Study On Dimensional Accuracy Of Parts Manufactured By Selective Laser Melting And Its Application In Manufacturing Non-assembly Mechanisms Directly

Selective Laser Melting(SLM)has many advantages over traditional processing methods,it can manufacture complex metal components of high density and good mechanical property directly. But the dimensional accuracy of SLM parts is bad. In order to improve the dimensional accuracy, this paper analyzed the dimensional error source of SLM firstly, then studied the influence of process parameters on the dimensional accuracy of SLM parts, finally,non-assembly mechanisms of favorable dimensional accuracy was manufactured by SLM.The main research contents and acchievements of this paper are as follows:1)Systematic analysis on the dimensional error sources of SLM is studied. The sources can be classified into three types: preliminary data processing, SLM forming and post processing. The error sources during preliminary data processing inlude tranfering of CAD model into STL format, improper supports structure and slice processing. The error sources during SLM forming include machine error, laser deep penitration, spot diameter, shrinkage distortion of material, powder adhesion, process parameters, material properties and some other specific factors. The error sources of post processing include removement of support,circumstance changing of the parts, polishment, burnishment, repairment, coating and so on.2)The relationship between process parameters and dimensional accuracy of SLM parts is studied. When tool compensation is 0, the dimensional accuracy is becoming worse with laser power or volumn power density becoming bigger, and the dimensional accuracy is becoming better with scanning speed or scanning hatch becoming bigger. When it comes to scanning strategies, the S type single scanning stratergy is better than Z type, inter-layer stagger and orthogonal are better than single direction scanning strategy, raster will reduce dimensional accuracy, S type orthogonal inter-layer stagger is better than contour offset scanning strategy. Corresponding relation is set up between tool compensation and scanning error, volumn power density. Tool compensation value is optimized and dimensional accuracy of parts is improved.3)Manufacturing ability and dimensional accuracy of typical geometric structures and clearance structures are studied. Thin wall of 0.15 mm thickness, cylinder of 0.1mm diameter,upright hole of 0.4mm diameter, overhang circular hole of 0.5mm diameter, overhang squarehole of 0.3mm side length, horizontal overhang structure of 3mm span and 0.2mm clearance feature are obtained by SLM. Dimensional errors of thin walls, shop corners and cylinders are becoming bigger with dimensions becoming bigger. Dimensional error of upright hole changes from negative to positive and then becomes bigger. Circular degree error of overhang hole is becoming bigger with dimension becoming bigger. Dimensional accuracy of clearance is becoming better with tilt angle becoming bigger and is becoming worse with power density becoming bigger.4)Non-assembly mechanisms with high accuracy are manufactured by SLM-----orchid bracelet and bike driven by double crane connection rod. Structure of non-assembly is optimized. Assembling form, display mode and support structure are improved. The dimensional accuracy of manufactured non-assembly mechanisms kept in ±0.1mm.