Suggestions for a smoother surface for my plug

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#1

Just wondering what ideas people have for getting a plug surface nice and smooth before going on to make the mold from it?

For example I have a part that has a textured surface ( as many bike parts do to give them a “flat” not gloss appearance), what I did, and it took way too long and too much effort was to spray the thing with many layers of a water based polyurethane and eventually it lost most of its texturing. The problem was that with overspray I frequently ended up retexturing it (also I was spraying with a air brush…). The thing is that I needed to keep the plug in new shape so that I could return it to my friend that lend it to me to play with…

would bondo or some other filler and then sanding back work?

#2

If you are wanting to make a mould that is going to be used to make parts with a textured surface, then why not use an original part as a plug, rather than make one?

#3

the original is textured, and I want to make parts that are untextured. what I need are suggestions on what to do to get rid of the texturing before I make a mold.

#4

Spray it with polyester surfacing primer. Sand it up to 1500. Polish with Aquabuff 2000. It will come out looking like a mirror.

#5

exactly…

#6

thanks guys, what is the polyester surfacing primer like exactly? gel coat?

I don’t have gelcoat spray stuff…

what would be suitable for spraying this primer?

#7

Duratec primer. It’s polyester primer that you catalyze with MEKP.

http://www.fibreglast.com/learning_center_brochures/gray_surfacing_primer.pdf

Fibreglast.com sells it and so does US.Composites. The later having the better price. About $70 a gallon or so. It fills very good from what i hear and can be sanded or it can be buffed to a high gloss shine. Take a look at TET’s mailbox plug. I believe that is Duratec primer he used. I was doing some research last night on that product.

I think it will be permanent and ruin the original finish of your loaner part.

#8

what are guys using to buff? eliptical buffer…polishing pads, felt disks or fluffy fabric disks? Also what kinda time do you buff for after 1500 sand?

#9

For small corners I use Astro pnuematics 3" 2500 rpm buffer with a wool pad. I like to keep the speed low and do several passes. Its easy to burn the paint with this little dude.

For the larger areas I use an 8" electric sander/polisher (variable speed). No more than 3000rpm. Use a wool bonnet. Absolutely beautiful results this way vs. using a small polisher.

With Aquabuff your part will shine in 1 pass. To get it perfect it may take 2 to 3 applications in a given 2 foot area. So basically buff until your happy.

With polyester primer wait 2 hours after you apply it before you start to sand. Then sand it up to 800 and let it off gas for 8 hours. The next day continue your sanding up to 1500 grit. At this point the paint will be hard and ready for polishing.

I made this mould using the exact method above. Used 1/4" plywood as the plug.

#10

You can save yourself some spray build materials if you first sand the texture itself down before the Duratec primer.
Depending upon the depth of the texture to begin with…more or less pre-sanding will be needed.
Long block sand flat areas and use small hand forms for sanding if you want to “perfect” the parent part as a plug.Repeat ( but with finer grits)after the primering and then polish.
Vinny

#11

Polyester primer first (which can be thinned to reduce orange peel, and amount of sanding needed), then a couple of coats of 2k colour, which is pretty easy to bring to a mirror finish. You do need to make sure 2k material is fully hardened before laying up on it though.

#12

All the replies have been absolutely right. However, I think that
20RC may have very limited resources in equipment etc. and it may not be worth buying a gallon of Duratec or similar for this project. Bondo applied carefully would get rid of the textured finish and if carefully sanded could be polished and a mould taken. Bondo polishes up to a shine very nicely and would make a very respectible mould. Not class “A” finish, but good. I think there is a project from Baznos which describes similar moulds taken from textured parts, but in his case he didn’t want to ruin the origionals.

#13

This Poly fill primer is also available at body shop supplies places too. Spray primer can work but it takes time and effort anyway you look at it.

That’s one reason quality molds costs so much: Time and Experience

#14

If you dont have access to proper equipment needed to apply products like polyester spray primer/surfacer, and want to achieve a good surface finish, with the minimum of sanding, then something like a high viscosity glazing putty is the thing to use.

I would think its quite possible to apply this with a brush and get reasonable results, its easy to sand, and is ideal if you dont have spray equipment, or only want to surface a smallish mould or plug.

http://www.u-pol.com/countries/us/navigate.htm

Have a look at the above URL, under body fillers.

#15

again guys lots of good info, giving me lots of ideas and possibilities.

#16

Find a local auto paint supply store and get some high build poly primer as many have suggested.

I can’t stand the wrinkle texture on car interiors…so I sanded a dash cap, sprayed with primer, sanded some more, and painted it gloss black.

#17

Some brand name polyester primers include Slick Sand and Feather Fill. Look for those if you can’t find the Duratec brand.