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The Origin and Solutions of Burrs& Chatter Marks on Aluminum Materials(2)
- May 13, 2017 -

1. The elastic deformation of the mold . 

During the processing  its die bearing is parallel to the direction of extrusion. But in the actual extrusion production, the mould  bears  high temperature and high pressure ,distorting the die bearing.This will produce adhesive “turning tool lumps” on the section aluminum ,causing burr and chatter marks.

2. If the relief empty is pretty shallow,sticky aluminum will gradually increase. The sticky aluminum that carried on the section aluminum transforms to burrs.Besides,The sticky aluminum  that  not on the section aluminum and that does not fall off  with the rebound of  mould  will form a  flash,coarse grain etc.

3 . The  metal flow  blind  zone 

Generally,most of the aluminum plant will not peel cast rods.  Thus,the impurities both on the surface of and in cast rod   will  cluster around the  metal flow  blind  zone of the mould. As the increase in the number of  extrusion rod,  impurities in the blind  zone are constantly changing.Some  flow out with normal metals, accumulating  in the  deformation of the space of  die  bearing .The others will make friction with the normal flow of aluminum metal ,bring  defects like flash and coarse grain etc.

Solutions

1.Select the appropriate number of holes and models.Pick best mold specifications  through  the profile  of the circumcircle  diameter of the section aluminum, wall thickness, unit  weight, the size of the extrusion ratio, the  available  models, reducing   sticky aluminum as well as   burrs  or chatter mark.

2.Improve the strength of the mold.

In fabrication, the greater the amount of elastic deformation of the mould is ,the higher the possibility of  burrs  or chatter will be .Take porous mold as an example, various and dense  shunt holes  correspondingly  reduce  the strength of the mould. Thus, in the design of mold,we should spare no efforts to improve  stiffness and strength of the moulds and reducing moulds’ elastic deformation in the fabrication  of  aluminum materials. The thickness of the front pad and its inner hole form must  effectively support the mold. 

3. Reduce mould’s blind zones.

The mold cavity of the  transition between  surfaces and the  transition between R bit  and the surface in the  of mould’s cavity shall avoid sharp corners .  The surface of metal flow should be  smooth and flat.

4.Before the  nitriding of moulds, smoothness of  the mold cavity,  working

belt  and   parallelism  of the working belt should be checked . Trim  sandblast and polish them , so as to improve the smoothness of the mold. After nitriding,   hardness and  smoothness will be enhanced, then this can  further improve the smoothness of the mold.

5.Die-filling

Before die-filling, polish the mould, and spray rust inhibitor on the surface of  the mold's parts and the welding chamber.The bolt must be locked,when the mould is set up .