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topic 46143

Shot blasting to remove die-casting defects in aluminium heat-sink


A discussion started in 2007 but continuing through 2019

2007

Q. Dear Madam /Sir,

I am going to apply shot blasting to remove aluminium die-casting defect in heat-sink thus get a dull luster,but I am not sure which kind of blasting media (material and grain grade) and blasting process(such as air pressure, etc.) is better for it.

Thanks.

Shijiang Zhang
designer - Shanghai, China


2007

A. You didn't mention how much material you need to remove. I suggest you look at glass beads for a luster finish, but it will not remove much material. The larger the size the beads the brighter the finish; however, you may also get a dimple pattern.

tony kenton
AF Kenton
Hatboro, Pennsylvania


2007

Q. Thanks, AF Kenton.

The material will be removed is not much, only the die-casting defect, something like the flashing, flow-mark,burrs ,shallow scratch & blister, etc. My customer is critical on the surface cosmetics. After blasting, there is chromate conversion such as Alodine (Cr+3), the final surface looks dull luster(which can cover some appearance defect).We are blasting #120 aluminium oxide, the result is not very good, especially the final surface color difference.

Shijiang Zhang [returning]
designer - Shanghai, China


2007

A. As mentioned, the glass bead may produce better results if you want to blast finish. Another alternative is to try burnishing these parts in a mass finishing operation using either porcelain or steel media. There is no abrasive in either media and the deflects will not be removed but blended or flattened for a uniform finish.

tony kenton
AF Kenton
Hatboro, Pennsylvania


July 30, 2009

Q. Dear Madam /Sir,

Is there any equipment or something to know how much the pressure impact to the work piece results by shot blasting process for aluminium material (like Almen gauge in shot blasting work piece steel material)?
Thank you.

yunianto catur
manufacturing - indonesia



December 14, 2018

Q. Myself TN DUBEY -B TECH IN PAINTS TECH FROM HBTI KANPUR. WORKING AS PLANT HEAD IN A AUTOMOTIVE IND.

CAN WE GET ALODINE ON SHOT BLASTED SURFACE WITH COLOURLESS PASSIVATION?
SUGGEST PARTY SUPPLIER.

tribhuvan_dubey
TRIBHUVAN NATH DUBEY
MFG OF AUTO PARTS - Binola, Gurgaon, Haryana, India
  ^- Privately contact this inquirer -^


December 2018

A. Hi Tribhuvan. Colorless chromate should not be a problem on shot blasted aluminum (but readers should recognize that you can't chromate steel). People can suggest sources in private, but we don't post public sourcing suggestions (why?). Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


January 4, 2019

Hello Mr. Dubey,
If you plan to have Aluminum parts Alodined or otherwise Chromated, the type of 'shot blast' you use matters greatly. Glass bead or other Silicon bearing media could embed in the Aluminum and this type of contamination is damaging to Chromate conversion coating processes.
You should consider using only clean, uncontaminated Aluminum oxide blast media that is never used for other types of metals. As a company that offers blasting services as well as several types of chemical coatings... we would never use anything else. It is very reliable, and the chemistry is compatible with the substrate and tanks -- even the bit that manages to escape the blast room does not contaminate the plating tanks or interfere with the conversion coating reaction.

rachel_mackintosh
Rachel Mackintosh
Plating Solutions Control Specialist / Industrial Metals Waste Treatment - Brattleboro, Vermont



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