How would i make a custom urethane lip?

[fatalexception]

Does anyone know how to go about making a custom lip outta Urethane?

Im workin a custom lip made from fiberglass at the moment, but im afraid that shortly after i finish it its gonna get broken over the first driveway i enter... Urethane should flex like the stock bumpers, theoretically.

i can find information on how to make a mold FROM urethane, but not how to make a urethane part from a mold, or how to make the mold that would be appropriate for that task.

Anyone got any suggestions?

[c1celi]

Good luck hope you get some advise because I would definitely want to know as well. Ima subscribe...
Dont mean to jack thread but how would you make a mold and custom shape it. For example, mold stock bumper and change a few angles, creases and/or open/widen holes?

[fatalexception]

for the mold making, what ive figured out, is that you wanna somehow make a physical prototype of what youd like to cast in urethane. For me, I got a stock lower lip from another celica, and sculpted the additions outta foam insulation board. I plan on using generous amounts of a bondo/putty/spackle like substance to smooth everything out.

From there, I can create the a mold, using any hard mold making substance I can find... such as plaster, fiberglass, or even a soft urethane material.

From what ive experienced and read, you really wanna have a prototype to make your mold from, rather than modifying the mold of a standard part. Its much easier to see what your doing that way... (its kinda hard modifying a negative image of the part)

[bman365]

Make the part..get it as perfect as you can. Make the mold and pour polyurethane casting resin in it.

Once yall get into spending money on the mold and casting the part...you wouldn't want to do it. Make it in fiberglass, keep the mold and make more if one breaks.

[horty222]

From what ive been to molds are pretty expensive ordeal. To make molds for the lawnmowers where i work the can cost as little as 8k up to 50k. Thats proffesional sruff though.

[2KGTrd]

at school, we got a slab of wax, carved it and then covered it in clay. Let it harden and then melted the wax to have a perfect mold.

I'm sure something else could be used other than clay.

[blitzceli]

Here is the correct way for urethane.

Make the part, bring it to a CNC shop. Have them write software for a negative. Have it milled out of aluminum. Once you have a negative now take a positive of the back side. Once you place the molds together you will have a empty mold. You then tap each end. You need some sort of pump and something to heat the urethane. Pump the urethane into the mold, once you see it come out of the bottom, plug it. This means no air is in the mold and filled with urethane. Remove the hose from the top and let cool. Once dry open the mold and trim the "flange line."
The mold will cost around 2-3K for the software and material. The pump, urethane and heating system will cost anywhere from 1-3K. It is going to cost roughly 6K for you to make this part correctly.

Make a fiberglass mold and make them out of fiberglass. When/if you break it, make a new one. The mold out of fiberglass will cost about 150 bux. That is the most cost efficient way to make your part.

[c1celi]

Ok, if you make a mold and want to add creases or make the holes bigger how would you change the design if the mold is made? For ex. if you make a mold of the stock bumper lip but want too add more of a design like small holes inside the lip or make the lip bulk out, how would you do that? Im sorry, I'm if I'm complicating this.

[blitzceli]

Ok, if you make a mold and want to add creases or make the holes bigger how would you change the design if the mold is made? For ex. if you make a mold of the stock bumper lip but want too add more of a design like small holes inside the lip or make the lip bulk out, how would you do that? Im sorry, I'm if I'm complicating this.

You dont modifiy a mold. You MUST have the part how you want it before you take the mold. If you dont you will waste alot of money on mold materials.

[blitzceli]

Here is a quick example of a fiberglass mold I made to make carbonfiber door inserts for a mr2.

http://i5.photobucket.com/albums/y157/flatline16/fg/Bj0w0gBWkKGrHqMH-CEEsZjgm8KjBLTStfL.jpg

http://i5.photobucket.com/albums/y157/flatline16/fg/001.jpg

http://i5.photobucket.com/albums/y157/flatline16/015-2.jpg

http://i5.photobucket.com/albums/y157/flatline16/001-16.jpg

http://i5.photobucket.com/albums/y157/flatline16/100_1692.jpg

[bman365]

Here is the correct way for urethane.

Make the part, bring it to a CNC shop. Have them write software for a negative. Have it milled out of aluminum. Once you have a negative now take a positive of the back side. Once you place the molds together you will have a empty mold. You then tap each end. You need some sort of pump and something to heat the urethane. Pump the urethane into the mold, once you see it come out of the bottom, plug it. This means no air is in the mold and filled with urethane. Remove the hose from the top and let cool. Once dry open the mold and trim the "flange line."
The mold will cost around 2-3K for the software and material. The pump, urethane and heating system will cost anywhere from 1-3K. It is going to cost roughly 6K for you to make this part correctly.

Make a fiberglass mold and make them out of fiberglass. When/if you break it, make a new one. The mold out of fiberglass will cost about 150 bux. That is the most cost efficient way to make your part.

Couldn't you make a mold from fiberglass for the urethane? I know they'll be problems with warping maybe, but I guess that depends on how much support you add to the mold.

[blitzceli]

Couldn't you make a mold from fiberglass for the urethane? I know they'll be problems with warping maybe, but I guess that depends on how much support you add to the mold.
You could but the injection urethane is different from plain casting urethane.

[fatalexception]

So basically, if i wanna make a urethane part, its gonna cost a truck load of cash. Thanks for the info, [/END IDEA]

Now with that said, once I finish the prototype, I just cover that with the fiberglass, pop it off, and use that part as a mold for the finish product? What kinda release agent should I look at?