Selection of Thermal Transfer Media for Industrial Applications (End User's Perspective)

Transcription

1 Seection of Therma Transfer Media for Industria Appications (End User's Perspective) An Appications Overview Whitepaper Dr. James R. Wiiams Poyonics, Inc. Copyright, Poyonics, Inc. A rights reserved. 1

2 Overview Therma transfer printing has evoved from a technoogy-driven market (pushed by barcode technoogy), to an appications or customer-driven market. Continued growth through new appications deveopment requires an ordery engineering process for assessment of new appications, not ony for use of therma transfer printed abes, but aso for any type of product identification. This is mandatory for success in the adoption of barcode AutoID systems in industria or "harsh" environment appications. A Bit of History Not too many years ago the major concern of therma printing aficionados was to try and maximize optica density or "backness of print" at the owest energy or therma output of the print head possibe. By 1994, the major issues regarding therma transfer printing deat with print speed, edge definition, and abrasion resistance (as defined by finger smudge, and scratching by a fingernai). By this time marketeers were using generic descriptions of the ribbons to correate performance with description (wax "soft", wax "hard", "wax/resin", "pure resin", "premium resin", and now "super premium resin"). Other than describing the reative ratios of wax to resin in each ribbon (since waxes are used in a therma transfer ribbons), the descriptions were not very usefu in terms of describing their potentia usefuness for tough abe appications. Therma transfer printing proiferation did not arise from reiance on generic description of ribbons, but from successfu performance. Based upon successfu performance, therma transfer printed barcode abes have become widey used in the eectronics, automotive, aerospace, aircraft manufacturing, mass transportation, chemica, nucear, and other manufacturing industries. The initia use of therma printing was the use of direct therma printing for fax transmitta. Wax therma transfer printing came into use in the subway systems in Japan, and in the retai chain stores in the United States during the ate '70s and eary 80's. The driving force for this new technoogy ceary was the ease of use and simpicity of operation of the new therma transfer printers reative to those for dot matrix impact, fixed font, and other types of highy mechanica printing devices then in use. As therma transfer printers gained wider acceptance due to their ease in use, the ribbon manufacturers began to see widespread use of therma transfer printing technoogy, specificay for bar code abe printing. Wax ribbons quicky showed their tendency to smear when abraded, opening the door for the introduction of so-caed wax/resin ribbons. Resin ribbons foowed suit for simiar reasons, i.e., higher performance prints for more demanding environments. In each case, printer technoogy had to evove to provide the features necessary to meet these new requirements. As depicted beow, with the passage of time, wider acceptance of the technoogy enabed changes in ribbon technoogy. However, as the opportunities for therma transfer printing have broadened, the appications have become more and more compex. Copyright, Poyonics, Inc. A rights reserved. 2

3 Initiay the technoogy of therma transfer printing pushed the substitution of therma transfer printers for other printers, which pushed the deveopment of better ribbon technoogy. Today, customer driven requirements and appications for bar code abes to withstand harsh environments, generate the need for new ribbons and abe materias. A too often, though, in the eary steps of a new project, either the requirement for a abe s surviva is overooked unti the ast moment, or the project dies, because scattered and random attempts at abe definition were both random and inadequate. How does one go about specifying the proper materias and printer for a new harsh environment industria bar code abe printing requirement? Functiona specification Users have needs which can be quantified or speed out in a very "functiona" way. There is ceary a difference in the statement "boiing water", versus 100 C water, since water wi boi at ower temperatures under reduced pressure. The first is a generic description, whie the second is a more functiona description. "Kapton" abe is a marketing description, whie "abe to withstand 250 C " is a functiona description. So, from a user's perspective the printed bar code abe must be "good enough" to work, it must ast "ong enough" resuting in some type of cost/benefit criterion. The criterion may be economic (such as cost savings, quaity, process throughput, and the ike), statutory (LOGMARS, AIAG, or Wa-Mart), or even aesthetic (abe must ast the ifetime of the product). A functiona definition requires the answer to the question "what must the abe do?". The foowing may serve as a beginning mode for the answer: The abe must stay on (some surface) when appied at (appication temperature) for (some time period). During this time period the abe wi be exposed to (sovents, dust, other environmenta contamination) for (ist here the time for each environmenta exposure). Operating Copyright, Poyonics, Inc. A rights reserved. 3

4 temperatures wi be from (from what to what) for (how ong). The maximum/minimum temperature wi be (what/what) for (how ong). This definition by no means is meant to be a incusive, but rather to be a good starting point. Each type of business situation encountered may require modification of its functiona definition. Checkists vs. Process Simuation Most abe vendors today have deveoped an appications checkist as shown in Appendix 1. These checkists serve the customer (and a Saes Engineer) pretty we for most ordinary appications today. The checkist presents a summary, static means of coecting data; however, as the appications become more chaenging, the checkist becomes ess usefu. The information-gathering must refect the reaity of today's dynamic manufacturing processes. The muti-steps manufacturing processes encountered today suggest that "process simuation" using a dynamic checkist is more appropriate than a one time checkists. In the dynamic approach more work is required upfront. First the engineering must define the process steps. Second, of the checkists are then appied to each step, individuay, so that the emphasis is not ony on specific exposures, but aso on those exposures in actua sequence. The functiona specification marks the beginning of harsh environment abe appications matching methodoogy, as shown in the fowchart beow. Copyright, Poyonics, Inc. A rights reserved. 4

5 OVERVIEW THERMAL PRINTING MODEL In fowchart terms, the customer need eads to functiona definition/specification of the requirements for the barcode abe and what it must "DO". Don t be hesitant about waking away from the appication if a functiona specification eudes definition. The risk is known as " Creeping Specifications Syndrome, or Creeping Eegance. Stated more succincty, the project wi never reach competion, in a reasonabe timeframe, or in readiy justified economic terms. Once the customer need is defined functionay, the engineering effort can then move to proper seection of the ribbon/receptor which wi sove the customer's requirements. Copyright, Poyonics, Inc. A rights reserved. 5

6 Usuay many combinations of substrates and ribbons may be offered to fufi the harsh environment abe appication. To sort them out, one must weigh performance against cost, i.e. cost/benefit anaysis. If reasonabe cost/ benefit cannot be achieved then perhaps the functiona requirements specified are unreaistic, or the budgetary constraints are unreaistic. In genera, remember the higher the performance expectations, usuay means higher costs. Let's ook at a coupe of exampes. Price/Performance Tradeoffs for UV Resistant Labes The reative cost is defined as $1 per unit area of abe materia or a reative cost factor of 1. So, the first exampe (paper-pp) is the east cost materia for outdoor exposure, at the owest Copyright, Poyonics, Inc. A rights reserved. 6

7 price for this famiy of materias. However, you' note that it is ony suitabe for intermittent use outdoors due to " wicking " (water being absorbed at the edges of the abe by the paper fibers, resuting in an utimate abe faiure). The next exampe (pastic-vp) shows good performance for six months -one year, but at a price 80% higher than that for paper-p P. The next step up in performance (pastic-m M/Myar abe with Myar over aminate), is good for 5 to 10 years, but at 4.7 times the cost of the first exampe. As outdoor exposure performance increases into the year range, the cost factor increases fivefod; and finay, Auminum abes for outdoor exposure (giving indefinite performance), cost amost 100 times as much as the first exampe above. This correation between increasing performance and increasing cost of materias is not unique. Labes used for circuit board manufacturing exhibit the same price/performance correation. Again, using paper abes as the east cost (again, east performance) case, with the reative cost of 1, you can see a simiar pattern of increased performance requiring increased reative cost, up to 75 times as much for the " PI/Siicone " exampe, when compared to Paper. In the case of high temperatures, the cost driving force is the cost of the fim-the higher the temperature required, the higher the cost. Copyright, Poyonics, Inc. A rights reserved. 7

8 Simpified Cost/Benefit Anaysis So how does one go about a cost/benefit anaysis? The tabe beow dispays an exampe of 3 aternative security abes, each with different requirements (benefits), with each benefit having a cost. The costs are summarized, and compared to the expected benefits for each proposed soution: Tamper evident Non Photocopyabe Hoogram Micro-trace partices Hard to cut/sit and remove Soution 1 Soution 2 Soution 3 Cost 1 Cost 2 Cost 3 Compared to Expected Expected Expected Benefit 1 Benefit 2 Benefit 3 Continuing with the exampe of printed circuit board manufacturing, figure 1 dispays the eements of a typica PCB manufacturing process environment. Copyright, Poyonics, Inc. A rights reserved. 8

9 Figure 1. It is stepwise, as shown in this very simpified schematic, with each step exhibiting different environmenta characteristics, incuding chemica exposures and therma profie characteristics. No checkist can capture the dynamic changes in this type of stepwise manufacturing process, hence the need for dynamic process anaysis described above. Once the cost/benefit reationships have been estabished and accepted, the next ogica choice is to examine the hardware required to deiver the functiona bar code abe. Copyright, Poyonics, Inc. A rights reserved. 9

10 The combination of ribbon and receiver sheet chosen dictate the therma energy needed for proper abe performance. Much to the consternation of coeagues in the printer business, it is cear that for harsh environment abe appications, not a printers are "created equa". If the same ribbon/receptor combination is printed on three different printers, the performance characteristics are inevitaby different. If one examines the ribbon waste (the spent ribbon which is eft over after the abe is printed) one wi see from the "negative" of the bar code image that a so-caed five mi x dimension dot wi in fact measure 5 mis on the spent ribbon. If one then turns to the abe, and measures the positive image of that same x dimension five mi dot, one may find in the case of printer A in fact that the x dimension is a 6 mis in the case of be it might be 5 mis, and in the case of see, perhaps it might be 4.5 mis. If one then takes each of these abes and exposes them to a variety of chemica abuse, one may find different performance characteristics in the surviva of the printed image on the abe materia. In a confidentia study we observe the same characteristics. Printer A with a ribbon receptor combinations perform a dramaticay differenty than did printer B. In some cases in which printer 80 readiy printed in specific ribbon/substrate combination, printer B woud not even print at a when using the same combination. So, printers do matter in the fina performance of the bar code abe, reative to its harsh environment requirements. We do beieve is a matter of therma output of the print head together with print speed it through the print head. In a cases observed, chemica resistance of a printed image increases when the temperature is highest and the print speed is sowest for a given combination of ribbon/receiver sheet. We offer no comprehensive theory regarding these resuts, but find it most provocative to report them. For further discussions of these phenomona, see the Poyonics Whitepaper entited Copyright, Poyonics, Inc. A rights reserved. 10

11 Therma Printing Deveopments for Harsh Industria Environments avaiabe in the documents center of Poyonics website Performance testing protocos (which ead to QA methods) must mirror the critica eements of rea word appications. Once a functiona definition and specification are achieved, the needs can then defined in numeric, repeatabe test methods. Performance of the new materias in aboratory simuated manufacturer s processes can then be measured against these metrics. For exampe, the arge number of variabes found in circuit board manufacturing operations requires that the foowing testing protocos be used. Labes are printed independenty on three different printers. The abes are then used in three process environments, ambient, preheat, and soder process conditions. Approximatey 12 ribbons are tested on this new materia Each abe printed it is exposed to 24 different sovents and ceaners. This resuts in 2,592 tests. This is quite different than in the case of abes for outdoor exposure. Up to three printers are used With 12 different ribbons The printed abes are exposed to Acceerated weathering (simuate UV from sunight) The printed abes are exposed to hydrauic fuids, gasoine, ois, and water immersion. This resuts in up to 150 different tests, quite different than in the case of circuit board manufacturing. Summary The ast decade has seen a dramatic shift in bar code abe uses throughout a manufacturing industries. Unike the ate 1970 s, 80's and eary 90 s, as therma transfer printing technoogy was pushing its way into the bar code word, generating a market for abes, today new appications requirements are puing therma transfer printers and new materias into the abe market. These new appications are imited ony by avaiabe ribbon and receiver sheet combinations to withstand the environmenta exposures. The keys to success for this new era ceary require functiona definition of the customer needs, with simutaneous, strenuous appications testing of the resut. Copyright, Poyonics, Inc. A rights reserved. 11

12 APPENDIX I APPLICATIONS CHECKLIST Performance requirements Temperature (Max, Min, Exposure time) Chemicas (Sovents, Type, Other, Exposure time) Outdoors (Direct/Indirect sunight, Sat spray, Freeze/Thaw,Other, Exposure time) Misceaneous (Autocave, Abrasion, Steam, Other, Exposure time) Mutipe combinations, process steps Reguatory (UL, CSA, FDA, MIL SPEC, Other) Product surface characteristics Pastics (HSE, LSE) Gass PVC Meta (Oiy, rusty, type) Painted Other Shape, conformabiity Fat Curved/Convex/Concave Fexibe Rigid Aesthetics Muticoors/Overprinted Goss, Matte, Metaized Opacity Adhesive requirements (Thermoset, Permanent, Removabe, Tamperevident) Appication conditions (Temperature, Wet/dry surface) Dispensing (Hand, autoappy, other) Other specia properties (Masking, antistatic, etc.) Copyright, Poyonics, Inc. A rights reserved. 12