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Investment removal


#1

I do some small scale casting and have had some difficulty removing
all traces of investment from my casts. My usual method is just to
pick it out using a very fine needle probe and then lightly scrubbing
with a brush under running water. I was wondering if there is an
easier way that is less time consuming. I saw two products in the Rio
catalog which seem promising but want others’ feedback on use before
I buy. Both products require an ultrasonic cleaner which I don’t
have, but would be willing to purchase a smaller one, if that is
effective for my purpose.

The first is Blastoff Investment Remover, a liquid. The second is
Break-Away Investment Remover, a powder. Would either of these
products work without an ultrasonic? If you’ve tried either, I’d love
to hear about your experience and preferences. Or would an ultrasonic
be good alone without a specialized product?

Any other suggestions for getting those last traces of investment?
I’ve tried tumbling with steel shot which helps immensely but not the
whole answer. Thanks in advance-- I know I’ll come away with some new
insights into this. The Orchid forum is amazing!

Peggy


#2

Hi Peggy,

I usually manage to clear most of the investment from my casting at
the quenching stage using a toothbrush and a sharpened chopstick.
Once I have cut the castings away from the sprues, I was under a tap
and working into the crevices with the pointed end of a bamboo satay
skewer. (Yes we cook a bit of Asian food). Sometimes I find I have
to heat the pieces and drop them into cold water to release some more
stubborn traces. I normally raise the surface silver on my pieces by
heating to oxidise the copper and pickling in sulfuric acid. This
usually takes care of the final traces. Finally I finish my pieces
when finally assembled in a vibratory tumbler with stainless steel
shot and Rumble Bright.

All the best
Jen


#3

I am very happy with what I use to clean off investment, and no
chemicals are required for the investment removal.

I use a “spot cleaning gun” This is used to clean spots out of
cloth. It is a high pressure spray that comes from a hand held “gun”.
This high pressure spray blasts away the investment and gets into all
small crevices. I use distilled water in it without any other
chemicals. (The distilled water will extend the life of the gun).
After cleaning with the high pressure water, I use ordinary hot
pickle to remove oxides and any flux from the cast. This high
pressure spray has also proved to be useful for many cleaning
purposes around the house.

I suggest that you do an internet search for this tool. Just use
"textile cleaning spray gun" as your search. You will find it
available from many sources including Amazon. I have seen these for
as little as $65.00 US dollars.

regards,
Franklin


#4

VERY FINE glass bead blasting works VERY WELL but requires a
compressor, blasting cabinet and some peripheral equipment. Using
lower than normal air pressure can remove investment and cause very
little “fogging” of the piece. There are also mini bead blast air
brush units that could be the best unit to look at. Mant ways to do
this job. John


#5

Cheaper and works well is a water pik ($30 to about $100 on Amazon
or look at goodwill or other such establishments). These do not
recycle the water so no dirt in the water so no ware and tear on the
workings. They last a long time and cheap…John


#6

Hi Peggy,

In our production shop we use a combination of ultrasonic cleaning
and a steam nozzle, the ultrasonic gets most things clean, sometimes
we have stubborn deep spots that we spray out with the steam nozzle,
there are some pretty reasonably priced units that are both with an
ultrasonic bath and a steamnozzle. We don’t use anything special for
investment in our ultrasonic, just a solution called Oakite.

Aaron Stafford


#7

Franklin,

YES! These things are pretty darned useful! This works just as well
as a steam nozzle at removing stubborn investment, and you can use
this spray gun to clean up wax models sometimes too, we occasionally
get waxes from our CAD guy that have shavings all over them still,
we got one of these spray guns and it cleans up the shavings well
without damaging the wax (as long as you’re careful about settings).

Aaron Stafford


#8

I leave the castings in an old plastic cream cheese tub filled with
water overnight and let them soak. In the morning I put the tub in
the stainless steel basket in the sonic and let it run. That removes
all of the investment inabout 20 minutes. They just need a rinse and
quick steam. Works great.


#9

Franklin has got it right. The water blaster is what I use also. It
is dangerous for skin but you learn that pretty quick. At arms
length the spray gets investment out of everywhere. The only issue is
that you are aerosoling the investment again so use a mask or
ventilation.


#10

I knew I could count on all you for some help with stubborn
investment traces. Such good ideas! I think I’m going to start with
the water guns & piks first, since they are likely least aggressive
and also least expensive and then try out an ultrasound a bit later,
if that doesn’t do the trick. I’m wary of anything very aggressive
since these are fairly detailed castings (that’s part of the reason
I’m having such difficulty-- its stuck in all those tiny crevices). I
have a tumbler that I might try with some media other than steel
shot. What ceramic media would you suggest?