Masking for Plating, Anodizing and Painting Part 1
Masking for metal finishing is the black hole of the industry. It’s hard to quote, hard to inspect, hard to do and too often, hard to swallow… Based on a statistical study I was once involved in, masking was the #1 cause for rejects in the shop. And I may still be underselling just how difficult it is.
So why do it? Why not just process parts that are “Plate All Over” Well, that market is shrinking, at least here in New England. There’s a huge amount of work that gets masked and it’s almost a pre-requisite that you do it… And you do it well.
Now I speak from experience. In fact, I’m the 2nd best masker I ever knew. Yes I said 2nd best. I worked with a woman who could mask just about anything successfully. So as 2nd best I had to work harder, and usually later, and quite often had to be as creative as MacGyver…
I have used every masking tool in the catalog, every liquid masking, even unusual items from the fastener aisle… I have had custom fixtures made out of stainless steel, plastic, silicon, brass and titanium… I have had jigs machined, turned, molded, laser, water jet and die cut… I’ve had custom dots, tapes and gaskets made…
A Punching Bag?
And once I used those balloons with the elastic on them that you can use as a punching bag. A little bigger, a little thicker gauge than your standard ballon and very colorful. We inflated them inside a large bore to be masked from hard coat anodize. Just another metal finishing example of doing whatever it takes.
And of course… We haven’t even touched on the most difficult part of the process… Are we masking the right holes, surfaces, bores or cross hatched areas on the drawings? I swear parts are designed and prints are made and just before the engineer heads home on Friday night he grabs a marker and decides “mask this, that and those” shuts off the lights and goes home. Thanks for that…
So once you know what to mask, or at least you, QC, the shipper, the lab tech, “Debbie from the office” and whoever that was you spoke to on the phone from the machine shop, agree on what the blue print says, then you have to apply the right masking medium. And you know what? You can be sure you put the tape, or the plugs or the balloons where you wanted them but… You can’t measure if it’s going to work.
How do you measure if the tape is going to stick in a 190F electroless nickel bath? How do you measure if that tapered mouse tail plug is going to stay in that .080” dowel pin hole that’s so critical? How do you measure if the balloons are going to pop in the 180F black dye tank? Well they did but that was a good place for them to pop. At least they were out of the 32F hard coat anodize tank.
So you’ve masked the right spots but… Now you just have to cross your fingers and hope the tape etc… sticks enough.
Money for Nothing
And I almost forgot. You charged what you thought was a whopping masking price when you quoted the job but… Oh no! The prints didn’t clearly show that that "Surface A" was recessed and it took 9 times longer to mask than it should have. And half of them came out bad and needed to be redone. So you took a financial bath as well… As a coworker used to say, we’d have been better off taping $20 bills to the parts and sending them back.
So masking… Damned if you do, damned if you don’t, and possibly double damned if you do… What do you do? There must be easier ways to go out of business. Order a keg and wait for the bank to show up? I suppose. Call me if you do. I’m fun at parties. Or you could try some of these thoughts…
Set Yourself Up For Success
Involve the Customer - When you quote a masking job ask for a set up part in advance of the order. Mark it up and have the customer sign off on it. Or have them come in and approve the masking. At least you’ll know it’s masked in the right places. With a sample part you can order the right plugs or caps rather than hope the ones you have work.
Build Quality In - Can a fixture be made? Can the masking be die cut so it’s the right size when you apply it? Can the machine shop or fabricator add “witness marks” so the masked areas are defined mechanically right on the part? Anything that eliminates measuring or uses a mechanical method to do the masking or hold the masking in place will save time and money and help prevent mistakes.
Post Machine Surfaces - Can some of the critical surfaces that need masking be machined after plate? If it can that’s always a good route. The machine doesn’t make mistakes. I worked with a shop one time that machined 4 incredibly tight tolerance bores, the only area that needed plating, into what looked like a scrap piece of aluminum with the 4 bores in it. After plating the part was returned to the machine shop and the rest of the part was completed. After an incredible amount of finish machining, something quite different, and quite expensive, was returned for passivation. We did the riskiest part of the process while the stakes were low. Instead of masking and hoping, we worked together.
Have Quality Sign Off - Have someone on your Quality team or even from management sign off on 1st articles and completed jobs. Increase the Quality Level so that more experienced inspectors and operators are involved. Try and use your best people to catch and prevent rejects and possibly increase their own masking knowledge.
Train and Educate Maskers - Invest some time in educating the masking team so that they’re not just sticking tape on a part. Have your best masker work with the others so that you have a strong group, however small, that knows what they’re doing. I suggest even giving them Quality Levels so that level 1 maskers only put plugs in holes, Level 2 maskers can apply tapes and dots, level 3 can use liquid masking. Whatever works for you but… You need your own version of “the best masker I know” and sorry, it’s not going to be me!
Have the Right Tools - I used to buy the sample kits that have like 12 of every plug in them. They cost a few bucks but, we always knew what the right plug or cap was for the job and could order them right away if needed.
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Those are a few suggestions and don't stop there. Develop your own ways to set yourself up for success and add them to mine. Masking is an art and a culture not a science. You need to find what works for you.
This is Masking Part One of Two. Next week I’ll share a few horror stories and a few victories. And I’m happy to share a few tricks and solutions developed along the way.
Second Best! But Second to None!
And I do this for 2 reasons… The 1st is I’ll never be the “best masker I ever knew” but I do enjoy talking about it.
And 2nd…
Did you know Marathon sells masking supplies?
We represent a large manufacturer of every kind of plug, tape, cap or gasket. We also sell the liquid masking materials. And perhaps best of all, we’ve been in your shoes and faced what seemed to be an impossible task with no time to do it and figured out a way to get it done.
There are other masking suppliers but I’m yet to meet another one who knows what it’s like to be peeling liquid masking off his fingers at 9PM so that the parts could be processed at 6AM because like me, you have a customer/good friend who called at 3:30 that afternoon and said “I’m sending you a job that needs to be masked and run for tomorrow and you can’t say no”. For me it was my friend Michael and he didn’t cry wolf. If he said he needed them tomorrow I couldn’t say no. He really needed them.
Let us help you by selling you the best materials, inventing a better way to use them and building in the Quality and efficiency you need. Masking isn't easy, it isn’t quick and there can be pain along the way. Kind of like running a marathon. You need Marathon on your side. More to follow...