Zinc Door Handle Casting Parts Finishing

In this article, we will discuss a case for door handle casting parts finishing. These door handle parts are made from zinc alloy which is the common material for casting parts. Zinc material is a lightweight material with specific gravity 1.73.

 

1.   Parts condition before finishing

zinc parts before polishing

Material: Zinc alloy

Appearance: The parts surface is dark and dull before tumbling. The surface seems covered with an oxidation layer which generates from the casting process. No big burr or scale is observed with the naked eye.

Shape: The door handle parts have a simple geometry. So we can choose the smaller size media that able to enter the edge.

Size: 109*20*16mm

Process before finishing: Die Casting

Process after finishing: Electro Plating

 

2.   Parts Surface requirement

  • Smoothing parts surface without damage parts
  • Remove the black layer generate from the die casting process
  • Reduce surface roughness prepare for plating process

 

3.   How we process the parts

Step(1)Grinding(2) Drying
MachineVibratory Finishing Machine (without separation)Vibratory dryer
Tumbling Speed50/60HZ (full speed)50/60HZ (full speed)
Chip TypePlastic Media TET/Cone Light cuttingCorn Cob tumbling media
Media to Parts Ratio4:18:1
Compound TypeLC-13, PH 8 (mild grinding compound)
Water LevelJust cover the mass
Tumble Time1 Hour30 Mins
Notes—Manually take the parts out of the machine, and rinse themAbsorb water content and clean part surface

 

4.   Parts condition before and after polishing

 

zinc parts before and after polishing 1
zinc parts before and after polishing 1

 

After vibratory tumbling process, you can see black layer removed. The zinc handle surface formed a matte texture.

 

zinc parts before and after polishing 2
zinc parts before and after polishing 2

 

You can see in detail that the oxidation layer at edge and step is removed. This is because we choose a mixture of cone shape and Tetrahedron shape plastic media.

Since zinc is a softer metal, and we did not see big burr and scale, therefore light cutting plastic media is used for the process.

 

5.   Other considerations

Zinc is very easy to corrosion when exposed to water and air at the same time. Therefore we need to clean and dry the parts as soon as the wet tumbling process finished.

During the separation step, manually take out the parts can prevent parts on parts impingement. Especially the zinc parts are softer and delicate.

We can also use barrel tumbling machine process, but that takes a longer time. Generally, the barrel tumbling process creates a smoother surface with the same media.

Some manufacturers developed a dry tumbling media to eliminate water process. So there will be no corrosion problem. This process is carried out with a specially designed vibratory finishing machine and a dust collector. However, parts surface is better with the wet process.

 

6.   Conclusion

In this article, we show an example of zinc door handle parts smoothing with plastic media. This process can be used also for belt buckles, sliders, key chains, and souvenir that made from zinc.

Firstly, we discuss the parts condition before finishing. Secondly, we show parts surface requirement from clients. Thirdly, we show the process that we did for the zinc parts in details. Later, we compare the surface before and after mass finishing. At last, we discuss other possibilities for zinc parts deburring and polishing.