Masking for Plating, Anodizing and Painting: Part 2
If you read part one of my Masking for Plating, Anodizing and Painting you may have sensed I have a lot to say on this subject. Being the “2nd Best Masker”, I have been through the wringer and enjoyed some great successes. Masking does bring with it the highest of highs and yes, the lowest of lows… And by lowest of lows I may be referring to your profit margin!
To try and sum up the how, why and when of masking rejects, I thought it best to list the “Top 10 Most Common Masking Rejections”. These are based on my experience and while I suspect we share a lot, you may have different causes and/or put this in a different order altogether. Feel free to adjust as you see fit but here is my Top 10.
Marko's Top 10 Most Common Masking Rejections
#10 - The Damn Plug/Tape Fell Off
This may be the most frustrating of rejections as you did so much so well. Masked in the right places… Handling, processing and thickness all perfect… Yet that masking dot floating on the surface of the plating tank is a tell tale sign something went wrong. Heart breaking and discouraging. Hard to determine the cause and all you can do is pre-treat to the best of your capability and cross your fingers. No way to measure adhesion of tape or if that tapered plug will stay in the dowel pin hole.
#9 - Accidental Masking
Nothing like using a liquid mask and finding it had smeared almost invisibly on a surface that was to be plated. Or a stray scrap of tape that was stuck on a bottom surface and somehow survived the process. Both leave rejectable voids, usually in the most visible or critical place. Handle with care, keep the work station clean and… Watch that water break!
#8 - Wrong Plug
Well, we thought we had the right plug. Until we saw them floating around the Hardcoat or Electroless Nickel tanks. Maybe that tapered plug was too small and it fell out, maybe it was too big and wasn’t quite all the way in the hole. Maybe that plug you used to mask the threaded hole was a little too small and the solution traveled all the way down the thread and now that tapped hole is a salty, cement like mess. However it happened the right plug for the job makes a difference.
#7 - Can’t Take the Heat
How many times have we seen masking break down due to the heat of the process tank? Liquid masking that turned brittle and developed pinholes in a heavy build Electroless Nickel process? Heat is our enemy in most cases and here’s two other places you can get burned: If you masked the parts and then go through a soak clean (as you should) or an etch be careful! That heat can break down or lift masking and… Heat that caused air to expand inside the part and that expansion popped out your plugs or caused the masking tape over a hole or opening to burst. Better think about heat in every step of the process when masking or selecting your masking methods.
#6 - The Customer Said So
You didn’t mask a surface or a hole based on verbal instructions from the customer did you? And if they shot you a quick email you saved it in a folder right? Many customers have a good grasp of what needs to be masked or how masking works and they can be a resource. A few haven’t learned the lessons we may have and may mislead you or give you bad direction. Occasionally a misunderstood masking call out or a challenging masking requirement can be made impossible on this advice. You need the customer involved but be careful who you ask and of course, document any direction given.
#4 and #5 - And It’s a Tie!
Time is a critical factor in masking. Not just the time to actually mask the parts but, the time for pretreatment that is so critical to the success and the time to allow masking to set up and fully cure. Since both of these are dependent on time I linked them (pun intended) here. There are no shortcuts to pretreatment. If you need to wipe the parts with thinner or alcohol you better do it well and thoroughly or that masking just won’t stick. If you need to passivate a part, particularly with a hex yellow over aluminum, the coating may need time to cure fully. Otherwise your taping over a coating that has too much water in it and is effectively like taping a wet part. And if you’re using a liquid masking? It requires time in between coats and time to fully harden so it can do it’s job. In other words there are no shortcuts.
#3 - The Blueprint Lied
Or something like that…You interpreted the drawing one way and it was actually something or someplace else. Remember that note that said “Mask 7 places” and you only found 6? Surface A actually continued over to the left hand view as well? That dotted line that didn’t mean “opposite side” but was just how this engineer decided to draw the masking view? I try and keep Linked In articles to 1000 words or less… This cause for reject warrants a 1000 words by itself. But sadly, you knew that.
#2 -Nobody Signed Off
How many rejects could have been avoided if someone else had reviewed and signed off on the masking? A lot of them. Some rejects can be avoided just by having QC or Estimating or the renowned “Debby from the office” review and sign off on masking. A second set of eyes, someone maybe not “in the weeds” of production and desperate to get the customer their parts, maybe just someone with more than 30 seconds of time to take a look and ask some questions can be a huge help. And help us avoid tragedy.
#1 - They Can’t be Fixed
This isn’t a case for reject, it’s a result of a reject but… THE most painful of occurrences is when you have made a mistake and the parts are now junk. Tight tolerances, materials that can’t be stripped, polished or critical surfaces that will permanently be ruined if reworked… If you have a particular job in house, are warned about a job, suspect something about job or woke up at 2AM having bad dreams about a job that requires masking… Do something! There are many things that can be done before a job gets processed and rejected and we can’t go back to ensure success. Involve the customer, build masking jigs or fixtures that build quality in, have the lab do some extra analysis… Those are just a few of the disaster avoiding efforts that can be made. You have your own list and your own preventative undertakings you can implement. But be sure you do.
Next! Part 3: The Empire Strikes Back
In part 3 of my masking odyssey I would very much like to share some success stories. In Parts 1 and 2 I painted a rather bleak picture of masking. Enough that some may want to cry uncle and "no quote" the masking jobs that come in. There’s no need.
Like many problems and issues we face it’s the 10% of the things we do wrong that dominate the conversation not the 90% we do right. Many jobs do come and go without issue and are profitable and go relatively smoothly. But when things do go wrong it’s usually high profile, affects the customer tremendously, ruins schedules and sends portions of the shop into a tailspin. I look forward to sharing some of the best things we ever did and developed.
Meanwhile please keep Marathon in mind for your masking requirements. I’m right now in the middle of 3 rather challenging masking projects that will solve some problems, build quality in, reduce cost and save time. Custom die cuts, manufactured masking fixtures and a trial of a tape that is cheaper and safer than the lead tape we hope to replace. Oh and a liquid masking removal system that will save time and acetone as well as improve quality.
Marathon will work worth you and bring fresh ideas, methods and materials to your masking requirements. As always, I’ll be around!