CN105058806A - Device and method for achieving laser rapid molding of superhigh molecular weight polymer - Google Patents

Abstract

The invention relates to a device and method for realizing laser rapid prototyping of ultra-high molecular weight polymers. The device includes: a laser emitting end emitting a laser beam for irradiating and melting ultra-high molecular weight polymer powder; It is used to compact the ultra-high molecular weight polymer at the laser beam sintering position; the infrared thermometer is used to monitor the temperature change of the sintering position; the signal processing device is used to feed back the process parameters according to the temperature signal to adjust the signal to the main control system ; The main control system controls the laser emitting end and the pressure roller according to the process parameter adjustment signal. The method includes the steps of powder pre-laying, parameter preset, sintering compaction, real-time control and molding end. The present invention can effectively avoid air holes in molded parts, and prevent oxidation and decomposition of ultra-high molecular weight polymers due to excessive temperature or heat accumulation, thereby realizing high-quality molding of ultra-high molecular weight polymers and obtaining good ultra-high molecular weight polymerization. Things take shape.

Description

A device and method for realizing laser rapid prototyping of ultra-high molecular weight polymers

technical field

The invention relates to a laser rapid prototyping device and method, in particular to a laser rapid prototyping device and method for ultra-high molecular weight polymers.

Background technique

As a new generation of engineering plastics, ultra-high molecular weight polymers have many excellent properties such as high specific strength, good toughness, wear resistance, corrosion resistance, low temperature resistance, stress crack resistance, impact resistance, adhesion resistance, and self-lubrication. Agricultural production, medicine and national defense construction are playing an increasingly important role. However, this type of material has extremely high molecular weight, and ultra-long, entangled molecular chains, the melt is highly elastic, and the melt index is approximately zero; the molding temperature range is narrow, and it is easy to oxidative degradation; the critical shear rate is low, the friction The coefficient is small, so it is not easy to form and process.

In recent years, due to the advantages of high precision, fast speed, short cycle, and no need for molds, laser technology has developed rapidly in the field of material processing, especially in the rapid prototyping of polymer materials. It is rarely used in the molding process. In order to make full use of the advantages of laser prototyping technology, it is necessary to develop a laser rapid prototyping solution suitable for ultra-high molecular weight polymers.

Through a lot of research, we found that the laser rapid prototyping of ultra-high molecular weight polymers has the following problems:

First, the ultra-high molecular weight polymer is in the powder state of discrete accumulation before molding, and there are a lot of gaps between the powder particles. Since air is a poor conductor of heat, it affects the conduction of heat during molding. In addition, the fluidity of the polymer in the molten state is extremely poor, the relative position between the particles changes little, there are a large number of pores inside the molded part, and the density is low, which seriously affects the molding quality.

Second, the processing temperature range of ultra-high molecular weight polymers is narrow, and they are more sensitive to laser energy density and sintering position temperature. When the laser energy density is high, the temperature of the sintering position is too high, causing the polymer to oxidize and decompose, and the chain scission reaction occurs to form double bonds and free radicals. The breakage of molecular bonds will lead to a decrease in the performance of molded parts. At the same time, the molecular chain is also closely related to the crystallinity, and the crystallinity will affect the stiffness, tensile strength, hardness, heat resistance, solvent resistance, air tightness and chemical corrosion resistance of the product, and sometimes even directly lead to the molded parts void.

Contents of the invention

Based on this, the present invention provides a device and method for realizing laser rapid prototyping of ultra-high molecular weight polymers, which effectively realize laser rapid prototyping of ultra-high molecular weight polymers.

The technical scheme adopted in the present invention is as follows: a device for realizing laser rapid prototyping of ultra-high molecular weight polymers, the device comprising:

Laser emitting end, the laser emitting end emits a laser beam for irradiating ultra-high molecular weight polymer powder and melting it;

Pressing rollers for compaction of the UHMW polymer at the laser beam sintering location;

An infrared thermometer for monitoring the temperature or temperature change of the sintering position;

The signal processing device is used to feed back the process parameter adjustment signal to the main control system according to the temperature signal monitored by the infrared thermometer;

The main control system controls the laser emitting end and the pressure roller according to the received process parameter adjustment signal.

Furthermore, the laser emitting end and the infrared thermometer are fixed together, and the detection position of the infrared thermometer coincides with the laser irradiation position of the laser emitting end, so as to ensure that the two move synchronously and realize real-time synchronous monitoring of the temperature of the laser beam sintering position .

The laser emitting end is located at the front of the pressure roller in the forward direction. Preferably, the edge of the laser beam emitted from the laser emitting end is tangent to the edge of the pressure roller. More preferably, the circular section of the pressing roller is as small as possible to shorten the time difference between melting the powder by laser beam irradiation and compacting by the pressing roller, so as to realize real-time compaction.

The main control system controlling the laser emitting end and the pressing roller according to the received process parameter adjustment signal includes adjusting the process parameters of the laser emitting end and the pressing roller according to the process parameter adjustment signal, wherein the process parameter of the laser emitting end includes the moving track of the laser emitting end , moving speed and output laser power, the process parameters of the pressing roller include the height of the pressing roller and the moving rate along the horizontal direction. Preferably, the main control system is also used to preset the process parameters of the laser emitting end and the pressure roller.

The ultra-high molecular weight polymer powder is preferably ultra-high molecular weight polyethylene and/or ultra-high molecular weight nylon.

A method for laser rapid prototyping of ultra-high molecular weight polymers using the aforementioned device, the method comprising the steps of:

Step 1: Pre-spread ultra-high molecular weight polymer powder on the powder bed, adjust the position of the laser emitting end and the pressure roller through the main control system, so that they are located above the powder bed;

Step 2: Preset the process parameters of the laser emitting end and the pressure roller in the main control system;

Step 3: Turn on the laser emitting end and the pressing roller through the main control system, and the laser emitting end and the pressing roller move simultaneously with their respective preset process parameters to sinter and form the ultra-high molecular weight polymer powder and compact it in real time;

Step 4: Turn on the infrared thermometer and the signal processing device. The infrared thermometer feeds back the temperature of the laser beam sintering position to the signal processing device in real time. The signal processing device makes a logical judgment on the temperature of the laser beam sintering position and then feeds back the process parameter adjustment to the main control system Signal, the main control system adjusts the signal according to the process parameters to control the laser emitting end and the pressure roller, so as to realize the real-time control of the temperature of the laser beam sintering position;

Step 5: After forming, close the device.

Further, in the step 1, the laser emitting end and the pressing roller are located directly above the starting end on the left side of the workbench, and the laser emitting end is located in the front of the pressing roller in the forward direction, and its height meets the requirements of the ultra-high molecular weight polymer forming for the laser. Requirements for the amount of defocus; the pressure roller is located at a set height, which can effectively compact the ultra-high molecular weight polymer at the laser beam sintering position.

In the step 2, the moving track of the laser emitting end only needs to ensure that the velocity component of the laser emitting end in the moving direction of the pressing roller is the same as the moving speed of the pressing roller, so as to realize the ultra-high molecular weight polymerization of the pressing roller to the laser beam sintering position Simultaneous compaction of objects.

In the step 4, the main control system adjusts the laser emitting end and the pressing roller at the same time, and ensures that the velocity component of the laser emitting end in the moving direction of the pressing roller is the same as the moving speed of the pressing roller in real time, and finally realizes the laser beam sintering position Real-time adjustment and control of temperature.

This method can not only realize two-dimensional plane forming, but also realize multiple two-dimensional cross-sections layer by layer along the height direction, that is, three-dimensional forming.

Beneficial effects of the present invention:

The present invention uses pressure rollers to realize real-time compaction of ultra-high molecular weight polymers, promotes the flow of molten powder and fills gaps during powder melting and molding, and avoids pores in the molded parts; at the same time, it adopts a temperature closed-loop control mode to monitor the temperature of the sintering position in real time. Control the temperature of the sintering position within the allowable processing temperature range to prevent oxidation and decomposition of ultra-high molecular weight polymers due to excessive temperature or heat accumulation, so as to achieve high-quality molding of ultra-high molecular weight polymers.

Description of drawings

Fig. 1 is a schematic structural view of the present invention.

Fig. 2 is a schematic diagram of the moving track of the laser emitting end and the pressure roller.

Fig. 3 is a flow chart of the method of the present invention.

Among them, 1-Laser emitter, 2-Press roller, 3-Infrared thermometer, 4-Workbench, 5-Main control system, 6-Signal processing device.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings. However, those skilled in the art know that the present invention is not limited to the drawings and the following embodiments.

Fig. 1 is a schematic structural view of the ultra-high molecular weight polymer laser rapid prototyping device involved in the present invention. The ultra-high molecular weight polymer laser rapid prototyping device includes: a laser emitting end 1, a pressure roller 2, an infrared thermometer 3, a workbench 4, a main control system 5, and a signal processing device 6. The laser emitting end 1 emits a laser beam for irradiating and melting the ultra-high molecular weight polymer powder; the pressing roller 2 is used for compacting the ultra-high molecular weight polymer at the laser beam sintering position; the infrared thermometer 3 is used for Monitor the temperature or temperature change of the laser beam sintering position; the workbench 4 carries the pressure roller and the powder bed arranged on the workbench 4, and the powder bed can also be a part of the workbench 4; the signal processing device 6 is used to process the infrared thermometer 3, and feed back the process parameter adjustment signal to the main control system 5; the main control system 5 controls the laser emitting end and the pressing roller according to the received temperature signal.

The laser emitting end 1 is located at the front of the pressing roller 2 in the advancing direction. Preferably, the edge of the laser beam emitted by the laser emitting end 1 is tangent to the edge of the pressure roller 2 , but it is ensured that the laser beam cannot be irradiated onto the pressure roller 2 . The circular cross-section of the pressing roller 2 is as small as possible to shorten the time difference between melting the powder by laser irradiation and compacting by the pressing roller, so as to realize real-time compaction.

The moving trajectory, moving speed and output laser power of the laser emitting end 1 are set and adjusted by the main control system 5;

The laser emitting end 1 can be fixed together with the infrared thermometer 3, and the detection position of the infrared thermometer 3 coincides with the laser irradiation position of the laser emitting end 1, so as to ensure that the two move synchronously and realize the temperature control of the laser beam sintering position. Real-time synchronization monitoring.

The infrared thermometer 3 measures the temperature of the sintering position in real time, and feeds back the temperature data to the signal processing device 6 . After the judgment is made by the signal processing device 6 , a process adjustment signal is given, and then the process adjustment signal is fed back to the main control system 5 . The main control system 5 completes the adjustment of the laser emitting end 1 and the pressure roller according to the process adjustment signal, ensuring that the temperature of the laser beam sintering position is within the processing temperature range of ultra-high molecular weight polymers, and ensuring that the pressure roller 2 is aligned with the laser beam sintering position Simultaneous compaction of ultrahigh molecular weight polymers.

The device for realizing laser rapid prototyping of ultra-high molecular weight polymers of the present invention is applicable to all ultra-high molecular weight polymers. The ultra-high molecular weight polymer in the present invention can be a kind of ultra-high molecular weight polymer, or a mixture of multiple ultra-high molecular weight polymers. Preferably, the ultra-high molecular weight polymer is ultra-high molecular weight polyethylene or ultra-high molecular weight nylon, or a mixture of ultra-high molecular weight polyethylene and ultra-high molecular weight nylon, or a combination of high molecular weight polyethylene and ultra-high molecular weight nylon with other ultra-high molecular weight nylon Mixture of molecular weight polymers.

The schematic diagram of the moving track of the laser emitting end and the pressure roller is shown in Figure 2. The solid line in Figure 2 is the moving track of the laser emitting end 1, and the dotted line is the moving track of the pressing roller 2. The laser emitting end moves along the "Z"-shaped fold line on the horizontal plane, while the pressing roller moves in a single direction on the horizontal plane, ensuring that the velocity component of the laser emitting end in the moving direction of the pressing roller is the same as the moving speed of the pressing roller in real time, thereby realizing continuous molding Simultaneous compaction with real time. Figure 2 is just an example for ease of understanding. In the process of forming with this device, the trajectory of the laser emitting end and the pressure roller is not limited to Figure 2. Various trajectories can be used to obtain the expected molding pattern, as long as the The velocity component of the laser emitting end in the moving direction of the pressing roller is the same as the moving speed of the pressing roller in real time.

Fig. 3 is a kind of flow chart of the method that realizes ultra-high molecular weight polymer laser rapid prototyping provided by the present invention, and this method comprises the following steps:

Step 1: pre-spread ultra-high molecular weight polymer powder on the powder bed, adjust the positions of the laser emitting end 1 and the pressure roller 2 through the main control system 5, so that they are located above the powder bed.

Step 2: Preset the moving track, moving speed and output power value of the laser emitting end 1 in the main control system 5, as well as the moving speed of the pressure roller 2 along the horizontal direction.

Step 3: Turn on the laser emitting end and the pressing roller through the main control system 5, and the laser emitting end 1 and the pressing roller 2 move at the same time according to the preset trajectory and parameters, sintering and forming the ultra-high molecular weight polymer powder, and compacting in real time.

Step 4: Turn on the infrared thermometer 3 and the signal processing device 6 . The temperature of the sintering position is fed back to the signal processing device 6 in real time by the infrared thermometer 3, and the signal processing device 6 feeds back the process parameter adjustment signal to the main control system 5 after logic judgment, and the main control system 5 controls the laser emitting end 1 and the pressure roller 2 The process parameters are adjusted, and the temperature of the sintering position is controlled in real time.

Step 5: At the end of molding, turn off the laser transmitter 1, infrared thermometer 3 and signal processing device 6 at the same time, but keep the pressure roller 2 moving forward until the ultra-high molecular weight polymer in the molding area is compacted and then stop.

Wherein step 1, the molding powder pre-laid on the workbench 4 includes all ultra-high molecular weight polymer powders, preferably ultra-high molecular weight polyethylene, ultra-high molecular weight nylon, etc.

In step 1, preferably, the laser emitting end 1 and the pressure roller 2 are located directly above the starting end on the left side of the powder bed; the pressure roller 2 is located at a set height, which can effectively compact the ultra-high molecular weight polymer at the sintering position , the laser emitting end 1 is located at the front of the pressure roller 2, and its height meets the requirements of laser defocusing for molding.

In the step 2, the laser emitting end 1 can have any trajectory, it only needs to ensure that the velocity component of the laser emitting end 1 in the moving direction of the pressure roller 2 is the same as the moving speed of the pressure roller 2, so as to realize the sintering position of the pressure roller 2 Simultaneous compaction of ultrahigh molecular weight polymers.

Wherein step 4, the main control system 5 adjusts the laser emitting end and the pressure roller at the same time, and ensures that the velocity component of the laser emitting end 1 in the moving direction of the pressing roller 2 is the same as the moving speed of the pressing roller 2 in real time, and finally realizes the sintering Real-time adjustment and control of position temperature.

Among them, this method can not only realize two-dimensional plane forming, but also realize multiple two-dimensional cross-sections layer by layer along the height direction, that is, three-dimensional forming.

The following are examples of the present invention.

Example 1

Laser rapid prototyping of ultra-high molecular weight polyethylene (UHMWPE) with a molecular weight of 4.5 million was performed using a 1064nm Nd:YAG all-solid-state laser. Among them, the output laser power of the laser emitting end is 10W, and the spot diameter is 0.8mm; the scanning speed of the laser emitting end is 0.8mm/s, and the horizontal moving speed of the pressure roller is 0.1mm/s. During the forming process, the temperature of the sintering position is controlled within the range of 210-240°C. Finally, a good molded part without pores is obtained.

Example 2

Laser rapid prototyping of ultra-high molecular weight nylon (UHMWPA) with a molecular weight of 2 million using a 10.6um _CO2 continuous laser. Among them, the output laser power of the laser emitting end is 35W, and the spot diameter is 1mm; the scanning speed of the laser emitting end is 0.6mm/s, and the horizontal moving speed of the pressure roller is 0.1mm/s. During the forming process, the temperature of the sintering position is controlled within the range of 200-230°C. Finally, a good molded part without pores is obtained.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above-mentioned embodiments. For example, the number of laser emitting ends, pressure rollers, infrared thermometers, etc. involved in the present invention is not limited to one, and multiple ones can be used; The bed is pre-compacted, and the gas between the powder particles is expelled to a certain extent; the laser source used includes various types of lasers. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A device for realizing ultra-high molecular weight polymer laser rapid prototyping, characterized in that the device comprises: Laser emitting end, the laser emitting end emits a laser beam for irradiating ultra-high molecular weight polymer powder and melting it; Pressing rollers for compaction of the UHMW polymer at the laser beam sintering location; An infrared thermometer for monitoring the temperature or temperature change of the sintering position; The signal processing device is used to feed back the process parameter adjustment signal to the main control system according to the temperature signal monitored by the infrared thermometer; The main control system controls the laser emitting end and the pressure roller according to the received process parameter adjustment signal. 2. The device according to claim 1, wherein the laser emitting end and the infrared thermometer are fixed together, and the detection position of the infrared thermometer coincides with the laser irradiation position of the laser emitting end, thereby ensuring that the two are synchronized Move to realize real-time synchronous monitoring of the temperature of the laser beam sintering position. 3. The device according to claim 1 or 2, characterized in that the laser emitting end is located at the front of the pressure roller in the advancing direction. Preferably, the edge of the laser beam emitted from the laser emitting end is tangent to the edge of the pressure roller. More preferably, the circular section of the pressing roller is as small as possible to shorten the time difference between melting the powder by laser beam irradiation and compacting by the pressing roller, so as to realize real-time compaction. 4. The device according to any one of claims 1 to 3, wherein the main control system controls the laser emitting end and the pressure roller according to the received process parameter adjustment signal including adjusting the laser emitting end according to the process parameter adjustment signal And the process parameters of the pressure roller, wherein the process parameters of the laser emitting end include the moving track, moving speed and output laser power of the laser emitting end, and the process parameters of the pressing roller include the height of the pressing roller and the moving rate along the horizontal direction. Preferably, the main control system is also used to preset the process parameters of the laser emitting end and the pressure roller. 5. The device according to any one of claims 1 to 4, characterized in that the ultra-high molecular weight polymer powder is preferably ultra-high molecular weight polyethylene and/or ultra-high molecular weight nylon. 6. A method adopting the device according to any one of claims 1 to 5 to realize ultra-high molecular weight polymer laser rapid prototyping, characterized in that the method comprises the steps: Step 1: Pre-spread ultra-high molecular weight polymer powder on the powder bed, adjust the position of the laser emitting end and the pressure roller through the main control system, so that they are located above the powder bed; Step 2: Preset the process parameters of the laser emitting end and the pressure roller in the main control system; Step 3: Turn on the laser emitting end and the pressing roller through the main control system, and the laser emitting end and the pressing roller move simultaneously with their respective preset process parameters to sinter and form the ultra-high molecular weight polymer powder and compact it in real time; Step 4: Turn on the infrared thermometer and the signal processing device. The infrared thermometer feeds back the temperature of the laser beam sintering position to the signal processing device in real time. The signal processing device makes a logical judgment on the temperature of the laser beam sintering position and then feeds back the process parameter adjustment to the main control system Signal, the main control system adjusts the signal according to the process parameters to control the laser emitting end and the pressure roller, so as to realize the real-time control of the temperature of the laser beam sintering position; Step 5: After forming, close the device. 7. The method according to claim 6, wherein in said step 1, the laser emitting end and the pressure roller are located directly above the starting end on the left side of the workbench, and the laser emitting end is located at the front of the pressure roller in the forward direction , its height meets the requirement of laser defocusing amount for ultra-high molecular weight polymer molding; the pressure roller is located at the set height, which can effectively compact the ultra-high molecular weight polymer at the laser beam sintering position. 8. The method as claimed in claim 6 or 7, characterized in that, in said step 2, the moving track of the laser emitting end only needs to ensure that the velocity component of the laser emitting end in the moving direction of the pressing roller and the movement of the pressing roller The speed is the same to realize the simultaneous compaction of the ultra-high molecular weight polymer at the laser beam sintering position by the pressure roller. 9. The method according to any one of claims 6 to 8, characterized in that in step 4, the main control system adjusts the laser emitting end and the pressure roller at the same time, and ensures that the laser emitting end is in the moving direction of the pressure roller The speed component above is the same as the moving speed of the pressure roller in real time, and finally realizes the real-time adjustment and control of the temperature of the laser beam sintering position. 10. The method according to any one of claims 6 to 9, characterized in that the method can not only realize the forming of two-dimensional plane, but also realize the forming of multiple two-dimensional cross-sections layer by layer along the height direction, that is, three-dimensional forming.