Abrasive flow machining
Abrasive flow machining (AFM) was firstly developed fifty years ago by Extrude Hone Corporation, USA. By using the liquid viscoelastic material with easy flowability made of polymer and abrasive grains, AFM can be used to polish, deburr and radius for the workpiece. There are three kinds of AFM: one-way AFM, two-way AFM and orbital AFM . In this case to manufacture the cylinder heads, consider of two-way AFM is much more widely used and its technology is more mature, we also choose the two-way AFM to do the surface finishing. Schematic of two-way flow shows in figure below.
Figure 1 principle of material removal mechanism in two-way AFM process  Prior to machining, liquid abrasive will be put into the lower medium cylinder, the designed fixture which clamping the workpiece will be fixed between two cylinders. The upper medium, lower medium cylinder and fixture will form a confined space. After heat the whole system to working temperature, by forcing the lower piston (usually by hydraulic), the liquid abrasive will be pressed into the channel formed by clamp and workpiece, then flow into the upper medium cylinder. After the stroke of lower piston finished, the upper piston will force the liquid abrasive back into lower cylinder , an operating cycle will be finished.
2. Three key elements of AFM
1) Machine tool
Use to fasten the workpiece and fixture, and control the pressure applied on the workpiece, to adjust the degree of abrasive accuracy. 2) Liquid Abrasive
Liquid abrasive is abrasive tool in the AFM, it should has following properties, a) Non-corroding and don’t adhere to the workpiece and human skin. b) Good adhesive properties between different abrasive grains. c) Be able to maintain the viscoelasticity for a long time
d) Non-volatile and non-deteriorate after a long time preservation. e) Strong cohesion.
For these properties, the conventional liquid abrasive is made from...
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