By Greentree Masking Solutions

07/07/2010 MASKING 101
Still manually masking products before they go to your finish shop? When do die-cut tape masks make sense? Or should you be using custom molded masks?

When Ruben Dominguez walks into a finishing shop and sees workers using razor blades to remove excess tape from masked areas, he knows he has a solution to what could be a significant production bottleneck. "Any time a worker uses tape and then cuts away excess material in order to protect a surface prior to the application of paint, e-coat or powder coat, they’re almost certainly a candidate for a die-cut tape or molded mask," says the masking expert. Citing higher throughput, better finish quality, worker safety, and overall finish line efficiency as the main benefits of manufactured masks, Dominguez knows what he’s talking about – his employer is Shercon, a leading producer of die-cut, molded and custom masking solutions. Dominguez is one of their top designers."Masks are like anything else you do on your production line – if you can possibly do it faster, easier, better and even cheaper, then you should take a close look at the options."

Masking Choices

Masks are used to prevent finish deposition on product surfaces during wet paint, powder coat and e-coat processes. They can be as simple and "low-tech" as a single strip of masking tape applied to a flat surface before wet paint is applied, or as high-tech as a custom-molded Ultrabake mask that protects a complex, three-dimensional surface from a nine-stage coating process.


Common masking methods

• Application of tape right on the finishing line – often cut to fit by workers using razors or X-acto knives
• Precision die-cut masks, usually "punched" onto a tape surface and delivered on a roll – masks have an adhesive surface, and are simply peeled off the roll and applied over the surface to be masked
• Molded masks manufactured from high-tech rubber materials (reusable and capable of masking three-dimensional spaces like threaded holes or zerc fittings)

Given the advantages in productivity, there are often significant economic benefits to using die-cut and molded masks. In addition, many production lines are moving from wet paint finishes to E-coat and powder-coat lines, and discovering that their old masking process simply won’t stand up to the new finishing regime. Masks manufactured from materials capable of resisting hostile environments are needed to produce consistent, reliable results. As a result, a lot of companies are looking at die-cut and molded rubber masking solutions, and taking advantage of the advancements offered by the newest, high-tech masking materials. So with so many choices available –tape or molded, custom or standard – how do you determine which is right for your application?


Key factors to consider are:

• Price (The Economics of Die-Cut & Molded Masks)
• Consistency & Coverage Requirements (Quality)
• Ease of Application
• Ease of Removal
• Worker Efficiency
• Lead Time
• Volume

The Economics of Die-Cut & Molded Masks

While each situation is different, "peel-and-stick" die-cut masks typically become more economical than individually taping and cutting at fairly low production rates. If workers only have to mask one area every day, then "peel and stick" masks won’t represent much of savings unless the masking project is highly complicated, requiring 30 minutes or more to cover. However, masking even a dozen parts daily offers a compelling economic argument for die-cut masks on the basis of time savings: 12 x 10 minutes for taping and cutting vs. 12 x 10 seconds for "peel and stick" die-cuts. Multiply the time savings over days, months and years, and the numbers quickly add up. The rule of thumb is this: the higher the production rate – or the more complex the masking situation -- the more compelling the economic argument for die-cut masks. Unfortunately, there’s no hard-and-fast way to estimate the savings without knowing the demands of each application.

Oscar Puluc – a Shercon design engineer -- says: "Any time you’re creating your own masks, then you should probably look hard at a die-cut or molded mask. And if you’re hand-finishing anything after a finish step – like buffing out bores or manually removing finish from any part of your product – then you should look for a masking solution that eliminates that step. Otherwise, you’re wasting time and money."


Consistency & Coverage Benefits

When operators apply and cut a new tape mask each time a product rolls down the line, inconsistencies are bound to occur -- and these are amplified when a different operator starts making masks. Contrast this inconsistency with the precision of a die-cut mask, which are typically accurate to within .005 of an inch. Widths as narrow as .030 of an inch are feasible, and if the right material is used (polyester tapes are popular in e-coat and powder coat environments), they are dimensionally stable. In truth, the only variable facing die-cut mask users is mask application, and today’s mask designs can minimize alignment difficulties. For example, guide holes and tabs allow for extremely precise, rapid alignment of die-cut masks on a product surface.

Slitback designs -- which allow mask application in steps – also ease application. Developments like transfer liners even allow precise alignment of multiple, unconnected mask elements – like the letters of a word. Finally, coverage consistency of modern, polyester film masks is excellent, even when exposed to wash/coat/wash/coat finishing environments like e-coat and powder coat. As a result, finish quality is better, rejection rates are lower, and overall product quality is better.


Ease of Application

Obviously, the faster you apply a mask, the less time you invest in the finishing process. "The time it takes to apply a mask is important when it relates to the cost of manufacturing" said Shercon’s Dominguez. "But people forget to consider overall throughput – if your finish shop is a production bottleneck, then time spent on inefficient masking only makes the bottleneck worse."
"If applying finish holds up your production line, then you should absolutely look for ways to relieve that bottleneck. Better masking is often the fastest, easiest, least-expensive way to speed a finishing process."

Obviously, speed is not always the only issue; lifting excess tape away from a masked area requires a sharpened edge of some kind, endangering both the operator and the surface of masked area. Given growing concerns over worker safety (including concerns like carpal tunnel and repetitive motion syndrome) and the financial impact of worker health problems on a company, it’s clear that reducing masking application efforts can impact a company’s bottom line.


Ease of Removal

Once a product is finished, masks must be removed – without marring the finish. This process adds to production time as surely as mask application; according to Shercon’s Dominguez, removal is "the forgotten aspect of masking – saving twenty minutes on removal is just as good as saving it on application." Clean mask removal also has a significant effect on product finish if clean, sharp finish lines are desired. Shercon’s Oscar Puluc is a die-cut mask expert who leverages all the material advantages available to him. "Removing a mask with a knife or sharp edge is dangerous – both in terms of worker safety, and in what can happen to your brand-new, perfect finish." Puluc advocates a tool-free removal whenever possible, and facilitates this through the use of tabs added to die-cut mask designs. "Adding adhesive or non-adhesive tabs to a die-cut often makes sense. These tabs really speed removal, and help give you a sharp, unmarred finish edge." In applications where removal is difficult, custom molded masks can be created with ergonomic pull handles, speeding the removal process to a simple tug.


Mask Availability

In prior years, mask prototyping and production could be time consuming, yet recent advances in materials and manufacturing have revolutionized mask making. Today, companies like Shercon can deliver prototypes in 24 hours, and production parts in 2-4 days. "In most cases, if someone sends us a part drawing before noon our time, we’ll get prototypes out to them the same day via overnight shipping," said Shercon’s Dominguez. "They’ll have custom die-cut samples they can use on their production line the next day." Once a prototype mask is approved for production, laser cut steel dies are made, allowing masks to be stamped in large quantities. Creating dies takes 2-3 days, and production of custom die-cut masks is usually a same-day affair. Short production runs can even be carried out on special prototyping machines. Customers don’t pay for the production of a steel die, but the cost per mask is usually higher.


Die-Cut Tape Masks vs. Molded Masks

Molded masks represent a step up over die-cut tape masks in longevity, protection and speed. They can be used to mask areas like threaded bolt holes and bearing surfaces, or cap protruding surfaces like grease zercs. Since they are reusable (often 25-50 uses), they are ideal for high-volume applications where their longevity outweighs the initial engineering costs and higher per-mask cost.

Dominguez is one of Shercon’s expert on molded masks. "They install quickly, remove even faster, and provide the best coverage possible. Because the material conforms to the product surface, the seal is much better than hard plastic products. They’re basically plug-and-paint and provide huge improvements in efficiency." He related how a manufacturer of giant earthmoving equipment used to individually mask multiple stud holes and the hub surface of a huge wheel assembly -- using simple tape. It was a time-consuming process. Shercon developed an all-in-one Ultrabake molded mask that masked the stud holes and the bearing surface with a single, "plug-and-paint" mask installation. Time savings – in both installation and removal phases – were immense.
Because they can be designed with ergonomic grips and pulls, molded masks integrate well in fast-moving and robotic finishing environments. And finally, because they can be molded from Ultrabake, EPDM and other substances, they can be built to withstand extreme temperatures or corrosive/abrasive environments.

The downside? "Molded masks are more expensive than die-cut masks," said Dominguez. "But they can handle almost any application."


Summary

Manufacturers face growing competitive pressures and increasing concerns for worker safety. Custom masking solutions can result in significant throughput gains by dramatically reducing the time needed to install and remove masks during the finishing process and significantly improve the quality of the finished product.

At the very lowest production levels, customer-installed masking solutions (e.g. manually applying tape, then removing excess with a razor) are often slow to apply and remove, and the use of tools can imperil the existing finish. Still, they can make sense in low-throughput applications using non-hostile finishing environments.

Standard and custom die-cut masking solutions offer the benefits of "peel-and-stick" simplicity and speed, often at an initial cost only slightly higher than simple tape. The results (consistency and coverage) of a properly engineered die-cut mask are excellent – and the range of materials and techniques available (e.g. guide holes) make these the choice of many modern production lines. They are fast, affordable, and easy.

Molded masking solutions are the overachievers of the masking world – they thrive in high-throughput production environments and in applications that couldn’t be handled any other way. While standard molded plugs and caps are available, these solutions are often custom-engineered, and then created from high-tech materials capable of resisting extreme temperatures, highly corrosive finishing processes, and even extremely abrasive environments like sandblasting. Engineering and mold production costs have fallen significantly over the past few years, and molded masking solutions are now starting to be found on production lines everywhere.