Research On Micro Dish-shape Parts By Laser Flexible Dynamic Impact Forming

As the development of lightweight and miniaturization for micro parts,the market see a growing demand for micro devices and a variety of micro-forming processes have emerged such as micro deep darwing,bending,blanking,embossing and so on.The use of progressive die and compound die is required when it comes to manufacturing micro parts.However,due to the mold manufacturing difficulties,parts handling and punch-die alignment problems,the micro parts size is always limited to a certain range.In this dissertation,laser flexible dynamic impact forming technology was employed to manufacture dish-shape micro parts ususlly used as gaskets whose outer diameter is 1.4mm,realizing compound process of micro drawing,punching and blanking.Laser flexible dynamic impact forming technology was analyzed through the feasibility study of micro compound die,the experimental study and the numerical simulation of deformation process and the main work and conclusions are as follows:(1)The experimental platform of laser flexible dynamic impact forming was established and three different micro compound dies were designed.The fabrication of micro dish-shape parts was carried out on T2 copper materials with a thickness of 40?m and four aspects,including forming perfomance,process sequence,process completion and removable ability,were analyzed to verify the feasibility of dies by using the KEYENCE VHX-1000 C microscope to observe the morphology.For micro whole-height combined punch and matrix,compound process can be completed,but the quality of fracture is poor and micro parts cannot be taken out from the die;For micro semi-height combined punch and matrix,the punching process cannot be completed and micro parts still cannot be taken out from the die;For micro compound die,compound process can be completed.The process sequence is micro deep drawing,micro punching and micro blanking.The quality of morphology and fracture is good and micro parts can be taken out from the die.Hence,the micro compound die is suitable for the fabrication of micro dish-shape parts.(2)Experiments were carried out using the micro compound die.The forming height,micro punching quality,types effect of process on the dimensional accuracy,micro parts thickness,the influence of soft punch thickness on the forming process were discussed.In addition,the surface roughness and hardness of the specimen were measured.Through the measurement of forming height,it was found that the forming height increased first and then decreased with the laser energy.The diameter dimension and fracture were analyzed through three dimensional optical microscope and scanning electron microscope.It was found that the diameter of the micro punching hole increased first and then decreased with the laser energy.Under the high strain rate loading,larger rollover and no obvious burnish and fracture appeared.However,in terms of single process of micro punching,smaller rollover,burnish and burr occured showing difference with the compound process.The dimensional accuracy of micro punching and micro blanking saw similar trend wih the laser energy but the former one was negative and the latter one was positive.The influence of the difference of material properties,mold characteristics and laser energy on workpiece's thickness distribution were researched.The maximum thickness thinning of T2 copper and 304 stainless steel was both found in the neck area,but the minimum thickness thinning occured in the middle area and flange area respectively.At the same laser energy,when the thickness of soft punch increased,the forming process of the workpiece would be delayed.By measuring the Ra value in different regions using Axio CSM700,it was found that the surface roughness of the flange and neck area increased with the laser energy and just dropped rapidly when micro blanking was completed.On the flip side,surface roughness of the bottom area decreased with the laser energy all the time.The nano-hardness test showed that the nano-hardness of both T2 copper and 304 stainless steel were improved compared with raw materials.Their average hardnesses were both the highest in the neck area.(3)The influence of the mold characteristics on the process sequence,the soft punch thickness on the forming process and the springback during the forming process were discussed through the ANSYS/LS-DYNA simulation of the laser flexible dynamic impact forming process,which further explained the deformation rules.