The Milling Report

By David Savastano, Ink World Editor | 09.09.05

Equipment manufacturers are hopeful that the gains they saw in capital expenditures at the end of 2002 will continue into 2003.

While 2002 was another slow year for the printing ink industry, there was some improvement in sales in the second half of the year. The same can be said for many mill suppliers to the ink industry, who saw some projects released in the latter part of the year.

Considering the interest in Six Sigma and other manufacturing processes, there is much interest in equipment that improves efficiency and consistency. The growing field of nanotechnology is also leading ink companies to investigate finer particle sizes. Whether these trends will lead to a surge in mill orders in the coming year remains to be seen.

Among the new mills are, clockwise from top, Eiger Machinery’s Alpha production mill; Premier Mill’s QMAX Supermill, and Buhler’s ZR 120 ‘Nano-Mill’ centrifugal bead mill.
Capital Spending in 2002
Most equipment manufacturers reported that they saw a slight surge in orders during the fourth quarter of 2002, as companies found that there was room in their budgets for some equipment purchases.

“At the end of 2002, it seemed that more companies had some extra money left in the budget which allowed them to fund some capital improvements that have been held over due to the economy and concerns about 2003,” said Dave Peterson, vice president of Eiger Machinery.

“We have seen a surge in equipment orders during the fourth quarter that resulted from projects that were on hold through 2001-2002,” said Harry Way, manager of research and development at Netzsch. “We also see an increase in new projects and applications that indicate the capital equipment market is on the rise for Netzsch. For our fiscal year 2000-2001, we saw roughly a 20 percent increase in sales; 2001-2002 was basically flat. Considering the events and the state of the North American economy for this period, although we did not see an increase in sales, we feel we were still successful.”

“2002 was better than expected,” said Richard Lindstrom, product line manager, inks and industrial coatings for Buhler. “While not great, there was good activity. Looking forward to 2003, there is strong interest in conventional milling equipment as well as continuous process and our process engineering capabilities. Digital is not a large market yet, but will continue to grow into a major market.”

“2002 was a modest year for many areas although some high-performance companies in coatings and specialty inks have bought new equipment to enhance production/quality capabilities,” said Dave Pagor, national sales manager for CB Mills.

Mr. Lindstrom said that there is renewed interest in dry pigment processing.

“The low price of dry pigment being sold from off-shore sources had definitely had an effect on the U.S. ink industry, and ink companies are investing to capitalize on this change,” Mr. Lindstrom said.

Equipment manufacturers have found that in spite of budgetary constraints, ink companies will buy equipment that gives them an advantage.

“Traditional capital expenditures for ‘replacement equipment’ are still on hold,” said John Sneeringer, technical director at Premier Mill, a Lightnin Company. “We have seen scattered new projects that are driven by technical considerations and are not limited by the same capital constraints.”

Key Requirements
When ink companies are analyzing equipment, they are looking for certain qualities, such as the ability to create finer particles and provide better consistency.

“Everyone is looking for higher production rates and better quality products,” Mr. Peterson said. “There’s a lot of interest in equipment that can proof raw materials before production begins.”

“Quality requirements are changing in some industries, such as electronics, ceramics and automotive dispersions,” Mr. Sneeringer said. “Our customers require finer particle size and more narrow particle distributions. In viscous mixing applications, customers require more uniform paste mixing and shorter mixing cycles.

“However, I would say the key requirement our customers are looking for is higher productivity, meaning more pounds per hour, or more gallons per hour,” Mr. Sneeringer continued. “Our customers are being pressed by competition to make their same quality much faster, more efficiently with less manpower. This translates to lower manufacturing costs. More and more mixing and dispersion equipment is being purchased with automatic process monitoring and control systems to provide process data, insure repeatability, and minimize the potential for operator error.”

“Our customers are looking for smaller particles, many new nanoparticle applications, consistency, reproducibility, better color development, greater transparency and higher gloss, and as always, max throughput,” Mr. Pagor said.

“As business becomes more competitive and margins are compressed, our customers have requested machines and technologies that allow them to be more efficient in two main areas,” said Randall Seaman, Latin America sales manager for Hockmeyer Equipment Corporation. “First, in manufacturing productivity – batch process times and conversion costs have become two critical indicators of manufacturing efficiency as looked at by our customer base. There is a demand to produce the same or greater volume of production in less time as measured by both labor hours and equipment utilization. Our machine technology, especially mills, have received ongoing engineering to produce more product, in less time and with reduced maintenance downtime. In some cases, we have improved production efficiencies by 400 percent to 600 percent over previous methods.

“The second is product quality and batch repeatability,” Mr. Seaman said. “Many of our clients are ISO certified or participate in some other equivalent ‘total quality’ system. The quality systems are driving our customers to continually tighten the quality acceptance parameters of their products.”

Color accuracy is one of these critical components.

“Among these quality parameters is the indicator of ‘first time right,’ Mr. Seaman said. “Most paint and color-related products are generally rejected by quality assurance for being off color as received from manufacturing. This requires time and additional materials to be added to the batch to bring it into the formulated color specification. Most often, out-of-spec colors result from inconsistencies in the milling process as measured by the ‘Hegman’ grind system.

“In order to provide more accurate measurement of pigment deagglomeration and particle size reduction, we have developed technology to statistically analyze individual particles in the batch,” Mr. Seaman said. “By measuring and controlling particle size to statistical specifications, we can offer our clients technology that significantly improves ‘first time right’ performance and batch-to-batch repeatability indicators.”

The area of nanoparticles is particularly promising, and in order to reach those sizes requires advanced milling techniques.

“There’s a lot of interest in nanoparticles, and companies are investigating the potential in this area,” Mr. Peterson said.

Value, service and delivery time also remain concerns.

“Our customers seek improved technology at a competitive price,” Mr. Way said. “This means machinery that improves the product quality at increased production rates while decreasing operator supervision and maintenance costs for basically the same price as existing technology. Quicker delivery times for machines have been one area where we have seen improvement not only in our company but from our competitors as well.”

“Customers are more value-orientated now rather than buying strictly on price,” Mr. Lindstrom said. “Service is also a key issue.”

New Products
To meet the requirements of ink manufacturers, mill manufacturers have developed a variety of new products.

Buhler’s ZR 120 and Eiger Machinery’s Alpha production mills are two of the new generation of mills that can produce nanoparticles.

“The ZR 120 recirculation mill can handle micro-media and produce dispersions into the sub-micron (nano-meter) range,” said Mr. Lindstrom of Buhler.

According to the company, Buhler’s ZR 120 ‘Nano-Mill’ centrifugal bead mill produces high-quality inks with especially fine particle size. To reduce pigments to a size in the nano-range, the grinding media used in the ZR 120 have a diameter of no more than 0.2 or 0.3 millimeters. The pigment particles are reduced to such a tiny size that if one million particles were lined up, this would produce a line no longer than 10 centimeters.

Eiger Machinery’s Alpha production mills can produce ultra-fine dispersions as well as standard products on the same mill. According to Eiger, the Alpha mill includes an efficient and increased open area media separation system that allows single pass processing or high flow recirculation milling to be achieved with a wide variety of grinding beads. Media sizes down to 0.2 mm can be used, which are important for producing nano-type dispersions. There are a number of options available for computer monitoring and control of the Alpha mill, and historical data can be obtained and reviewed during and after milling.

“Our mills can produce batches as small as 50 ml that will give realistic results, and our new Alpha series can be used to produce nanoparticles as well as regular dispersions,” Mr. Peterson said.

Mr. Sneeringer said that Premier Mill’s QMAX Supermill provides ultra-fine particle size and narrow distribution that ink companies are seeking.

“The QMAX High Flow Recirculation Supermill with Navigator is a perfect example,” Mr. Sneeringer said. The QMAX Supermill high flow recirculation mill contains a new grinding configuration that is unlike those in other conventional disc or peg type media mills, according to the company. The QMAX uses a specific orientation of grinding components to create a unique, multi-directional acceleration of grinding media. A highly aggressive and pulsating flow pattern of the product/ media mix is achieved, resulting in a significant increase in the maximum shear level, compared to conventional disc or pin arrangements. It is designed for use with grinding media as small as 0.1 mm (100 microns).

Mr. Pagor said that CB Mills’ ECM high-energy mill with the Mill-Rite has been the “hot-mover” for CB Mills. “The unique ‘accelerator’ design has been proven by our customers in head-to-head evaluations to be a most versatile and efficient mill system,” Mr. Pagor said.

Mr. Way said that Netzsch’s NKM mill and De-Aerator offer advantages to ink manufacturers.

“The NKM is specifically designed for processing UV inks,” Mr. Way said. “Recently we ran tests on a UV product that showed in one pass we improved color strength by more than 100 percent, and product operating temperature was kept at ambient temperature, less than 75°F. The De-Aerator has shown the potential to reduce batch time as much as 30 percent by processing a premixing through the machine prior to milling. Removing the air from the premix, forcing wetting of the pigment particles by removing the air interface increases the efficiency of the dispersion process.”

Mr. Seaman said that Hockmeyer Equipment has focused its technical effort on the development of a complete particle size reduction package. The system is based on three machinery components. The first is the Hockmeyer HSD Immersion Mill, a rapid throughput ‘immersion’ type mill that allows users to mill pigments to repeatable specifications in shortened production times. The second, the Hockmeyer MicroMill, is a laboratory scale mill which gives formulators true ‘scalability’ to their formula designs and provides consistency and reproducibility to the full-size production scale HSD mills, according to Mr. Seaman.

The third component is the Hockmeyer HPAS Particle Size Analyzer, which Mr. Seaman said is effective when used with any commercially available production technology designed to amend particles in a liquid matrix. It is a computer-driven optical analysis system that takes a photomicrograph of the particles in a sample, counts them by individual particle size, then provides a statistical histogram.

Above, Netzsch’s NKM Mill. At right, Hockmeyer’s MicroMill. Below, the accelerator on CB Mills’ ECM Poly Model.
“Together, these three machines provide manufacturers with a fully integrated formulating, manufacturing and analysis system designed to increase manufacturing productivity while ensuring greater batch-to-batch repeatability and reduced manufacturing costs,” Mr. Seaman said.

While capital improvement budgets have been tight for most ink companies, the importance of providing innovative products to printers does take precedence, which translates into a strong interest in new equipment that can make a difference in production.

“If a company sees that a new piece of equipment will give them a technical or performance advantage, they’ll go ahead with the purchase,” Mr. Peterson said.

The mill manufacturers who can best help their ink customers achieve their production goals will be the ones who will thrive in the future.

Process Improvements and Milling
There has been much discussion in the industry about Six Sigma and process improvements, repeatability and reproducibility and the need to provide a consistent product, and improving efficiency and diagnostics. How are companies meeting these more stringent standards?

"In our industry the key to Six Sigma relies in more efficient equipment, higher energy input and ability to work at higher viscosities and an increasing trend to more automation," said Richard Lindstrom, product line manager, inks and industrial coatings for Buhler. "In the future, I feel the industry will also have to move from batch to continuous processing to further reduce the effect of human error. This will place more demands on equipment suppliers as well as demand consistent, high quality raw materials."

"Most out of spec batches in the paint and color products industries results from inconsistencies in the milling process," said Randall Seaman, Latin America sales manager for Hockmeyer Equipment Corporation. "To achieve consistent tint strength and color development requires that pigments be milled to repeatable specifications for 'total surface area.' This is a statistical function based on the mean particle size bracketed by the standard deviation. Only by analyzing each particle in the matrix and calculating the min/max and mean/standard deviation values for the lot can reasonable assessments be made of batch to batch repeatability.

"In contrast, the Hegman grind system is an observational instrument that allows technicians to see only the largest particles in the sample," Mr. Seaman continued. "This system has two majors flaws: It allows only a narrow particle size measurement range. It is the particle size distribution band which determines batch uniformity and repeatability. Two lots of the same material - both of the same Hegman grind - can have widely different tint strengths due to differences in the particle size distribution band. Also, it only determines the largest particle size, which typically has the least impact on the characteristics of tint strength and color development. The largest particles will have an effect on gloss and film texture, but it is the smaller particles which contribute the greatest pigment surface area. Uniformity of tint strength is important to both mono-pigment grinds such as dispersions and colorants, as well as pigment co-grinds (where the relative strengths of each pigment in the package determine the product color.) By measuring the entire particle size distribution band, then controlling the grind process to achieve the tightest band possible, manufacturers can reduce variability in the milling process."

To meet these needs, milling manufactures offer a variety of control systems.

"Fundamentally these standards can be met with our standard Voyager control system," said Harry Way, manager of research and development at Netzsch. "In the grinding process, monitoring the energy input and controlling the process by automatic adjustment of the energy input and flow results in consistent dispersion quality. With our Voyager system we control the grinding process by running the mill agitator speed by the energy draw of the motor or by the operating temperature of the mill. We control the pump flow by the pressure level in the mill. This automatically optimizes the operating conditions. By entering the amount of grinding energy required for a particular product, a process that is determined either by history or lab experiments, we know that the same product quality will be achieved on a consistent basis. The Voyager has a standard alarm history function that allows in-house maintenance and Netzsch service personnel evaluate what has been occurring with the machine as far as machine faults. This leads to increased production efficiency due to the reduction in downtime and mean time between failure (MTBF), while reducing maintenance costs by eliminating operating errors."

"Premier Mill offers the Navigator Auto Process Control System which can be added to most of our sophisticated processing equipment," said John Sneeringer, Premier Mill's technical director. "The Navigator is an automatic process monitoring system, which includes a PLC with network communication capabilities. This provides the information and 'degree of accuracy' and 'repeatability' that most companies now must apply to their manufacturing processes."

"Our PLC package, Mill-Rite, is included on many of the ECMs and specialty Dyno-Mills," said Dave Pagor, Dave Pagor, national sales manager for CB Mills. "This monitors the specific-energy required to obtain the proper degree of dispersion on documented products. The value must be determined experimentally, but once determined, can be used to program the mill to deliver that required amount of dispersion energy. This ensures consistent results from batch to batch."

"To overcome the shortcomings of the Hegman system, we have developed the Hockmeyer HPAS 2000 Particle Analysis System," Mr. Seaman said. "The HPAS analyzer is a computer-driven optical analysis system that takes a photomicrograph of the particles in a sample, counts them by individual particle size, then provides a statistical histogram (particle size distribution curve) of the total sample along with calculated min/max and mean/std dev values. Whereas with the Hegman system formulators would have indicated a qualitative product specification of, say, grind to a 7 Hegman, we now can create a quantitative, statistical product specification of, say, 5 microns average particle size with a standard deviation no greater than 3 microns. Statistically analyzing and approving production samples by this method allows manufacturers to narrow allowable batch tolerances and provides greater batch repeatability and reproducibility. We believe this technology conforms well to both the spirit and application of Six Sigma and other Total Quality Management protocols."

- David Savastano

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