A little How To. (round Pattern)

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

I get asked alot how i make certain things. So i thought i would do a quick run through of how i made this radar dish Vacuum form pattern. I will list supplies at the end. If i miss anything just ask me. This is an Old school technique, as with model making and patterns theres always more than one way to do it. this is how i did this. its very cost effectve and the pattern will last forever.


I started by getting the basic shape and transferring that to the foam. I used Urethane but pink or blue foam will work for this process too. i cut the shapes out and glued them to my pattern base.


Next i made a sweep, all a sweep is is the reverse of the shape cut out and put on a tube to revolve around the pattern. This is the only thing i dont have a good pic of but i will post a better picture later. i insert a large tube into the center of the pattern that the sweep will telescope into. and that will swing around the pattern. The sweep can be seen at the top of the picture.


Ok so what i did in this picture mix a big batch of bondo. quickly spread it around the pattern and insert the sweep and rotate it around the pattern. make sure to remove excess bondo and stop your sweeping before it starts to harden. This was just the first coat. it took 3 coats to get the surface smoth and ready to primer. Heres a few pics of the additional coats of bondo.


And on the last coat when i was satisfied i was ready for primer i filled the center hole with bondo
 
Last edited:

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Ok, Now for some Primer. as usual prime and sand as needed to get it to where your happy.



Now i do a final sanding with between 400-600 grit. you can even wet sand if you want. after you sand. then you apply 4 to 6 coats of wax. to act as a mold release. the part should start to get nice and shiny.


Once your satisfied you have a good release on the pattern. then you mix your Ultracal 30. I do two thin coats to cover the pattern. i will discuss how to mix the ultracal later. for this part its just a waste mold and no reinforcement is needed. you actually dont want any. your going to want it to break apart.

 
Now that the concrete is dry, you can pry it off the pattern. it should pop off nice and easy with the mold release.




Now you grab your wax again and do your 4-6 coats of wax inside the concrete mold. then again mix up some Ultracal and pour into the mold. the first coat should be to cover the whole mold with a thin layer of ultracal. when using ultracal theres no breaks so as soon as you finish the first coat move onto to how ever many other coats it takes to fill the mold. For this it took 4 pours.. Pour 2-4 i reinforced the part with wet burlap. its like adding rebar to a side walk. help give it strength and the plug will last forever.



So i let that dry for a few hours and then i broke away the splash mold. by lightly tapping it with a hammer. and it just cracked and fell off.



And now your left with a big hunk of concrete that you can use to vac form over and over. what i like to do is put a few coats of wax on the plug. it helps the styrene to slide over the plug easier and also helps to release the styrene after it cools. heres a few pics of the vac formed part.





 
Heres a list of what i used to make this.

Foam. i used Urethane foam 5 pound density. but for this you can use pink or blue foam it doesnt matter.
To glue the foam to the base i use either hot glue or C/A
Carnuba wax. can get it at a boat or auto supply store.
Ultracal 30. a concrete supply or dental supply house. i think Smooth on even sells it now. but try to find a concrete supply a 100 pound bag here is only $25
Primer and sandpaper i get at the local autobody supply. dont buy sandpaper at Lowes or Home depot your getting royally Shafted on that. Bondo too get at the body supply. I buy regular bondo and metal glaze. but heres a trick to turn cheap bondo into a good glaze. just add fiberglass resin to the bondo until it gets nice and smooth. will spread nice and smooth.

I have a big former so Styrene at a plastics supplier. I usually buy 4x8 sheets.

Hope this helps, any questions just ask. Thanks for looking.

Al
 

cdr6

New Member
Good stuff! Thanks for sharing the info...

"Ya don't know what ya don't know..."-D. Krol

Regards,
Chuck
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Randy13

Well-Known Member
This is great Al. Thank you for this. It's something I've been wanting to try for quite a while.

I do have a question. If a circular base was cut out at the foam and Bondo stage, would it be possible to vacuum over that instead of making the Ultracal plug?
 
Its possible. But if you use pink or blue foam the heated styrene will cause the pattern to melt and crack. With the concrete you never have to worry. If your only doing one part i say go for it. But if your planning on multiple pulls. Be safe go with the concrete
 

trooper

Sr Member
RPF PREMIUM MEMBER
hey Al, great tips, love to see this kind of stuff :)
I hope you don't mind me sharing this on your thread....

you can also use this same method to make a mold for casting resin parts.

here is the scraped/sweeped patterns primed, they were maxed a couple times and then sprayed with mold release
IMG_2232.JPG



I used a brass tube for centering the molds and as an insert on the part, I poured in some resin and squished the two parts together

IMG_2234.JPG

I then cleaned the new resin part and molded it in silicone.

IMG_2243.JPG
 
Sure. No problem.

The concrete is good for vac forming. But for more complex shapes. The foam still works. But instead of concrete you can pour silicone. Then i like to make parts in fiberglass. I will do another thread on that soon.
 

bwayne64

Well-Known Member
Nice tut man ! I'm doing something similar for my 5 foot Falcon Model. Just wish I could get ultracal here. Looked high and low and can't get it. To have it shipped cost more than the plaster, LOL. That's what I get for living in Middle Georgia. Love it here, but can't get specialty stuff . Cheers,

Joe
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

trooper

Sr Member
RPF PREMIUM MEMBER
Nice tut man ! I'm doing something similar for my 5 foot Falcon Model. Just wish I could get ultracal here. Looked high and low and can't get it. To have it shipped cost more than the plaster, LOL. That's what I get for living in Middle Georgia. Love it here, but can't get specialty stuff . Cheers,

Joe

joe, I ran into the same thing here in Washington state, I called the company that makes the stuff, the rep. I talked to said the hydrostone is pretty much the same thing but with more concrete and is harder, but it does kick off a little faster, depending on what your doing that could be good or bad.
look to see if you can find that stuff.
I was able to get the local gypsum rep's #, he was able to point me to the closest place, 5hours away.but maybe th elocal rep to you can help you find something
 
Last edited:

bwayne64

Well-Known Member
Thanks Man, I can get hydrocal here in small 1 lb containers. It's similar to hydrostone. This area is a dead zone for stuff like this. I like to buy plaster in 100 lb bags. It's cheaper that way. I can go as low as 50 lbs, thats still cost effective. It's just that when you go to have it shipped it cost three times as much. I will look for hydrostone. It's funny when you call companies that sell plaster and building supplies around here, they've never heard of the stuff. If I were near Atlanta I could probably walk down the street and trip over bags of the stuff, :) Of course I'd eat a bullet if I had to live in the city, LOL.
 

trooper

Sr Member
RPF PREMIUM MEMBER
Thanks Man, I can get hydrocal here in small 1 lb containers. It's similar to hydrostone. This area is a dead zone for stuff like this. I like to buy plaster in 100 lb bags. It's cheaper that way. I can go as low as 50 lbs, thats still cost effective. It's just that when you go to have it shipped it cost three times as much. I will look for hydrostone. It's funny when you call companies that sell plaster and building supplies around here, they've never heard of the stuff. If I were near Atlanta I could probably walk down the street and trip over bags of the stuff, :) Of course I'd eat a bullet if I had to live in the city, LOL.
I found that building supply companies just don't carry the stuff, but shops that carry gypsum supplies will...generally lol
 
Guys thats because its not used for building supplies. Try a dental supply house. Thats its original use. To make teeth castings at the dentist
 

trooper

Sr Member
RPF PREMIUM MEMBER
yes, but the dental supply places here will not sell to anyone with out a dental license.
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Thats crazy. I can walk in mine and buy just about anything. I also buy dental impression material for doing teeth casts for work. And no one says anything.
 

cavx

Master Member
RPF PREMIUM MEMBER
I have Ultracal 30 in my supplies now and after using about half of the bag so far, was wondering what the difference between it and concrete is. The 50 pound bag (26KG) cost me $50 from a molding supply place. No-one else seemed to even know what Ultralcal 30 was much less be able to supply it. A 50 pound bag in concrete is about $15.00.
 
I have Ultracal 30 in my supplies now and after using about half of the bag so far, was wondering what the difference between it and concrete is. The 50 pound bag (26KG) cost me $50 from a molding supply place. No-one else seemed to even know what Ultralcal 30 was much less be able to supply it. A 50 pound bag in concrete is about $15.00.
Here try this. Originally a tooling cement. used by Dentists and Industrial designers.

http://www.usg.com/content/usgcom/en/products-solutions/products/industrial-specialty/tooling-&-prototyping/ultracal-30-gypsum-cement.html
 

cavx

Master Member
RPF PREMIUM MEMBER
I am in Australia, so shipping that from the US is out. Like others have said, dental suppliers only seem to want to supply to dentists.
I am also after that green seaweed stuff (Alginate?) used for life casts so I can take a mold of my feet for a custom pair of shoes. But again, either pay a premium through a mold/cast supply place or find something else.

As for Vacuum forming, I am working on female tooling and will probably use fiberglass for all the tools. Far better details and eliminates the heat/suction issues I have had in the past.

Your vacform seems to be working properly.
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Top