DIY Rotational Molding - How to hollow cast a sculpture

I make DIY rotational molding machines to rotocast resin. In this video I demonstrate the materials and techniques used to make hollow resin castIngs. It’s easy to build simple and very effective rotational molding machines that are hand powered and cheap to make. Rotational molding is one of my favorite techniques for resin casting and it’s a lot of fun to do!
Would you like to mold and cast something but have no idea how to start? Send pics of your project to me and maybe I’ll do it as a KZbin video.
Here’s a .pdf with the info:
www.dropbox.com/s/pjb0l6fr7zj...

[@fernando749845]

I'm adopting you as my grandfather.

[@robinbunn]

That was the first thing I thought! Look, we're cousins! ^^

[@mikeoliver6742]

I feel like the real star of this video is the friendly cobbled-together shop vac with mannequin arms in the corner.

[@youngsam4895]

Thank you so much. The most useful video I’ve ever watched. Currently pre planning my process for casting resin sculptures and this solved all my issues

[@dianeharris2687]

Very interesting. Can't wait to see how you paint her. Am always intrigued by your thought process as you work.

[@beefknuckles]

Very cool, Robert! I need to build one of these ASAP! Such a great material saver... which is key because it's expensive now! Thanks again. Cheers!

[@ArcticFlies56]

That really worked out very well. This is second rotational pour I saw you do. The first one didn’t work out so well but you win some and lose some. I really like the rotational machine you made. Very cool device.

[@esfandyar17]

Thanks for the lovely video on rotational molding. Thoroughly enjoyed it.

[@RobertTolone]

Thanks for watching!

[@cacostta]

Thanks for the video! Great job!

[@RobertTolone]

Thanks for watching and commenting Carlos!

[@Napkinholdin]

Wowwww, I never knew that's how they do that!!

[@ravereviews6853]

Love your sculptures aswell

[@RobertTolone]

Thanks!

[@countryhoney1766]

Robert, very cool.

[@natalieshark]

I have been wanting to do something like this, and this was very helpful!

[@RobertTolone]

Glad you found it useful, Natalie. Thanks for watching!

[@iwshpo7873]

Please .... Wats the name of mold n toy material .....

[@runin1wild]

Very nice!

[@blakelycreative3171]

the casting machine is really cool...

[@humblehombre9904]

It really did not leak much at all, Robert. I am going to make one with your design. Thank you. What do you think about putting a large circle disc of plywood on the end of the outer frame, as a “steering wheel” so you could turn one frame slowly, while spinning inside frame with other hand? I’m certain you have already thought of this. You never miss a trick.

[@jozefa1234]

I owned a MAKO machine 40 years ago , and could not find any inforrmation about it. same machine much smaller wat makes puppets of plaster of paris. it has gears and one handle to turn both axis. So I found your video and think making one myself instead of looking for something long ago for google excisted. thank you very much

[@rotten_comics]

Thank you,

[@paulhayton3423]

Great information..

[@RobertTolone]

Thanks, Paul!

[@fsecofficial]

My guy bust out the triple beam. Master P said unnnhhhhhh. 😂

[@lalucoo]

I need to make one of these! *__*

[@chaumas]

I wonder, with a motorized one, how hard it would be to make it auto-balance. I think you'd need some counterweights on linear actuators, and then some way to detect wobble so that you can tell which way the counterweights need to shift.

[@RocketPunchHero1]

That's the bung, that's the hole... Bunghole. LOL I see what you did there. ;)

[@ericmillen7840]

great video., thanks for sharing! i was originally looking to see if i could find how hollow chalkware was made from the late 1800s to the early 1900s. do you think it was a technique like this or did they create hollow chalkware with a different technique? anyone know?

[@jimintaos]

Very interesting. Do you suppose this could be used for casting a sculpture in hydrocal or plaster of paris?

[@pamfiloabionjr4529]

Thank you for this tutorial, it helps me a lot, can you please tell me What kind of resin did you used on this one, and is epoxy resin will do for this kind of project or not? Thanks!

[@RobertTolone]

I used a urethane casting resin. I have never used epoxy resin for rotational molding. But it’s possible that there are epoxies made for that purpose.

[@humblehombre9904]

Rob, could I make a blanket mould out of latex? I have the latex, because it was cheap enough for me. I really want a mould of a carving, and you have convinced me that doing a blanket will be cheaper in materials. Any advice on latex use?

[@chrisschellberg4753]

Great tutorials! Helped a lot. But, I'm a long way off on some of my more complex parts.. How do I contact you for some mold and casting work?

[@deancampbell8856]

Wow, this is just amazing. Can you give us downloadable plans on this rotational mold castor machine???

[@RobertTolone]

I don’t have plans because the machine is simple and can be built to almost any size and shape configuration. The key concepts are that the two frames rotate on axes that are 90° from each other. There must be good clearance between the two frames and between the outer frame and the supports that hold it up. That clearance is required because of things that are attached to the inner frame such as clamps and cradle parts. I have built rotators in all shapes and sizes, even built a machine to spin a specific mold. The rotational speed is so slow that you don’t need bearings. Just regular bolts through holes in the wood are sufficient. The best thing for you is design a machine that fits the work that you want to do.

[@motos_classicas333]

Hello Robert, I am writting from Brasil, very nice your roto molding machine. Do you think I can do for making side cover for motorcycles??normally they have a pot format, Feel free to give you experienced hits. Regards Flavio

[@TheosResearchDiary]

Hi Robert. Thanks for sharing the knowledge. Were the Clairemont sculptures polyurethane? I had a hollow polyurethane rotocast piece out in the sun last year that deformed a bit with heat. It was painted black and hollow with a thin shell, but still curious what plastic you used and how you approached it.

[@RobertTolone]

Yes, they were Rotocast in the same resin I am using now. But after casting the pieces were assembled and filled with urethane foam. Also there is a aluminum armature in each one. The wall thickness was around 1/4 “ so they are pretty tough! I was afraid that children would climb on them, etc.

[@ravereviews6853]

Hi, loving the rotation mould technique. Just finished my product design masters and am wondering if this could be done with a rubber type material to make a rubber dog-toy like product? Essentially hollow that can be squeezed? I'm wondering how they leave a hole in it for the squeaker. Can you cut it away from the bung hole part? Annnd I'm assuming if you're doing a few small objects you could rotation mould a few at a time?

[@RobertTolone]

There should be rotational casting elastomers out there but I have never tried it. The trick in molding several at once is getting the molds loaded with material fast enough so it doesn’t set up before getting rotated.

[@chaucer44]

I love your rotational rig. Is there a place where we can download plans for it to build at home?

[@RobertTolone]

I don’t have plans because you can build one to fit any requirement. It’s just a frame inside a larger frame. The larger frame rotates on some sort of stand and the inner frame rotates at 90 degrees to the outer frame. Leave clearance between the two frames and the ground. You don’t need bearings or other fancy hardware.

[@paulperth4205]

Hi Robert, firstly thanks for the great tutorial videos, I have now Subscribed. I'm interested in casting plastics as I've just started restoring motorcycles and plastic panels and lenses are rediculosly hard to come by.. so again thanks, However other than making projects in one solid colour, is there any way of making a "tie dye" type of colour scheme on a finished project? Many thanks, Paul in Perth Australia.

[@RobertTolone]

You can try mixing batches of different colored resins and pouring them into the mold at the same time. I believe that that is how they make bowling balls. How well it works will depend on the type of resin you use and the shape of what you are pouring. To be honest I have never had much success pouring multicolored resin in one object. But then I haven’t really spent much time playing with that process. In my shop it is much more common for us to paint the castings.

[@paulperth4205]

@@RobertTolone thanks for the quick reply, I thought thatg maybe putting 2 different colours of resin in at the same time would make the colours "bleed" together.. it's something I'll have to play with in the future.. thanks again :)

[@RobertTolone]

@@paulperth4205 I have found that a lot depends on the shape of your mold. If your mold is open backed like a picture frame you can drizzle the colors in and they don’t mix much. If you are pouring through a funnel and a sprue the colors will pretty much mix together.

[@satoshinakamoto9416]

Nice video. Which materials do you use for your castings, i.e. 100 grams A and 100 gran B? That is a great help, thank you.

[@RobertTolone]

I am using a urethane resin suitable for rotational casting. I use Silplastic sold by www.silpak.com.

[@jayturner5435]

Can this technique be used when trying to make a hollow casting using a platinum silicone about shore strength 00-20/00-30?

[@RobertTolone]

I have not used platinum rubber to make brush-on type molds. In theory they should work fine as long as any additives like thickening agents are compatible with the rubber. I would test all your materials: the model, release agents, additives and casting material, etc to check for compatibility. Platinum rubbers are more sensitive to other materials than tin-based rubbers are.

[@jesussotosotomolinez1010]

Hi Robert, thanks a lot for this, i have a question, does the roto casting eliminate the bubbles that you would get on a traditional cast?

[@RobertTolone]

It can but it can also trap bubbles. On casts with a lot of surface details you often have to brush the resin onto the mold before doing the Roto casting.

[@design321]

Robert, is there a list somewhere showing the order to watch your videos in, if you are a beginner and want to learn the basics, then move on to the more complex?.

[@RobertTolone]

I’m afraid I was not that systematic about planning my videos. They are not really a series of tutorials from beginner to expert. Rather they are individual videos on different projects. You can use the playlists to help focus on specific topics.

[@AndrewRandston1]

are you rudy giuliani's cozen or something? thanks for the cool video

[@imVexedBruh]

Woah are those construction guys still in claremont? I live near I'd love to go see them

[@RobertTolone]

Last time I looked they were. 1616 Monte Vista Ave.

[@georgetirebiter4343]

A teacher I had recommended pantyhose to tie molds together, but she also woukd use a plaster mother mold to prevent the silicone mold from flopping around. So the pantyhose would grip the surface of the plaster.

[@RobertTolone]

Have to say I never tried the pantyhose method! Great example of using what you have at hand.

[@gladiatormechs5574]

Is it a special type of resin that is used for rotocasting, or can i use SMOOTH ON 66 D which i know is AQUARIUM SAFE ?

[@eross21]

so i love casting in urethane. however it does get expensive for the materials. do you recommend any other ( lower cost) casting material that can do a similar job for rotational casting like this one?

[@RobertTolone]

Water extended polyester. You actually do mix the resin with water to create an emulsion. This lowers the per-gram cost quite a bit. It’s a pretty cool material and it rotocasts really well. Biggest downsides are that it has a strong stinky polyester smell and the castings do shrink over time. Not a huge amount but enough to be noticeable. The cured polyester is also not as strong as most urethane castings.

[@eross21]

@@RobertTolone very cool,im gonna check that out. thanks sop much for the help

[@1985cactus]

Can you fill the hollow sculptures with some cheaper material to make them heavier and sturdier?

[@RobertTolone]

Yes, you could use hydrocal or plaster of paris.

[@1985cactus]

@@RobertTolone Thank you very much.

[@Curleification]

Wouldn't that cause problems for the plaster as the moisture has no where to go, considering that you seal the bottom in PU resin as well?

[@karolinakiwicreations5738]

What is the working time of that resin? is it a slow casting one?

[@RobertTolone]

Depending on the temperature, just a few minutes.

[@ThisOLmaan]

did you say Bung Hole, 6:27 LoL i heard that word on Bevis and Butthead LoL really I did, Robart Tolone, you make a lot of these videos? different types of dyes mixing, mold making, as well as casting, with all types, of different products, like plastic, clays, wood etc? well, it was a great video and ur Gal came out HOT Pink Sexy, Mister piece did come out fabfabulous 👍🏼 oh ur video just came on while I was looking for Canon Lenses, on Ebay and wanted to go see whats you making ha.

[@RobertTolone]

It’s a very old word. A bung is a stopper that plugs the hole in wooden barrels. The opening is therefore the bung hole. Of course, we know what Beavis and Butthead were referring to when they said bunghole!

[@SeasonalFrostbite]

Could you show us how to motorize it?

[@RobertTolone]

I am considering it as a video project. The motors, wiring and control would be simple enough. But I will definitely need help with writing the code. One of the big advantages to hand control is that each shape you cast needs it’s own rotation strategy and doing it by hand means you can adjust the movements to the shape very easily. With a computer you would need a program that allows you to set the parameters of rotation to cast the shape. Thanks for your interest!

[@kaioken654]

Man, beavis and butthead destroyed the definition of bung hole, I had no idea until now it doesn't mean ass hole

[@RobertTolone]

😄

[@alejandrolojo8526]

Hey there. Do you make action figure accessories on demand?

[@warrengoodwin5905]

Hi can roto casting work with say silicone or do you need to more or less let it sit like a two or three part silicone mold ?

[@RobertTolone]

Do you mean, can silicone itself be rotocast?

[@warrengoodwin5905]

yes :)

[@RobertTolone]

Warren Goodwin Warren Goodwin I’ve never tried it but it should be possible. It would be best to use a fast setting silicone or you’ld be spinning it for a long time!

[@warrengoodwin5905]

@@RobertTolone mmm indeed, just can't be bothered with putting in a third inner mold for injecting the silicone i mean i don't mind standing there with random rotation for ages but yea might need a test i think - not sure if rotating the silicone in the mold would disturb the release agent - which i also have, but yea

[@simitchell]

What dye are you using? What key words do I use to find it?

[@RobertTolone]

Here is a link to the materials that I use. The dyes are under resin colorants at the bottom of the first page. I am not sponsored by or affiliated with this company, they are simply my material supplier. www.dropbox.com/s/kz6mhmf7v5vpy7l/Material%20and%20Suppliers.pdf?dl=0

[@simitchell]

@@RobertTolone thank you so much - you are a massive help with my research- so thank you

[@ethanwinters7716]

Will this limit air bubbles?

[@RobertTolone]

Done properly you can get bubble-free castings by rotocasting resin.

[@waxxtoonstm941]

What kind of resin is that?

[@RobertTolone]

It is a Urethane casting resin called Silcast II from www.Silpak.com.

[@vampers10]

Does this way cause bubbles

[@RobertTolone]

No, usually the castings are bubble free. If you have a sculpture that has a lot of surface texture it may be more likely to catch bubbles in the details. But the resin does a good job of wetting the surface. Only trying it will tell you if it works for a particular piece.

[@vampers10]

Robert Tolone thanks

[@pival801]

Is there any other way to hollow cast other than rotocasting?

[@RobertTolone]

With resin casting the only other way I know is to create the object as front and back shells. Then you would need two separate front and back molds. After cast the shells you glue them together to create the finished hollow part.

[@pival801]

@@RobertTolone I was thinking the same thing, but I'd like to avoid having to glue them after they've hardened because I fear that there will be a visible seam line. Do you think it's doable to attach the two molds while the resin is not yet fully hardened, or would it not make a difference?

[@RobertTolone]

@@pival801 Anything you mold and cast will have a visible parting line that you need to clean up. That’s why I advocate cut molds because they have the cleanest lines.

[@SBecktacular]

I can see my fingers getting caught in that gyroscope lol If u put the uprights on the inside, U could put a turning handle on the frame

[@RobertTolone]

you could put a handle on the outer ring but to put cranks on both rings requires a system of gearing or pulleys. It works but it’s more complicated than is necessary.

[@iwshpo7873]

Anyone knows the name of polymers.....for mold n toy

[@Scoutdeath572]

I'm just guessing here: polyurethane or polyester resin for the toy and rubber silicone for the mold

[@Scoutdeath572]

Don't know about the exact product, but you can google it and find out wich ones you can buy

[@mikrvanschaffel1826]

where you get that angry woman sculpture i luv it

[@RobertTolone]

I sculpted her in a couple videos before this one. Scroll back through my videos.

[@RoySATX]

How to hollow cast a sculpture, or as I prefer to refer to it, How to cast a double entendre!

[@connieschneider2401]

ARE YOU STILL UP TO DUPLICATING WITH ROTATIONAL MOLDING MACHINE

[@RobertTolone]

Yes, rotocasting projects are always in the mix.

[@bigdaddyrc4642]

You look just like Bob Newhart...lol

[@Cwjespersen]

I was expecting it to leak from its bunghole, not the screw holes.

[@RobertTolone]

lotta times they leak from every hole. 😭

[@althafrahuman9332]

Add a L shaped handle rotator

[@RobertTolone]

I used to motorize my rotators, then I went through designs with cranks, handles etc. Now I just keep them as simple as possible. Less work to build and just as functional.

[@mykolkurtz]

lol you said bung hole lol

[@RobertTolone]

Bung is a proper word, we just made it naughty! 😆

[@gladiatormechs5574]

how did you know how much resin was needed .. 50 grams of A and 50 grams of B... is that basically your best guess from experience.

[@RobertTolone]

Yes, just a guestimate.

[@golden7676ify]

SPIN TOO FAST

[@RobertTolone]

Nope.

[@user-dd6id9bn1e]

Thank you ! But with all due respect you are wasting time by using antique scale - it is not as accurate as electronic scale,takes WAY more space and time consuming to use … Speaking of rubber bands - why not to use a glue gun to secure a mold it will take WAY less time and will hold a piece with higher security…