What are the running-in methods for metal band saw blades?
In the current fiercely competitive market environment, we all want to reduce costs and increase efficiency. In metal material cutting and processing, some people think that reducing equipment investment costs or the price of a single saw blade can reduce production costs. In fact, this view is Got it wrong. Simply reducing equipment investment or the cost of a single tool cannot guarantee the ultimate goal of cost reduction and efficiency improvement. This goal can be achieved through a reasonable layout of equipment and technology and more precise operation and management of the sawing process. So, let’s talk in detail about how to break in a saw blade and the principles of break-in.
1. How to break in metal band saw blades
In the cutting process, efficient cutting means reducing the frequency of saw blade replacement and reducing the downtime of the band saw machine. If the metal band saw blade and cutting parameters are correctly selected and the metal band saw blade is correctly run-in, Downtime can be appropriately reduced. However, different metal band saw blade products, such as bimetal band saw blades and carbide band saw blades, have different running-in methods, and the selection of running-in parameters should also be different for different sawing materials and material shapes.
The first is to determine the initial cutting speed. When cutting carbon steel and annealed medium and low alloys with a bimetal band saw blade, the sawing speed can remain unchanged. For example, the No. 45 solid round steel with a diameter of 200mm uses a speed of 70m/min, and 42CrMo Use 50m/min speed. If you are cutting pipes with a wall thickness of less than 20mm or the clamping is not firm, the sawing speed needs to be appropriately reduced to less than 80%. If you are cutting steel with hard skin or materials with a hardness higher than 30HRC, the sawing speed also needs to be reduced to less than 80%. Of course, when cutting steel with hard skin, it is best to use materials without hard skin to run in first. When running in the carbide band saw blade, the linear speed is generally reduced to about 50% of the normal value. However, alloy band saws that cut aluminum at high speed generally do not need to reduce the linear speed.
In addition, the feed speed is set. If it is a solid material of more than 100mm and a pipe with a wall thickness of more than 20mm, the feed speed of the bimetal band saw blade can be reduced to 50% of its normal speed. For the carbide band saw blade, it is best to initially set the minimum feed speed. to 10%, and then slowly increase the feed speed. When adjusting upward, take the absence of vibration as the standard. If there is vibration, lower the feed a little and run for a while until the feed speed is adjusted to 50%. If it is a pipe with a wall thickness of less than 20mm, the sawing speed should be further calculated based on the feed depth of each tooth.
Feed speed = 40*band saw line speed*TPI*standard feed depth per tooth
Feed speed: mm/min
Band saw line speed: m/min
TPI: tooth pitch, 3/4 tooth is 3.5, 1.4/2.0 tooth is 1.7, and so on.
The feed depth per tooth varies depending on different materials, ranging from 0.02 to 0.05mm. The overall feed per tooth should be lower than its normal feed per tooth.
The feed speed should not be set too low. If the feed rate is too low for a long time on work-hardened materials (such as stainless steel), it may cause serious blunting of the tooth tips and affect the life of the tooth tips. The third picture below shows the shape of the excessively worn tooth tips.
After the initial linear speed and feed speed are set and run-in for a period of time, gradually increase the linear speed and feed speed to normal values on the premise that the vibration does not become larger.
The third is to determine the overall running-in area. The running-in area is also related to the sawing material. For soft materials such as medium and low carbon steel and aluminum alloy, the running-in area is 320cm2 to 640cm2, which is roughly equivalent to 4 to 8 pieces of 100mm diameter round steel. The grinding area of difficult-to-cut materials needs to be appropriately reduced. The total area is approximately between 160cm2 and 480cm2, which is approximately between 2 and 6 knives for a round steel with a diameter of 100mm.
In short, there are two basic principles for correct running-in of saw blades: 1. Control vibration during cutting; 2. Control the feed amount of each tooth to be lower than the normal feed amount (this is related to the matching of linear speed and feed speed, not just to related to feed speed). After the metal band saw blade is run in, the cutting sound will be reduced, and the surface of the workpiece will be smoother.
2. Principle of running-in of metal band saw blades
The picture below shows the comparison between the broken-in metal band saw blade tooth tips and the unbroken-in tooth tips at the early stage of use.
After the metal band saw blade tooth tip is just processed, there will be tiny burrs on the tooth tip formed during the manufacturing process. If these burrs are within the tolerance range, they are qualified, as shown in the figure below.
If the new cutting edge undergoes normal running-in, the small burrs on these cutting edges will be blunted, and the entire tooth tip will form a rounded corner, so that all parts of the cutting edge can participate in cutting evenly during normal cutting in the later stage. And if the new saw blade is used for strong cutting as soon as it is installed on the band saw machine, then these small burrs will suddenly detach from the cutting edge due to a relatively large impact force. When it detaches, it will not only detach itself, but also part of the cutting edge itself. It is also taken away, causing a relatively large gap to be formed on the cutting edge at the beginning of sawing. In our industry, it is called “teeth chipping” or “tooth tip micro chipping”. This kind of cutting edge has many cutting edges during later cutting. Some parts cannot apply force evenly, which will affect the life of the band saw. When cutting with carbide band saw blades, special attention should be paid to running-in, because the alloy head is very brittle. If the cutting edge cannot be applied evenly, the chipping phenomenon will be more serious. The picture below shows the chipping of the alloy tooth tips that have not been broken in.
3. Conclusion
The running-in procedures for metal band saw blades of different materials and working conditions will be slightly different. If the user wants to check whether the running-in of the saw blade is normal, he can purchase a 10x to 20x magnifying glass or microscope to inspect the running-in tooth tips, and then determine the specific running-in procedures for different materials.
After the metal band saw blade is broken in, the life of the band saw blade can be significantly extended by 20% or more. Although some metal band saw blade manufacturers currently passivate the tooth tips of the band saw blade, in order to ensure the normal life of the band saw blade, It is recommended that customers should explore more ways to use each band saw blade when using it, in order to maximize the effectiveness of the metal band saw blade.
