Author Topic: General Casting Questions  (Read 5983 times)

Offline Smartypants1635

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Re: General Casting Questions
« Reply #60 on: June 15, 2006, 11:06 AM »
Yeah, I still can't get 2 part molds like that.

Offline Ruprecht

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Re: General Casting Questions
« Reply #61 on: June 15, 2006, 11:11 AM »
Yes, let it sit for a minute or three, depending on what you're casting with. 

After I pour it in each half, I take a minute to poke out the air bubbles with a toothpick.  Normally after that, it takes a minute or two more before it's viscous enough to put them together with minimum leakage.  Sometimes I nudge the mold a bit, and when the resin appears "Jello-y," it's time to put the halves together.

Offline Smartypants1635

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Re: General Casting Questions
« Reply #62 on: June 15, 2006, 11:30 AM »
I have pot life of 10 minutes :-\ how long should i wait
the whole 10 or 8 or what.

Offline Glassman6

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Re: General Casting Questions
« Reply #63 on: June 15, 2006, 01:17 PM »
When it stars to cure, the resin usally starts clouding up.
When i see the clouding start is when i flip the molds.

I also pour with them side by side, so the flip motion doesnt have much horizontal movement to
it, just flip and press.

My plastics have a 3-4 minute cure time, so i see the clouding start imediatley after i'm finsihed pouring.
By the time i've wiped any spillage off the cup, its flip time.

If you wait too long, then you dont get as good of a press and you dont squeeze out most of the remaining plastic. That can make the difference between paper thin excess and thick excess that has to
be dremeled off.

Offline Smartypants1635

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Re: General Casting Questions
« Reply #64 on: June 15, 2006, 02:25 PM »
thanks GM I'll try that.

Offline RollaJedi

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Re: General Casting Questions
« Reply #65 on: June 15, 2006, 03:34 PM »
yeah, me too! 
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Offline CommanderKorbra

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Re: General Casting Questions
« Reply #66 on: June 16, 2006, 10:37 PM »
Here's a general question. Can anyone cast some stuff for me? I need more of an advanced caster, and I need a few things casted in a certain way. I'd send the stuff to you to get a few copies of and then you can send everything back. PM me if intrested. Thanks.
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Offline Straxus

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Question for experienced Mold/Casting people...
« Reply #67 on: October 7, 2006, 08:04 AM »
I posted this question over at Iron-Cow but figured I would post it here as well in hopes that someone can help with this problem.

I have been doing some limited molding and casting for a few months now. The main problem I run into is the air bubbles in molds and sometimes the plastic resin. This is a big problem with trying to make molds of very small parts. Fingers, antennas, etc... dont always get plastic resin to them due to air bubbles. I can use toothpick or bent paperclip to get rid of airbubbles but this is not always successful or possible depending on the molded part.
A vacuum compressor would really help but most I have seen cost hundreds of dollars. Any one out there have any low cost suggestions for someone with a severely limited budget? (Preferably less than $200... less than $100 would be even better...)
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Offline Ruprecht

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Re: Question for experienced Mold/Casting people...
« Reply #68 on: October 7, 2006, 12:52 PM »
1 cheap way to reduce air bubbles in your casts is to dust the mold with baby powder prior to pouring the resin.  For molds, follow Glassman's tutorial and pour the rubber s l o o o w l y.

Another way that I haven't tried yet is on Sarge's website, and looks like a good way to make fairly bubble-free molds.

I have been trying pressure molding/casting lately and have had good results so far.  All the equipment cost me about 60 dollars.  The only drawback to using a pressure system is it takes a lot more time to build a mold box, at least with the method I've been using.  This list of parts is what Master Gunzz recommended, and what I use:

Pressure Cooker:  Presto 6-quart - $45 with shipping from amazon.com
Tire Valve:  Generic brand - $3 at Wal-mart
Silicone Caulk:  Clear kitchen caulk - $4 at Wal-mart
Tire pressure gauge:  Generic brand - $2 at Wal-mart
Tire pump:  Any pump, I use the kind that stand up and you push up and down, as it'd take too long to use a small hand pump.

You take out the rubber stopper in the lid and put the tire valve in it.  Then you seal around the valve and metal piece in the middle of the lid with the caulk.  When you build the mold box and fill it with the rtv rubber, just place it in the cooker, close it, and pump it up to the desired pressure.  Bantha5 once mentioned that he pressurizes to 40 psi, so that's what I use and it works well.

As for the method I've used to build the mold box and cast the part, the guys at Goregoregore.com have some good tutorials with pictures and all.

Offline Sarge

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Re: Question for experienced Mold/Casting people...
« Reply #69 on: October 7, 2006, 01:34 PM »
Well, thank ya, Ruprecht for the plug. Basically my tutorial is the FFURG tutorial, but just with pictures. The main thing I have experienced over the years with air bubbles is using patience. That is the key. Some try to rush the process and get a lot of bubbles. When pouring the resin you need a slow, narrow stream. Once the resin is in I tap the mold gently during the first 60 seconds of the hardening process.

Mike aka Sarge
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Offline Smartypants1635

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Re: Question for experienced Mold/Casting people...
« Reply #70 on: October 7, 2006, 03:23 PM »
E-mail master gunzz, I know he has a recipe for a homemade air compressor.

Offline Ryan

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Re: General Casting Questions
« Reply #71 on: October 7, 2006, 08:43 PM »
I went ahead and merged Straxus's thread with the general casting question thread just so this is all in one place and is easier to find in the future. :)
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Offline Straxus

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Re: General Casting Questions
« Reply #72 on: October 8, 2006, 01:10 AM »
Thanks Ryan! Though I got a little confused at first when I check on here for my thread and didnt find it...heheh. Until I saw this thread and figured it got merged I had started to assume that I was just really really tired last night and forgot to hit post before I closed the window...hehe. (I have done that alot in the past)

Thanks for the info guys! I will save this info into my collection of tutorials. Since my current supplies are almost out I will have over a week to reveiw the new information and start a new shopping list for when I get my next pay check.
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Offline BrentS

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Re: General Casting Questions
« Reply #73 on: October 8, 2006, 11:55 AM »
Sarge, that is a most excellent photo tutorial!

Offline Sarge

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Re: General Casting Questions
« Reply #74 on: October 8, 2006, 07:17 PM »
Sank you very much. There was an instructional page that came with the kit I got from Micromark. I expanded it and based it on FFURG's tutorial and those instructions.

Mike
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