can a plastic container of this shape be manufactured?

[funtech]

Hi, I'm not well versed in blow molding. I need to make a container in the shape of the following pictures.

Essentially, it's just a regular bottle, but with two openings (protrusions) on the side, for connecting to tubes.

Can it even be manufactured? How can the protrusions on the side be manufactured? I talked to a maker of conventional bottles and they said they "don't have the machines to make the protrusions on the side."

thanks

 

[MikeHalloran]

You didn't include a picture.

Maybe I can illuminate the issue anyway.

You can't blow nipples out of the sides of a bottle, where e.g. the wall of a milk bottle is super thin.

You _can_ blow multiple necks in a bottle. The trick is to make the mold so that the neck portion just above the bottle has two or three lumens. ... which rejoin each other above that, into a single neck that can be blown on most any machine. Then the neck trim operation cuts off the waste above the multiple necks.

It's sort of like blowing an integral handle at the top of a big jug, with the trim line through the handle, not above it. Of course the necks must share the same parting plane.



Mike Halloran
Pembroke Pines, FL, USA

 

[funtech]

Hi,
thanks for the reply. I will try to absorb what you've said.

here is the picture:

http://s4.postimg.org/f8k9n91l7/bottle1.jpg

If you can't see it, then try here:

https://www.flickr.com/photos/124719011@N02/14012731067/

https://www.flickr.com/photos/124719011@N02/14199320155/in/photostream/

Let me know if there are any additional insights now that you've seen the pics. The two protrusions are on opposite sides of each other.
thx

 

[btrueblood]

You could rotationally mold that part, if you aren't too picky about tolerances.

 

[MikeHalloran]

No, you can't do that.

Here's an example of what you can do:

http://www.containerandpackaging.com/item/B204

In your case, the extra nipples would have to be parallel to the neck on the top, generally parallel to it, and close enough together so that their outer walls lie inside the extruded parison.

Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

Mike,

yes you can...unless you were replying to the op's 2nd post...

 

[TheTick]

Possibly blow-molded, as long as all the openings are on the parting line and you're not picky about wall thickness.

 

[MikeHalloran]

"Connecting to tubes" suggests the OP will eventually need to be picky about wall thickness, whether (s)he realizes that now or not.

Pulling a nipple with reasonable wall thickness out of what is already the thinnest part of a bottle is not possible.

With rotational molding, yes, it's possible, but the cycle time will make it an expensive part, relative to blow molding.




Mike Halloran
Pembroke Pines, FL, USA

 

[funtech]

Thanks for the help guys.

So in conclusion. The part can most likely be made with rotational molding, though it might be expensive. (I'm not too concerned with tolerances).

With blow molding, it's hard to get a decent wall thickness for the nipples, so it will most likely not work.

 

[drawoh]

funtech,

Have you talked to your favourite blow/rotational moulder yet? I strongly recommend it.

--
JHG

 

[funtech]

Hi, I will talk to a rotational moulder ASAP.

In the meantime, I'm interested in making a prototype first before investing in an actual production mold. For production, it seems like rotational molding is the way to go. But if I want to build a couple of prototypes first (to test the concept), I guess my best bet is to just take some existing similar containers and try to add those nipples myself via plastic welding or other attachment method? There are no better methods to make a prototype is there? short of actually making a mold.

 

[MikeHalloran]

You misunderstand.

With rotational molding, it will always be a $20 part, no matter how many you buy.
With blow molding, it will be a sub $1 part if you buy a bunch at once.

You should, however, make a nice drawing and talk to a couple of molders of each type. There probably aren't many people who do both.

Both types of molder will want to know the minimum acceptable part weight, which is usually all the inspection they will do for free. Your CAD system may be able to help with that, if you adjust the wall thickness to be similar to parts that actually exist. The blow molded part is fairly difficult to model in that respect, because the wall thickness is never uniform. Slice a milk bottle and some detergent containers to understand that.

Molds for blow molding and molds for rotational molding are generally much cheaper than molds for injection molding, because of the lower process pressures. Each molder you meet will have a unique set of preferences or peeves about part design and its influence on molds. That's why you need to meet them in person. Make two identical markups for each vendor; bring one back.




Mike Halloran
Pembroke Pines, FL, USA

 

[EnergyMix]

Now that all the pros and cons of blow and rotational molding have been discussed, is this one of those cases where 3-d printing would come in handy? Not that I know anything about it, but from what I've heard, it seems designed for parts like this.

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[MikeHalloran]

Additive manufacturing is ideal, if you only need one part, or one part a day, and the finish doesn't have to be real good, and you don't mind an occasional pinhole, and you're not going to pressurize it, and a part cost of a couple hundred bucks is okay.

Consideration of blow molding suggests the production volume, not stated, will exceed dozens of units per day if all goes well.


Mike Halloran
Pembroke Pines, FL, USA

 

[tygerdawg]

I'm curious:
(1) what is object size?
(2) what is object material?
(3) what is object wall thickness?
(4) what is production volume requirement?
(5) are you strictly limited to this exact shape?

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[funtech]

Tygerdawg,

1) The container holds roughly 5ml of fluid, with a diameter of 20mm and height of 25mm roughly. It's small part.
2. I want to use PE or LDPE for material
3. Wall thickness for the bottle should be 1mm roughly. I can accept a lower thickness for the nipples if they can blow mold it. The nipples are to be mated to silicone tubing. I think I can make the nipples larger and just insert the tubing inside the nipple, rather than the other way around. This way, a thin wall will not cause problems. The system will not be subject to any significant pressure. As long as it doesn't leak, it'll be acceptable.

4. Probably will want to make 1000 at a time.
5. This shape is the most desirable because of the special application.

thanks for the help so far guys.

 

[MikeHalloran]

Ah. Given that the part is that small, I'll accept that the part can be blow molded, in a relatively large machine. You can just blow the side nipples out of the parison.

I'd suggest also molding barbs or beads in the nipples, and pushing the silicone tubing over them. Allow some length so you can shrink some shrinktube over the assembled hoses if need be.



Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

Agree with Mike, for the size. Also on having the tube over the nipple. If you think about it, having the stretchy part (tube) on the inside is a guaranteed leak - any pulling on the tube results in a contraction of the tubing, tending to peel it away from the more rigid wall, opening up a crack that eventually leaks. You never see such a construction in the real world, at least not without some other elastomeric element to make up the seal.

 

[KENAT]

Back to additive manufacturing, may be an option though with that size and wall thickness you may have to be careful exactly what process you pick.

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[KENAT]

Sorry, meant to say for the 1 or 2 prototypes.

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