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mrcadman Newbie
Joined: 04 Nov 2010 Posts: 11
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Posted: Thu Nov 04, 2010 3:52 am Post subject: Plug from Balsa |
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Hey! I'm new to this
I was commissioned to make a tool that will be used on a 2x4 proto-form machine. (pics below)
Its 35"L x 5"W x 7"H with 3 & 7 degree tapered sides. IGNORE the little hump as it's been removed now.
I need to make a cast of this and then a tool from that cast.
I am NOT going to go fiberglass.
The process i hope will work..................
Seal the wood.
Pour something like VytaFlex 40 or 50 in a trough and then hang form into it. Of course, i can fasten it down and pour on top of it as well.
When the cast cures, remove the balsa.
Then use Kwick-Kast or Kwick-Kast2 to make the final tool for the vac machine.
I cannot express how nice it would be to obtain local materials for any part of this. I hold little hope for that, but would very much welcome alternative methods for turning this balsa model into a productive tool.
Hundreds of pulls are expected using 40/1000's Kydex or ABS.
NO, Fiberglass is not going to happen, and if you suggest a material, please mention it's release agent as well.
Any input and I'll be your best friend all day! |
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Fredo Master
Joined: 21 Mar 2007 Posts: 251 Location: Kingdom of Nye Area 51
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Posted: Thu Nov 04, 2010 10:51 am Post subject: |
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I've been looking to upgrade my molds to an alum. filled urethane. This site www.alumilite.com has a product, Vac-Master 50. They have 2 six minute vidios, showing how to use it. They also have an 800 number you can call for more info..........Fredo _________________ If someone has a gun and is trying to kill you,
it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001 |
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mrcadman Newbie
Joined: 04 Nov 2010 Posts: 11
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Posted: Fri Nov 05, 2010 1:06 am Post subject: |
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Thanks Fredo! When we are finished prototyping, we will probably cast our permanent mold from that Vac50.
Today we got responses from both The Engineer Guy and Smooth-on.
TEG suggested.............
coat the balsa with a finishing resin or even bondo's resin.
Use Vytaflex 40 for the casting
Kwick-Kast2Blue for the Tool.
Universal spray-on release between everything.
While both companies sell these products for the same prices, Smooth-on suggested a silicon type casting and a very low heat something for the finished tool. At about double the costs. Given that we will have to make several of these to accomodate changes and learning curves, we are leaning towards the TEG suggestion. Both companies were very helpful and friendly.
Anybody see a problem with the Kwik-Kast2Blue and the 40/1000's Kydex or ABS? We'll be forming smooth side down............ |
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Fredo Master
Joined: 21 Mar 2007 Posts: 251 Location: Kingdom of Nye Area 51
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Posted: Fri Nov 05, 2010 1:08 pm Post subject: |
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Start your learning curve using ABS instead of Kydex. Wasting a sheet of abs is a lot cheaper than a sheet of kydex. Each plastic has its own learning curve. Kydex is not a cost effect replacement for abs. Even virgin abs is cheaper than kydex. You'll need a dryer box for abs, it absorbs water that can cause bubbles when heated to forming temps. I dry 12-2'x2' sheets of .125 abs for about 4hrs. at 145f. Loading from the dryer to the former gives me more even heat and a faster cycle time that suits my vacuum former. About the blue I haven't a clue..........Fredo _________________ If someone has a gun and is trying to kill you,
it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001 |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Sat Nov 13, 2010 10:54 am Post subject: |
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Fredo is very correct on ABS needing to be dry. The thicker the sheet the longer the drying time. On my dryer, it seems that after around 3-6 hours the humidity in the dryer needs to be below 25% for the ABS to be properly dried.
The problem I had with Smooth-On stuff was a direct result of ordering from secondary suppliers. Material was dated and not handled properly so it didn't set up correctly.
I like casting products from a 'local' company, BCC Products in Franklin, Indiana. I use the Slo Kast Gray since the molds I make are fairly large and need plenty of work time. My molds have close to a hundred hits on them now and show no signs of wear. THey also make aluminum filled casting products that should last even longer. BCC is real good about customer service.
http://www.bccproducts.com _________________ DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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mrcadman Newbie
Joined: 04 Nov 2010 Posts: 11
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Posted: Sat Nov 13, 2010 4:33 pm Post subject: |
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Thanks for the great responses about the ABS and drying it. I'm not even to that stage yet as my primary concern right now is getting a final plug.
Things have changed somewhat!
We are now going with this new 2 part form. The smaller part cant be removed until the ABS is lifted. No physical locks, so it should slip out nice.
We have also decided on using SLoKast Bcc8009 for the final plug, but........................
We are on the edge about the Vytaflex for the casting. Have any of you cast something this large? It simply MUST hold it's shape.
We expect to get hundreds of pulls from the SloKast, but intend to make the next mold using an Aluminum product. Hopefully, the SLoKast will stand up to the heat????
Pictured below is new shape. Not shown is the trim-band to help hide the seam, nor the 3/4" slope out that surrounds the entire bottom.
The gap between the two pieces will be machined to minimal.
What
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Mon Dec 20, 2010 3:59 pm Post subject: |
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Any update? _________________ DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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mrcadman Newbie
Joined: 04 Nov 2010 Posts: 11
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Posted: Mon Dec 20, 2010 9:51 pm Post subject: |
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Ok, huge updates on the model-casting-plug process!!!
We went with VytaFlex 40 and SloKast BC8009 from The Engineer Guy.
Universal spray release.
No bad odors, little mess really. No real rush either.
Despite several coats of hardener and sealer, clearly the VytaFlex found lots of woodgrain. The entire surface of the SloKast needs sanding, but that was expected. It's much easier to correct SloKast than balsa.
The VytaFlex is very durable, and the SloKast resin measures 100 shore A. Very machinable and zero shrinkage.
Now what i really need is someone in the Knoxville area to pull 10 of these right away while i build the protoform. Client needs displays NOW. We have three 10gal tanks, valves, the pump. We dont have the single hole platen or the heaters yet. Client is shying away from Nichrome too. I figure to be finished cylinders, heaters and all in 2 weeks.
Comments under each pic.
This is the Part-A at Demold.
Part-A casting
Look at the grain!!!!!
Part-B at demold. This had to be a 2-part/stage cast due to the lock shape
Part-B casting ready!
Both resin casts ready to fit!
HOLY CRAP 44Lbs plus 13Lbs!!!!! It's the 13Lb side that has to LIFT 4 inches in order to get the ABS to release!!!!!! We'll either make a cam lever or use cylinders to lift with the yet to be built protoform.
Still, this needed to be much lighter.
Everything fits, just some shape fitting and surface sanding. Yay! |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Fri Dec 24, 2010 9:59 am Post subject: |
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Some quick suggestions....
See if you can find a local commercial vac former that will test your molds. I found a local guy here, around Louisville KY, that has helped me out a lot.
Securely mount the mold to the platen. Many plastics shrink as they cool. With the near vertical sides of your mold the plastic may require a lot of force to remove. Applying force is much easier when the mold is mounted to the platen. See posts by Spektr on this subject. (You do have at least 5 degrees of draft on the verticals?)
Be more concerned about the strength of the mold then the weight. A massive amount of force will be applied to the mold when being vac formed and you don't want the mold to implode. A complete vacuum of 30inHg is roughly equivalent to 15psi. Doesn't sound like much till you multiply that by around 800 in2 of platen surface and come up with over 10,000lbs of force being applied.
If you're not too far into your build yet, consider getting the ProtoForm plans from Doug Walsh (kayker43) at http://www.build-stuff.com. The plans saved me tons time, money, headaches, redesigns, and failed ideas.
Good luck & have fun with it.
DougN _________________ DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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mrcadman Newbie
Joined: 04 Nov 2010 Posts: 11
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Posted: Wed Jan 19, 2011 10:12 am Post subject: |
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Thanks DougN. I bought those plans right from the beginning. They are a great starting point and the core of our build efforts.
I have mixed feeelings about the Slo-Kast, as one part held perfect, but the smaller warped crazy. That is due to the shape though. The material itself is literally rock hard.
I invite (beg) you to examine my post further logging this odyssey in the general vac forum.
http://www.tk560.com/phpBB2/viewtopic.php?t=1659 |
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