed rotation movement in the opposite direction. The number of cutters is designed to be three to meet cutting force requirements and improve cutting efficiency.
The size and position distribution of the mesh on the sieve plate are random. This kind of design has certain advantages. Different plastics to be crushed have extra softness. To ensure the extruded plastic can pass through the mesh of the sieve plate and be cut by the cutter, the requirements for the size of the mesh of the sieve plate are different. Under the condition of random distribution of mesh size and position, Plastic Crusher can crush various types of film plastics. The material used to make the sieve plate requires good rigidity and wear resistance. The thickness of the sieve plate should be moderate.
When the crushing mechanism is working, the tool spindle drives the blade to rotate clockwise at high speed. At the same time, it causes the sieve plate to rotate counterclockwise at low speed via the small pulley, large pulley, small spur gear, and large spur gear.
The purpose of keeping the slow rotating of the sieve plate is to prevent the squeezed materials from clogging and accumulating at a particular corner due to the static sieve plate. The materials in contact with the sieve plate at any position can be effectively used to leak out. The speed of the sieve plate should not be too high so that the material can be cut in time after passing through the mesh. After the sieve plate is reduced in speed through the belt drive and the gear drive, the rotating torque will be significantly increased. Thus to ensure that it can still rotate under the more excellent frictional resistance of the compressed material. In addition, the reverse rotation of the sieve plate and the blade also increases the relative shear rate and improves the shearing and crushing efficiency of the film plastic. The belt drive in the transmission chain has the effect of overloading and slipping, avoiding improper operation or emergencies from causing hard damage to the running machine or even causing accidents.
The pressing structure of the film Plastic Crusher is shown in Figure 5. It mainly includes hydraulic cylinders, feed ports, storage cylinders, and extrusion pistons. The hydraulic cylinder and the storage cylinder are connected and installed on the upper part of the fixed support frame by bolts. Before turning on the power of the hydraulic system, the initial position of the squeeze piston is at the outermost end of the storage cylinder. The operator puts the waste film plastic into the storage cylinder through the feed port. After the material is complete, turn on the power of the hydraulic system and open the control valve. The squeezing piston moves forward slowly under the push of the hydraulic cylinder, The material in the cylinder is squeezed. The compressed material passes through the mesh on the sieve plate and then is sheared and crushed by the high-speed rotating blade.
The circuit diagram of the hydraulic system in the pressing mechanism is shown in Figure 6. Its working principle is: after the hydraulic pump is turned on, the electromagnet of the electromagnetic directional valve is energized, the oil in the oil tank enters the hydraulic pump through the filter, and the hydraulic pump converts the mechanical energy the prime mover into liquid.
The overflow valve has the function of adjusting the working pressure of the hydraulic system. When the pressure of the squeezing piston to squeeze the material is too high, the overflow valve can protect against overload and overflow. It prevents the squeezing piston from forcibly packing the material and causing severe damage to the Plastic Crusher screen.
The shearing and crushing efficiency of the Plastic Crusher is related to many factors such as the material characteristics of the material to be crushed, the advancing speed of the extrusion piston, the screen area, the mesh area, the mesh size distribution law, the rotation speed and number of the blades, and so on. Therefore, it is difficult to directly carry out the theoretical calculation. According to the equipment specifications of similar products in the market, the parameters for selecting the three-phase asynchronous AC motor are model Y180M-4, rated power 18.5kW, and full load speed 1470r/min. The motor power unit is shown in Figure 7. The motor fixed on the fixing support frame of the Plastic Crusher is connected to the high-speed shaft of the single-stage gear reducer through a coupling. The low-speed shaft of the reducer is also connected to the tool spindle through the coupling。 With this, it realizes the power input function of the device to the crushing mechanism.
Film plastics with high malleability are difficult to crush with traditional crushing methods. Therefore, we have designed a type of film Plastic Crusher, mainly including a material pressing structure, a crushing mechanism, and a motor power device. When the Plastic Crusher is operating, the squeezing piston inward in the storage cylinder slowly moves. Hence, the plastic is compacted, making it finely penetrate the holes of different sizes on the sieve plate. A shearing effect is formed between the high-speed rotating blade and the sieve plate. The plastic that passes through the plane of the sieve plate is cut and separated, thereby realizing the crushing function of the soft and malleable waste film plastic.
The design of this Plastic Crusher has significant practical value for recycling and utilizing soft, ductile waste film plastics.