Author Topic: Short sprues and air vents on sand molds  (Read 1330 times)

Offline ironman

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Short sprues and air vents on sand molds
« on: September 25, 2016, 07:48:10 PM »
Hi everyone.

When I pour cast iron I use very short sprues and risers also no vents on my sand molds. So I melted some aluminium which is so much lighter than cast iron and see if the mold will still fill up using the same method as cast iron. Have a look at the video to see what happens.   https://youtu.be/5dNq0w_vp9E

Offline Will_D

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Re: Short sprues and air vents on sand molds
« Reply #1 on: September 26, 2016, 06:02:59 PM »
Fair doos Ironman, You showed us how to do it. Now lets wait for the armchair critics to respond*!

*Ah so this is MadModder we don't have ACC's
Engineer and Chemist to the NHC.ie
http://www.nationalhomebrewclub.ie/forum/

Offline micktoon

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Re: Short sprues and air vents on sand molds
« Reply #2 on: September 26, 2016, 08:22:11 PM »
Hi Iron Man,  another good video and interesting about the vents, the proof of the pudding is in the eating as they say and you did the test and it worked, very interesting , thanks for posting it.
  Cheers Mick

Offline ironman

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Re: Short sprues and air vents on sand molds
« Reply #3 on: September 27, 2016, 01:39:55 AM »
Will_D Yes every forum has their fair share of armchair critics, it is always easier to criticize than to get of that armchair and do it.

Offline PekkaNF

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Re: Short sprues and air vents on sand molds
« Reply #4 on: September 27, 2016, 03:34:33 AM »
Nice one. Very well demonstrated.

Proof of pudding etc. Of course there are philosphos who never get around of doing anything and men who have done something only one way last 30 years. The group of people that annoys me most are the ones that know too much and have too little practical experience. Often they will get nothing done, because see only challenges.

This bunch here sees learning/teaching  opportunities and are willing to share. Good work.

Pekka

Offline Pete W.

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Re: Short sprues and air vents on sand molds
« Reply #5 on: September 27, 2016, 05:06:46 AM »
Hi there, Ironman,

That's an interesting demonstration, as said above, 'the proof of the pudding etc.'

But one ingredient of the 'pudding' is the moulding sand - please tell us more about the sand you use.

Could it be that some folks in other parts of the world use sand that is less porous than yours and so needs more feed head and venting?  Maybe because of the additives they use to make their sand cohesive?  Or constituents that are in the sand because of the geology of its source? 

I guess foundry videos would get a bit boring if there's too much ramming of the sand shown but some other makers' videos seem to ram harder and longer than you do - could this also be a result of your sand being naturally more cohesive?

I've never done any casting in my life but I have watched a lot of videos - I'm not challenging your results, I just ask these questions to prompt discussion about this aspect. 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline ironman

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Re: Short sprues and air vents on sand molds
« Reply #6 on: September 29, 2016, 01:00:47 AM »
Pete W.

 The sand I use is a waste product that is left over after all various grades of sand are sifted out. It is very fine sand with a lot of dust and other contaminants.

It is very cheap, $10 for a trailer load. I have been told by foundry sand experts that it is a poor quality foundry sand. It works for me so I do not need to buy expensive graded sand.

 This sand has poor porosity so moisture content cannot exceed 5%. It works equally well with cast iron and aluminium for the size castings I need.

So if someone is brave enough make two molds with the same pattern and gating but make one with a short sprue and the other with a tall sprue and see if both molds fill up. This is how I learnt because I was not afraid to experiment.

Offline Beone

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Re: Short sprues and air vents on sand molds
« Reply #7 on: September 29, 2016, 11:30:43 AM »
The pattern also has a lot to do with it.  I cast a lot of small thin pieces such as medals with a lot of small raised text and riser height can be significant. The difference in a 2 inch versus 2 1/4 inch can mean the difference between 50% and 90% turn out.  I usually have 8 to 10 medals per sprue.
Dave