Sawing non-ferrous metals can be challenging, but with the right band saw blade and material cutting plan, fabricators can achieve high quality cuts and a long lasting blade.
Non-ferrous metals (those that do not contain significant amounts of iron) are often chosen for their various properties. In most cases they are light, corrosion resistant, highly conductive and non-magnetic.
However, these materials present a unique set of cutting challenges. It is helpful to know in advance what you are likely to encounter when sawing these materials. This is the first step in solving and overcoming the problems of cutting non-ferrous metals.
The range of non-ferrous metals includes, but is not limited to, aluminium, copper, lead, tin, titanium and zinc. Copper alloys such as brass and bronze are also part of the collection. Depending on the composition, some of these materials may come in multiple grades, so cut parameters and considerations will vary.
What sawing challenges do operators face when working with these materials? They have to deal with material abrasion, sticking characteristics, insert chipping tendency, insert root capacity and maintain optimal insert speed.
In general, soft materials such as aluminum and copper are easier to machine than harder and stronger materials such as titanium, but soft materials can be bulkier under the saw blade teeth.
Non-ferrous metals such as aluminum and brass have a lower melting point than harder metals. If you don’t take proper precautions, the heat from sawing can easily cause molten aluminum to get on your throats and teeth, rendering them unusable and making them smooth. In addition, operators should be aware that while they can use higher feed rates, they must control the factors that affect chip count.
Alveolar overloading of the teeth can lead to problems such as teeth pulling away from the base (also known as stripping), blades jumping in the material, and rough cutting. One way to solve this problem is to use coarse toothed blades instead of fine toothed blades. This facilitates the evacuation of chips from the esophagus, prevents compaction, and hopefully clears the incisions before they are completely filled. Also, soft materials do not require as much feed pressure during sawing as hard materials because the teeth do not need as much pressure to engage the material.
When cutting soft materials such as aluminum and copper, it is best to use lower feed pressures, higher feed rates, and higher blade speeds. This will ensure good blade penetration and timely chip removal.
Another thing to consider is that while soft metals are easier to machine, getting the desired surface can be more of a challenge when you consider the actual micromechanics of the material coming off the saw teeth. Choosing the wrong blade, a blade without a positive rake angle, can compress the microstructure of the material, making it harder to cut. Softer materials may seem easier to cut, but extreme care must be taken when sawing these materials to avoid chipping or damaging the bandsaw blade.
Non-ferrous construction materials, such as copper pipes or aluminum profiles, exacerbate the problem because not only do they suffer from standard non-ferrous metal cutting problems, but the intermittent cuts that occur as the saw teeth move in and out of the material can damage the blade. . (When sawing these materials, it can be difficult to find the ideal tooth pitch because the teeth change from larger to smaller cross-sections during sawing.) selection and uneven asphalt.
Gear loading problems are less common when cutting harder, stronger non-ferrous metals such as titanium and zinc, which do not load teeth as easily as softer materials. This allows more teeth to be used when cutting hard materials, increasing productivity. One of the main differences between sawing hard and soft metals is that harder metals require more feed force, resulting in better saw tooth penetration.
These types of hard materials cannot be machined quickly, so lower feed rates and lower insert speeds are used to allow the insert to penetrate the material and remove the necessary chips along the way.
Bi-metal band saw blades provide fast, high-quality cutting of non-ferrous metals and can withstand the rigors of fast cutting. They can also last a long time if used properly.
Blade manufacturers typically use high speed steel (HSS) for blade teeth, which are attached to the back of high strength carbon steel by various methods, including laser welding or electron beam welding. This combination gives operators the desired cutting speed along with the durability that non-bi-metal blades lack.
Generally, a saw operator can use more blades when cutting hard materials, but this depends on whether hard and soft materials are being compared. Bi-metal band saw blades can be a good option to extend the life of your saw blade. For example, M51 HSS bimetal inserts offer comparable cutting speeds to M42 HSS inserts and provide longer tool life. M51 is more wear resistant than M42 which helps to extend blade life.
In addition, the cutting properties of high speed steel are significantly improved by alloying with cobalt and vanadium. These alloying elements significantly increase heat resistance and wear resistance.
Cutting with conventional bi-metal blades can cause heat build-up and create a heat-affected zone (HAZ) that compromises the integrity of the metal. However, one of the newest manufacturing processes used today to make bimetal blades eliminates the heat affected zone, which helps reduce rack and pinion flaking problems.
This process uses the principle of solid phase diffusion welding to join two high speed steel wires to a solid phase steel substrate. Solid state processes use only 10% to 20% of the heat generated during soldering. This bonding process allows blades to be produced with HSS backing, allowing for faster cutting speeds without sacrificing quality.
Another anti-flaking agent involves solder contact between the backing material and the teeth. Unlike the electron beam welding process, the diffusion welding process provides 170% more weld contact with the teeth, so there is significantly less breakage and blade breakage.
In addition, diffusion-welded blades have a preferred tooth geometry. For example, HSS wire is bonded to the sides of the strip and parallel to the fusion zone (the part where the metal melted) of the tooth, forming a slotted tooth geometry. The tooth geometry creates two cutting surfaces that are separated by a blade. Shortly after the initial use of the blade, the teeth create a U-shaped groove between two HSS edges 0.001 to 0.002 inches deep, changing the area of the blade involved in cutting. The grooves have a constant depth and wear at the same rate as the teeth.
Advances in band saw blade design can lead to better cutting results. For example, a bimetal blade made using a diffusion welding process forms a serrated geometry when used—two cutting surfaces separated by a blade. The teeth form a U-shaped groove between two high speed steel (HSS) edges 0.001″ to 0.002″ deep. This tooth profile helps to remove chips, which is a major barrier to successful cutting.
Double chips, also known as split chips, are the result of tooth geometry. The advantage is that they can be easily removed from the incision, which is important as chips remaining in the incision risk clogging the alveoli and sticking to the tooth. Split chips are easier to remove because they curl and fall away from the cut. As a result, the cutting speed is 25 percent faster than blades made using conventional electron beam welding.
In addition, the U-groove provides increased coolant flow to the cutting surface, the correct coolant flow not only cools and lubricates the blade, but also flushes chips stuck in the inner space of the pipe, for example.
When cutting soft materials such as aluminum, some end users prefer to use carbon blades over bi-metal blades because carbon blades can have a longer pitch and lower initial cost. However, the disadvantage of carbon blades is that they do not last as long as bi-metal blades.
Carbide band saw blades have solid or serrated cutting edges for high fatigue strength. They can accurately cut a wide range of non-ferrous and predominantly non-metallic materials such as steel belt tires, composites, reinforced plastics, composite graphite and fiberglass. These saw blades perform best at higher blade speeds than standard band saw blades for metal cutting.
Carbide inserts are commonly used for cutting hard ferrous and non-ferrous materials for manufacturing purposes. As mentioned earlier, cutting non-ferrous metals with carbide blades gives the best results when the band saw is able to operate at a high speed of rotation of the blade. Depending on the application, this can mean 1000 to 7000 fpm or more if high throughput is the goal.
This isn’t to say you can’t cut non-ferrous metals slower with carbide blades, but carbide blades and carbide grains work best in a production environment.
One particular manufacturer had a problem sawing 15 inches. Titanium wheel (6Al-4V). The sawing process is difficult due to the short blade life and extremely rough cuts with carbide blades. It was found that stress on the esophagus caused a “washboard” effect on the incision and excessive stress on the teeth.
By switching to a coarser profile when adjusting blade speed and feed rate, the customer was able to increase blade life by about 40 percent, as well as increase productivity. The cut itself is even, without lines.
Another manufacturer encountered sawtooth gullets that were loaded with chewing material as well as rough cuts when cutting 8 inches. Solid aluminum that can be described as a general purpose saw. The maximum blade speed is about 270 feet per minute. In addition, the machine requires only 1-in. inserts, which limits the tooth profiles available in bimetal and carbide inserts.
In this case, the only possible option is to find a coarser tooth. The solution is to use 1.3 pitch carbon blades. Due to the operating conditions, one would think that carbon blades would not work or last as long as bi-metal blades, but in fact carbon blades are superior to bi-metal blades. It lasts longer and cuts faster.
In both cases, the band saw specialists helped both manufacturing companies find the right saw blade. Sawing non-ferrous metals should not be an everyday task. The right bandsaw and sawing parameters can change the world.
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Post time: Apr-20-2023