Archive for the 'process capability' Category

#68: Sustainable Green Printing

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by
Jim Raffel
on February 7, 2008
in measurement and process capability
. 0 Comments

What is this new and latest buzzword sustainability? If I have offended you by calling it a buzzword I am not apologizing. Please do not misunderstand me; I think sustainability is a good thing. Smart printing businesses have been engaging in most if not all of the components of sustainability for years. The reason is quite simple - PROFIT.

Recycling is a key component to a sustainability program. Has anyone reading this been around long enough to remember the late Roger Dickeson’s War on Waste (WoW) waged by web printers back in the 70’s, 80’s and early 90’s? Did they do this to be “green” or “sustainable?” Personally I think not - they did it to MAKE MORE MONEY!

Did the web printer I worked for in the 80’s and 90’s commit more resources to better segregation of waste paper streams, including office paper, to be green or sustainable? Did we find ways to recycle even the cores from our rolls of web paper to be more sustainable? No, we did these things to reduce the cost of waste disposal and increase the revenue received for recyclable product. The net result of course was that we became more sustainable and green.

I suspect the sustainability ‘consultants’ out there are screaming right now that he does not get it! While you may be right, I do understand that there are other components to a complete sustainability program including a social responsibility component. I am sure even the social responsibility component of sustainability, when properly executed, can and will result in more of that dirty word - PROFIT.

What caught my interest about sustainability is that improvement must be measurable. Then I got to thinking - if the sustainability movement repackaged WoW, what else have they repackaged and re-labeled? Deming’s Statistical Process Control (SPC) that’s what. The past twelve years of selling and servicing ColorMetrix color verification and process control software has provided me with a good knowledgebase in this area. I have also written quite a bit about the topic on this blog.

Since you can read all the past posts, I will keep my explanation of using process control in a sustainability campaign short and sweet. Following is a simplified ink jet proofing example:

  1. Establish a baseline of ‘bad’ proofs as a percentage of the total produced.
  2. Utilize color verification and process control tools like ColorMetrix and ProofPass.com to verify color quality of all proofs produced.
  3. Review process control charts and other data to establish when and why variation/drift is occurring.
  4. Fix/Improve the causes which can be fixed and improved, and learn to ignore the special causes.
  5. Return to step one and compare current results with the baseline.

SPC works and Quality is NOT free, it is instead an investment with a return.

#58: I Still Love the Smell of Ink in the Morning

Published
by
Jim Raffel
on June 28, 2007
in calibration, color, color bars, density, measurement, press run and process capability
. 0 Comments

I have been so immersed in virtual proofing over the last several posts, that I had almost forgotten how much I still love the smell of ink in the morning. Last week I had the privilege of spending two days assisting a customer in the set-up of our software primarily for use as a pressroom monitoring tool.

The experience reminded me of #55: Just Measure It! The customer is a web offset shop and has the same problem that most of our digital printing customers have (Oh, I love the smell of toner in the morning too!). The problem is that their press product is finished product and has no trim. Color bars are not an option on production work, and changing the design to incorporate color swatches would also be impractical at this time.

The solution turned out to be the same solution we employee with our digital printing customers. A test form is put on press twice a day and the results of those measurements are used to verify conformance to density standards across the web. A second control strip can be scanned to gather other print metrics like TVI, Print Contrast, etc.

The results in a sister shop have been improved consistency from day to day and the ability to monitor changes in density and TVI from morning (cold press) to afternoon (warm press). In a perfect world I would love to see color bars on every job, but we thought outside the box and found them a solution that allowed us to measure. Once they started measuring quality and consistency improved. Profitability and productivity are never far behind quality and consistency improvements.

I raise the challenge again…today start measuring something in your color workflow that you are not measuring today. Within seven days those measurements will point the direction you need to go to improve the quality and consistency of that process.

#51: Proper Press Fingerprinting takes Commitment

Published
by
Jim Raffel
on March 21, 2007
in blogging, calibration, color, curves, education, measurement, press run and process capability
. 0 Comments

In this installment we will address the third question Dale raised in #47. Dale’s first two questions got answered in #48 and #49 which can be reviewed at JimRaffel.com.

Now, onto Dale’s third question:

3. In fingerprinting our presses, we’ve run up against the dreaded “Hurry up and do it, but don’t put too much work into it.” What are your recommendations for impressing upon the higher ups that doing color balancing and working out the calibrations takes time?

I would suggest you have your management read JimRaffel.com. The reality, however, is that the culture required for completing successful fingerprints starts at the top and does not get worked up from the bottom. I spent the better part of the first ten years of my career trying like heck to change the culture of a printing company (now out of business I might add) from the echelons of lower and middle management. While I hesitate to use the words “It can’t be done” (and not because my Mom the English teacher told me to never use contractions), I believe this is one place where this expression applies.

I have been very fortunate in my career. At 21 years of age before I had even graduated from RIT I was able to observe one of the pressruns used to set the early SWOP press standards. A lot of very smart people participated in this run and the scientific procedure was impressive. Then, not a year later I was the guy doing all the print quality measurements on a brand new Baker-Perkins G14 that cost about 9 million dollars back in 1986. While I was just one member of a very large team, the owner of the company made it quite clear that he was not making his first lease payment until we had a press that was printing correctly.

Over the next 3 years I had the same responsibility as 2 more new presses started up in that facility. In both cases, the purchase contract was very clear that we did not make lease payments until the press met our print quality standards. While the company in general had an difficult culture, in the case of all three of these press startups the message from the very top of the organization was “Do whatever it takes to get a solid press fingerprint.” The reason was simple, without a solid benchmark at startup how could we ever know what condition the press was in later?

Dale, it takes a great deal of time, money and a great team to perform a successful and meaningful press fingerprint. During the press startups above, the fingerprinting process could go on for a week or more. The press was fully crewed and lots of paper was run during this time. All the support staff had to be available from pre-press, plating, maintenance, materials handling, and more. I don’t think it’s an understatement to say that these fingerprint cost $100,000 or more.

Now, not all fingerprints need to cost that much. I took part in a very successful fingerprint within the last 30-days that probably cost no more than about $10,000 including our software and professional services time. It is, however, a matter of scale. The client for the 10K fingerprint was simply making the first investment in end-to-end color process control. All the key players in this organization participated in the meetings and remained on-site during the 2 (14 plus hour) days required to complete the fingerprint.

The results on the second day (and in follow-up calls the last three weeks) continue to be impressive. In the case above the press is not brand new but instead a fairly old and well worn pieces of iron which is now printing at an impressive level.

My conclusion is simple. If senior management of a PRINTING company is not willing to invest the time money and effort necessary to perform a proper PRESS fingerprint, one must really question the value of performing the fingerprint.

#48: Make Proofs That Match Your Press

Published
by
Jim Raffel
on February 16, 2007
in GRACoL, L*C*h*, L*a*b*, TVI (Dot Gain), color, color bars, delta E, measurement, process capability and proofing
. 0 Comments

Since #45 in December we have been discussing resolutions to improve the quality of your proofs. In order to gain the full benefit of this installment one should have read and implemented the suggestions in #46 & #47.

Proceeding forward it does not matter if you are utilizing a methodology like GRACoL G7, or a more traditional color management approach. In either case you will include a target on each print job with the same color bar swatches that you output on the proof (#46). This will allow you to measure the press ok sheets and compare them to the proofs, thus building even a larger statistical database to call upon.

When utilizing software like our ColorMetrix and ProofPass.com products for process control and print certification purposes it does not matter if you are using a methodology like G7 or traditional color management. While there are some new formulas out there to run the collected data through the tried and true colorimetric data (L*a*b* and derivatives along with some version of Delta E), do a great job comparing two similar or dissimilar imaging systems.

Unlike density and dot gain values which must be used with pigment sets designed for 4/color process printing, L*a*b* values allow the comparison of an inkjet proof and an offset press sheet. This is possible because we are looking at the actual colors, not values derived from a formula which assumes a certain pigment set.

Not only will you be comparing the measurements of the proof to the press sheet, but you will be building a history of what is a “normal” print condition of each press and paper combination. Some refer to this as finding the “sweet spot” of the printing press.

Overall, as your volume of collected data grows you will be able to refine the system in small steps by reviewing the proofing and press information both independently and together. Using numeric results, charts, and graphs you will be able to see small differences in color that can be adjusted for over time. No system is stable over time, so continuous monitoring is a must in order to maintain stable color.

#44: Why process control works

Published
by
Jim Raffel
on November 17, 2006
in TVI (Dot Gain), blogging, density and process capability
. 0 Comments

Earlier this month I was visiting a customer who utilizes multiple ColorMetrix licenses to monitor and control; plate making; proofing; and pressroom. Several years ago this customer used ColorMetrix in his plate making operation to uncover a processor replenishment problem that not even the plate vendor was able to unravel. During this visit, he told me about a recent experience involving a pressman who came to him asking for a new plate so that he could achieve a match on press. For some reason he could not get the cyan to fall in appropriately. My customer consulted his ColorMetrix plate database and confirmed that the plate was properly made. He then measured a press sheet provided by the pressman and compared it to his historical data for that press and paper combination. The cyan dot gain (TVI) was about 10 points away from the expected values.

He agreed to make a new plate with an adjusted curve in the interest of getting the job off press with acceptable color, but also suggested the pressman take a long hard look at the cyan printing unit. Before the plate was even processed the pressman returned and said to never mind he had uncovered a roller problem in the cyan unit.

Yes, all the data collection our client does takes time and effort, but what is an hour of your press time worth? He pointed out that this is not an isolated occurrence. Just having a densitometer and measuring density and dot gain would have done no good in this situation. My customer and his pressman needed to know what the expected density and dot gain would be on the press and paper combination being run.

By simply measuring the OK sheet from most jobs, within 30 days you will have a very substantial database to fall back on when problems like the one illustrated above occur. So, process control is not free, but instead an investment with a fairly easy to calculate return. There are more examples of how process control has saved our clients money at here at JimRaffel.com, so feel free to read the archives.

#37: Monitoring Digital Presses

Published
by
Jim Raffel
on August 9, 2006
in blogging, calibration, guidelines, measurement, paper, press run and process capability
. 0 Comments

At ColorMetrix we have some new and potential new customers who will be using our products (both ColorMetrix and ProofPass.com) to monitor and control digital presses like the HP Indigo, Xerox 8000, and NexPress. During our sales presentations most of these folks have expressed concern that the device is constantly self calibrating and correcting itself, so why would I need to do external process control?

My short answer: “Do you really want to let the fox watch the hen house?”

For the most part the internal controls on digital presses are built to keep the device in calibration. While these devices are different than conventional printing presses, they are not so different that we conventional printers do not understand them. There is a certain amount of variation that a conventional press self adjusts for like automatic register controls and the like. So, if we follow this augment to a logical conclusion that would mean process control would be useless on a conventional press as well. If you are reading this article I am fairly certain you do not believe that.

In general the act of process control requires the user to view the device (press in our case) as a black box. By measuring the resulting print the device produces, we are taking into account everything that happens in the device and the environment the device is in.

For example, several of these devices “self-calibrate” by imaging on a drum or a belt between actual substrate impressions. It seems to me we have removed a pretty important piece of the quality puzzle from that equation. What if our substrate is stored in a warehouse with no air conditioning and our press is in a climate controlled room? A week or so ago it was almost 100 degrees with very high humidity in the mid-west. If we bring that paper from the warehouse into the production room and do not provide 24 hours for the paper to acclimate, do you think we would get the same print result as we would with paper that had been acclimated?

If you said NO, please call me for a free trial version of ColorMetrix or ProofPass.com so you can measure it yourself.

In conclusion, all the variables that contribute to a printed piece like; faulty RIPs, toner changes, device wear and tear, paper changes, etc are viewed by a process control system like ColorMetrix as a black box. Process control systems like ColorMetrix measure the finished piece in order to accomplish two goals:

  1. Confirm that the finished print quality is within acceptable quality guidelines
  2. Provide detailed enough information to track back the problem portion of the process when #1 above is not achieved

Overall, the goal of the manufactures self-calibration procedure to stability of the imaging process itself. The goal of a system like ColorMetrix is overall print and color quality of the printed piece you put in the hands of your customer.

#32: Tales from the Press Trial (Part 2)

Published
by
Jim Raffel
on April 28, 2006
in TVI (Dot Gain), blogging, curves, density, measurement and process capability
. 0 Comments

This week I will be providing more information about the MacDermid Printing Solutions Stabil-X press trial April 17th and 18th . This week I will review the variation data from two of the trial conditions:

  • STX opt – Stabil-X blanket run at optimum packing level
  • Press std – The set-up of the press when we arrived

The TVI graph from last week showed the mean 50% dot gain for the STX opt. to be 24.817 and the Press std. to be 25.556. In addition to the lower overall dot gain with the Stabil-X, the standard deviation of the Stabil-X opt. was only .752 compared with 1.088.

The density of the two runs are very similar as well as the associated standard deviations: STX opt. 1.489 and .018; Press std. 1.522 and .016.

Standard.jpg

Stabil-X.jpg

These two graphs plot each of the 10 samples measured for each trial condition. The graphs also show the mean as well as 3 standard deviation +/- control lines.

If you would like more information about the MacDermid Stabil-X blanket, please contact me and I will put you in touch with the right people at MacDermid.

#31 Tales from the Press Trial

Published
by
Jim Raffel
on April 21, 2006
in TVI (Dot Gain), color, color bars, curves, densitometers, density, measurement, press run and process capability
. 1 Comment

On April 17th and 18th I had the pleasure of participating in a press trial with MacDermid Printing Solutions to evaluate the effectiveness of their new Stabil-X offset printing blanket. I am writing today about the TVI curve of the various trial conditions.

Stabil-X TVI

We ran five different conditions during the course of the trial. All the trials shown in the graph involved only one printing unit running magenta ink. The curves also represent the averaging of 10 press sheets. The five trial names and descriptions are:

  • STX opt - Stabil-X blanket run at optimum packing level
  • Press std - The set-up of the press when we arrived
  • STX -.003 - Stabil-X purposely under packed by 3 thousandths
  • STX +.002 - Stabil-X run at 2 thousandths over
  • STX +.004 Stabil-X run at 4 thousandths over

As one might expect the STX -.003 has not only the lowest TVI, but also a very poorly formed curve. A pretty good example of why you do not want to run your press under packed.

The Press std curve shows how this shop runs the press on a regular basis. Notice the hump in the TVI curve from 25 to 50%. Not an uncommon condition on many presses.

The STX opt curve is much smoother than the Press std curve, missing the hump from 25 to 50%. Also, run at virtually the same densities the dot gain (50%) and overall TVI is lower at all points than the normal press set-up.

Even the two STX over pack conditions produced smoother overall TVI curves than the press standard set-up. While the TVI is higher in most cases this is to be expected when adding that much squeeze to a blanket that really does not need it.

I will continue to write about this press trial for a least 2-3 more weeks. There is a great deal of data and information to still go over. I even have some sheets here I will be doing additional readings on.

If you would like more information about the MacDermid Stabil-X blanket, please contact me and I will put you in touch with the right people at MacDermid.

I still love the smell of ink in the morning

Published
by
Jim Raffel
on April 19, 2006
in TVI (Dot Gain), blogging, curves, densitometers, density, measurement, press run and process capability
. 1 Comment

Over the coming weeks I will be writing a great deal about my last two days in Chicago. Kevin Kocher of MacDermid Printing Solutions (offset blanket manufacturer) invited me to a press trial of their new Stabil-X blanket. So, right about now if I was one of my readers I would be thinking how exciting can an off-set blanket be? In a word this blanket is cool. It truly is the first revolutionary technology change in blankets in decades. In short this blanket is a patented combination of a polymer backing (instead of fabric) with Kevlar fibers running through it as well as synthetic fibers to replace the nitrile rubber and cotton.

We took a great deal of measurements during this trial, and while I have not had time to fully review the data I can tell you that this blanket printed better. Better being lower dot gain at the same density levels as conventional blankets, a smoother shaped TVI curve than traditional blankets, and most importantly less density and dot gain variation in sequential pulls.

Over the coming weeks I will be including both numeric and graphical results of this test, showing how we utilized ColorMetrix to confirm the visual results with objective factual data.

Golden Nugget #8…Specification, Guideline, or Process Capabilities?

Published
by
Jim Raffel
on August 9, 2005
in GRACoL, guidelines, process capability and specification
. 0 Comments

*** Introduction ***

If you noticed there was not Golden Nugget last week, it is because I was on vacation. Please remember you can always visit www.JimRaffel.com to review an archive of previous Golden Nuggets. There is still time to register for our User’s Group Conference coming up August 21-23 at the Mirage Hotel in Las Vegas, NV. You will need to call us directly at 262-820-1131 to make all arrangements at this late date.

*** Jim Raffel’s Week 8 Golden Nugget…Is it a Specification, a Guideline or a Process Capability? ***

We are often asked how to set both reference values (sometimes called target values, or gold standards), and the tolerance window associated with the reference values that have been set. I will start by saying my choice with all other factors being equal is to set both the reference and tolerance based upon process capabilities. Process capabilities are the most difficult of the three to explain so I will begin with the other two.

We define a specification as a reference value and tolerance range provided by the print buyer. For example, consumer product company K writes into the print contract that all special colors must be maintained within 2.5 Delta E of the L*a*b* values they provide for the color. If you are thinking a specification is something like SNAP, GRACoL, or SWOP (not a breakfast cereal by the way), please read on to see the way we define them.

We consider SNAP (Specifications for Newsprint Advertising Production), GRACoL (General Requirements for Applications in Commercial Offset Lithography), and SWOP (Specifications for Web Offset Publications) to be industry guidelines. While I am POSITIVE I will get several e-mails letting me know how wrong I am on this, let me explain. I look at it this way. Unless one of the above guidelines has been written into a contract, it is just that a guideline. Once a print buyer adds a clause to the contract that says print will conform to SWOP, it becomes a specification. What’s the difference? Well, you loose money and customers if you do not achieve specifications written into contracts. Guidelines on the other hand are a great aim point for jobs and customers who do not provide written specifications.

Process capabilities are a whole different ball game. I will not be able to do the topic justice here, but we are devoting almost 1/2 day at the User’s Group Conference in less than 2 weeks to this topic. Basically process capabilities are determined by operating under normal conditions for an extend period of time. Over this period of time samples are collected and measured. For example, in an ink jet proofing environment you would run for an entire month to collect samples on different shifts and under different temperature and humidity conditions. The samples are then analyzed using statistical methods to determine mean (average) L*a*b* values, and the accompanying standard deviation of the aforementioned values. Your reference (or target) is then set to the mean L*a*b* values, and the tolerance is set to a factor of the standard deviation. In ink jet proofing we have found a plus tolerance of three standard deviations to be achievable 99% of the time. When speaking of Delta E, the minus tolerance is not a factor. If your mean is Delta E over time is say 1.5, and you then run proofs with a mean Delta E of .1, they will be visually acceptable.

So, for my week 8 Golden Nugget, I have once again chosen to enter controversial waters. I look forward to the e-mails questioning my statements above and offering alternative views. Also, remember you can simply add comments to each golden nugget at www.JimRaffel,com, and all readers will seem them even if they are not included in a later golden nugget.