Application of steel plate welding bed structure in laser cutting machine

Many practitioners in the laser industry have a misunderstanding that the welding bed must be worse than the casting bed. In fact, the two bed making methods have their own advantages, and we can't be too absolute.

In 2020, our company began to manufacture special equipment using dozens of steel plate welding beds in the technological transformation. We have realized that the use of steel plate welding structure is not only suitable for manufacturing heavy-duty machine tools but also suitable for manufacturing general special equipment. While steel plate welding is superior to square tube welding, it is also superior to cast bed in some aspects.

The steel plate welded bed can be manufactured quickly and cost less, which is particularly advantageous for customized equipment. Use an ordinary AC welding machine to weld the bed of the machine tool by hand arc welding. Generally, welding a bed with a length of five to six meters can be completed in about two to three weeks by two workers. If the general casting method is used to manufacture the machine bed, not only the modeling must be considered, but also the core iron and sandbox must be prepared. After casting, the sand must be cleaned and reshaped. Even if the model manufacturing cycle is not included, it is often better than the welded structure. The manufacturing cycle of the bed is longer and requires more manpower. Another reason for the low manufacturing cost of the steel plate welded bed is that the use of steel plate welded bed can avoid the problem of casting defects due to casting defects. Gas cutting, welding repair, splicing, and processing of materials are very convenient. Due to the many advantages of the steel plate welded bed, it has been more and more widely used at home and abroad in recent years.

At the same time, the weight of the welded bed is similar to that of the cast bed. If you want a heavier bed, you can thicken the raw material plate.

We paid attention to the following issues when designing the steel plate welded bed:

1. Pay attention to the difference between welded components and castings when designing

Since the value of the elastic modulus E of steel is larger than that of cast iron, the wall thickness can be appropriately thinned, generally by about one-third. The rounded corners should be reduced as much as possible because it is more troublesome to make rounded corners with steel plate welding structure, which is not as convenient as castings, but it can also be rounded when necessary. Since the copper plate is relatively flat, no processing is required for the unimportant surfaces, such as windows and the mounting surfaces of the support that are not demanding. Figure 1 shows the bed of a simple sharp knife grinder. Several windows do not need to be processed. Try to use straight lines instead of curved surfaces to avoid the difficulty of bending and forming the steel plate. It is best not to design the weld on the surface to be processed so that the weld will affect the strength and regularity of the weld.

2. Consider welding process ability when designing

It is necessary to minimize the weld on the bed because long welds are prone to deformation when welding. In order to reduce the welding seam, try to avoid repeated welding of the steel plate, so the size of the plate should be considered in the design. When designing the weld, try to make the operator use fillet welding and flat welding to reduce vertical welding and no overhead welding. Also, pay attention to whether the welding is easy to reach each welding part and consider the welding sequence. If necessary, design some process holes. In places where welding operations are difficult, do not design too long welds, but segment welds.

3. Design of ribs

The layout and form of the ribs have a direct effect on the rigidity and vibration resistance of the machine bed. When designing, in addition to considering rigidity, attention should also be paid to the welding process. In the case of satisfying rigidity, do not design too many ribs to reduce deformation caused by welding. Therefore, sometimes the wall thickness can be appropriately thickened to reduce the number of ribs, and large deformation is likely to occur when welding thin steel plates, and the increase in wall thickness will also reduce the welding deformation. Oblique bars have better bending and torsion rigidity than straight bars, but they are not as easy to weld as straight bars.

4. Several other issues that should be paid attention to

In the vicinity of the location where the anchor screws are installed, ribs should be laid on the inner wall of the bed, which is beneficial to the adjustment and installation of the machine tool.

We paid attention to the following issues in the process when manufacturing the steel plate welded bed:

1. Because it is easy to deform when welding a more complicated bed, and there is no special welding fixture, we use all the ribs and wall panels to be "spotted" (or spot welding), and then welded in a certain order. .

2. The more heat is added per unit length of the weld (high current, low welding speed), the wider the heating range, the greater the deformation and stress, so generally you should try less welding, fast welding, and less heating. Short welds can be welded in one direction at one time (through welding), medium-length welds can be welded from the middle to both ends, and long welds can be welded in segments. As the length of the weld is longer, the heat spreads on the steel plate The wider the range, the greater the shrinkage stress caused. Segment welding can be about 100-200 mm.

3. After the bed is welded, heat treatment is carried out to eliminate internal stress and improve the metal structure. In order to relieve stress, the bed must be heated to 600 to 650°C. At this time, the yield point is low, the rigidity of the structure is reduced, plastic displacement occurs, and the stress is eliminated. However, it should be noted that when heating in the furnace, do not put many other parts to be heat-treated on the bed, and the bottom of the bed should be firm when the bed is in the furnace, and do not hang in the air to avoid additional deformation during heating.

4. Before machining, a base surface must be processed. At this time, the bed should be firmly padded on the worktable and then pressed tightly. Be careful not to make the surface of the bed uneven due to improper clamping of the machining fashion. Misunderstood as deformation caused by welding stress.

Judging from the use of the machine bed welded with copper plates in our factory in the past few years, the accuracy is relatively stable, and it has been used normally in production, under heavy cutting conditions.

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Arisa Yin、

WhatsApp: +86 153 1541 6150 

E-mail:arisa@leapion.com