Based on the development requirements of printing equipment, the system design, system processing, installation and debugging, performance testing experiments, system trial operation and system improvement of 3D printing equipment are studied in several stages, and the technical standards for the relevant machinery and control systems of the equipment are studied. Design and optimization were carried out, and the development of the equipment was completed

Yu, Jiatong

English

Electronics Science Technology and Application (E-Journal)

-12- Electronics Science Technology and ApplicationResearch on Mechanical and Control System Design Basedon 3D Printing EquipmentJiatong YuShenyang Institute of Technology, Shenyang 110043, China.Abstract: Based on the development requirements of printing equipment, the system design, systemprocessing, installation and debugging, performance testing experiments, system trial operation and systemimprovement of 3D printing equipment are studied in several stages, and the technical standards for therelevant machinery and control systems of the equipment are studied. Design and optimization were carriedout, and the development of the equipment was completed.Keywords: 3D Printing Equipment; Mechanical Design; Control System; Control SoftwareIntroductionSelective laser melting technology is an advanced manufacturing technology developed on the basis ofselective laser sintering technology that uses the superposition principle, that is, the "incremental"manufacturing method of layer-by-layer cladding to directly produce metal products. The process is: In thecomputer, Use CAD three-dimensional modeling software to establish a three-dimensional digital model ofthe entity to be processed, and use preprocessing software to perform layered processing on thethree-dimensional digital model to obtain the model contour graphics.1.1 The working principle and composition of SLM 3D printingequipmentThe working principle of SLM 3D printing equipment is shown in Figure 1. When f The workingprinciple of SLM 3D printing equipment is shown in Figure 1. During forming, the powder spreading shaftspreads the powder material from the powder feeding cylinder into the working cylinder, and then the laserbeam is controlled by the control program according to the profile information of the section of the formedpart.[1] The powder material is scanned and sintered, and the scanned powder melts and then falls below themelting point, and is bonded to each other to obtain a sintered surface.1.2 General requirements for the development and design ofSLM 3D printing equipmentThe overall requirements for the development and design of SLM 3D printing forming equipment areas follows: The movement accuracy of the powder feeding cylinder is generally controlled to 0.01 mm; thepositioning accuracy of the powder spreading roller guide rail is controlled to be 0.0025 mm; etc.; processVolume 9 Issue 4 -13-software and control software can be used alone or together, supporting remote maintenance and remotemonitoring Function; Adopt servo closed-loop control; Substrate and fast laser composite preheatingtechnology[2].2. System DesignUse CAD 3D modeling software to establish a 3D digital model of the entity to be processed, and thenperform layering processing. On the laser 3D printer, control the laser point according to the contourgraphics of each layer to sinter the powder material on the working platform, layer by layer, and finally Athree-dimensional solid prototype consistent with the designed model is obtained, and the process flow isshown in Figure 2.Figure 2 3D printing process diagram2.1 Mechanical system design2.1.1 Mechanical design requirementsThe weight and volume of the whole machine are as small as possible, it can be handled as a whole,and the transportation is convenient; the operability, maintainability and economy of the system should betaken into account in the structure; The machine works reliably and has a long service life; the appearancedesign should be beautiful and the assembly is convenient.2.1.2 Structural design schemeIn order to make the designed product meet the above-mentioned mechanical design requirements, atthe same time of structural design, the characteristics of the overall production are considered, and attentionshould be paid to the structural design: when assembling the position of the design hole, it is generallydesigned to be matched for processing, Reduce assembly problems caused by inaccurate positioning; inorder to ensure the realization of the structural process design, the assembly process and processingtechnology should be specified in detail.2.1.3 Overall structureThe overall structure of 3D printing adopts the design scheme of separating the working host unit andthe control cabinet unit to reduce the overall size and weight of the host unit and facilitate transportation.The control cabinet unit is separated in layers to improve the space. The utilization rate of the working hostis shown in Figure 3.-14- Electronics Science Technology and ApplicationFigure 3 Schematic diagram of the host structure2.2 Design of Laser Scanning System2.2.1 The working principle and selection of the dynamicfocusing unitThe dynamic focusing unit is introduced to overcome the "arc effect" of the scanning system in the 3Dprinting system. In an ordinary scanning system without a dynamic focusing unit, the focal spot trajectoryformed by the two galvanometers is an arc, as shown in Figure 4, the focal spot scanning trajectory (arc)and the working surface only coincide at the center point C, and the center The two are separated outsidethe point, and the separation is the largest at the edge A of the workpiece, and the larger the workpiece orthe smaller the deflection radius of the beam, the greater the separation. At A', the light beam convergesinto a point and then diverges, and when it reaches A, a larger-sized light spot is formed, and the powerdensity is reduced, which affects the sintering quality and precision.Figure 4 Schematic diagram of arc effectThe double galvanometer scanning head controls the light spot to scan in the x-y plane, and thefocusing error ΔS of the double galvanometer system is:∆S = S2 − S1 = a2 + y2 + b2+ �2 − � + � # 1In practical engineering, in order to ensure the reliable response of the linear displacement of thenegative lens to the scanning speed of the galvanometer, the axial displacement of the negative lens iscontrolled within ±5 mm. Assuming that the maximum scanning angle of the galvanometer is ±20°, and thedistance from the galvanometer to the working surface is 465 mm, the focusing error of 60 mm can beobtained, and the change of the system focus position is ±ΔS /2 = ±30 mm. The HLP-350I moldingmachine adopts the varioSCAN 40 dynamic focusing unit of SCANLAB Company, and its focal lengthvariation is ±38.5 mm.Volume 9 Issue 4 -15-2.2.2 Galvanometer mirrorThe HLP-350I molding machine is a low-power laser system, and the mirror does not need to becooled and dissipated. Therefore, the mirror substrate is made of ordinary optical glass, and then coatedwith a multi-layer dielectric film, with a reflectivity of more than 99%. The size of the mirror must be largeenough to not cut the beam during deflection. For any laser system, the focal spot size is determined bydiffraction and spherical aberration, where the focal spot diameter affected by diffraction is:d1 =4�2����# 2The diameter of the focal spot affected by spherical aberration is:d2 =��3�2# 3In the formula: :M2is the quality factor of the laser mode (:M2=1.4 in HLP-350I); f is the focal lengthof the focusing element, f = 630 mm; λ is the laser wavelength, λ=10.6 μm; D is the aperture diaphragmDiameter, D = 40 mm; k is a factor related to the focusing element material.d1 and d2 are 0.298 mm and 0.005 mm, respectively. Focal spot diameter, i.e. d = d1 = 0.298mm.2.2.3 Demonstration of laser power and laser selectionThe parameters of PS powder and wax powder are listed in Table 1. When the laser power is P = 20 W,δ= 0.2 mm, d = 0.3 mm, it can be seen that when the laser power is 20 W, the PS is completely melted Thescanning speeds of powder and wax powder are 2.12 m/s and 1.96 m/s, respectively, so the scanning speedof the universal extraction system is 2 m/s. The actual scanning speed after process optimization is about1.3m/s, so the laser power can be appropriately reduced.parameterMaterialC(J/g•℃) ρ(g/cm3) T℃ T0℃ D mm δ mm ν (mm/s)PS 1.25 1.05 185 65 0.3 0.2 2116.4Wax powder 2.9 0.9 90 25 0.3 0.2 1964.82.3 Control system design2.3.1 Hardware Design of Control SystemIn the 3D printing system, the control system controls the coordination of each component in the entiresystem according to a predetermined program. The laser 3D printing system is composed according to thestructure, mainly including: scanning system control[3]; working cylinder and feeding cylinder motioncontrol; powder spreading mechanism motion control; power distribution control; lighting control;preheating system control; cooling induced draft motor control; exhaust air Filtration system control.2.3.2 Software design of molding systemIn the laser 3D printing system, the software system is mainly composed of three parts:three-dimensional graphics software, processing software and control system software[4].-16- Electronics Science Technology and Application2.3.3 3D graphics software3D CAD graphics software is a key component of 3D printing forming technology, and its mainfunctions are 3D model design of parts and surface triangulation of 3D models.SummaryAccording to the requirements of the development task of HLP-350 3D printer, the system design,system processing, installation and debugging, performance testing experiment, Several stages such assystem trial operation and system improvement were studied, [5]the technical standards of the relevantmachinery and control systems of the equipment were designed and optimized, and the development of theequipment was completed.References[1] Albar A, Chougan M, Al-Kheetan M J, et al. Effective extrusion-based 3D printing system designfor cementitious-based materials[J]. Results in engineering, 2020, 6: 100135.[2] Liu YM. Research on control system design of micro-jet forming 3D printing equipment based onSTM32 [D]. Huazhong University of Science and Technology, 2019.[3] Sathish T, Vijayakumar MD, Ayyangar AK. Design and fabrication of industrial components using3D printing[J]. Materials Today: Proceedings, 2018, 5(6): 14489- 14498.[4] Wu JJ, Huang LM, Zhao Q, Xie T. 4D Printing: History and Recent Progress[J]. Chinese Journal ofPolymer Science, 2018, 36(05): 563-575.[5] Bharat Bhushan, Matt Caspers. An overview of additive manufacturing (3D printing) formicrofabrication[J]. Microsystem Technologies,2017,23(4).

Research on Mechanical and Control System Design Based on 3D Printing Equipment

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Research on Mechanical and Control System Design Based on 3D Printing Equipment

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Electronics Science Technology and Application (E-Journal)