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How to fix porosity in an aluminum mold for roto-molding

October 18, 2010

Hi everyone,

Just looking for some insight into how I might fix/fill some porosity holes in a sand cast aluminum mold I am currently using for rotomolding plastic parts.

It seems after a few attempts at sand casting our mold we still can't escape the porosity from showing up after we've finished polishing the mold and it's leaving a pretty undesirable finish on our rotomolded parts.

Is there a good (preferably cost effective) solution to filling in all the showing porosity holes, and/or putting some sort of smooth coating on the aluminum mold to finish it?

- Anthony

Anthony Yap
Boat manufacturer - Kuala Lumpur, Malaysia

October 27, 2010

WE have thermally sprayed Aluminium onto cavities, holes of cast moulds. thermal input less than 80° C.

- Shah Alam, Malaysia

December 11, 2010

Depending on geometry of surface, wall thickness, number and depth of pores and other relevant parameters additional options to the ones already mentioned may include:
A) Same metal than mold:
1- Micro TIG welding with aluminum rod
2- ESD welding with Al rod

B) Different metal than mold:
3- Brush plating with special Ni+alkaline Cu+acid Cu+Ni
4- Conventional electroplating (cyanide+acid Cu+Ni)
5- Alkaline EN+acid EN+acid Cu+EN.

Intermediate and final dressing of surface will most surely be required.
G. Marrufo

Guillermo Marrufo
Monterrey, NL, Mexico

December 12, 2010

Thanks for the responses guys, lots to think about.

Thanks again guys.

Anthony Yap
- Kuala Lumpur, Malaysia

December 14, 2010

Just to add another possibility you could consider vacuum impregnation to fill the porosity before plating to give your final finish.

Brian Terry
Aerospace - Yeovil, Somerset, UK

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