CN105538712B - A kind of 3D printing method of laser compound-contoured scanning - Google Patents

Abstract

The invention discloses a laser composite profile scanning method for laser 3D printing. In the process of laser 3D printing, beams with different beam diameters are obtained by adjusting and changing the laser beam spot diameter and energy density, that is, high energy density. Small-spot beam; low-energy-density large-spot beam, which performs compound scanning on the model profile, uses a low-energy-density large-spot to achieve contour-scanning bonding and curing, and uses a high-energy-density small-spot to realize contour-scanning failure, and finally completes to meet dimensional accuracy And strength requirements of the shell type production.

Description

A 3D printing method of laser composite contour scanning

technical field

The invention belongs to the field of 3D printing (additive manufacturing), and relates to a 3D printing device and method for laser composite contour scanning.

Background technique

Rapid prototyping technology is also known as 3D printing technology. Since its development in the 1980s, its superiority has been recognized by the world. At present, many universities, research institutes and enterprises at home and abroad are conducting research on 3D printing technology. 3D printing technology is a typical stacked manufacturing technology. The 3D model of the target part is sliced and processed layer by layer according to a certain layer thickness to obtain 2D data, processed layer by layer, and layer by layer.

At present, the laser is used as the energy source and the printing powder materials are mainly divided into the following methods: Selective Laser Sintering (SLS), Selective Laser Melting (SLM), Profile Failure (Profile) Invalidation Laser Rapid Prototyping, PIRP), among which the SLS and PIRP methods are mainly used in large-format industrial-grade 3D printing. Although the PIRP method only scans the contour for failure, it has the advantages of high efficiency and high precision compared with SLS, but it requires a heating system to pre-consolidate the entire width of the surface. The larger the width, the longer the heating time, which affects the overall processing efficiency. The utilization rate is low and it is difficult to remove waste materials for parts with complex inner cavity structures. How to improve printing efficiency, material utilization and printing accuracy of complex structural models has increasingly become the focus of attention.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a 3D printing method of laser composite contour scanning. In this method, a large-spot laser is used for contour scanning bonding and consolidation combined with a high-efficiency scanning failure process of PIRP contour failure to realize composite contour scanning to complete the printing of shell parts.

This method specifically comprises the following steps:

(1) Draw the three-dimensional CAD model of the part on the computer, use slicing software to slice the CAD model, generate model slice information, obtain the two-dimensional profile of each layer of CAD model, and obtain the two-dimensional profile data, as shown in Figure 1; each described The layer thickness of the layer CAD model is 0.05-1.0 mm.

(2) process the two-dimensional contour data of the CAD model, obtain the contour scanning bonding path and the contour scanning failure path; set the process parameters of the laser scanning in the bonding and failure process in the computer; the process parameters include laser power of 50W～2500W, scanning speed is 200～1500mm/s.

(3) The piston of the forming cavity is lowered by a layer thickness, and the powder spreading system spreads the loose coated sand in the forming cavity to complete the powder spreading process; the layer thickness is 0.05 mm to 1.0 mm.

(4) Import the scanning bonding path, scanning failure path and process parameters obtained in step 2 into the control system, and the control system uses the laser large spot to perform rapid contour scanning on the coated sand according to the scanning bonding path, so that the coated sand Consolidation by heat to form a consolidated shell consistent with the two-dimensional contour of each layer; the control system scans the failure path and uses a small laser spot to quickly scan the contour of the consolidated shell, so that the consolidated shell will lose its consolidation when it is heated above the failure temperature Performance, forming a failure dividing line consistent with the two-dimensional outline of each layer. The diameter of the large spot is 2-12 mm; the diameter of the small spot is 0.03-0.3 mm.

(5) Repeat steps (3) and (4) to complete the contour scanning of the entire CAD model layer by layer, complete the printing process, and obtain a shell shape with a size slightly larger than the CAD model in the molding cavity, and the failure segmentation line constitutes the failure segmentation Layer, the failure segmentation layer divides the shell into residual shell and effective shell, and the one that intersects with the entity corresponding to the CAD model is the effective shell, otherwise it is the residual shell.

(6) Clean up the loose film-coated sand residues outside the shell, coat the shell with raw sand, then heat the covered shell as a whole, and remove the original sand after cooling to room temperature to obtain a Consolidation of a thin residual material shell. The wall thickness of the residual material shell is 0.5 mm to 5 mm to facilitate the peeling off of the residual material.

(7) Peel off the residual shell of the consolidated part to obtain a three-dimensional entity consistent with the CAD model.

The invention retains the failure process of the original PIRP method, so it has the original characteristics of high precision and high surface finish, and uses a large spot laser to scan and bond the contour to complete the contour heating and consolidation, eliminating the need for the PIRP method to radiate and consolidate the entire surface , greatly improving printing efficiency and material utilization. The residual material is greatly reduced, which makes the process of stripping the residual material easier in the later stage, thereby greatly improving the structural complexity and molding accuracy of the printed part.

Compared with the forming process of the SLS method, the method of the present invention adopts contour scanning bonding and non-full area scanning bonding, and the scanning line width of the large spot is much higher than that of the SLS scanning line, so the forming efficiency is much higher than that of the SLS method. The processing time of the printing method of the present invention is mainly proportional to the surface area of the part, while the printing time of the SLS method is mainly proportional to the volume of the workpiece. With the increase of the volume of the workpiece, the processing efficiency advantage of the method of the present invention will be greater.

The beneficial effects of the invention are: high printing precision, good surface finish, greatly reduced processing time and residual material amount, and improved printing efficiency, material utilization rate and printing precision of complex structural models.

The 3D printing method of laser composite contour scanning provided by the present invention will be further described below in conjunction with the accompanying drawings.

Description of drawings

Fig. 1 is a schematic front view of the system and scanning of the present invention;

Fig. 2 is a schematic top view of the scanning of the present invention;

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

Figure 4A is a schematic diagram of the blank;

Fig. 4B is a three-dimensional partial cross-sectional view of the blank;

Fig. 4C is a schematic diagram of peeling off the residual shell;

Figure 4D is a schematic diagram of the entity;

In the figure: 1 computer; 2 powder spreading system; 3 laser system; 4 molding cavity piston; 5 split layer; 6 coated sand; 7 residual material shell; 8 effective shell; 9 working platform;

specific implementation plan

The present invention proposes a laser composite contour scanning 3D printing method, which uses a composite process of large spot laser scanning contour bonding and small spot laser scanning contour failure to carry out shell printing and manufacturing of printing materials. Specifically include the following steps:

(1) Draw the three-dimensional CAD model of the part at computer 1, use slicing software to slice the CAD model, generate model slice information, obtain the two-dimensional profile of each layer of CAD model, and obtain the two-dimensional profile data, as shown in Figure 1;

(2) Process the two-dimensional contour data of the CAD model to obtain the contour scanning bonding path and contour scanning failure path;

(3) The molding cavity piston 4 descends a layer thick distance, and the powder spreading system 2 spreads the loose coated sand 6 in the forming cavity 10 to complete the powder spreading process;

(4) Import the scanning bonding path, scanning failure path and process parameters obtained in step 2 into the control system 11, and the control system 11 uses the laser large spot to perform rapid contour scanning on the coated sand 6 according to the scanning bonding path, so that The coated sand 6 is heated and consolidated to form a consolidated shell consistent with the two-dimensional contour of each layer; the control system 11 scans the failure path and uses a small laser spot to quickly scan the contour of the consolidated shell, so that the consolidated shell is heated to failure The consolidation performance is lost above the temperature, and a failure dividing line consistent with the two-dimensional contour of each layer is formed, and multiple dividing lines form the dividing layer 5;

(5) Repeat step (3) and step (4), complete the contour scanning of the entire CAD model layer by layer, complete the printing process, and obtain a shell shape with a size slightly larger than the CAD model in the molding cavity. Shaped parts are divided into residual shell 7 and effective shell 8, among which the intersection with the entity corresponding to the CAD model is the effective shell 8, otherwise it is the residual shell 7.

(6) Clean up the loose film-coated sand 6 residues outside the shell, coat the shell with raw sand, then heat the covered shell as a whole, remove the original sand after cooling to room temperature, and obtain Consolidation with a thin shell 7 of residual material.

(7) Peel off the residual shell of the consolidated part to obtain a three-dimensional entity consistent with the CAD model.

Below, take coated sand as an example to print "convex" font entity combination as an example, and the accompanying drawings will further discuss the present invention.

First, complete the modeling design of the "convex" three-dimensional CAD model in the computer 1, and then carry out the layering of 0.3 mm in the Z direction, and extract the contour line information of each layer as the master data, and generate the contours according to the data. Two classes of paths for scanning bonding and profile scanning failures.

The control system 11 is started, and the laser spot diameter and energy density are classified and set to meet the process parameter requirements of the two scanning methods. The powder spreading system 2 spreads a 0.3mm layer of coated sand 6 on the working platform 9, and the laser beam 3 is controlled by the control system 11. Firstly, the spot diameter and energy density are adjusted, and a large spot laser is selected to coat the layer. The sand is bonded by two-dimensional contour scanning in a "convex" shape, so that the coated sand 6 is heated and consolidated in the molding cavity 10 to form a shell. Wherein the thickness of the shell 7 covering the model residue depends on the relative distance between the bonding path of the contour scanning and the failure path of the contour scanning.

After the data processing is completed, select a small spot to scan the contour of the current consolidated shell along the contour scanning failure path, so that the temperature of the coated sand 6 is raised above the temperature of carbonization of the resin, so that it loses its consolidation performance, and forms an effective shell 8 and Cut and separate the segmented layer 5 of the residual material shell 7 to complete the composite contour scanning, and the inside and outside of the shell shape are loose coated sand 6 . Then the control system 11 controls the piston 4 to descend by 0.3 mm to carry out the next layer of powder spreading and composite contour scanning until the contour scanning of the entire model is completed.

The post-processing process after the printing process is shown in Figure 4. The unconsolidated coated sand is removed first, and the blank shell shape is obtained as shown in Figure 4A, of which Figure 4B is a three-dimensional partial cross-sectional view. It mainly includes the residual material shell 7, the effective shell 8, the coated sand 6 and the separation layer 5 covered by the core. The raw sand with the same thermal properties as the coated sand is used to backfill the blank shell into the molding cavity, and then the overall heating is finally strengthened. The heating temperature and time refer to the result of the process experiment, which is 180°C for 1h. After heating and curing, the blank shell shape is taken out, and the residual shell 1 is peeled off to obtain a molded piece as shown in Figure 4D.

Claims (5)

1. A kind of 1. 3D printing method of laser compound-contoured scanning, it is characterised in that comprise the following steps：

   1) part three-dimensional CAD model is drawn on computer (1), CAD model is cut into slices using Slice Software, generation model Slice information, the two-dimensional silhouette of every layer of CAD model is obtained, obtain two-dimensional silhouette data；

   2) the two-dimensional silhouette data of CAD model are handled, obtain profile scan bonding path and profile scan failing path；Calculating The technological parameter of laser scanning in bonding and failure procedure is set in machine (1)；

   3) forming cavity piston (4) declines a thickness distance, and precoated sand (6) is laid in forming cavity (10) by powdering system (2), complete Into powdering process；

   4) scanning obtained in step 2) is bonded into path, scanning failing path and technological parameter to import in control system (11), Control system (11) carries out quick profile scan, precoated sand using laser large spot by scanning bonding path to precoated sand (6) (6) by hot consolidation, the consolidation shell consistent with every layer of two-dimensional silhouette is formed；Control system (11) is by scanning failing path, using sharp Light small light spot carries out quick profile scan to consolidation shell, and heated be warming up to more than invalid temperature of consolidation shell loses consolidation performance, shape Into the failure cut-off rule consistent with every layer of two-dimensional silhouette；Described large spot diameter range is 2~12mm；Small light spot diameter model Enclose for 0.03~0.3mm；

   5) repeat step 3) and step 4), the profile scan of whole CAD model is successively machined, completes print procedure；Into Obtain the shell mould part that size is slightly larger than CAD model in die cavity (10), shell mould part is divided into defective material shell (7) and effective by failure cut-off rule Shell (8), wherein, entity corresponding with CAD model have common factor for effective shell (8), be otherwise defective material shell (7)；

   6) outer precoated sand (6) defective material of shell mould part is cleared up, shell mould part is coated with roughing sand, then the shell mould part after cladding is carried out Overall heating, removes roughing sand after being cooled to room temperature, obtains the consolidated articles with defective material shell (7)；

   7) the defective material shell (7) in consolidated articles is peeled off, obtains the 3D solid consistent with CAD model.
2. 2. 3D printing method according to claim 1, it is characterised in that the layer of every layer of CAD model in described step 1) Thickness is 0.05~1.0mm；The thickness distance declined in described step 3) is 0.05mm~1.0mm.
3. 3. 3D printing method according to claim 1 or 2, it is characterised in that defective material shell wall thickness is in described step 6) 0.5mm~5mm.
4. 4. 3D printing method according to claim 1 or 2, it is characterised in that described technological parameter includes laser power For 50W~2500W, 200~1500mm/s of sweep speed.
5. 5. 3D printing method according to claim 3, it is characterised in that described technological parameter is including laser power 50W~2500W, 200~1500mm/s of sweep speed.