Moulders make their (cutter) mark on productivity.
If a productivity challenge were issued between woodworking machinery with the winner being judged on the amount of sawdust generated, moulding equipment would surely make the finals. Long associated as a workshop workhorse, moulders perform the basic function of profiling smooth faces so they can either take a finish evenly or allow adhesives to effectively penetrate the wood surface. Couple this responsibility with today's increased productivity demands, and modern moulding equipment is being pressured into meeting all of these needs.
But some companies may be sacrificing productivity and finish quality by operating moulders with incorrect feed speeds and improper tooling, or failing to properly adjust to the set-up requirements of the specie of wood being machined. In addition, some new technology can provide an additional boost to productivity without requiring a new machine purchase.
The key to recognizing some of these problems may be right under the operator's fingertips. One telltale way to find out if a moulder is producing an optimum finish is to look at a freshly machined piece and examine not only the quality and feel of the surface, but also check the knife marks left by the moulder.
Arguably the most important indicator of moulder performance is the tiny, scalloped moulder marks left on a freshly moulded piece of wood. Knife marks per inch (KMPI) is the number of times a knife from the cutterhead strikes the wood in a 1-inch section, and can speak volumes about a moulder's performance.
"The number of knife marks per inch required can range from just nine to over 20 KMPI, depending on the produces application and industry standards," said Jon Morris, marketing manager with Michael Weinig Inc. "A piece of hardwood moulding may have as many as 20 KMPI to meet Architectural Woodworking institute (AWl) 'Custom' standards, while an exterior trim moulding installed high on the wall may need only 12 KMPI. These industry standards have generally developed according to the visible acceptance for the specific application."
The number of cuts depends on the feed speed of the machine, the rotational speed of the cutterhead and the number of knives in the cutterhead. (See sidebar on page 89.)
"Regardless of the type of wood being used, if you change the feed speed up or down, the finish will change," said Gary Fredrickson, sales manager with Diehl Machines. "Too slow of a feed speed can be just as bad as too fast concerning finish quality."
Too slow feed speeds may offer a finish that is pleasing to the touch, but can limit knife life and create a defective surface.
"Too slow conditions cause the knives to dull more quickly. In addition, the finish on the surface is so smooth that the pores of the wood are sealed, which prevent stains from penetrating," said Start Paszkowski, national product manager-moulders with SCMI.
Too slow feed speeds can also cause other quality problems.
"Because of the smaller chip size at slower speeds, more heat builds in the knives, leading them to dull much faster," said Morris. "And dull tools are a common reason for poor quality since they significantly increase cutting forces, which causes irregular knife marks and chatter if the wood is not controlled properly."
Too fast feed speeds may cause fewer knife marks per inch, and thus result in poorer surface quality. This loss of quality in finish can cause production bottlenecks down the production line, such as more time needed to sand down the planer marks before finishing.
In the case of moulding MDF, feed speeds which produce boards requiring a minimum of sanding require 20 KMPI instead of the accepted 16 KMPI for natural wood, according to the National Particleboard Assn. (NPA). If feed speeds are too fast or when the cutterhead has too few knives or rotates slowly, these ridges will be farther apart and can be large enough to be objectionable.
Adjusting feed speeds
Optimal feed speed is determined by a number of variables including finish required, depth and width of cut, type of material being cut, length of production run or capacity of the moulder. If a company desires to increase its moulder's feed speed, it must remember that finish may be sacrificed at the cost of increased output. Companies should check to see if their moulders can be adjusted to accept a feed increase or decrease.
"Increasing the feed speed without jointing the cutterheads will only widen the distance between knife marks," said Fredrickson. "On moulders with belted spindles, cutterhead jointers are required when you want to maintain finish quality at increased feed speeds. If the machine is not equipped with cutterhead jointers, little can be done to increase the feed speeds and maintain the same finish quality, unless jointers are added to the machine. Direct-drive-type moulder spindles can use cutterhead jointers and/or high-frequency drives to increase the feed speed."
Hook angles can improve finish
If surface quality is less than expected, another area which can result in a poor finish is incorrect knife hook angles in the cutterhead when machining a certain specie of wood. Hook angle is the angle of the knife when it is secured in the cutterhead. This is set by the cutterhead manufacturer and generally ranges from 10 to 22 degrees.
"Knife angle and speed variation between softwoods and hardwoods can make a difference in the finish quality," said Howard Pruitt, vice president of Pruitt Machinery Inc. "Generally, there should be less hook angle for hardwoods and more hook angle and less speed for soft pines. Also, by jointing and balancing knives, one can get more knives into the cut and therefore run at faster speeds and still have the desired 16 knife marks per inch."
"The one area that is routinely consistent in improving the quality of the finish is the cutterhook angle," said Paszkowski. "Many woodworkers don't consider the hook angle, they just use whatever head happens to be available. To pick the right hook angle for a particular specie of wood, refer to the charts in the many tooling catalogs. Tooling manufacturers are now offering dual hook angle cutterheads which allow users to use one head for both hard and soft woods."
When machining MDF, the MDF from Start to Finish pamphlet from the National Particleboard Assn. recommends that tooling angles should generally be greater for MDF than for natural wood with hook or rake angles between 10 and 25 degrees, depending on the board and design.
Different woods, different needs
The type of wood being machined plays a key role in determining the quality of finish which will be achieved. Because of such differences as densities between species, man-made versus natural material and other factors, operators must identify what they are machining and make the correct adjustments. But sometimes, experience is the best guide.
"Wood characteristics can change from batch to batch depending on the moisture content, geographic origin and even how it was dried. The best results are achieved through trial and error," said Paszkowski.
"The choice of feed speeds depends primarily on the type of wood used," said Jan Bultiauw, sales manager with Guilliet, distributed by Atlantic Machine Tools. "For hard or wet timber, one has to slow down the feed speed. The knives used to dress such types of wood should range between 30 and 40 degrees."
Engineered wood products, such as MDF, have gathered much acceptance in the industry as a more cost-effective alternative to solid wood in some situations. Because MDF is made with different wood species and binders, and in different densities, the highest quality cutting tools should be used on MDF because it is generally denser than most natural woods and contains thermosetting resins which are abrasive, according to the NPA.
Lacking grain and other characteristics found in lumber, MDF must also be treated with its own moulding rules. Because of its sharp, clean edge machining with minimal treatment, MDF can be machined to configurations similar to natural wood.
"MDF moulding is becoming more popular as the price of solid wood keeps climbing," said Paszkowski. "My experience has shown that MDF can be fed at a higher rate of speed to achieve a good finish."
"Carbide tooling is commonly used with MDF," said Fredrickson. "MDF finishing characteristics are different from wood fiber, and knife marks are not as prominent."
Faster set-up times
With such factors as just-in-time manufacturing and shorter production runs resulting in more frequent tool changes, the industry is demanding that moulders be able to juggle a wide variety of setups and cutterhead patterns.
"Moulders with traditional set-up features can kill your productivity," said Paszkowski. "Most moulders in operation and some new ones can take 30 to 45 minutes for most setups. We won't even include the amount of moulders still in use which were built in the '30s, '40s and '50s that may take as long as two hours to set up.
"Using 30 minutes as an average, if I do six changeovers per shift, it will take three hours to complete (30 minutes x six changeovers). Take another one hour for lunch and breaks and that leaves four hours of running time. If the moulder is running at 35 fpm, the production will be 8,400 lineal feet per shift. But a fast set-up moulder averages five minutes per setup. The savings in time is 2 1/2 hours per shift or an increase in production of 5,250 lineal feet per shift. This represents a 62 percent increase in production," Paszkowski said.
Ability to network
There is new technology on the market which allows management to keep track of productivity not only on moulders, but on other equipment also. Called management information systems (MIS), the data provided by MIS can help management to create production schedules and streamline the manufacturing process. The goal of the system is to help moulding operations and other areas become more productive and profitable.
"MIS can be installed on any age or manufacturer of moulder," said Fredrickson. "MIS monitors and collects data in several areas including shift evaluation, operator performance, profile efficiency, causes of downtime, actual production time, set up times, material yield, etc. This information is collected in a historical database, and is used by management to help make better decisions in the future. Knowing where problems have been helps management avoid making the same mistakes twice."
By using the correct feed speed, knife marks per inch and knife hook angles, moulder operators can improve surface finish quality. Couple these machining operations with the modern technology of decreased set-up times available on many of today's moulders and current MIS technology, and a moulder operation can experience maximum productivity with a high-quality finish.
The following roundup contains some of the moulding equipment available to the woodworking industry. For additional information, circle the corresponding numbers on the Reader's Service Card or consult the 1996 Red Book Buyer's Specification Guide.
The Superset 23 moulder from SCMI uses tool diameter data to automatically set working parameters such as finished size, feed rollers, pressure shoes and fences. The non-CNC set-up is accomplished in as little as four minutes including tool changeover, according to the company. Additional benefits include a direct gear driven, multi-roller feed system for smooth throughfeed and the ability to handle profile tooling diameters up to 200mm and machine workpieces as short as 435mm in length.
Iida moulders from Pruitt Machinery Inc. come in a range of 4 in. wide to 15 in. wide and feed speeds range up to 400 fpm. Manual set-up, to digital, to full computerized set-up is available.
The Martin T-90 moulding unit from Eric Riebling Co. Inc. features a planing width of 22mm to 260mm, planing height from 6mm to 160mm, advanced digital control with pre-selectable dimensions of workpiece, short downtime for cutter changes and automatic lubrication of machine table. Additional features include variable feed speed from 4 to 25 m/min., feed drive with automatic brake and pneumatic pressure control of feed rollers with centralized pressure adjustment.
The computerized positioning system (CPS) is offered on the 400 and 600 series moulders from Diehl Machines. According to Diehl, the system is reported to offer first piece accuracy, 75 percent improvement on set-up time, simplified programming, capacity to store thousands of patterns online, networking capabilities and ongoing moulder performance data. The data collected on the CPS allows management to monitor and evaluate the operator, pattern, and machine performance and estimate production times.
The Pinheiro Model 1000/4 planer/moulder from Auburn Machinery Inc. features the Quickset Tooling System. The system uses stacked tooling and moving side spindles to minimize set-up time without the use of computers. They are modular in construction to allow additional spindles, arbors and feed rolls to be added at any time. Auburn says the system can also lower tooling costs by utilizing the entire knife of the blade, as well as lower maintenance costs by being able to control the wearing of tables, feeding and guiding components.
The Guilliet Model KXR four-side straightening moulder from Atlantic Tool Inc. features hydraulic counterbearings, standard throughfeed speeds of six and 36 m/min. Higher feed speeds up to 120 m/min. are optional. The machines can be obtained in any spindle configuration and several options are possible, such as straight or profile jointers for a precision finish.
The Hydromat 23 moulder from Michael Weinig Inc. features a high feed speed of up to 260 fpm, reported ease of set up and tool jointing with Weinig's new Auto Joint system. The moulder is also reported to meet Europe's new stringent CE safety requirements, and the Hydromat 23 is offered in a broad range of configurations to meet production goals and budgets.
The Paulson moulder from Tyler Machinery Co. Inc. has four high-speed cutterhead spindles mounted to a compact and rigid cast iron machine frame. Stock is fed through the machine using four spring-tensioned powered feed rollers. A fifth cutterhead spindle for pre-surfacing or a sixth spindle for outfeed machining are standard options. The moulder has a maximum lumber cross section capacity of 2 in. thick and 6 in. wide.
The Kuwahara Model KPF-5S-220 compact moulder from Tekmatex Inc. is a moulder capable of operating with or without computer controls. Additional features include machine hood to reduce cutterhead noise and dust extraction chutes.
Wadkin's XE220 moulder is reported to offer feed speeds up to 60 fpm, resulting in fast throughput and quality finishes, according to the company. Other features include cast-iron body, radial chip breakers fitted to top and near side spindles that eliminate setting of chip breakers, and fully interlocked safety cover with large windows for visibility.
Wilke Machinery offers Bridgewood moulders including the BMW-314 planer/moulder and the BW-462M four-sided, five-spindle motor with a moulding capacity of 6 in, by 2 1/4 in. Heavy cast iron construction and variable infeed rates are additional features.
The SP Series moulder/planer from Mida-U.S.A. Inc. can be used as a heavy-duty roughing planer, a cabinet planer or a large moulder for sizes up to 8 in. to 28 in. Helical carbide heads for rough planning, six knives for standard planer heads for fine finishing or special moulding heads for profile work can be used. Feed speeds are rated at 25 to 185 fpm.
Mattison Woodworking Machine Co. reconditions moulders including the ability to add variable hydraulic roll feed, solid state spindle controls and digital readouts.
RELATED ARTICLE: FIGURING YOUR MOULDER'S KNIFE MARKS PER INCH
Finding the amount of knife marks per inch (KMPI) on your moulder can be the key toward obtaining the best possible finish. Too few KMPI can offer a rough finish requiring additional sanding. Too many KMPI can cause burning or glazing of the planed surface.
Sixteen KMPI is a good number for achieving a quality finish. To figure the amount of KMPI, use the following formula:
Machine RPM x number of knives(*)/Feet per minute x 12
Example: With a moulder using 6,000 rpm spindles and a feed rate of 31 fpm, the KMPI would be 16.
* NOTE: When applying this formula, use one knife in your calculations regardless of the knives in your cutterhead unless you are using a jointed moulder.
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|Publication:||Wood & Wood Products|
|Date:||Apr 1, 1996|
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