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Join Date: Apr 2008
Location: Somewhere near BF, Arizona. ...seriously! ...we're that close.
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Are Rotational Molds Movable From Shop To Shop?

05/09/2013 10:03 PM

We're looking to get some vessels made in polyethylene that are < 1/4 Cu Ft. made using the rotational molding process. Does anyone know if mold tools can be moved from shop to shop? I'm hoping the small size of these would make that easier, but I'm prepared for it being the opposite.

Can anyone recommend a shop that is ISO 9000 (or that has some kind of quality system) that can handle such a job?

Thanks,

Tucson Don

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Pathfinder Tags: Roto Mold Roto-Mold
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#1

Re: Are Rotational Molds Movable From Shop To Shop?

05/09/2013 10:31 PM

Yes. It's just a tool.

Don't know of any shops, been out of the industry for years.

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#2

Re: Are Rotational Molds Movable From Shop To Shop?

05/09/2013 11:22 PM

Yes move it! What is the real question?

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Associate

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#3

Re: Are Rotational Molds Movable From Shop To Shop?

05/10/2013 11:12 AM

My question has to do with the specifics of the process and the tooling. Is the process as simple as rotating a mold that has pellets within it inside a big enough oven? Specifically regarding the rotational means, is it a 2 or 3 axis motorized gimbal, or how do they do it? And whatever the means of rotation, are molds specific to one single shop's rotating method such that a shop would prefer to make their own rather than take one made elsewhere?

Thanks, Don

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#4
In reply to #3

Re: Are Rotational Molds Movable From Shop To Shop?

05/10/2013 11:43 AM

Except that the plastic is usually powder, not pellets, the process is pretty simple.

Put a pre-determined volume of powder in one half and close the tool. Move to heating zone and rotate the tool in two axes for a predetermined period to melt all the charge.

Then, on to cooling zone and then de-mold.

Most shops can accommodate different tools since the machines are essentially rotating clamps that secure the tooling in place for rotating.

This: Inca Plastics rotational molding video - YouTube gives a good overview.

Good luck, be up front with the molders you talk to about your level of knowledge in the field.

Here's a web site to look at. Association of Rotational Molders. This organization can probably give you the names of some southern AZ roto molders. I'm in Phoenix and never dealt with any shops in Tucson.

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Guru

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#5

Re: Are Rotational Molds Movable From Shop To Shop?

05/11/2013 5:42 AM

The moulds have to fit onto the arms that impart the rotation. Each machine maker is likely to have unique hole centres or clamping arrangements to complete the fixing. From the moulding company's point of view this ties a particular mould to their make of machine and makes mobility between suppliers more difficult, resulting in repeat orders even if they are not the most cost competitive. Building a mould with a universal fitting that can attach to several makes of machine would be one solution, with a small cost premium, but it would also alert your initial supplier to the possibility of you changing after the first production run. This may not put the price up but it would certainly affect your relationship with the supplier.

In the UK I often work in conjunction with the component supplier who contributes to both the design and cost of the tool, in order the secure the business long term. Apart from the financial considerations this allows me to tap into their expertise in an area where my own knowledge is weak. I do not know if this "joint ownership of the tooling" relationship occurs in the US.

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#6
In reply to #5

Re: Are Rotational Molds Movable From Shop To Shop?

05/14/2013 1:20 PM

GA. I used to work with a number of rotational molders. Made quite a few castings in my day. Most were cast with some sort of mounting feet which I used to riser off of. Practically any mold could be re-mounted by the molder depending on the machine he was going to utilize. Many were actually bolted to some sort of spider arm where there was a great deal of flexibility in holes to bolt to. Any molder will adapt your mold to his frame at nominal if any cost just to get the business.

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