Matching Screen Frames…To the Need

by Douglas Grigar, Master Screen Printer

(A version of this article originally appeared in the March 2007 issue of PRINTWEAR.)

 

Many of us tend to become focused on the minute details of an issue, but not take the final result into our calculations. When dealing with screen frames, we tend to forget that we sometimes need to focus on the end result rather than the steps from here to there. Yes, the details are very important, but how do we use the details to make a good final choice? How do we logically justify the frames we choose as a foundation on which to attach our even more critical selection of mesh?

Logic in Application

Frames come in three basic choices and they are all prolific in the industry. We have the traditional wooden static frames, the metal static frames made of mostly aluminum alloys, and the retensionable frames. There are ingrained prejudices in the industry from all directions, so rather than chose a side and start flinging mashed potatoes across the proverbial school lunchroom table, let’s shine a little light on the choices, both good and bad.

Taste Trends

I recently spent a few days getting to know a screen-frame manufacturer and several of his employees, while attending an industry trade show. While this is not the only frame manufacturer I’ve visited or worked with, it was the first time I was able to speak about frames in a format where we could talk openly about industry trends, compare products, and analyze the current buying habits of screen printers. Some years ago, the highest proportion of screens purchased were traditional wood frames; whereas now, metal and retensionable frames have closed the gap on the simple wood frame to the point where the frame man with whom I spoke had opened a second manufacturing location to handle the increase in demand for static aluminum frames. We also talked of the steady expansion and growth in the use of retensionable frames, both in established plants and new start-ups.

The Styrofoam Coffee Cup

Wooden screens may be thought of as similar to the common Styrofoam coffee cup: they are functional and provide adequate service for the intended job. Wood frames are available from just about any supplier and are relatively inexpensive. For most basic jobs wood frames provide a reasonable platform for printing. Some would argue that, just like drinking premium coffee from a Styrofoam cup, wood frames can print premium print jobs. The point is valid, but there are limitations.

As with the disposable nature of the Styrofoam cup, the wood frame has aspects to its nature that are difficult to overcome with extended use. Printers who remove emulsion and recycle their wood frames back into the process repeatedly find that the weaknesses of the product causes loss of tension, warping, and excessive flex while printing.

Wood is a beautiful and renewable resource for building, but wood frames bathed in chemicals while in wash sinks and on the press will quickly lose most of their sealant products (not to mention the glue that attaches the mesh). What’s more, it is not uncommon to see brand-new wood screens come directly out of the box from the factory in a warped condition, wood being largely incapable of holding high mesh tension without yielding. Untreated wood exposed to liquid while reclaiming will absorb moisture and produce negative results – the tighter the mesh (causing the wood grain the spread), the worse the results. Wood also does not hold up as well to the pressures exerted by movement and strain produced while printing.

[Figure 1: If you can’t see the forest for the trees, it could be on account of your wooden frames having lost so much integrity they can no longer reproduce sufficient detail. On the other hand, if you print lower-tolerance work, they may be ideal for your requirements..]

 

Knowing the limitations of wood frames in production, however, will allow you to choose jobs that match or at least forgive the inconsistencies inherent in such frames. Single-color prints or jobs with less than critical alignment needs are the appropriate realm of the wood frame. Shops with the need to shoot simple jobs, or print and repeat the same job, will enjoy the economy of a lower initial price when they place their wood frames into storage and cataloguing for later repeated use.

The Ceramic Coffee Mug

Just like the standard ceramic coffee mug we all use in the office, our screen frame equivalent would be the static aluminum frame. The ever-dependable static aluminum frame is used for just about any regular job and as long as it is not damaged and the mesh it holds is in good shape, it will chug along each day doing what it does best. (Until, as with its ceramic coffee mug alter-ego, somebody drops it getting it out of the dishwasher.)

The static aluminum frame is, for the most part, unaffected by our typical chemicals, is waterproof, and is strong enough to hold its initial tension without excessive warping. A good quality aluminum frame can also be stripped of its mesh, cleaned of glue, and have new mesh attached many times (throughout its lifetime, in fact); and most screen frame manufacturers also offer re-stretching services.

The static aluminum frame may present its biggest weakness in the fact that it is so “ordinary” and, well, static. The static nature of the frame contrasts starkly with the rather dynamic nature of the mesh it supports. Once mesh is glued to the frame few changes can be made. The mesh cannot be returned to or tightened to a higher tension; changing the mesh on the individual frame requires a razor knife which renders the mesh unusable (unless on a smaller frame). The static nature of the aluminum frame, therefore, dictates that the occasional need for higher tension or special applications may not be well served by this frame.

[Figure 2: If your production scenario is one that doesn’t include a significant amount of routine screen reclaiming, the other attractive attributes of rigid- (that is, non-retensionable) aluminum frames might be the ideal solution for your screen-making needs.]

 

[Figure 3: If yours is the average production scenario – not so much in terms of size, but in the nature of your work – retensionable frames offer the desirable characteristics of rigid-aluminum with the added benefit of being able to re-tighten and “work-harden” your mesh.]