In this article, we will discuss a case for automotive parts surface deburring. This automotive part is made from magnesium alloy (specific gravity 1.80). It has the advantage of high strength, large modulus of elasticity, good heat dissipation, good shock absorption, and greater impact load capacity than aluminum alloy. These superior characters made it popular in automotive components.
1. Parts condition before finishing
Material: Magnesium alloy
Appearance: The parts surface is silver color before tumbling. Some area is smooth feeling, while some other area is horny. No big burr or scale is observed with the naked eye.
Shape: This part has complex geometry. So we need to choose the right size media that not lodge in holes or recess.
Process before finishing: Die Casting
Process after finishing: Electro Plating
2. Parts Surface requirement
- Smoothing parts surface without damage parts
- Remove the molding line from the die casting process
- Remove the burr and oxidation layer
- Reduce parts roughness
3. How we process the parts
|Step||(1) Grinding||(2) Drying|
|Machine||Vibratory Finishing Machine (without separation)||Conveyor dryer or natural drying or oven|
|Tumbling Speed||50/60HZ (full speed)|
|Chip Type||Plastic Media TET/Cone Middle cutting|
|Media to Parts Ratio||6:1|
|Compound Type||LC-13, PH 8 (mild grinding compound)|
|Water Level||Just cover the mass|
|Tumble Time||1 Hour||30 minutes|
|Notes—||Manually take the parts out of the machine, and rinse them||Absorb water content and clean part surface|
4. Parts condition before and after polishing
After vibratory tumbling process, you can see dark layer removed. The magnesium alloy surface formed a matte texture.
You can also find the mold line is ground off and parts edge is rounded. So the parts are easy to handle and assemble for operators. In addition, parts finished with plastic media have lower surface Ra value which means lower friction force.
5. Other considerations
Usually, the automotive manufacturer has very huge production volume every day. They want to achieve the most possible automation level. For the big size component, sometimes we should balance between productivity and surface quality.
The magnesium parts are heavy, so parts on media ratio need to consider. These parts can also finish with centrifugal disc finishing machine. In that case, rotational speed has to be lower to prevent damage.
The size of the media should choose carefully. Small size media is likely to lodge into parts hole and recess.
To prevent lodging issue, we have to sieve out the undersized media after the process.
In the fully automatic finishing machine or continuous flow-Thu vibratory finishing system, we can design double layer sieve to collect undersized media, right size media as well as finished parts in the same step.
In this article, we discuss a case study of magnesium parts finished with plastic media. This process can be used also for aluminum parts because they are the soft metal by natural.
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 magnesium parts in details. Later, we compare the surface before and after mass finishing. At last, we discuss other possibilities for magnesium parts deburring and smoothing.
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