I was told by the local powder coater that they would not do MDF because it warps under the heat. They had me do a test of the material I was using and sure enough at the temps that they use it warped. So how did you get past that problem?
well, in such *DIY* case, just ask a car painter to handle it
they can make it shine like a Steinway
in any case, I think plywood is much worse to paint
like I said, a matter of continious painting and sanding, filler, sanding, filler, paint, sanding ... endlessly
just a matter of keeping it going until the result is ok
every project teaches you something 😀
they can make it shine like a Steinway
in any case, I think plywood is much worse to paint
like I said, a matter of continious painting and sanding, filler, sanding, filler, paint, sanding ... endlessly
just a matter of keeping it going until the result is ok
every project teaches you something 😀
A car painter could as long as he sealed up well first. An automotive primer sealer may work?? Then your base primer and finally some colour. Epoxy resin does a good job of sealing MDF. After a light scuffing its accepts base primer well.
I've had a lot of metal parts powder coated, coating MDF seems so foreign to me I had no idea that could be done.
I've had a lot of metal parts powder coated, coating MDF seems so foreign to me I had no idea that could be done.
I had no luck with auto guys. They didn't want the trouble and they were swamped with higher paid auto work.
Epoxy resins bond one layer to the next, so feather edges are an issue. Polyester resin melts in and becomes monolithic so feather edges are not a problem.
I have cured resin at 170 degrees many times with no warping. Power coat I think is more like 250 to 450 F , so who knows what would happen. That is in the "cooking" temps remembering MDF is basically paper.
Thinking of tough finishes, I forgot about good old Por-15. That may make a really good base coat.
As I said, I was told that it couldn't be done, not without some warping, which for some parts may not be a problem - like a flat piece with no stress in it. But for a manufactured enclosure the stresses from the construction will warp it at the temps required to flow the powders binder. Remember that MDF is just a sawdust in a binder and its binder will go plastic at the same temps that the power does.
I just want to thank everyone for all of the great advice on this thread!
Sooooo…..I guess the painting part of this is going to take a while. Since I really don't want to wait "a while" to start enjoying these, I went ahead and wired up two of them and am listening to them right now. I figure I can paint the center channel and two rear channels while I listen to these two and then I can rotate the others in as I finish them and rotate these two out to paint. For now I have primer on them which at least gives me some peace of mind that someone absentmindedly placing a glass on them won't leave a big fluffed up section of mdf from the condensation.
I still need to get some big chunks of felt to put above and below the tweeter, but even without it they sound better than anything that I have ever listened to out of a department store box. I may be biased though 😛
IMAG0303 by jg1996business, on Flickr
IMAG0307-1 by jg1996business, on Flickr
Sooooo…..I guess the painting part of this is going to take a while. Since I really don't want to wait "a while" to start enjoying these, I went ahead and wired up two of them and am listening to them right now. I figure I can paint the center channel and two rear channels while I listen to these two and then I can rotate the others in as I finish them and rotate these two out to paint. For now I have primer on them which at least gives me some peace of mind that someone absentmindedly placing a glass on them won't leave a big fluffed up section of mdf from the condensation.
I still need to get some big chunks of felt to put above and below the tweeter, but even without it they sound better than anything that I have ever listened to out of a department store box. I may be biased though 😛
IMAG0303 by jg1996business, on Flickr
IMAG0307-1 by jg1996business, on Flickr
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You only use enough heat to gel the polymer in the first step --when it is in this "glass" state you hit it with UV and the matrix or lattice forms almost instantly.
You're probably speaking with someone who does thermal curing.
This is as fundamental a change in process chemistry as when ARCO started to directly attach a hydroxyl to ethylene.
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I refinished wooden for many years and what you need is an epoxy "fairing compound" followed by a "high-build" epoxy primer. WEST systems make their own fillers to add to their resin to make the putty. It's like car body filler but you have a longer working time and it sticks better to wood. If you want a Piano finish you can build with MDO which is a high grade plywood with a very thin paper bonded to it. It cuts down on a lot of priming and filling. AwlGrip makes a high build primer that can be applied with a roller. Your going to have to do the sanding by hand with a longboard to get the look your after. 3M makes good sanding blocks and 3" wide paper with the adhesive already applied.
I've been experimenting for a few years on different methods on painting MDF and hiding the seams. Here is a thread I did a few months ago that seems to work quite well if you are looking to do an automotive finish.
Continuum Speakers Using my Trench Method on the MDF Seams
I've found the less moisture you introduce to the MDF the better. Applying body putty directly to the routed edges in a thin coat will seal them right up so one to two coats of primer while work well.
Dave
Continuum Speakers Using my Trench Method on the MDF Seams
I've found the less moisture you introduce to the MDF the better. Applying body putty directly to the routed edges in a thin coat will seal them right up so one to two coats of primer while work well.
Dave
Has anyone checked out shinobiwans thread "how to for high gloss finishing "over in the construction tips forum ? A lot of good info there.
Wow! The finish on those orange speakers you built is absolutely fantastic! I'm curious about the seam problem. Does the finish actually crack along the seam, or does the seam just start to show through as a slight linear dimple in the finish along the seam?
I have used a sanding sealer for wood.
http://generalfinishes.com/sites/default/files/Tech-Data-Enduro-Sanding-Sealer-020210.pdf
General finishes will also help you if you have questions during the application stages. Their product is a little more expenisve but worth every dime.
Note most of the auto finishes are designed around covering metal not wood.
Noted earlier that wood "moves" over time way more than metal does.
http://generalfinishes.com/sites/default/files/Tech-Data-Enduro-Sanding-Sealer-020210.pdf
General finishes will also help you if you have questions during the application stages. Their product is a little more expenisve but worth every dime.
Note most of the auto finishes are designed around covering metal not wood.
Noted earlier that wood "moves" over time way more than metal does.
There has been some pretty heated discussions on the topic. I've had people tell me they have no problems with seam telegraphing through the finish and all they do is prime and paint. Maybe it has to do with your geographic location. I think it has more to do with how close you look. I'm in an area that heats in the winter and cools in the summer so the humidity swing is about 80% to 35% and that's enough to cause problems.
Anyway what I have found is that MDF expands mostly in thickness. It is compressed tightly when manufactured. When moisture is introduced is expands then when it drys out it shrinks back. It's enough to either cause ghosting in the seam or even crack the finish. If enough moisture is added it will break down the glue causing it to become less stable. Then there is more movement to deal with I've experimented only with what is available at the box stores.
Best thing to do is avoid the seems where possible or run a groove bit down the seam to enhance it. Some have had luck using a 45 degree miter. I've found with high gloss automotive finish it will still show but much less noticeable. On the stands of the project I posted the link to I used 45 degree miters, then used a round over bit, then put a thin layer of body putty over them. The body putty sealed the roughness, from routing out the end grain, and with using one coat of primer the pits where filled in. If you read the post you will also see that after sanding the MDF surface with 120 grit sandpaper the primer soaked in a lot and after two coats still showed pits after sanding. I skimmed the flat sides with glazing compound and one coat over that was ready for paint.
My point is that I find its best to seal all the MDF with a product like body putty, that will not introduce moisture to the wood, then prime and you are 3 steps ahead.
As far as the seams go the trench method allows the body putty to float over the joint keeping it from telegraphing through the finish. It's also important to skim the whole cabinet because the transition from MDF to body putty will show a wave over time on a high gloss finish. You do have to catch it in the light to see it though.
Hope that helps
Dave
That helps a lot! I'm curious if anyone has ever tried taping the seams, similar to the way that drywall installers will tape the seams of drywall. Basically run a thin coat of body filler, press in a strip of paper tape, and then run another layer of body filler on top of everything.
I feel like I have already used up my chance to use sanding sealer. I already have 3 coats of primer on the mdf. I'm thinking very seriously about seeing if the auto body shop down the street will paint them. I'm just not sure that I want to risk all of my hard work building these things on a second rate paint job done by my inexperienced hands.
I like to know IF they will do it - none that I talked to would - and if so then what did they charge. (I would expect about $400 each, but that's just a guess.)
I had a shop do a sample and it was gorgeous, but when it came to actually doing the speakers they backed out. Nobody else would even consider it.
I had a shop do a sample and it was gorgeous, but when it came to actually doing the speakers they backed out. Nobody else would even consider it.
I've never had the body putty crack so I don't think its necessary. I've even set my sample piece up on a ledge above my shower for two weeks then let dry out and it showed no signs of the seam showing. That was about three years ago and it still looks good.
Dave
I should clarify I only left it in the shower for two weeks. It's been on a shelf in my storage room since
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