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Wood Planer | Discussion on planing processing of solid wood furniture

Wood Planer | Discussion on planing processing of solid wood furniture

26 Feb 2022

After the processing stage of "ingredients", the wood is made into specification wool. In order to further process it into parts that meet the requirements of size, shape and surface quality, then planing is called "wool processing". , laying a solid foundation for more refined and richer follow-up processing.

As one of the most important processing methods in "wool processing", planing processing is highly valued by the furniture manufacturing industry. Therefore, this paper discusses the planing process in combination with modern wood processing technology.

1 Theoretical basis of planing

1.1 Basic requirements of "wool processing" process

Machining of wood is the process of "transforming wood into a value-added product by altering its geometry or improving its surface finish". After the "batching" process, the surface of the obtained wool is rough and uneven. In order to obtain the correct size and smooth surface of wooden furniture parts, it is necessary to ensure that there is an accurate positioning when processing each surface. As the benchmark for subsequent process processing, and gradually process other surfaces, processing the reference surface is the basic requirement of the "wool processing" process.

1.2 Quality points

From the perspective of industrial production, as shown in Figure 1, the surface quality of the work obtained by planing is often characterized by two indicators, namely pitch (P) and peak height (h). According to the principle of wood milling, any surface of the workpiece formed by planing will leave regular ripples. The pitch (P) can be understood as the length of the corrugation, that is, the distance between the starting point and the end point of the wood surface when each guiding cutting edge cuts the wood during the planing process. The size of its value is related to the feed rate (F), the rotational speed of the tool shaft (R) and the number of cutting edges (N) on the tool. The relationship between them is shown in formula (1):

P=1000F/RH ——(1)

Where: P——Pitch, mm

F——feeding speed, M/min

R——The rotational speed of the cutter shaft, r/min

N——Number of cutting edges

The peak height (h) is the depth of the blade cutting into the wood, and its value is related to the pitch (P) and the cutting circle diameter (D) of the tool. The relationship between them is shown in formula (2):

h=p2/4D ——(2)

Where: h——peak height, mm

p - pitch, mm

D——diameter of cutting circle, mm

In terms of work surface machining quality, the shorter the pitch, the smoother the workpiece, and the smaller the peak height, the better the surface flatness of the workpiece. However, in actual production, too small pitch often causes rapid wear of the tool, and the peak height is related to the size of the pitch. Experience shows that in furniture production, when the pitch is controlled at 1.5-1.7mm and the peak is controlled at 0.001-0.005mm, good surface quality can be obtained, and at the same time, the wear of the tool can be reduced and a certain processing efficiency can be guaranteed. It can be said that understanding the relationship between pitch and peak height is particularly important to ensure the quality of workpiece surface machining.

2 Choice of planing scheme

The wool material is processed by various planers to the required shape and size and becomes the net material. Plane cutting mainly includes the following process methods, the characteristics are as follows:

(1) Planing is used to process the datum plane and side surface, and press planing to process the opposite surface and edge. Using this processing method can obtain accurate shape, size and high surface quality, but this processing method is labor-intensive and low in production efficiency, and is suitable for non-standard wool and small-scale production.

(2) Plane one or two datum surfaces (edges) first, and then use four-sided planers to process the other surfaces. This method has a slightly lower machining accuracy and a rougher surface, but has a relatively high productivity, and is suitable for non-standard wool and some medium and small-scale production.

(3) First, two opposite surfaces are processed by double-sided planer or four-sided planer, and then the other surfaces are processed by longitudinal dissection with multi-blade saw. The processing accuracy is slightly lower this time, but the labor productivity and wood yield are relatively high, which is suitable for wool specifications and large-scale production.

(4) Use a four-sided planer to process four sides at a time. Using this method requires the wool to be relatively straight. Because there is no pre-processing of the reference surface, the processing accuracy is poor, but the labor productivity and wood yield are high, and it is suitable for wool specifications and large-scale continuous production.

(5) Press planing or double-sided planing several times to adjust the four sides of the processed wool. This method has poor processing accuracy, low production efficiency, and wastes materials, but the operation is relatively simple, and is generally only suitable for inner core materials with low processing accuracy requirements and small batches.

(6) Planing to process the datum plane and edge, and milling machine (lower shaft vertical milling) to process the opposite surface and edge. This method has low productivity and is suitable for side processing of folded surfaces, curved surfaces and wide wool.

In actual production, planing equipment and process procedures should be reasonably selected according to the quality requirements of parts to ensure processing quality and processing efficiency.

In actual production, the processing equipment and processing methods should be reasonably selected according to the quality requirements and production volume of the parts. After the sawed finely cut wool is processed on the reference surface and the opposite surface, its processing quality can be evaluated according to the dimensional accuracy, starting accuracy and surface roughness of the obtained net material to determine whether it can meet the requirements of interchangeability. The net material and size and shape accuracy are guaranteed by the equipment used and the selected processing method, while the surface finish quality depends on the process specification of the planing process.

Wood planing equipment is a large product series. The main equipment includes traditional planers for processing wool benchmarks, pressure planers for processing the opposite surfaces of benchmarks, and double-sided planers that can process the upper and lower planes of the workpiece at the same time. The high-efficiency four-sided planer also includes special planing equipment that can plan the wool on both sides to a fixed thickness and then longitudinally cut it with a multi-blade saw to produce a product with smooth four sides and consistent cross-sectional dimensions.

The traditional planing process is to plan the reference surface on a flat planer, and then use a press planer to determine the thickness and plan the opposite surface. Although this planing scheme has the advantages of high precision, accurate shape and size can be obtained, and the surface is relatively smooth and so on. It has been widely used, but due to its high labor consumption, low production efficiency, especially the common unsafe factors in operation, it has been gradually replaced by new equipment in the production of modern wood furniture.

The appearance of the four-sided planer has made a qualitative leap in the planing process. Although the early four-sided planer needs to cooperate with the traditional planing equipment to ensure the machining accuracy in the processing of wool. However, with the development of technology, the new four-sided planer integrates many advantages such as high precision, high efficiency, safety, and one-time molding of the profile, which makes it gradually used in production and has truly become a square material "wool processing". Mainstream options.

The four-sided planer adopts mechanical feeding, and the process is centralized. It can process four surfaces of the workpiece at one time, and can process various forming surfaces with different beginnings. With a flexible tool spindle configuration, roughing and finishing are separated, resulting in high-quality parts. And it has the advantages of low labor intensity of workers, high feed rate, high labor productivity, high equipment utilization rate, and high wood yield. At the same time, the four-sided planer is also the main equipment for enterprises that produce wooden doors and windows, picture frames, floors and decorative wood moldings.

3 Overview of four-sided planing technology

3.1 Typical processed products

After the wool is planed on four sides, it can be planed into the desired cross-section in the width and thickness directions of the finished product. Through four-sided planers with different arbor arrangements, almost any shape of linear products can be produced.

3.2 Typical processing process

When the wool is sent to planing on all sides, the first bottom knife (flat knife) is used to plan a plane as the base bottom surface; then the second inner knife (flat knife) is used to plan the inner base plane, which is also a plane; The third outer knife (shaped knife) and the fourth inner knife (shaped knife) are used to plan out the forming side (the processing in the width direction is completed at this time); the fifth top knife (shaped knife) is used to plan the top shape; The sixth bottom knife (shaped knife) is used for planing and shaping; finally, the seventh top knife (shaped knife) is used for fine cutting and shaping, and the four-sided planing operation is completed.

The above is just one of the four-sided planing mechanisms. In actual production, the cutting mechanism of the four-sided planer is more complicated. Different four-sided planers will present different configuration forms of tool shafts in terms of the number of tool shafts, tool shaft structure and tool shaft layout, so as to achieve the processing functions required by different workpieces.

In addition, the above-mentioned cutter shaft structure is only the basic cutting mechanism of the four-sided planer composed of the bottom planer axis, the vertical milling axis and the horizontal milling uranium. , sawing shaft or split saw device. Among them, the universal tool axis, sometimes also called the displacement tool axis, is a special tool axis that is often configured. The functions of four cutter shafts, down, left and right, greatly expand the processing performance of the four-sided planer.

3.3 Main technical parameters

The characteristic of the four-sided planer is that the processing of four surfaces is simultaneously completed in one feeding process, so as to obtain more accurate dimensions in the two directions of width and height. Therefore, the maximum processing size (width × height) has become the primary technical parameter of four-sided planer products.

3.4 Tool

Similarly, the equipment is inseparable from the cooperation of good tools. The machining accuracy of the four-sided planer is inseparable from the excellent tools and installation and positioning system. Figure 5 shows the commonly used tool series for four-sided planers.

Although the dullness of the tool due to wear is a common problem of most wood processing equipment, this problem is particularly prominent for the four-sided planer. The dulling of the tool will cause a series of problems in the process of the four-sided planer. It will also affect the normal feed of the workpiece, and even cause the control problem of the workpiece passing through the integrated machine tool.

At present, the technical focus of cutting tools in the technical field of four-sided planing mainly focuses on three aspects: improving tool wear resistance, shortening tool replacement time, and improving tool installation and positioning accuracy, which is also the focus of competition among planing equipment manufacturers. .

3.5 A weapon for digitalization of wooden furniture enterprises

The modern new planing equipment, especially the four-sided planer, is different from the traditional planing equipment, which is reflected in the greatly improved feed speed and cutter shaft speed, especially in the degree of automation.

Some scholars have shown that the time used for auxiliary operations such as clamping usually accounts for about 70% of the machining time, which means that the "real" machining time of cutting materials with a tool is only about 30%. Cutting time accounts for only about 5% of the time it spends on the shop floor. The four-sided planer is a multi-process equipment composed of complex systems such as a cutting mechanism with multiple tool shafts, a pressing device and a feeding device. If there is no automatic operation and control device, the "real" processing time of the four-sided planer cannot be guaranteed. , and can not guarantee the adjustment accuracy, resulting in high manufacturing costs, and it is impossible to adapt to the flexibility challenge of today's "small batch and multi-variety" production mode of wooden furniture.

Therefore, four-sided planer manufacturers have devoted themselves to the research of automation technology in terms of digital display control, numerical control and computer control, in order to reduce the time for tool adjustment and tool change of machine tools, improve efficiency, and at the same time improve the adjustment accuracy of four-sided planer equipment. The four-sided planer is integrated into the furniture integrated manufacturing system.

Practice has shown that many wood furniture enterprises have achieved returns in improving product quality, reducing defect rate and increasing output per unit time after choosing high-automatic four-sided planing equipment.