Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing process
seems on the surface to be simple. I guess transport / distribution of a
bulky product could be costly. Anyone got some ideas?

"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?

The process is simple---bolt a steel mold together, dump in a quantity of
plastic
powder, heat and rotate/tumble/turn through 3 axis while the powder melts
and
coats the inside of the mold. Cool, open mold and remove part. On smaller
parts like spot sprayer tanks, there may be several molds on the framework
at the same time. Big parts like water tanks are one or two

The process is time, labor and energy intensive, in addition to being very
inefficient
on freight.

Where are you? Might be cost effective to do a pickup at the factory.

"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?


How big? They are formed in ovens MUCH larger than the tank, and the mold
cycle times are very long when compared to injection molding.

"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?

Also there are economies of scale involved. Not physical size but volume.

There are probably an uncountable number of guys here who could take make
you a machine nut by taking a piece of steel, drilling a hole in it, taping
it, and then cutting the outside so you could grip it with a wrench. It
would probably take me an hour to make one nut that way in my shop. I
charge $80 for my time (I do not make that much by a long shot). There are
a few more guys in this group who could take iron ore. melt it, add some
other stuff, and then produce your one nut in their shop.

Or, they could buy some production equipment for a few hundred thousand
dollars and make your one nut.

In any case the material is cheap. In the first case the labor is
expensive. IN the second the equipment is expensive, and for one nut the
setup, electric, fuel, and labor are expensive along with the several
hundred thousand for the production tooling in the factory. However, if
they make one nut or a million the tooling cost doesn't change. In fact the
tooling cost probably doesn't start to change much from tool replacement and
repair until they have made a few hundred thousand of them.

So in the first case it costs $81 for one nut.

In the second it costs $500,000 to make one nut.

Now add in overhead, additional fuel, insurance, repairs, etc.

The first shop could make a 1,000,000 nuts for $81,000,000 dollars, and they
are still $81 each.

The factory could make 1,000,000 nuts for $750,000. Their nuts cost 75¢
each to produce.

Fortunately the demand for nuts is in the trillions in the world, and
factories all over the world are geared up to produce billions of them.
This production volume drives the production cost down. The consumer demand
keeps the volumes high enough to keep the factories operating at their most
efficient level, and competition between factories keeps the profit margins
charged reasonable.

I would bet real money the demand for nuts is in the trillions. What is the
demand for roto-molded tanks?

They might be able to make them for a few dollars each if they could gear
upto produce them continuously in the hundreds of millions.

Heck, have you ever seen a blow mold operate? Milk jugs go in as a slug of
plastic and come out as a plastic jug and go right into the bottling part of
a milk plant. They cost pennies a-piece. But they make hundreds of
millions of them. That plant to make them cost a million dollars to setup.

Nutz wrote:

Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing process
seems on the surface to be simple. I guess transport / distribution of a
bulky product could be costly. Anyone got some ideas?

What everyone else said about time and labor costs.

The interesting thing to note is that unlike injection or blow molding,
roto-molding does have some home shop DIY potential since the mold
doesn't have to be super strong (like injection molding), doesn't
requite complex support systems (like blow molding), and doesn't even
require a big oven if you install heaters on the mold itself and so some
simple slip rings to get the power to them.

"Bob La Londe" wrote in message
...
"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?

Also there are economies of scale involved. Not physical size but volume.

There are probably an uncountable number of guys here who could take make
you a machine nut by taking a piece of steel, drilling a hole in it,
taping it, and then cutting the outside so you could grip it with a
wrench. It would probably take me an hour to make one nut that way in my
shop. I charge $80 for my time (I do not make that much by a long shot).
There are a few more guys in this group who could take iron ore. melt it,
add some other stuff, and then produce your one nut in their shop.

Or, they could buy some production equipment for a few hundred thousand
dollars and make your one nut.

In any case the material is cheap. In the first case the labor is
expensive. IN the second the equipment is expensive, and for one nut the
setup, electric, fuel, and labor are expensive along with the several
hundred thousand for the production tooling in the factory. However, if
they make one nut or a million the tooling cost doesn't change. In fact
the tooling cost probably doesn't start to change much from tool
replacement and repair until they have made a few hundred thousand of
them.

So in the first case it costs $81 for one nut.

In the second it costs $500,000 to make one nut.

Now add in overhead, additional fuel, insurance, repairs, etc.

The first shop could make a 1,000,000 nuts for $81,000,000 dollars, and
they are still $81 each.

The factory could make 1,000,000 nuts for $750,000. Their nuts cost 75¢
each to produce.

Fortunately the demand for nuts is in the trillions in the world, and
factories all over the world are geared up to produce billions of them.
This production volume drives the production cost down. The consumer
demand keeps the volumes high enough to keep the factories operating at
their most efficient level, and competition between factories keeps the
profit margins charged reasonable.

I would bet real money the demand for nuts is in the trillions. What is
the demand for roto-molded tanks?

They might be able to make them for a few dollars each if they could gear
upto produce them continuously in the hundreds of millions.

Heck, have you ever seen a blow mold operate? Milk jugs go in as a slug
of plastic and come out as a plastic jug and go right into the bottling
part of a milk plant. They cost pennies a-piece. But they make hundreds
of millions of them. That plant to make them cost a million dollars to
setup.

Rotomolding costs lots of heat energy. Watched a kayak factory make them.
13' Kayak, 14' mold, 18' long oven. And the the mold was not cheap. And
then the equipment has to rock and rotate the mold in this high heat oven to
get the plastic to flow.

"Pete C." wrote in message
ter.com...

Nutz wrote:

Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process
seems on the surface to be simple. I guess transport / distribution of a
bulky product could be costly. Anyone got some ideas?

What everyone else said about time and labor costs.

The interesting thing to note is that unlike injection or blow molding,
roto-molding does have some home shop DIY potential since the mold
doesn't have to be super strong (like injection molding), doesn't
requite complex support systems (like blow molding), and doesn't even
require a big oven if you install heaters on the mold itself and so some
simple slip rings to get the power to them.

The DIY aspect is what got me interested, I had a bit of a look on youtube.
It seems there are a few of us toying with rotomolding in our workshops.
Heating the mold is an interesting idea.

"Calif Bill" wrote in message
m...

"Bob La Londe" wrote in message
...
"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?

Also there are economies of scale involved. Not physical size but
volume.

There are probably an uncountable number of guys here who could take make
you a machine nut by taking a piece of steel, drilling a hole in it,
taping it, and then cutting the outside so you could grip it with a
wrench. It would probably take me an hour to make one nut that way in my
shop. I charge $80 for my time (I do not make that much by a long shot).
There are a few more guys in this group who could take iron ore. melt it,
add some other stuff, and then produce your one nut in their shop.

Or, they could buy some production equipment for a few hundred thousand
dollars and make your one nut.

In any case the material is cheap. In the first case the labor is
expensive. IN the second the equipment is expensive, and for one nut the
setup, electric, fuel, and labor are expensive along with the several
hundred thousand for the production tooling in the factory. However, if
they make one nut or a million the tooling cost doesn't change. In fact
the tooling cost probably doesn't start to change much from tool
replacement and repair until they have made a few hundred thousand of
them.

So in the first case it costs $81 for one nut.

In the second it costs $500,000 to make one nut.

Now add in overhead, additional fuel, insurance, repairs, etc.

The first shop could make a 1,000,000 nuts for $81,000,000 dollars, and
they are still $81 each.

The factory could make 1,000,000 nuts for $750,000. Their nuts cost 75¢
each to produce.

Fortunately the demand for nuts is in the trillions in the world, and
factories all over the world are geared up to produce billions of them.
This production volume drives the production cost down. The consumer
demand keeps the volumes high enough to keep the factories operating at
their most efficient level, and competition between factories keeps the
profit margins charged reasonable.

I would bet real money the demand for nuts is in the trillions. What is
the demand for roto-molded tanks?

They might be able to make them for a few dollars each if they could gear
upto produce them continuously in the hundreds of millions.

Heck, have you ever seen a blow mold operate? Milk jugs go in as a slug
of plastic and come out as a plastic jug and go right into the bottling
part of a milk plant. They cost pennies a-piece. But they make hundreds
of millions of them. That plant to make them cost a million dollars to
setup.

Rotomolding costs lots of heat energy. Watched a kayak factory make them.
13' Kayak, 14' mold, 18' long oven. And the the mold was not cheap. And
then the equipment has to rock and rotate the mold in this high heat oven
to get the plastic to flow.


Thats what got me interested. There is a one man kayak factory round the
corner from our workshop - I may go and bother him for a "tour".

Did a tour of the Raven Industries rotomold facility in Sioux Falls SD in
2000 or so.

Probably a nice place in the winter--it gets COLD in SD, but this was July
and it
was way past pleasant, especially when they opened up the oven for the
cooling cycle.
Fun and interesting to watch several molds rotating through 3 axis motion on
the
mechanism in the oven. Biggest setup was fairly large, had molds on it
for large "nurse tanks" used for ag spraying.

Fun part of the tour was the balloon facility. IIRC the assemble table was
800 ft long.

For DIY applications thermoset resins might be a more cost effective
choice. No ovens or heated molds are needed and the molds can be very
inexpensive. Especially if only a few castings are needed. Polyester,
polyurethane, and epoxy resins are available with a wide range of
properties. The cycle times are generally longer but if you only need a
few castings it might work fine.
--
Billy Hiebert
HIEBERT SCULPTURE WORKS
Small Part Injection Molding
http://www.hieberts.com

Calif Bill wrote:
"Bob La Londe" wrote in message
...
"Nutz" wrote in message
...
Sure its not metal but it's not politics or global warming!

I was wondering why rotomolded plastic water tanks are so expensive.

The raw materials are generally regarded as cheap, the manufacturing
process seems on the surface to be simple. I guess transport /
distribution of a bulky product could be costly. Anyone got some ideas?
Also there are economies of scale involved. Not physical size but volume.

There are probably an uncountable number of guys here who could take make
you a machine nut by taking a piece of steel, drilling a hole in it,
taping it, and then cutting the outside so you could grip it with a
wrench. It would probably take me an hour to make one nut that way in my
shop. I charge $80 for my time (I do not make that much by a long shot).
There are a few more guys in this group who could take iron ore. melt it,
add some other stuff, and then produce your one nut in their shop.

Or, they could buy some production equipment for a few hundred thousand
dollars and make your one nut.

In any case the material is cheap. In the first case the labor is
expensive. IN the second the equipment is expensive, and for one nut the
setup, electric, fuel, and labor are expensive along with the several
hundred thousand for the production tooling in the factory. However, if
they make one nut or a million the tooling cost doesn't change. In fact
the tooling cost probably doesn't start to change much from tool
replacement and repair until they have made a few hundred thousand of
them.

So in the first case it costs $81 for one nut.

In the second it costs $500,000 to make one nut.

Now add in overhead, additional fuel, insurance, repairs, etc.

The first shop could make a 1,000,000 nuts for $81,000,000 dollars, and
they are still $81 each.

The factory could make 1,000,000 nuts for $750,000. Their nuts cost 75¢
each to produce.

Fortunately the demand for nuts is in the trillions in the world, and
factories all over the world are geared up to produce billions of them.
This production volume drives the production cost down. The consumer
demand keeps the volumes high enough to keep the factories operating at
their most efficient level, and competition between factories keeps the
profit margins charged reasonable.

I would bet real money the demand for nuts is in the trillions. What is
the demand for roto-molded tanks?

They might be able to make them for a few dollars each if they could gear
upto produce them continuously in the hundreds of millions.

Heck, have you ever seen a blow mold operate? Milk jugs go in as a slug
of plastic and come out as a plastic jug and go right into the bottling
part of a milk plant. They cost pennies a-piece. But they make hundreds
of millions of them. That plant to make them cost a million dollars to
setup.

Rotomolding costs lots of heat energy. Watched a kayak factory make them.
13' Kayak, 14' mold, 18' long oven. And the the mold was not cheap. And
then the equipment has to rock and rotate the mold in this high heat oven to
get the plastic to flow.