Dowel Mills - Production Methods

By Alan Froome on TimberLineMag.com 5/1/2004

RATON, New Mexico — Western Wood Products Inc. is not new to the post and pole business. Owner Ray Levengood has been running a plant in Mountain View, Wyoming since 1991 where his company produces about 6,000 components daily. The plant produces poles and posts ranging from 3-8 inches in diameter.
“We recognized an opportunity and decided to build a second plant,” said Ray. He picked a location in Raton, New Mexico and started to design a new mill. “Very few people are as serious as we are about the post and pole business,” said Ray. “I wanted to build the best plant I could and traveled all over, looking at ways to process small logs.”
WWP has been operating dowel mills since 1993 when the company invested in equipment from Round Wood Systems (RWS) of Montana. It bought two more machines in 1997.
Ray started discussions with Round Wood Systems in 2002 about an improved machine design for the proposed new plant in Raton. He specified consistent production, reduced maintenance and high quality product as his main priorities. Round Wood Systems subsequently supplied two machines that were custom designed to meet his specific requirements.
“We started to build the new plant in September 2003 and took delivery of the first RWS dowel mill in January 2004,” said Ray. “The second mill was delivered in February. The new mills are a tremendous improvement over the old ones at our other plant.” The new design features seal-less heads, and Ray expects the new machines to prove much more durable compared to the old machines.

New Plant
The new plant in Raton is designed to be a first class, state-of-the-art facility. Logs are debarked, electronically scanned to determine diameter and length, and then sorted according to eight sizes prior to processing.
The plant contracts for logging and usually works with logs from 4-12 inches in diameter and from 6-16 feet long; the preferred length is 8 feet. The logs are debarked by a Valon Kone Brunette (VKB) 16-inch ring debarker and then passed through a scanner that controls the eight sort system downstream. The sorting system was supplied by Precision Sawmill Sorting from Montana with a log scanner from WGBM.
“We sort them as we like to run all day without changing the cutter heads on the dowel mills,” Ray explained. “It takes about an hour to change a head.” He added, “We grind our own knives and replace them twice a day at Raton, but we are trying to get a full 8 hours with the new machines.” (On the older dowel mills at the Wyoming plant, the knives are changed three or four times daily.)
After sorting, the logs are fed by a belt conveyor into one of the two Round Wood Systems dowel mills. If a log has an extremely high taper, it will pass through the larger mill and then be kicked out to be processed on the small machine. A four-gang drill is used to drill holes in fence posts as required. Afterward the posts are transferred by belt conveyor to a 140-foot long green chain, and workers pull them off and stack them by size. After bundling and strapping, final length trimming is carried out by an L-M Equipment Co. package cross-cut saw.

Dowell Mills
Dowel mills are machines designed to process raw unbarked logs directly into dowels or other round wood products such as poles, fence posts, furniture parts and other round wood components that require accurate size and smooth finish. Logs must be delimbed before processing although debarking or rough sizing is not necessary before feeding them into the RWS machine.
RWS manufactures two basic sizes of dowel mills for either fixed mill floor installations or portable trailer mounting. The smaller RWS-6020H machine produces round wood dowels 2-6 inches in diameter from rough logs up to 9 inches in diameter; the larger RWS-8040H machine turns out dowels from 4-8 inches in diameter from logs up to 12 inches in diameter. An optional second head that will make 2-4 inch dowels can be fitted to the larger machine to extend its range.
The process of converting logs into round wood is accomplished in two steps. The infeed and outfeed systems accurately center and guide the log through the cutting head and prevent it from turning in response to the torque exerted by the knives. The log does not spin or turn.
According to Round Wood Systems, its machines can reduce labor by one half and increase production 100-200% compared to labor-intensive machines that turn the log. “We now have 30 machines in operation and have been building them for four years,” said sales manager Ed Smith. “Our latest design is improved so they run more smoothly and need less maintenance.”
The dowel mills can process logs at speeds up to 110 linear feet per minute, said Ed, although most companies run them at speeds of 50-80 feet per minute.
“The mills can process almost any length logs,” he added. “They are only limited by the log butt size. However, most mills run logs from 5 to 20 feet long.”

Round Wood Systems
Montana Hydraulics opened for business in 1998 in Helena, located in the forests of central Montana. In the beginning the company kept its machine tool and fabricating shops busy by provided mechanical and hydraulic service to anybody who needed it. This initially included work for the sawmill, logging, railroad, and construction industries in the region. This diversified service continues but today also includes the manufacture of precision-machined components for the aircraft industry.
In 2000 the company began supplying components to Montana Manufacturing, which was building dowel mills in the area. A year later Montana Hydraulics began building the complete machines, and in 2002 it bought the manufacturing rights for them from owner Harold Bouma.
It established a separate division to further develop these and other machines. Round Wood Systems (RWS) was formed in 2003 to focus on the design and manufacture of sorting systems, trim saws, dowel mills and their associated material handling and conveying systems. RWS employs about 20 personnel at present. Some of the key people include general manager Mark Ehlke, sales manager Ed Smith, purchasing manager Charlie Wiles and engineer Richard Hogan.

Dowell Mill Specifications
The RWS dowel mill has five main components: main frame, infeed, cutting head, outfeed and hydraulic system. There is also an electrical control console for the operator.
The main frame features one piece welded construction and supports pairs of feed rolls to guide the logs into the cutting head and prevent them from twisting as they go through the machine. Both the 6-inch and 8-inch dowel mills utilize the same frame design, but the 8-inch model is longer because it uses four pairs of feed rolls — compared to only three pairs on the 6-inch machine.
The mill infeed section guides the logs into the machine and comprises a number of smooth machined bed rolls. They work in combination with upper toothed rolls to grip the incoming log. The upper and lower rolls are mechanically linked to maintain a log center line concentric with the cutting heads and are mounted on cantilevered spindles. Squeeze pressure and roll drive is applied hydraulically, and the operator can adjust the squeeze stroke to optimize the log feeding action and resulting throughput. All roll bearings are sealed, tapered roller-type with grease-zerk fittings. To reduce maintenance, no ball bearings, roller chain or keyed shafting are used in the construction.
Cutting heads are supplied for three dowel size ranges: 2-4 inches, 2-6 inches and 4-8 inches. Each size head can be adjusted to produce a series of standard dowel sizes within its range. In addition, RWS can supply non-standard bushings on request to make custom sizes. For the most efficient operations, RWS recommends running the smallest size head capable of cutting the required post or pole diameter.
All RWS dowel mill heads use the same five bolt and three locating pin pattern, which ensures the head-machine centerline will be maintained irrespective of the size head fitted over the entire life of the machine. The heads are driven by an electric motor, and both the 6-inch and 8-inch capacity dowel mills have a drive platform designed to suit both 50 hp and 100 hp motors. Normally, the smaller machine uses a 50 hp motor and the larger machine use a 100 hp motor. In addition, a 20 hp electric motor is used on the hydraulic power pack.
Each head has three roughing knives that make the first cut and three finishing knives to make a smooth, finish cut. The knives are made of tool steel and ground to suit the individual application, depending on the customer’s wood species, moisture content of the wood, desired log feed speed, and other factors.
Head bearings are tapered roller type with adjustment by shim packs and lubricated by pressurized oil spray, which also provides cooling. Oil flow is provided by a gear type pump, belt driven by the main head motor to directly link the lubrication flow to the head rotation. The lubrication tank is separate from the main hydraulic system. Oil containment in the head is provided in a ‘seal-less’ manner using centrifugal force on the oil in the return direction rather than conventional lip contact type seals. According to RWS, this results in lower rotational drag, reduced maintenance and longer life.
The outfeed section continues to guide the material after it exits the cutting head. The resulting dowel is carried by smooth machined hour-glass shaped rolls mounted on cantilevered spindles with upper press rolls running in tapered roller bearings with grease-zerk fittings. Drive is provided by hydraulic motors, synchronized to match the speed of the infeed section.
The hydraulic system provides power to the infeed and outfeed rolls, the squeeze cylinders and outfeed kicker. A single 20 hp electric motor drives two pumps in a ‘piggy-back’ configuration. A tandem hydrostatic transmission pump supplies the feed drive, and a pressure compensated pump supplies the squeeze cylinders and kicker. The infeed hydraulic motors are connected in series, and the circuit is separate from the outfeed section; the outfeed motors are also in series. Both circuits are mechanically connected and actuated by a single electric device.
The hydraulic system oil tank is provided with a filter, heater for cold weather operation and a cooler to protect from overheating. An accumulator is also supplied for the squeeze cylinder circuit to provide compressibility and fast response.
RWS can also supply a belt infeed and outfeed conveyor to complete the customer’s production line. In addition to the dowel mills, RWS manufactures an automatic pointing machine to sharpen a point on fence posts or stakes plus a five-drill gang drill that can drill up to five holes in one pass.

Start at Western Wood Products
The most recent installation of an RWS dowel mill was at Western Wood Products in Raton, New Mexico. Two machines were installed in February. In March, when Ray talked with TimberLine, Western Wood Products was still in the initial ramp-up period.
“We are having a few glitches getting the new plant up to full production, but the new dowel mills are a tremendous improvement over the older ones,” said Ray. “Our target is 6,000 pieces per eight hour shift from the two mills, and we got 3,100 pieces from one machine on the first day, so we think it’s realistic.” By way of comparison, at the company’s plant in Wyoming, it takes three dowel mills to produce about 6,000 pieces.
The dowel mills supplied by RWS are new, improved designs that are intended to provide smoother running and require less maintenance.
When asked about debarking, Ray said, “We run lodge pole pine at our Wyoming plant and do not debark the logs. However, at Raton we run a mix of Ponderosa and yellow pine, and I have found it better to debark the logs first.” Ray added, “We also sell the bark for landscaping material and the shavings for animal bedding.”
Western Wood Products ships posts and poles all over the U.S. “When we introduced dowels to the fence post market, people were really impressed,” said Ray. “One lot of ranchers came all the way from Florida to buy our posts. Compared to peeler cores, which are all heart wood, the dowels are much more stable and don’t warp in the hot sun.”
The new plant employs 15 people but will increase to 22 when it is in full production. The company has been warmly received in Raton. “I have never been in such a great community,” said Ray. “The folks here are really awesome.”