An article by Geoff Bassett, published in TRADA Timber Industry Yearbook 2000.
Developments in machinery
During the last one or two decades if one were asked what was the most important influence on woodworking machinery the immediate reaction would be "Computer Numerical Control." Without it there would be no CNC routers or electronically controlled panel breakdown saws, point-to-point drilling machines and a host of other machines. Most of the ways in which computer control has enhanced the performance of woodworking machinery are well known so it may be opportune to look at other developments as well. To this end it is worthwhile examining the way in which the entire industry has made different demands on the suppliers of machinery and ancillaries.
A powerful influence has been the recognition of the need to keep the investment in work in progress as low as possible. Large stocks of parts tie up the company's capital so it is essential to turn every component into a saleable unit with a minimum of delay, which brought the change from making runs of panels in the order of thousands to making a set of parts as a complete group, assembling the product and despatching it. The name of the game was 'flexibility' and it brought dramatic changes to the woodworking industry, but not to the front end of the business, the sawmills which is a good place to start.
Profitable sawmills run continuously with logs butted to maintain a continuous high output. This means careful grading in the logyard to ensure that logs of identical diameter and length can be run together for long periods. Inside the mill however, a limitation is imposed by the life of the sawblade, usually either a half or whole shift. This has been recognised by the saw makers and about two years ago Swedish steelmaker Uddeholm introduced a new steel called Anka-R for long life bandsaw blades.
Anka-R is intended for use with Stellite tipping. It is a flexible steel with good tensile strength which does not suffer readily from cracking when run over the pulleys for long periods and, under suitable conditions, has run for periods well in excess of 20 hours. However, although the new steel will run for long periods the life of the blade is now limited by the Stellite tips which become dull after about 20 hours so new development work is aimed at improving the tip life, possibly by brazing tungsten carbide tips onto the steel sawblade in a construction similar to that of circular saw blades.
Bandsaw blade development is being approached very seriously and Skellingthorpe Saw Services of Lincoln has been granted a Department of Trade and Industry SMART award for a research and development programme for a high speed cutting bandsaw. This programme with a budget of £70,000 aims to increase the feed speed of the timber, reduce drag and friction and improve sawdust expulsion to a point where feed speeds can be doubled.
A British development, which has found widespread adoption in cold countries where frozen logs present a common problem, is an electrical control system developed by Fenner of Hull. This senses the electrical load imposed by the saw motor. When the load increases due to the hardness of the log the feed speed is slowed, allowing cutting to continue without overloading the saw. In the past, the control was exercised by the sawyer who often had to stop the line with a loss of output and users say that the Fenner control system has increased output and eliminated sawblade damage.
For flexibility in manufacture the most important sector is the cabinet industry where past practice was to produce long runs of panels, move them to storage and draw them off either for assembly or packing in the case of self assembly units. Holding large stocks was expensive and a method had to be found to make a cabinet as a continuous process, cutting all the panels simultaneously.
An early approach was to saw the faced board into strips, edge-band them and then cross cut to length for gables, tops, bases and shelves which were then edge banded on the short edges before final drilling and assembly.
The introduction of edge-banding machines with electronic control helped this procedure as it eliminated the need to set the microswitches which triggered the working heads whenever the panel lengths changed. A sensor at the front of the edge-bander read the leading and trailing ends of the panel and sent the information to a computer which already held the speed of the conveyor chain. With this data it timed the heads to operate on the approach of the panel and, since all the panels were the same width there was no need to change the setting of the machine.
Although this system gave good working for small batch production it was still not capable of coping with the random mix of panels if narrow shelves were included with gables tops and bases, but a solution could be found by using a suitable arrangement of single sided edge-banders.
A typical example is that devised by Spanish maker Egurko-Ortza who call their arrangement the Courtyard. It comprises two single sided edge-banders linked by a 180° transfer, the first machine usually having a short squaring unit at the front. This unit can be pre-set for the panel width from the central computer, using a bar code reader to scan a label on the panel. Although this takes only seconds it is usual to run several panels of the same width at a time.
When a panel is fed into the line it is squared, the length is read by the infeed sensor and it is banded along the right hand edge. The machine can be equipped with all normal heads including double-ended heads for post-formed panels.
On discharge from the first machine the panel is transferred laterally to the second edge-bander where the untreated edge is aligned to the fence of the machine and edge-banded, the second machine being equipped with the same working heads as the first. The entire system is quick, easy to set up and copes efficiently with any mix of panels required to complete a cabinet.
Staying with panel processing there is an increasing trend towards the use of vertical panel processing machines. Although the two principal makers of these machines, Brema and 2BR, introduced them some years ago they have only recently gained wider adoption, but they are now used not only in isolation but in complete working lines and it may be interesting to look at their background.
Past practice was to include through feed panel drilling machines in panel production lines after the edge-banders, but when edge-banders became faster and produced thirty or more panels per minute the drilling machines, running at about 20 to 24 panels per minute could not keep pace. At this point drilling was done off line, usually by combining two or three drilling machines to cope with complex hole patterns and adding feeding and stacking. These machines drilled from below so that the wood chip fell out and did not contaminate the panel.
Then came point-to-point drilling machines which had the benefit of flexibility, but were slower than the through feed machines and drilled from above, which imposed a need to remove the chips from panel and machine.
Standing the panel on edge on a conveyor belt, advancing it to a reference stop and then moving it back and forth under precision computer control to present it to clusters of drilling heads allows panels to be drilled from both sides and cutting grooves in the panel at the same time. A variant of the same machine was designed for end and top edge processing and by putting the two in tandem with a short conveyor the entire boring operation can be carried out. Then came gluing and inserting heads for dowels, assembly fitting and hinge inserters and specially designed feeding and stacking equipment.
Linked vertical processing lines are now achieving considerable success in Europe, providing the flexibility and productivity to match the single sided flexible edge-banding lines!
Vertical processing does not necessarily infer costly and complex machinery; SCM of Rimini has for some years made a competitively priced vertical drilling machine called the Unitech.
It is said that because finishing a product is the last process in manufacture it is also the last thing to get any consideration! Having dealt with some of the aspects of manufacture it is time to realise that developments in machinery are not the only advances that affect woodworking. The need to minimise discharges of organic solvents has brought changes to the finishing industry and powder coating, which is solventless, is making strong progress as a finish for wood-based sheet materials, especially MDF.
Sonneborn and Rieck have spent several years developing the process and now run three production lines making the powder which is sprayed from an electrostatic gun onto the pre-heated component and then cured at high temperature. The finish can be glossy, matt or textured and, being based on very tough resins, it is extremely durable and conforms perfectly to the shape of the article that is coated.
