Rough cost for plastic part 1

[brayle]

I need help with a rough cost estimate for what amounts to a 6" diameter hollow "sweep" (long radius) 90 degree elbow. If the elbow were straightened out the length would be about 30 inches. The material would be like that used for trash cans, I guess.

1/8th inch wall thickness.

Our needs are modest, 500 to 5000 per year.

Also, We could use 100 for market testing, is there any low cost way to produce some?
brayle

 

[insideman]

For your quantities, rotational molding seems to be the way to go. An aluminum mold would serve nicely, with an auxiliary bit of equipment to cut off the closed ends.

For prototyping, exactly the same mold would be needed.

 

[brayle]

Great, I'll research rotational molding. What kind of mold cost? Just order of magnitude like $5,000, $10,000, $100,000 would be very helpful.
brayle

 

[TheAnswerGuy]

brayle,

I have seen many questions answered by "insideman" and his answers have always been very accurate. I am not sure why he didn't offer this solution in the first place unless I am not understanding the question.

I think that you may want to explore making a thermoform of half of the tube and then bond both halves together.

Rotational molding does not offer a very consistant wall thickness and neither does thermoforming. Although a thermoform has much more control with regards to wall thickness.

 

[insideman]

Properly done rotomolding gives "satisfactory" wall thicknesses. Many rotomolded parts are "undercooked" in order to limit cycle time and part cost, but when properly coked, walls are good.

My guess at mold cost is $10.000.

 

[prototypeman]

Depending whether or not you have access to a cnc, you should be able to build a wooden vaccum form mold for under $5000. Possibly as low as $1000. if you are willing to put in some of your own effort.
The 2 halves would be vaccum formed, then you would need to use a saw and router to remove the excess material. The same mold could be used for both halves. Then with glue and/or a plastic welder you can bond them together for your sample prototypes.
I have used an oven to heat the sheet and a vaccum cleaner to produce the needed suction to produce rough samples in the past. If money is an issue, it works.

 

[brayle]

Prototypeman:
Thanks for your reply. I actualy did such a thing years ago in my kitchen, but with thin PVC. Do you think it would work 1/8 inch thick?
brayle

 

[baking]

Hi,
If you can use a standard 6" pvc pipe fill it with barley block both ends you should be able to make a simply jig to form the bend.This method is used by pipe manufactures to form special low volume orders.It might be worth a try and its cheap.

 

[prototypeman]

Brayle
I have done 1/8" before. It may take a few tries to get everything right.
Otherwise, like Baking says, You can bend PVC pipe by filling it with something and heating it uniformly in the area of the bend. I have used sand before for this.
If you feel ambitious and don't want to spend the money, there isn't much else you can do.
Good Luck!