Looking for information on molding custom o-rings or gaskets.
DIY stuff would be great.
Looking to make small runs (100-250 pieces over time) of irregularly
shaped o-rings.
(can be square profile, too. I'm not locked in to round)

Thanks,

Weyland

On 15 Apr 2006 20:15:24 -0700, "Weyland"
wrote:

Looking for information on molding custom o-rings or gaskets.
DIY stuff would be great.
Looking to make small runs (100-250 pieces over time) of irregularly
shaped o-rings.
(can be square profile, too. I'm not locked in to round)

Thanks,

Weyland

What is special about them? Can't you design around off the shelf
ones?
-- Randy Replogle

My wife says I'm doing my Christian duty...
annoying the hell out of her.
Randall Replogle 2006

Randy,

No, I can't design around commonly available ones.
I've tried, but the profile I *need* to
have makes using stock ones problematic.
There's 8 outside curving bends, and 4 inside
curving bends that are necessary to move around
obstructions and stay within the sealing surface.
Plus, I've tried altering the path of the groove I insert
them into but can't get it to fit a stock size perfectly, either.
So... any leads on DIY rubber gasket/o-ring molding?

Best,

Weyland

In article . com,
says...
Randy,

No, I can't design around commonly available ones.
I've tried, but the profile I *need* to
have makes using stock ones problematic.
There's 8 outside curving bends, and 4 inside
curving bends that are necessary to move around
obstructions and stay within the sealing surface.
Plus, I've tried altering the path of the groove I insert
them into but can't get it to fit a stock size perfectly, either.
So... any leads on DIY rubber gasket/o-ring molding?


If you can use a standard round or square cross section and just need a
non-standard length, but o-ring cord stock and splice it with Loctite
404. See McMaster p.3217. Cord stock is on p.3282. Unfortunately, 404 is
expensive and has a relatively short shelf life, but it makes a
surprisingly strong joint that works fine for static seals.

http://www.mcmaster.com/

Ned Simmons

--You need to get into razor dies and "clickers"; watch your
fingers! :-)

--
"Steamboat Ed" Haas : I'll have the roast duck
Hacking the Trailing Edge! : with the mango salsa...
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Sun, 16 Apr 2006 12:23:26 -0400, Ned Simmons
wrote:

In article . com,
says...
Randy,

No, I can't design around commonly available ones.
I've tried, but the profile I *need* to
have makes using stock ones problematic.
There's 8 outside curving bends, and 4 inside
curving bends that are necessary to move around
obstructions and stay within the sealing surface.
Plus, I've tried altering the path of the groove I insert
them into but can't get it to fit a stock size perfectly, either.
So... any leads on DIY rubber gasket/o-ring molding?


If you can use a standard round or square cross section and just need a
non-standard length, but o-ring cord stock and splice it with Loctite
404. See McMaster p.3217. Cord stock is on p.3282. Unfortunately, 404 is
expensive and has a relatively short shelf life, but it makes a
surprisingly strong joint that works fine for static seals.

http://www.mcmaster.com/

Ned Simmons
Super glue also works for this. Though if exposed to water it may
fail. It sure doesn't when in an oily area.
ERS

Weyland wrote:
Looking for information on molding custom o-rings or gaskets.
DIY stuff would be great.
Looking to make small runs (100-250 pieces over time) of irregularly
shaped o-rings.
(can be square profile, too. I'm not locked in to round)

Thanks,

Weyland

if you know the length of your groove in linear dimensions based on the
inner dimension i can find you what you need , it may be a metric cross
section but there is something you can use .

dont forget when inserting an oring into a groove that will mate with
another flat plate it is usual for the oring to actually be about 5 % to
long and be inserted and held in place with a little silicone o-ring
jelly for assembly

Hi Ned,

This is exactly what I have been doing, but it's getting old,
fast, and ideally I'd like to be able to simply lay a gasket or
o-ring of matching profile into the groove I have machined for them.

Best,

Weyland

I thought about steel rule dies, but was thinking that
there'd be a lot of waste resulting from it, economically
negating any time savings I might actually gain.

This is approximately a 4" x 2.5" rectangular shape,
with both inside and outside radius bends at all four
corners for going around the four screws that are located there.

And the seal is only .063" and I can't go any larger.

Best,

Weyland

*THIS* is *exactly* what I have been contemplating.
I've been thinking to make two halves, pinned for
locating, and with some way of forcing (by way of
pressure) a medium into it to make the gasket/o-ring.

I'm just not knowledgeable about what material to use
and what's available that will fill my need while being
able to be used for making these things.

.... things like how do you cure them efficiently?

Are there sites that I can research this stuff on?

Thanks.

Best,

Weyland

There's something I might be able to use...
What's this "silicone o-ring jelly"?
I've been super-glueing them in place,
which is part of what's a hassle about it.

Best,

Weyland

Weyland wrote:
There's something I might be able to use...
What's this "silicone o-ring jelly"?
I've been super-glueing them in place,
which is part of what's a hassle about it.

Best,

Weyland

you can use grease or petroleum jelly , the oring should be a litlle
larger than the groov to allow for compression

there are form in place gaskets available , permatex and loctite make
them , just like running a bead of caulk , wont hold a ot of pressure
though

do you know your linear dimension [ how long the seal would be streched
out straight?

"c.henry" wrote in message
...
you can use grease or petroleum jelly , the oring should be a litlle
larger than the groov to allow for compression


Shouldn't the *groove* be a little larger than the O-ring?

Mike


--
NewsGuy.Com 30Gb $9.95 Carry Forward and On Demand Bandwidth

c.henry wrote:

there are form in place gaskets available , permatex and loctite make
them , just like running a bead of caulk ,

Ahh, okay.
That won't work for me in this instance.
I need to be able to lay the gasket/o-ring in the part.
The part gets shipped out for installation by the end user.

wont hold a ot of pressure
though

Pressure's not the enemy here. Moisture intrusion is.

do you know your linear dimension [ how long the seal would be streched
out straight?

Yes. 13.39128"
I could *theoretically* tweak this a bit more to get to 13.375, but it
all *SEEMS* (to my admitted ignorance) to come down to a "046" o-ring.
.... which in actual execution just doesn't seem to fit quite right...

Part of the problem, I believe, is the contours (the inside and
outside bends) at the corners making it want to not "stay" put.
I finally got an example of it for you guys, here -
http://solutionsmachining.com/images/oring_path.jpg

I'd very much like to just have these molded for me,
but like most others here, simply cannot afford it, which
is why I thought to venture into the DIY arena of molding for these.

Thanks,

Weyland

I'd very much like to just have these molded for me,
but like most others here, simply cannot afford it, which
is why I thought to venture into the DIY arena of molding for these.



How about water jet? You could find the material you want in a sheet and
have them water cut to the shape you want.

I agree that waterjet would probably be a good way to go. You can do
just about any shape from just about any material. (Or even cut
different materials glued together, etc.)

If you need to find a job shop to do work for you, visit:

http://www.waterjets.org/waterjet_jobshops.html

or

http://www.omax.com/jobshop.php

- Carl
http://www.waterjets.org


Dave Lyon wrote:
I'd very much like to just have these molded for me,
but like most others here, simply cannot afford it, which
is why I thought to venture into the DIY arena of molding for these.



How about water jet? You could find the material you want in a sheet and
have them water cut to the shape you want.

Just supply a small tube of form-a-gasket type stuff with the part and
be done with it. Ford uses some sort of stuff like that on their later
differential covers, no gaskets at all, just a groove for the goo.
Seems to work, I've had mine off a couple of times and other than the
hassle of peeling the old stuff out of the groove, it works just fine.
You just need to find a sealant that works in the conditions you've
got. Silicone won't work if there's gasoline around, for instance.

Stan

On Sun, 16 Apr 2006 22:10:08 -0500, "Mike Henry"
wrote:


"c.henry" wrote in message
.. .
you can use grease or petroleum jelly , the oring should be a litlle
larger than the groov to allow for compression


Shouldn't the *groove* be a little larger than the O-ring?

Mike

Yep, maybe he meant a little "higher". About 30%.



-- Randy Replogle



I've found that relationships are like a bell curve.
You love a few, hate a few, but most you're just indifferent to.
-- Randall Replogle 2006

In article .com,
says...
c.henry wrote:

there are form in place gaskets available , permatex and loctite make
them , just like running a bead of caulk ,

Ahh, okay.
That won't work for me in this instance.
I need to be able to lay the gasket/o-ring in the part.
The part gets shipped out for installation by the end user.

wont hold a ot of pressure
though

Pressure's not the enemy here. Moisture intrusion is.

do you know your linear dimension [ how long the seal would be streched
out straight?

Yes. 13.39128"
I could *theoretically* tweak this a bit more to get to 13.375, but it
all *SEEMS* (to my admitted ignorance) to come down to a "046" o-ring.
... which in actual execution just doesn't seem to fit quite right...

Part of the problem, I believe, is the contours (the inside and
outside bends) at the corners making it want to not "stay" put.
I finally got an example of it for you guys, here -
http://solutionsmachining.com/images/oring_path.jpg

I'd very much like to just have these molded for me,
but like most others here, simply cannot afford it, which
is why I thought to venture into the DIY arena of molding for these.


The foam-in-place gaskets don't need to be assembled wet, if that's your
concern. For example, most of the manufacturers of NEMA electrical
enclosures have switched to this stuff for door gaskets instead of
gluing on foam weather stripping. At the other end of the size spectrum,
the last couple hard disks I opened up were sealed with a foam-in-place
gasket that was apparently assembled after it had set.

The problem, at low volumes where dedicated equipment can't be
justified, is applying the goo in a controlled fashion. Perhaps a CNC
mill could be adapted to do this.

The nicest molded gaskets of this sort I've run across seal between the
sections in some stackable pneumatic valves - both MAC and SMC use them.
I've got an SMC gasket here that's about 5/16" x 1-3/16" and has 7
passages. I expect you're right about tooling costs and minimums being
prohibitive, but here's one place to check in case you haven't done
so...
http://www.applerubber.com/products/custom.cfm

Ned Simmons

--Ah. Well howzabout "casting" them in an open-top mold, using one
of the curable rubber compounds?

--
"Steamboat Ed" Haas : I'll have the roast duck
Hacking the Trailing Edge! : with the mango salsa...
www.nmpproducts.com
---Decks a-wash in a sea of words---

*THIS* is *exactly* what I have been contemplating.
I've been thinking to make two halves, pinned for
locating, and with some way of forcing (by way of
pressure) a medium into it to make the gasket/o-ring.

I'm just not knowledgeable about what material to use
and what's available that will fill my need while being
able to be used for making these things.

... things like how do you cure them efficiently?

Are there sites that I can research this stuff on?

First, I highly recommend the "bible" of oring seal design, the Parker
handbook, for oring groove design to match your oring size. Online at
http://www.parker.com/o-ring/Literature/00-5700.pdf (Biggest mistake
people make is to not make the groove a good bit wider than the oring so
the material has some place to flow into when you crush it.) You could
try injection molding using a caulking gun tube of RTV silicone - cheap
to try, available at any hardware or building supply store, but it's
going to be slow to cure even if you heat the mold up some. Might also
get bubbles if you can't get the pressure high enough. Next choice in a
castable might be polyurethane. My favorite vendor is www.smoothon.com
but this comes up pretty often here and others recommend a couple of
other vendors. Smoothon has some good online casting instructions,
including pressurizing the mold with air at 100 psi to squash any
bubbles while the stuff cures. They also have castable silicones but
not in caulking gun tubes. You could also think about a version of
Gingery's plastic injection molding machine, where you heat the mold but
not the injector (for silicones and polyurethanes), to get more
injection pressure. His book also covers moldmaking, which would
directly apply to your quest. If you want a round oring you will need
to ball mill the two halves of the oring into two facing plates that get
bolted or clamped together. If a square or rectangular cross section is
okay you could put the entire groove in one side and just use a flat
plate for the cover - half the machining. You will have to experiment a
little to find out how much shrinkage you will get (your orings will be
a little smaller than your groove dimensions). Like someone else
suggested, use a larger channel (sprue) to go from the tip on your
caulking gun to the oring mold groove, and on the other side have a
small vent path. Squeeze until it runs out, hope it filled both sides,
and bake it at something like 200 F for a few hours (?) to quick cure
it. Oh, smoothon sells a silicone spray mold release to use with the
polyurethanes, and I think you can wipe on a thin film of vaseline as a
mold release for the silicones.

--
Regards,
Carl Ijames carl.ijames at verizon.net

Mike Henry wrote:
"c.henry" wrote in message
...
you can use grease or petroleum jelly , the oring should be a litlle
larger than the groov to allow for compression


Shouldn't the *groove* be a little larger than the O-ring?

Mike


goove should be wider at .177-.186 for a standard 1/8 inch oring

the depth [ crush direction ] should be shallower or about .100-.110 for
a 1/8 inch oring

looser groove for a dynamic application , tighter for static

Carl Ijames wrote:
*THIS* is *exactly* what I have been contemplating.
I've been thinking to make two halves, pinned for
locating, and with some way of forcing (by way of
pressure) a medium into it to make the gasket/o-ring.

I'm just not knowledgeable about what material to use
and what's available that will fill my need while being
able to be used for making these things.

... things like how do you cure them efficiently?

Are there sites that I can research this stuff on?

First, I highly recommend the "bible" of oring seal design, the Parker
handbook, for oring groove design to match your oring size. Online at
http://www.parker.com/o-ring/Literature/00-5700.pdf (Biggest mistake
people make is to not make the groove a good bit wider than the oring so
the material has some place to flow into when you crush it.) You could
try injection molding using a caulking gun tube of RTV silicone - cheap
to try, available at any hardware or building supply store, but it's
going to be slow to cure even if you heat the mold up some. Might also
get bubbles if you can't get the pressure high enough. Next choice in a
castable might be polyurethane. My favorite vendor is www.smoothon.com
but this comes up pretty often here and others recommend a couple of
other vendors. Smoothon has some good online casting instructions,
including pressurizing the mold with air at 100 psi to squash any
bubbles while the stuff cures. They also have castable silicones but
not in caulking gun tubes. You could also think about a version of
Gingery's plastic injection molding machine, where you heat the mold but
not the injector (for silicones and polyurethanes), to get more
injection pressure. His book also covers moldmaking, which would
directly apply to your quest. If you want a round oring you will need
to ball mill the two halves of the oring into two facing plates that get
bolted or clamped together. If a square or rectangular cross section is
okay you could put the entire groove in one side and just use a flat
plate for the cover - half the machining. You will have to experiment a
little to find out how much shrinkage you will get (your orings will be
a little smaller than your groove dimensions). Like someone else
suggested, use a larger channel (sprue) to go from the tip on your
caulking gun to the oring mold groove, and on the other side have a
small vent path. Squeeze until it runs out, hope it filled both sides,
and bake it at something like 200 F for a few hours (?) to quick cure
it. Oh, smoothon sells a silicone spray mold release to use with the
polyurethanes, and I think you can wipe on a thin film of vaseline as a
mold release for the silicones.

--
Regards,
Carl Ijames carl.ijames at verizon.net


good ideas here ,

i would call loc-tite help line , i think their form in place stuff
would be right up your alley , esspecially if you need a limited number


also you can try these guys , they have done a couple of tough ones for me.

Weyland wrote:
c.henry wrote:

there are form in place gaskets available , permatex and loctite make
them , just like running a bead of caulk ,

Ahh, okay.
That won't work for me in this instance.
I need to be able to lay the gasket/o-ring in the part.
The part gets shipped out for installation by the end user.

wont hold a ot of pressure
though

Pressure's not the enemy here. Moisture intrusion is.

do you know your linear dimension [ how long the seal would be streched
out straight?

Yes. 13.39128"
I could *theoretically* tweak this a bit more to get to 13.375, but it
all *SEEMS* (to my admitted ignorance) to come down to a "046" o-ring.
... which in actual execution just doesn't seem to fit quite right...

Part of the problem, I believe, is the contours (the inside and
outside bends) at the corners making it want to not "stay" put.
I finally got an example of it for you guys, here -
http://solutionsmachining.com/images/oring_path.jpg

I'd very much like to just have these molded for me,
but like most others here, simply cannot afford it, which
is why I thought to venture into the DIY arena of molding for these.

Thanks,

Weyland

where are you having the worst trouble , the reverse radius on the left
end of the jpg?

can you use a larger o-ring?


i have seen some trapezoidal grooves cut where a cutter similar to a
dovetail is inserted and used to make the groove , this traps the o-ring
in place , i believe there is an iso or din standard for it , i will
look , but the down side is somewhere along the path there is a hole
from plunging the cutter in , it might be possible to use a small enough
cutter to avoid the entrance hole and profile both sides of the groove

Sounds great. Where can I find more info on that, please?

Thank you.

Best,

Weyland

Carl Ijames wrote:

First, I highly recommend the "bible" of oring seal design, the Parker
handbook, for oring groove design to match your oring size. Online at
http://www.parker.com/o-ring/Literature/00-5700.pdf

Excellent. Thank you.
(upon trying to get it, it timed out - I'll try again later)

Next choice in a
castable might be polyurethane. My favorite vendor is www.smoothon.com
but this comes up pretty often here and others recommend a couple of
other vendors. Smoothon has some good online casting instructions,
including pressurizing the mold with air at 100 psi to squash any
bubbles while the stuff cures. They also have castable silicones but
not in caulking gun tubes.

I'll check into them, thank you.

You could also think about a version of
Gingery's plastic injection molding machine, where you heat the mold but
not the injector (for silicones and polyurethanes), to get more
injection pressure. His book also covers moldmaking, which would
directly apply to your quest.

Great. Thanks. I'll order it up right away.

If you want a round oring you will need
to ball mill the two halves of the oring into two facing plates that get
bolted or clamped together. If a square or rectangular cross section is
okay you could put the entire groove in one side and just use a flat
plate for the cover - half the machining.

I'm not married to the o-ring profile, and for some odd
reason find myself actually liking the square profile better.
That, combined with your reasoning
above, makes that seem the choice to pursue...
I like the economy of effort presented by that flat plate.

You will have to experiment a
little to find out how much shrinkage you will get (your orings will be
a little smaller than your groove dimensions). Like someone else
suggested, use a larger channel (sprue) to go from the tip on your
caulking gun to the oring mold groove, and on the other side have a
small vent path. Squeeze until it runs out, hope it filled both sides,
and bake it at something like 200 F for a few hours (?) to quick cure
it. Oh, smoothon sells a silicone spray mold release to use with the
polyurethanes, and I think you can wipe on a thin film of vaseline as a
mold release for the silicones.

I really like this idea...
I could make a mold of say... 10 pieces that would easily
fit in a household oven (read -shop oven) using the above flat plate
mold, and rig up some way of pressure injecting the material into it.

Nice. Thanks.

Best,

Weyland

c.henry wrote:

also you can try these guys , they have done a couple of tough ones for me.

Errr... who?

Thanks,

Weyland

--Check out TAP Plastics if there's a store in your area; they've
got a variety of stuff. Another source would be Devcon; they've got a
zillion varieties of compounds, not just the metal-filled ones. Pick the
Durometer you want and go shopping.

--
"Steamboat Ed" Haas : I'll have the roast duck
Hacking the Trailing Edge! : with the mango salsa...
www.nmpproducts.com
---Decks a-wash in a sea of words---

steamer wrote:
--Check out TAP Plastics if there's a store in your area; they've
got a variety of stuff. Another source would be Devcon; they've got a
zillion varieties of compounds, not just the metal-filled ones. Pick the
Durometer you want and go shopping.

Thanks. No, no TAP stores down here. (Fort Lauderdale)
I did happen to ask about Devcon (Loctite now)
while in my bearing supply house today.
Seems I was missing what the guys were describing
when they were referring to the spray on type materials.
They (Loctite/Devcon) did show some pictures of them in caulking
gun type dispensers, so I'm somewhat more hopeful at this point.
I'll call them tomorrow for more info.

Best,

Weyland