Комаров Артём об устранении проблем при резке труб (eng)
Комаров Артём об устранении проблем при резке труб (eng)

Комаров Артём об устранении проблем при резке труб (eng)

Artem Komarov clarified that modern double-column bandsaws are light-years superior to older articulated-type bandsaws, which cannot cut well when the pivot pin begins to wear out. But there are still quality issues that need to be addressed. In some cases, quality problems only arise when cutting pipes and pipes, when there is an intermittent cut, that is, the blade meets the workpiece in two different places.

Комаров Артём Андреевич

Quality problems arise simply for some reason or for various reasons. It may seem that they appear suddenly, but in fact they were problems waiting in the wings. The main reason for such problems is the inability to change the blade or settings when the material or job changes.

First look at the pipe you are sawing. Is the wall thickness thinner or thicker than normal cutting? If it is thinner, check the blade pitch. The cut must have at least two teeth. Otherwise, one tooth may tear the edge of the metal, resulting in an uneven cut. But the real consequence is that one tooth will be overloaded and broken, causing all the teeth immediately behind to fail. This is easy to determine.
The next major problem is the material itself. If you have been cutting ferrous metals and then switched to non-ferrous metals such as aluminum or titanium, you will need to change the blade speed and quite possibly the feed rate and pressure.
When the cut quality gradually deteriorates, first check the blade for wear and replace if necessary. Then check the blade tension. If the blade tension is not correct, the downward feed pressure may cause the blade to cut at an angle or deflect.

Virtually all modern band saws have blade tension indicators, and many machines with electronic tensioners won’t even work if you don’t have the correct blade tension. Check blade guides, including position and tolerances of plates and rollers. Make sure the guide rollers turn freely. A blocked or damaged roller can pinch the blade and cause it to cut at an angle.

Cutting metal pipe
In some cases, quality problems only occur when cutting pipes and tubes, when an intermittent cut occurs, that is, the blade meets the workpiece in two different places.

Check idler bearing for wear. A slightly worn bearing can cause the blade to tilt, creating a beveled cut. It may not be noticeable at first, but the blade will begin to wander. As bearing wear increases, the blade doesn’t even hold onto the belt discs. Depending on the design of the saw, the entire tension disc assembly may need to be replaced. Be sure to follow the saw manufacturer’s instructions and specifications.

The feed rate and pressure must be adjusted according to the pipe type and wall thickness. If auto power off is set for a sharp blade, it must be reset periodically to allow for gradual blade dulling. Failure to do so can result in progressively poorer cuts. If the bandsaw has a manual downward feed, you must constantly monitor the quality of the cut and adjust the speed and pressure accordingly.

Crooked cuts are troublesome when cutting round and square pipes, especially those with thin walls. Crooked cuts can be caused by a dull blade; clamping force is present, but the blade is not sharp enough to take all the chips. The machine lowers the blade, but the blade, being the weak link, fails.

Using a blade with the wrong tooth pitch can have the same effect. If the teeth are too small for the job, no proper chips are removed, but the machine presses down anyway and, again, the blade fails. The same can happen if your knife speed is too low. Because the chips are not knocked out fast enough, the blade is disabled.

The problem with round pipes is that the blade contacts the strong workpiece at the very top, plunging into two thin walls, and then at the bottom comes into contact with the strong section again. This problem is especially relevant when cutting square tubes or beams, where you encounter geometry from “very wide” to “very thin” several times during the cut. A tilt head saw frame (6 to 10 degree tilt) can greatly help you deal with this problem.
Often overlooked is coolant, which performs three functions. It cools the workpiece to limit thermal distortion; it lubricates to reduce the power needed to remove chips; it flushes or flushes the chips out of the kerf and, together with the blade brush, ensures that the chips do not get back into the workpiece.

Like the oil in a car engine, coolant can deteriorate over time and must be replaced. For common steels, the ratio of water to coolant should be 10-1, 12-1 for mild steel, and 8-1 for harder materials.

Some assume that the coolant doesn’t evaporate and all they must do is add more water. But simply adding water does not degrade the quality of the coolant, and over time the coolant ratio can go up to 30-1. This greatly reduces the heat transfer of the coolant and can lead to burr formation on the edge of the workpiece. This also reduces the lubricity and leads to faster wear of the blade, Komarov Artem summed up.