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Compulsive chicken choker
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Discussion Starter · #1 ·
This isn't car related, but I guess folks on here have more technical expertise than the Indian company I'm trying to work with.....:wanker:

One of our products is a cast iron lid that is then powder coated and has to provide insulation up to 1kV. The first samples that I approved were nice and smooth with a decent thick powdercoated finish that passed the 1kV withstand test. The production parts are as rough as a badgers arse with powder coating that you can practically see through. They fail the 1kV insulation test easily.....

Is there any pre-coating (a primer of some kind?) that can be done before powder coating to smooth out the cast iron surface? Or is there a way of controling the powder coating thickness???? The rough cast iron surface is causing the (already thin!!!) powder coating to thin out on the "peaks" of the surface and provide very little insulation.
 

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Are you trying to remedy the problem over here, as the best solution would be to get them to make them with the same casting sand as they used for the prototype.

Are there hundreds of them, or could they be smoothed before coating?
 

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Pass the lump hammer
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550 Posts
Gary,

When they were after your business, they most likely sanded down the rough castings and then gave the part a couple of nice thick powder coatings. After that they cut all the corners going to cut costs on the production run.

Are they shot blasting the castings before powder coating, that can knock the roughness down a bit.

If you've already received a load and can't get any joy with India, you can get them overcoated by a local powder coaters, but it will be at your cost.

We had a similar problem with some alumimiun castings from India, samples were good, production items were more porous than a porous thing and useless in the compressed air application they were intended for. We finished up binning them and staying with a proven European foundry.

Steve

Steve
 

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Compulsive chicken choker
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6,504 Posts
Discussion Starter · #5 ·
Thanks... Yep, typical Indian parts. First set of samples spot-on perfect. First production batch made at the side of the road by a six year old.

Steve, I'll suggest the shot blasting and specify a minimum thickness as well as the insulation withstand test and see if they're any better. I'd love to have them made in the UK, but cast iron foundrys over here are few & far between as keeping on top of the H&S side is difficult. Seeing as our competitors use India, we end up having to follow them to stay competitive on price.
 

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Fat 'n' Loud
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Gary,

When they were after your business, they most likely sanded down the rough castings and then gave the part a couple of nice thick powder coatings. After that they cut all the corners going to cut costs on the production run.

Are they shot blasting the castings before powder coating, that can knock the roughness down a bit.

If you've already received a load and can't get any joy with India, you can get them overcoated by a local powder coaters, but it will be at your cost.

We had a similar problem with some alumimiun castings from India, samples were good, production items were more porous than a porous thing and useless in the compressed air application they were intended for. We finished up binning them and staying with a proven European foundry.

Steve

Steve
Yep, been there, done that, only with chrome plated die cast aluminium from China. Got another batch made, air freighted in. Ended up costing more and taking longer than it would have done to have them made properly in the UK. Still, the bean counters know best...:wanker:
 
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