Method for preheating large-size selective laser sintering sub region

Abstract

The invention provides a method for preheating a large-size selective laser sintering sub region. The method includes the steps that firstly, a large-size powder bed body is preheated, and two to three different heating layers are divided above the powder bed body at different height intervals; the heights of all the heating layers are adjusted, and a heating array composed of heating modulator tubes is distributed on each heating layer; secondly, the powder bed body is divided into a corresponding number of annular heating main influence regions automatically according to the number of the heating layers, and the annular main influence regions are overlapped to form a total heating region of the powder bed body; and thirdly, the heating array of each heating layer is controlled by a corresponding independent PID closed-loop, and the uniformity of the temperature field of the whole powder bed body is controlled and improved by controlling the uniformity of a temperature field of the heating main influence regions, corresponding to all the heating layers, of the powder bed body. By means of the method for preheating the large-size selective laser sintering sub region, the uniformity of the preheating temperature field of the powder bed body of a workbench top is improved, and therefore the quality of parts manufactured through an SLS process and working efficiency are improved.

Description

technical field [0001] The invention relates to the technical field of selective laser sintering, in particular to a large-scale laser selective sintering sub-area preheating method. Background technique [0002] Selective Laser Sintering (SLS for short) is a rapid prototyping technology that uses laser irradiation to sinter powder molding. In SLS processing, the powder must be heated to a certain temperature, and preheating and laser scanning are used to heat the powder to a certain temperature. Two necessary measures of temperature. If the temperature of the powder is increased only by laser scanning to achieve the purpose of absorbing a certain amount of energy and bonding, then, due to the poor heat transfer performance between the powder particles, the sintering time will be greatly extended, and the powder particles Due to the drastic temperature change, the volume of the powder particles changes, which further leads to a large movement of the particles, resulting in ...

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Problems solved by technology

However, this heating method cannot adapt to the uniform heating of the large-size workbench with multiple light sources, because it is difficult to install radiation heating lamps in the central area of ​​the workbench due to the restriction of the laser path in a multi-light source environment, and the concentrated area where the radiation heating lamps are placed is at work. the side near the edge of the platform

In this method, when the area is divided, the central area is too large to achieve uniform heating of the work surface, and this method of dividing areas is too complicated, requires too many temperature sensors, the reflector lampshade is not easy to control, and the installation is too troublesome in practical applications, which is not conducive to Construction of large-scale laser selective sintering equipment with multiple light sources

There is also a heating method proposed by Huazhong University of Science and Technology, which sets multi-layer heating layers above the powder bed body, and the height of each heating layer is controlled by a specially set up mechanical device, through which the height of each heating layer is controlled. The height further controls the overall temperature field of the powder bed, but the control of this preheating method is more complicated. On the one hand, the addition of mechanical devices increases the difficulty of building multi-light source and large-scale laser selective sintering equipment. On the other hand, only by pulling up the mechanical device Changing the height of the heating layer to control the temperature field of the powder bed is also difficult to achieve the goal of a highly uniform temperature field of the powder bed

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