Question about backlit signs

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Uthayne
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Question about backlit signs

Post by Uthayne » Mon Nov 11, 2019 10:57 am

Hello,

I'm fairly new to powdercoating and metal fab in general. I've been doing some signs that require offset mounting from wood so that they can be backlit with RGB LEDs. For the first sign, I welded nuts to 1/8" thick 2"x2" squares, and then used VHB and E6000 to adhere it to the 16ga sign. Although this worked, it was not ideal because if the nuts were ever so tilted, it made threaded a bolt from the backside hard. I am also worried about the long term bond strength of this solution.

For my second piece, I decided to tack weld 5/16"-18 bolts to the back of the 16ga sign; more akin to what a stud welder would do. I welded the bolt in an area where the next layer would cover it up, and I used as small a tack as I could (MIG). I lightly grinded the front side of the sign to blend any distortion and remove the discoloration; however, after powder coat it still shows through.

Is there a better way to mount signs like this? Is 16ga just too thin for stud/bolt welding without showing through PC afterwards? I have a TIG welder, so maybe that would be a less aggressive tack?

I'm just a hobbyist, so I am not really interested in spending $2000+ for a CD stud welder. Looking for cheaper alternatives, if any exist.

Thanks!
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plasmanewbie
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Re: Question about backlit signs

Post by plasmanewbie » Mon Nov 11, 2019 1:13 pm

Great looking sign! In my opinion 16g is too thin to get away with no distortion from a weld on the back without expensive equipment.

I did a similar project for outdoor use and bonded on small plates with the standoffs welded to them and it worked great.

Because this could be dangerous if the bond came loose I went with a 3m panel bond used for auto body applications and it worked awesome.

Size your standoff plates appropriately for the size and weight of the sign, the bigger the better since you can get more panel bond on a larger plate.

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acourtjester
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Re: Question about backlit signs

Post by acourtjester » Mon Nov 11, 2019 1:57 pm

What I have used for back lit signs is using a backer board and locate the bolts where you want them. Use a nut on the front and back of the backer board to hold them straight. Mark the locations of the bolts on the sign and drill small holes where each bolt is. Place the sign on the bolt heads and tig plug weld them from the front of the sign using small holes you should get away from warping and plug welds give full penetration with enough metal to grind smooth after. Use bolts with a shoulder long enough for you standoff distance.
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Uthayne
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Re: Question about backlit signs

Post by Uthayne » Mon Nov 11, 2019 3:27 pm

Thanks for both of the tips. I like your method with the backer board to keep the bolts straight. I'll have to practice my plug welding to get a nice smooth finish.

One benefit of having a 3d printer is I'm able to print whatever size spacer I need to get the appropriate standoff distance, and then choose a bolt long enough for that. Ensures even offset from the wood

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acourtjester
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Re: Question about backlit signs

Post by acourtjester » Mon Nov 11, 2019 7:42 pm

I have 3-D printed other optional tool attachments for my CNC table too.
viewtopic.php?f=122&t=27403
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Hole Shot Garage
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Re: Question about backlit signs

Post by Hole Shot Garage » Tue Mar 24, 2020 8:53 am

The 3M Panel Bond is some really good stuff just a bit heavy on the price, But really does work well..

Blackslacks
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Re: Question about backlit signs

Post by Blackslacks » Tue Mar 24, 2020 10:20 am

Ive welded standoffs to 16 gauge and didn't have a problem. The welds were small enough not to cause distortion. After welding I buff the whole other side with a fine flap wheel to remove all the weld marks and mill scale if using hot rolled.
I didn't powder coat though just paint. Maybe that makes a difference.

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rdj357
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Re: Question about backlit signs

Post by rdj357 » Tue Mar 24, 2020 10:31 am

I use a Capacative Discharge Stud Welder. It's a bit pricey ($3k for a good one) but very worth the investment if you're going to do a lot of layered pieces. I use the Midwest Fasteners Sure Shot II.
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