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 Post subject: Current projects
PostPosted: Mon Feb 17, 2003 11:27 am 
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Joined: Tue Oct 09, 2001 6:14 am
Location: Orange County, CA, USA
Here is a quick and dirty picture lineup of my recent puzzle projects, good and bad.

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"mini" Mental Block - It's finished. It works. It looks ok. But I'll be damned if I can ever get the air bubbles out of the damn polyurethane, so I'm giving up on it. The air bubbles tend to trap dirt so many of the pieces look dirty. I'll get around to stickering it some day, but other than that it'll probably fade into anonymity. A 30mm Skewb just isn't quite sturdy enough to support the weight of the cast pieces. Also due to the smaller size it is less tolerant of misalignment and the puzzle tends to bind fairly easily. I can see why a full size Skewb is a much more suitable medium for making this.

2x2x3 - The one in the back is my first attempt. I didn't like how the joined plastic corner pieces appeared when you turned the puzzle so on my second attempt I filled in the visible parts with black Milliput. This was an improvement in appearance when the puzzle was turned.

2x2x4 - Made using the method described on Ton's building pages. Two 2x2x2's were "sacrificed" to make this. I'm pretty pleased with the results although I was rather disappointed by the imprecise cube shape of the individual cublets. 2 part epoxy and credit card pieces were used to secure the pieces together. Milliput was used to fill in the gaps.

You can also see two attempts at building pieces to make a Fisher's Cube. I gave up and just bought one from Mark Longridge. Now I'm stuck with two half mutants which I keep around for sentimental reasons.

I'd like to especially thank Ton for his amazing puzzle construction pages which are practically step by step guides.


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 Post subject: Re: Current projects
PostPosted: Wed Feb 19, 2003 12:04 am 
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Joined: Wed Nov 24, 1999 12:18 pm
Location: Palerang Shire, NSW, Australia
Wow, Jin, you been pretty busy. What are the problems with the air bubles? I only ever had one type of polyurethane that I found difficult to work with because of bubbles. (can't remember which one, I check this up). Conap's Conathane UC-30 or equivalent is still the best. Also there's plenty of techniques to get around bubbles.

Do you use film canisters to stir in?

Do you allow time for the buubles to settle?

Do you scrape bubbles to the top of the mold surface and then drag them off completely?

How's your two part closing technique?


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 Post subject: Re: Current projects
PostPosted: Wed Feb 19, 2003 9:17 am 
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Joined: Tue Oct 09, 2001 6:14 am
Location: Orange County, CA, USA
Wayne Johnson wrote:

Q: Do you use film canisters to stir in?
A: No, I use standard clear plastic cups to hold the separate parts and for mixing, but what I used was large industrial syringes (Monoject brand) that hold up to 45 cc's of each component. If I wanted to mix up 70 cc's of polyurethane, I would draw in 40 cc's of one part and then squeeze out precisely 35 cc's into a cup and then use the same method with the other part. The reason for drawing in the extra 5 cc's was to avoid air bubbles possibly generated by squirting out that last little bit of material. Not to mention you can't precisely judge just how much air you have trapped at the top of the cylinder when you first pull back the plunger. The small excess I would then squirt into separate "holding" cups to allow air bubbles to settle out or to get poured back into their respective containers. Only drawback to this method was that it took quite a bit of arm strength to suck in the clear golden resin (the hardener?) and pulling too hard would make the rubber plunger come off the plastic part. Draw hard but slow and steady. Practically an exercise but I was getting perfect 1 to 1 ratio mixes for both the molding and casting processes.

Q: Do you allow time for the buubles to settle?
I believe so. I would pour out about equal quantities into separate cups, cover them to avoid contamination, and let them sit a while before I would use the syringes.

Q: Do you scrape bubbles to the top of the mold surface and then drag them off completely?
It sounds like a prelude to making a two part mold. I didn't do that simply because I never made any two part molds requiring closing. After making the pieces I actually spent some Time sanding to get the pieces to be nice and smooth. That's probably where I made a mistake. By sanding the pieces tiny particles of the sanding surface would get trapped in almost unseen airholes, making some surfaces look blotchy and ashen. This wasn't a problem on teh small pieces of my Mental Block. Only the large pieces had significant air bubbles. VERY annoying. But yes, I would try to scrape off air bubbles as they rose up. Unfortunately bubbles would still be rising at the 15 minute mark, at which point scraping off was a poor idea and possible a great way to ruin the shape.

Q: How's your two part closing technique?
See the above answer. :)

In retrospect maybe my mixing was introducing air bubbles. Problem is though you have to throroughly mix the two components to avoid uneven pieces which I'm sure you're aware of. I don't beat the two parts like scrambled eggs or anything but after mixing I can't exactly let the material sit to let the air bubbles escape. Sure I have 15 minutes with the Mark 15, but that still isn't a lot of Time to let bubbles completely escape.

It almost seemed that pouring the urethane into the molds, the molds themselves would cause unseen air bubbles to get trapped on or near any touching surface. Incredibly annoying situation.

I made my one mini Mental Block and it already has a prospective owner. I won't be playing with casting plastics for a while for various reasons (not from the discouraging results mind you) but I'll give it a go some months down the line.


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 Post subject: Re: Current projects
PostPosted: Wed Feb 19, 2003 10:31 am 
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Joined: Wed Nov 24, 1999 12:18 pm
Location: Palerang Shire, NSW, Australia
>Q: Do you use film canisters to stir in?
>A: No, I use standard clear plastic cups....

Sounds like a complicated way to go about it. The more complications, the less inclined you will be to continue with it. Simply use film canisters to resttict your movements. Don't worry about being so precice. Yes, try to be accurate, but not to scientific about it. Fill each clear canister with water to get the right amounts and then make markings so you get the pouring about right. Then dry it properly. Only need to do this once, of course, to make markings, then use the markings to measure.

>Q: Do you scrape bubbles to the top of the mold surface and then drag them off completely?
>It sounds like a prelude to making....

Ahh yep, internally microbubles cluster together and make bubbles during the chemical process. Unavoidbale and not usually a problem when doing two part molds. However, to get around your problem, do the sanding, then spread milliput over the surface and sand again.


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 Post subject: Re: Current projects
PostPosted: Wed Feb 19, 2003 9:57 pm 
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Joined: Mon Feb 03, 2003 6:54 am
Location: United States, Wisconsin
you made the mental block from a skewb! Cool! I didn't know thats how they were made :) a new wrinkle in the brain


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 Post subject: Re: Current projects
PostPosted: Thu Feb 20, 2003 10:31 am 
I asked one of those photo places if I could have some empty film canisters "for my daughter to do painting with". Thay gave me a huge bag full, must be over a hundred. ;)

Max


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 Post subject: Re: Current projects
PostPosted: Thu Feb 20, 2003 9:57 pm 
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Joined: Tue Oct 09, 2001 6:14 am
Location: Orange County, CA, USA
Here's a an older pic of my Mental Block "in progress" showing the internal mechanism (i.e. mini Skewb). Next to it obviously is a standard Skewb.

Image


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