Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Materials for making a mold

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

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On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


There is a polymer-modified, machinable gypsum that is made for CNC
test-cutting, which has been used for molds. Compared to aluminum,
it's dirt cheap. And there is another one, which I haven't seen for 10
years and the name of which I forget, that is made for casting
highly-finished molds for fiberglass molding. Maybe someone else here
knows brand names.

I'm sorry I can remember the product names. One thing to watch for
with polymer-modified gypsum cements: they don't dry very well. The
trick to using them to make a polished mold is to wipe them with
acetone and then to spray them quickly with lacquer before water
migrates back to the surface. They can take months to dry completely
but you can use them the next day with the acetone trick.

With the kinds of work you do, you should have the Freeman catalog:

https://www.freemansupply.com/catalo...manCatalog.pdf

I love plaster because I'm a real cheapskate. g And I like
styrofoam. I have made models from ordinary pink styrofoam insulation
board, glued together with a thin coat of white glue; painted it with
three coats of house paint; and then sanded them, buttered them with
bondo (screeding it on is tricky), sanded it, coated it with one-part
polyurethane paint, waxed the hell out of it, shot it with PVA, and
then pulled a fiberglass part off of it.

If you're a little less cheap than me, use high-density polyurethane
foam. It takes less finishing and you don't need the housepaint.
Polyester won't dissolve it. You probably won't need the bondo,
either. Just spray on some external gel coat, which you probably know
well.

In fact, you probably know all of these processes well. So why are you
asking us? g

BTW, the machinable plaster is pretty shiny after it's machined. Did I
mention that it's cheap? Just like me...

--
Ed Huntress
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Default Materials for making a mold

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


That's almost twice what I'd expect the shop to pay for that piece.

If you're cutting a large cavity in one side of a piece of 6061 plate
it's not going to stay flat. Cast tooling plate (e.g. Alcoa MIC6) is
stable, but is relatively gummy, so will be more difficult to machine
and finish to a polish. Also more expensive.

--
Ned Simmons
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Default Materials for making a mold

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


Eh, I forgot about Rayite MDM:

www.chavant.com/new_site/files/pdf/rayite.pdf

I don't think you can machine it, but it makes really good molds, with
extremely high accuracy. It may not be for this project but it's
something to remember for inexpensive fiberlass molding.

--
Ed Huntress


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On Tue, 16 Jun 2015 21:41:25 -0400, Ed Huntress wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


There is a polymer-modified, machinable gypsum that is made for CNC
test-cutting, which has been used for molds. Compared to aluminum, it's
dirt cheap. And there is another one, which I haven't seen for 10 years
and the name of which I forget, that is made for casting highly-finished
molds for fiberglass molding. Maybe someone else here knows brand names.

I'm sorry I can remember the product names. One thing to watch for with
polymer-modified gypsum cements: they don't dry very well. The trick to
using them to make a polished mold is to wipe them with acetone and then
to spray them quickly with lacquer before water migrates back to the
surface. They can take months to dry completely but you can use them the
next day with the acetone trick.

With the kinds of work you do, you should have the Freeman catalog:

https://www.freemansupply.com/catalo...manCatalog.pdf

I love plaster because I'm a real cheapskate. g And I like styrofoam.
I have made models from ordinary pink styrofoam insulation board, glued
together with a thin coat of white glue; painted it with three coats of
house paint; and then sanded them, buttered them with bondo (screeding
it on is tricky), sanded it, coated it with one-part polyurethane paint,
waxed the hell out of it, shot it with PVA, and then pulled a fiberglass
part off of it.

If you're a little less cheap than me, use high-density polyurethane
foam. It takes less finishing and you don't need the housepaint.
Polyester won't dissolve it. You probably won't need the bondo, either.
Just spray on some external gel coat, which you probably know well.

In fact, you probably know all of these processes well. So why are you
asking us? g

BTW, the machinable plaster is pretty shiny after it's machined. Did I
mention that it's cheap? Just like me...


I know one process for making molds. It starts with a high-quality plug
(which is often an original Ford body part that's been modified for the
purpose) and makes a fiberglass mold around it.

I'm working on a project with my brother that starts with a 3D model and
ends up with a part. Rather than having him make a high-quality plug,
then a mold, I'm thinking that it would be nice to send a 3D model to a
machine shop and get back a hunk of aluminum or whatever, polish the snot
out of it, and make parts.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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Default Materials for making a mold

On Tue, 16 Jun 2015 21:46:30 -0400, Ned Simmons wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


That's almost twice what I'd expect the shop to pay for that piece.

If you're cutting a large cavity in one side of a piece of 6061 plate
it's not going to stay flat. Cast tooling plate (e.g. Alcoa MIC6) is
stable, but is relatively gummy, so will be more difficult to machine
and finish to a polish. Also more expensive.


I knew about the issue with 6061 -- that's part of the reason that I'm
asking questions here!

I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can do
it without bubbles you certainly have something that you can polish to a
high shine.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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"Tim Wescott" wrote in message
...
I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com



Depending on desired finish quality and tolerances you could machine a
fiberglass mold out of any of a number of things, coat it with something to
seal it and use a good mold release. I imagine you could make it out of
wood if it was stable enough (which in general it is not - although there
are tricks).

There are guys who mold hot plastisol (350F) in plaster of paris molds
sealed with Elmers glue, and I have seen guys mold molten lead for a few
pours before it burns out in Bondo.

Silicone mold material is used for plastisol and lead casting all the time,
although you do need a master to pour a silicone mold from. I am sure if it
was left in a rigid form box to prevent distortion it would work fine for
your fiberglass part. All kinds of things are done quick and dirty with
silicone molds, and you might not even need a mold release. (you probably
want one on your master)

If you are just vacuum bagging then any materials that will managed the
temperature of your catalyst reaction will do. If you are going to
autoclave your parts then it needs to stand the temps in your autoclave.

The price for the piece of aluminum sounds a little high, but then price has
usually stopped me from buy from Speedy Metals or On Line Metals in the
past. I have gotten better prices on large orders from on-line metals by
having them submit a quote, but for me freight is usually a killer. I found
a local metal vendor finally for the the aluminum I use to make molds.

The real questions a How many of these fiberglass boxes do you need to
make? Would a hand made mold do? (wood frame, plywood box, hand filleted
inside corners. Maybe glassed sanded and gelcoated?) Do you have a machine
shop in mind that can make a 48" mold in a reasonable amount of time? Will
they do it for a reasonable price? Will they do it in one setup or multiple
setups? If multiple setups how accurately can they align one setup with the
next? Does it matter?

Something to note: A piece of aluminum that big might hold your mold
cavity, but I've found if you have large areas of thin web from large
cavities or multiple cavities to close together the total work piece can
start to distort from clamping force. It can be tricky to hold the piece
and hold tolerance. I personally don't do anything over about 18-20 inches.
If the piece is longer than the table it can sag causing some distortion.

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"Tim Wescott" wrote in message
...
On Tue, 16 Jun 2015 21:46:30 -0400, Ned Simmons wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


That's almost twice what I'd expect the shop to pay for that piece.

If you're cutting a large cavity in one side of a piece of 6061 plate
it's not going to stay flat. Cast tooling plate (e.g. Alcoa MIC6) is
stable, but is relatively gummy, so will be more difficult to machine
and finish to a polish. Also more expensive.


I knew about the issue with 6061 -- that's part of the reason that I'm
asking questions here!

I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can do
it without bubbles you certainly have something that you can polish to a
high shine.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com



One trick for pouring resins with few bubbles is to pour a long thin stream
from a long distance above the forms. However I am not sure if epoxy would
work well for what you are doing. I've found epoxy pours thicker than about
1/2" tend to scorch from their own reaction heat. Even 1/2" is pushing it.
I've had the small amount left in a mixing cup scorch once or twice if it
was still fairly thick. I've read that you can get past the issue with
epoxy by making multiple pours, but I seem to recall that you either need to
have your timing just right, or you need to let it fully cure and then prep
the surface before making the next pour. Sounds like a long tedious
process. There are other casting resins that might work better for thick
pours, but I really don't have any first hand experience with them.





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"Bob La Londe" wrote in message
...
"Tim Wescott" wrote in message
...
I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com



Depending on desired finish quality and tolerances you could machine a
fiberglass mold out of any of a number of things, coat it with something
to seal it and use a good mold release. I imagine you could make it out
of wood if it was stable enough (which in general it is not - although
there are tricks).

There are guys who mold hot plastisol (350F) in plaster of paris molds
sealed with Elmers glue, and I have seen guys mold molten lead for a few
pours before it burns out in Bondo.

Silicone mold material is used for plastisol and lead casting all the
time, although you do need a master to pour a silicone mold from. I am
sure if it was left in a rigid form box to prevent distortion it would
work fine for your fiberglass part. All kinds of things are done quick
and dirty with silicone molds, and you might not even need a mold release.
(you probably want one on your master)

If you are just vacuum bagging then any materials that will managed the
temperature of your catalyst reaction will do. If you are going to
autoclave your parts then it needs to stand the temps in your autoclave.

The price for the piece of aluminum sounds a little high, but then price
has usually stopped me from buy from Speedy Metals or On Line Metals in
the past. I have gotten better prices on large orders from on-line metals
by having them submit a quote, but for me freight is usually a killer. I
found a local metal vendor finally for the the aluminum I use to make
molds.

The real questions a How many of these fiberglass boxes do you need to
make? Would a hand made mold do? (wood frame, plywood box, hand filleted
inside corners. Maybe glassed sanded and gelcoated?) Do you have a
machine shop in mind that can make a 48" mold in a reasonable amount of
time? Will they do it for a reasonable price? Will they do it in one
setup or multiple setups? If multiple setups how accurately can they
align one setup with the next? Does it matter?

Something to note: A piece of aluminum that big might hold your mold
cavity, but I've found if you have large areas of thin web from large
cavities or multiple cavities to close together the total work piece can
start to distort from clamping force. It can be tricky to hold the piece
and hold tolerance. I personally don't do anything over about 18-20
inches. If the piece is longer than the table it can sag causing some
distortion.


If you go an with aluminum mold clamping/bolting it to a heavy backing plate
can help it retain its correct shape.




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"Tim Wescott" wrote in message
...

On Tue, 16 Jun 2015 21:41:25 -0400, Ed Huntress wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


There is a polymer-modified, machinable gypsum that is made for CNC
test-cutting, which has been used for molds. Compared to aluminum, it's
dirt cheap. And there is another one, which I haven't seen for 10 years
and the name of which I forget, that is made for casting highly-finished
molds for fiberglass molding. Maybe someone else here knows brand names.

I'm sorry I can remember the product names. One thing to watch for with
polymer-modified gypsum cements: they don't dry very well. The trick to
using them to make a polished mold is to wipe them with acetone and then
to spray them quickly with lacquer before water migrates back to the
surface. They can take months to dry completely but you can use them the
next day with the acetone trick.

With the kinds of work you do, you should have the Freeman catalog:

https://www.freemansupply.com/catalo...manCatalog.pdf

I love plaster because I'm a real cheapskate. g And I like styrofoam.
I have made models from ordinary pink styrofoam insulation board, glued
together with a thin coat of white glue; painted it with three coats of
house paint; and then sanded them, buttered them with bondo (screeding
it on is tricky), sanded it, coated it with one-part polyurethane paint,
waxed the hell out of it, shot it with PVA, and then pulled a fiberglass
part off of it.

If you're a little less cheap than me, use high-density polyurethane
foam. It takes less finishing and you don't need the housepaint.
Polyester won't dissolve it. You probably won't need the bondo, either.
Just spray on some external gel coat, which you probably know well.

In fact, you probably know all of these processes well. So why are you
asking us? g

BTW, the machinable plaster is pretty shiny after it's machined. Did I
mention that it's cheap? Just like me...


I know one process for making molds. It starts with a high-quality plug
(which is often an original Ford body part that's been modified for the
purpose) and makes a fiberglass mold around it.

I'm working on a project with my brother that starts with a 3D model and
ends up with a part. Rather than having him make a high-quality plug,
then a mold, I'm thinking that it would be nice to send a 3D model to a
machine shop and get back a hunk of aluminum or whatever, polish the snot
out of it, and make parts.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
================================================== ===========================

I've never done it, but seems to me you could glue together sheets of the
thickest MDF you can buy to get up to say double the height of your piece,
find someone with a cnc router to cut the mold cavity, sand it, then paint
with epoxy resin. Now you have the same surface you would if you were
pulling a mold off of a body part, so sand and polish like you do those. If
12x48" is big enough, buy a 4x8' sheet and cut that into up to 8 strips to
glue together to get plenty of thickness so it won't warp. I think you said
that this is for the carrying case. If so, you could even put in a line or
divot pattern and logo with the router and not sand at all, to get a nice
surface texture that would hide future dings and scratches. Have to keep
the sealing coat very thin and uniform. Anyway, just a suggestion from up
here in the cheap seats :-).

-----
Regards,
Carl Ijames


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"Carl Ijames" wrote in message
...
"Tim Wescott" wrote in message
...

On Tue, 16 Jun 2015 21:41:25 -0400, Ed Huntress wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


There is a polymer-modified, machinable gypsum that is made for CNC
test-cutting, which has been used for molds. Compared to aluminum, it's
dirt cheap. And there is another one, which I haven't seen for 10 years
and the name of which I forget, that is made for casting highly-finished
molds for fiberglass molding. Maybe someone else here knows brand names.

I'm sorry I can remember the product names. One thing to watch for with
polymer-modified gypsum cements: they don't dry very well. The trick to
using them to make a polished mold is to wipe them with acetone and then
to spray them quickly with lacquer before water migrates back to the
surface. They can take months to dry completely but you can use them the
next day with the acetone trick.

With the kinds of work you do, you should have the Freeman catalog:

https://www.freemansupply.com/catalo...manCatalog.pdf

I love plaster because I'm a real cheapskate. g And I like styrofoam.
I have made models from ordinary pink styrofoam insulation board, glued
together with a thin coat of white glue; painted it with three coats of
house paint; and then sanded them, buttered them with bondo (screeding
it on is tricky), sanded it, coated it with one-part polyurethane paint,
waxed the hell out of it, shot it with PVA, and then pulled a fiberglass
part off of it.

If you're a little less cheap than me, use high-density polyurethane
foam. It takes less finishing and you don't need the housepaint.
Polyester won't dissolve it. You probably won't need the bondo, either.
Just spray on some external gel coat, which you probably know well.

In fact, you probably know all of these processes well. So why are you
asking us? g

BTW, the machinable plaster is pretty shiny after it's machined. Did I
mention that it's cheap? Just like me...


I know one process for making molds. It starts with a high-quality plug
(which is often an original Ford body part that's been modified for the
purpose) and makes a fiberglass mold around it.

I'm working on a project with my brother that starts with a 3D model and
ends up with a part. Rather than having him make a high-quality plug,
then a mold, I'm thinking that it would be nice to send a 3D model to a
machine shop and get back a hunk of aluminum or whatever, polish the snot
out of it, and make parts.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
================================================== ===========================

I've never done it, but seems to me you could glue together sheets of the
thickest MDF you can buy to get up to say double the height of your piece,
find someone with a cnc router to cut the mold cavity, sand it, then paint
with epoxy resin. Now you have the same surface you would if you were
pulling a mold off of a body part, so sand and polish like you do those.
If 12x48" is big enough, buy a 4x8' sheet and cut that into up to 8 strips
to glue together to get plenty of thickness so it won't warp. I think you
said that this is for the carrying case. If so, you could even put in a
line or divot pattern and logo with the router and not sand at all, to get
a nice surface texture that would hide future dings and scratches. Have
to keep the sealing coat very thin and uniform. Anyway, just a suggestion
from up here in the cheap seats :-).

-----
Regards,
Carl Ijames


I LIKED IT!

You an actually machine a pretty decent surface finish in MDF, although I
don't use it much except as glued backers for special projects.




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Default Materials for making a mold

Tim Wescott wrote:


I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can do
it without bubbles you certainly have something that you can polish to a
high shine.


You could pour your own. But I think it would be
cheaper to buy something ready made. The patternmaker
suppliers have a number of products designed for CNC
machiningto make patterns, plugs or molds.

https://www.freemansupply.com/RenShape5179Foundr.htm
http://www.alro.com/divplastics/plas...ct_lab850.aspx

https://www.toolchemical.com/showcat...lanks&SiteID=5



A pattern shop in your area would probably be
your best bet for the machining and help in
getting type of finish you need.

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On Wed, 17 Jun 2015 11:30:09 -0500, Tim Wescott
wrote:

On Tue, 16 Jun 2015 21:46:30 -0400, Ned Simmons wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?


That's almost twice what I'd expect the shop to pay for that piece.

If you're cutting a large cavity in one side of a piece of 6061 plate
it's not going to stay flat. Cast tooling plate (e.g. Alcoa MIC6) is
stable, but is relatively gummy, so will be more difficult to machine
and finish to a polish. Also more expensive.


I knew about the issue with 6061 -- that's part of the reason that I'm
asking questions here!

I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can do
it without bubbles you certainly have something that you can polish to a
high shine.


But why aluminum? Nearly all fiberglass boats, for example, are made
using a fiberglass mold. Nearly always a female mold.
--
cheers,

John B.

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On Thu, 18 Jun 2015 09:41:37 +0700, John B. wrote:

On Wed, 17 Jun 2015 11:30:09 -0500, Tim Wescott
wrote:

On Tue, 16 Jun 2015 21:46:30 -0400, Ned Simmons wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me
that I could just make a 3D model of a mold and send it to a machine
shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a
machine shop? Is there any material that's significantly cheaper,
that can be tossed into a CNC mill and made into something mold like,
and then hand-
polished to a high shine?

That's almost twice what I'd expect the shop to pay for that piece.

If you're cutting a large cavity in one side of a piece of 6061 plate
it's not going to stay flat. Cast tooling plate (e.g. Alcoa MIC6) is
stable, but is relatively gummy, so will be more difficult to machine
and finish to a polish. Also more expensive.


I knew about the issue with 6061 -- that's part of the reason that I'm
asking questions here!

I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can
do it without bubbles you certainly have something that you can polish
to a high shine.


But why aluminum? Nearly all fiberglass boats, for example, are made
using a fiberglass mold. Nearly always a female mold.


Because machined fiberglass takes a huge amount of hand work to polish
up. To date, I know of no 3D printing technology that'll lay down
polished gel-coat.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


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On Wed, 17 Jun 2015 13:15:02 -0500, jim wrote:

Tim Wescott wrote:


I wonder if one could just pour a couple of gallons of epoxy casting
resin into a box, then send that off to the machine shop -- if you can
do it without bubbles you certainly have something that you can polish
to a high shine.


You could pour your own. But I think it would be cheaper to buy
something ready made. The patternmaker suppliers have a number of
products designed for CNC machiningto make patterns, plugs or molds.

https://www.freemansupply.com/RenShape5179Foundr.htm
http://www.alro.com/divplastics/plas...ct_lab850.aspx

https://www.toolchemical.com/showcategory.aspx?

CategoryID=590&SEName=tcc-tooling-planks&SiteID=5



A pattern shop in your area would probably be your best bet for the
machining and help in getting type of finish you need.


The one quote that I got (from Freeman) was more than the cast aluminum
slab!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that I
could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

========================
After reading the replies to this post, I have some
questions:

(1) What is your projected volume?

(2) Why fiberglass? How about alternatives such as vacuum
formed thermoplastic?

(3) Did you get quotes from enclosure/case vendors? The
size/shape appears close to a gun case.


--
Unka' George

"Gold is the money of kings,
silver is the money of gentlemen,
barter is the money of peasants,
but debt is the money of slaves"

-Norm Franz, "Money and Wealth in the New Millenium"
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On Thu, 18 Jun 2015 12:56:52 -0500, F. George McDuffee wrote:

On Tue, 16 Jun 2015 19:25:47 -0500, Tim Wescott
wrote:

I'm working on a project that may well end up having a case made of
fiberglass. As I'm working on a 3D model that will use mostly to make
pretty PDFs for my fiberglass guy and my customer, It occurs to me that
I could just make a 3D model of a mold and send it to a machine shop.

A 1.25 x 12 x 48 inch piece of 6061 costs $430 from Online Metals. Is
that pretty much what I would expect to pay for materials from a machine
shop? Is there any material that's significantly cheaper, that can be
tossed into a CNC mill and made into something mold like, and then hand-
polished to a high shine?

========================
After reading the replies to this post, I have some questions:

(1) What is your projected volume?


A few dozen a year.

(2) Why fiberglass? How about alternatives such as vacuum formed
thermoplastic?


First, it's the devil I know, and I know it'll be strong enough (I want
the thing to easily survive a drop from table height onto concrete).
Second, I have a strong personal tie with the vendor.

Vacuum-formed thermoplastic is certainly a contender, but I think that by
the time I get all the other properties I want, given my anticipated
production volumes, that I wouldn't be happy.

(3) Did you get quotes from enclosure/case vendors? The size/shape
appears close to a gun case.


A hinged case isn't a good starting point, I don't think. I've been down
this sort of road before, and I just don't see finding a case that'll
meet my needs that isn't custom-made.

(Enclosures are a bitch. With the exception of PC builds I have yet to
do an electronics project where the cost of a nice-looking case didn't
exceed the cost of the stuff inside it.)

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
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On Thu, 18 Jun 2015 13:03:46 -0500, Tim Wescott
wrote:

(Enclosures are a bitch. With the exception of PC builds I have yet to
do an electronics project where the cost of a nice-looking case didn't
exceed the cost of the stuff inside it.)


+1. Isn't that just f'n CRAZY? And it's not just for electronics.
Carry cases in general are gawdawful overpriced, too.

--
Find out what people will submit to, and you have found out the
exact amount of injustice and wrong which will be imposed on them.
--Frederick Douglass
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