Core77

Lets see you 3D print a kayak. Tooling for roto-molding is very cheap compared to other plastic forming techniques which gives 3D printing a huge hurdle to overcome to replace it.

Besides, I'd try blow molding that part first

Visited at rotational molder 2 years ago, seemed busy as ever. Why would that process be on the way out? It's still the best way to form large hollow parts and produces superior finish to blow molding.

If you are going to produce more than 10 of that watering can, you'd be better off rotationally molding it than printing it. You'd also get far superior finish, a WORKING prototype, vast material selection, ect.

Sure, anything is possible. But the printers it would make that possible would need to have resolution high enough to define surface texture (microscopic), be fast enough to produce the part in less time than the roto molding (~40 minutes), be able to handle ultra large format 50'x50'x50' (in the case of producing grain silos), be able to print thermosets and a variety of other thermoplastics, and be cost effective. I do not believe that in my lifetime rotomolding would be replaced by 3D printing - And honestly why would you want to.

Roto-molding is a process which I don't think will completely ever go away but I can see it being replaced by other methods additive manufacturing (RP) or other. I can see injection molded parts which are then sonically welded together which is much cheaper than RP and other methods. The main issue is the surface finish. As seen by the finish of the watering can in the article, replicating the finish in RP at this current point in time is impossible. The other main issue is durability, unless you freeze the watering can and drive over it with a truck its not going to break. RP durability (SLS or SLA) is difficult but not impossible however over the long run currently it will end up brittle (there are glass filled nylons you can get but they are a pain to finish). The other problem is size, a roto-molded kayak is relatively straightforward to make, I'm not even aware of a RP machine that could spit out something that big.

There are basically these three problems:
-Surface finish
-Durability
-Size

I see all three of these issues individually being overcome in a short timespan 3-8yrs however getting all three in one RP part is going to be extremely hard to do and I see that happing 10-20yrs. out. Hopefully by then the cost of additive manufacturing (RP) will have caught up with our needs.

When I saw, "on the way out?" in the headline, I knew you were referring to rotomolding. It would be interesting to know what decisions would guide the choice of rotomolding over blow molding, for example.

Newer production techniques like 3D printing give us different options to choose in solving problems (and even in selecting which problems we try to solve). But there are aesthetic, functional, and perceptual goals that are still best met by hand-forming clay to produce ceramics-- one of the oldest production techniques in existence.

Seen a plastic garbage can lately? Or maybe the Chester sofa(http://www.dwr.com/product/chester-sofa.do)?

RP materials and processes are improving, but this is a question that should be posed to people with knowledge of roto-molding and other processes, as well.

RP is not a silver bullet, despite what seems like an ID fascination with having a one-size-fits-all answer to manufacturing.

As for surface finish, there are RP machines(polyjet) that do pretty high resolution(.0006" layer thickness). With texture built into the build file, maybe surface finish will eventually not be an issue of "can we make it this way?" "Should we make it this way?" will remain though.

A more fundamental limitation comes into play. RP methods require high precision movements of the RP machine for every part. Roto-molding, like injection molding, blow molding, etc. requires high precision to build the tool, then much lower precision to build the parts.

Roto molding is still used alot in India and a very coomon use is for overhead water tanks like those made by Sintex.

http://www.sintex-plastics.com/build&con/build_constru_usp.htm

Cheers

Ken: Blow-molding would struggle with that interior hole--not impossible, but it would make things more expensive. Rotomolded parts also tend to have higher durability, and--most importantly, below 30,000 units roto-molding is often cheaper than blow molding to boot.

On the way out? Are you joking?

Rotomoulding is one of the quickest, cheapest and easiest ways to make large plastic objects.

Im not sure how you nearly forgot about it, our potential clients ask about it all the time.

Seriously what a BS article. You are comparing apples with oranges. Do you have any experience with both processes?
I see most of my grieves have been discussed above. But still here's my summary:
+ Rotomolding is not on its way out. It is still the best production technique for many applications and products.
+ Ever handeled a 3D-printed part. It's brittle and coarse. Sure the technique gets better and cheaper each day but we are a far way from having 3d-printed parts with the strength and surface quality of a injection-molded part.
+If you had that water can printed it'll probaly cost you about over 1000$. So no competion to roto-moulding.
+ And yep I would also blow-mould the can instead of using rotomoulding
+ If you want to write an article about 3D printing i suggest you mention this: http://www.technologyreview.com/energy/37540/

@atohms - Well said.

I like that this a article came out around Easter, with all the rotational molded choco eggs around

I wouldn't call your article "BS", but rotomoulding is definitely not on the way out. I recently designed a product (a childeren's toy) that was rotomoulded here in Holland and it was by far the best option of all, as long as your series are not in the tens of thousands.
The company that produced it is - as other commenters have said - busy as ever. Especially big hollow structures (e.g. junction boxes for telecoms, garden chairs etc.) are ideal to produce this way.

3D-printing / RP? You must be kidding. Most of the products that are ideal to be rotomoulded don't even fit in "mammoth" SLS-machines.
I would have expected a more informed article here. And no reaction from the writer?

I graduated in 2004 and I have designed several roto-molded products since then. Plus almost all of the designer vinyl toys are roto-molded. In fact my buddy just bought a small roto-molding machine and is making his own vinyl toys. I would not really say this method is on the way out. In fact with the vinyl toy market I would say it is growing again.

Rotational molding is excellent for mass producing:

- Large sealed volumes, i.e. many objects used in the marine industry.

- Large fluid transport flasks for assorted lubricants, detergents, mixing chemicals.

The rising cost of energy is the probably the only threat to rotational molding as heating the large tool conveyors is rather ineffecient.

I think the author should apply "expensive, and takes freaking forever." to the RP alternative, not the rotomoulding. When I was teaching at a local design school, they were obsessed with 3D printing. Little or no mention of other manufacturing techniques that allows cost effective reproductions of items.

What use would a SLS watering can be anyway? It would suck up half of the water!!

The journalistic merit of this article should definately be called into question, clearly the author has done very little research on either process. Not a balanced article Core77.

Rotamoulding is a growing industry internationally, certainly not in decline or in a position to be replaced. If anything we'll continue to see growth but more refinement and development in machinery/ processing. Interestingly, the impact of rapid manufacturing technologies is likely to affect rotamoulding as a process less than it will others. We will see advances in tooling. The process of heating, forming and cooling polymers will never be replaced as long as our demand for plastic products continues.

I want to see the Rapid Prototyping machine mold one of these 10,000+ pound parts with 100+ inserts, steel weldments, etc. like we do on a daily basis.

Rapid Prototyping is good for just that... Rapid Prototyping... lets not get too carried away here people... I guess I could see some people try to RP injection molded parts in lower volumes since so many people want to injection mold parts or components, but very few (USA-side) ever put their money where their mouth is because of the tooling costs....Rotomolding Tools don't have that issue... I don't think the DoD is going to start Rapid Prototyping Military Bunkers and Bomb Trays.... I really doubt any Nuke Waste Tanks ever get Rapid Prototyped.... or better yet... Could you see a Rabbi asking for the Kosher certifications on the Rapid Prototyping machine?? If your a rotomolder and your afraid of the RP machine effecting your business... you should have been worried years ago when Rotomolders started closing their doors like K Mart stores.... Some people need to realize that it wasn't technology that drove the Rotomolding industry down from the 500 and some odd molders in North America... it was the poor business practices, lack of innovations and the wh*res of the industry running jobs below costs "just to cover overheads" (I die laughing as hard as possible mentally every time I hear one of you guys say that too btw...) You see how many of those guys are still in business?