Where to begin?

by DD on Tue Jan 08, 2002 7:31 pm

I've got an application that seems well suited for RM. I have design experience with IM, Thermoforming, and extrusion but none with RM.

1. Where should I begin?

2. Are there any good molders in my region - Southern CA?

3. Where's the best place to find design guidelines/process limitations?

4. What are common mistakes made in the industry by fresh meat?

5. What kind of hidden costs are there?

6. What types of factors drive the price of parts?

7. Are metal inserts a reliable method of adding fasteners and various hardware to an RM part?

I'm sure that I could come up with more, but I would be more than pleased if anyone would be kind enough to answer any or all of these questions.

DD

by **Joel Martin** on Wed Jan 09, 2002 8:56 am

DD,

1. To begin, find some one to sit and talk the project trough with.
Try John Hammond at Mainland. 909-923-4353. They build cast aluminum molds in your neck of the woods and know a lot of molders.
2. See above
3. Contact ARM (Association of Rotational Molders) http://www.rotomolding.org
4. Tolerances are not typically as tight as you may be used to. Dependant on part size, shipping a lot of air with the parts.
5. Secondary operations
6. Graphics, inserts, special material, exceptionally low quantity.
7. Absolutely reliable.

There is a lot more to it, of course. Bring someone in with roto experience as soon as you can.
Will answer any other questions.

Joel Martin
Genex Plastics, Inc.

by DD on Wed Jan 09, 2002 12:30 pm

Joel,

Thanks for the info. By digging through a couple of links on the ARM site, I found this article http://www.rotationmag.com/article2.htm "The Basics for Designers". It's similar to an old article that I have, but more up to date.

Regarding factors that drive price, what did you mean by "exceptionally low quality?" Is that work, tools, design, resin or what?

I will be sure to mention your name when I contact Mainland Products.

DD

by **Joel Martin** on Wed Jan 09, 2002 3:44 pm

DD,
Oops, I meant "quantity".

Let me know if there is anything I can do for you.

Joel

by DD on Thu Jan 10, 2002 12:59 pm

Joel,

My fault. Not that I have any control of the quanitity demanded, but for curiousity sake what exactly constitutes extremely low for RM? Are you saying that mold fab and set-up costs can outweigh the cost of molding or is there another factor?

Also, who are some of the better material suppliers (for quality, consistency, processablility, technical assistance, etc.)?

Any advice on color selection (assume PE base resin if you want)? Which types are trouble-free, consistent from lot to lot, and uniform and which ones are trouble? How about effects like "granite" or something?

Thanks again.

DD

by **Joel Martin** on Thu Jan 10, 2002 4:08 pm

DD,

As far as the quantity issue a lot of fatcors weigh in. There may be a set-up fee for putting the mold on the machine if a certain minimum of number of parts or minimum dollar figure. Those numbers vary from molder to molder and would also be dependant upon mold size and a billion other things.
I do not use any resin suppliers on the left coast (we are based in Ohio), so I cannot give you an informed opinion on suppliers.
The main trouble with colors is how they are mixed. A coumpouded color is, in my experiance, the best for consistancy. With dry blending the consistancy depends upon the dry color, operator of the mixer (measuring the colorant) and the mixer.
I personally like running granite colors. The major thing to wacth is large flat surfaces, the granite motif tends to wash out in them.

Joel Martin
[email protected]