Questions and answers on cutting to length and further processing of pipes
The chipless cutting of pipes using the tear-breaking method offers decisive advantages over conventional cutting methods such as sawing:
a)No chips when cutting tubes
In the tear-breaking process, the cutting knife runs orbitally around the pipe until a predetermined breaking point is created. Then the two pipe parts are separated by tearing and breaking. In contrast to machining processes, there is no waste in the form of chips and thus an enormous increase in efficiency. With 30,000 cuts with a 2 mm thick saw blade, you lose 60 m of raw material that you have more at your disposal when cutting without cutting.
b) Fewer downstream operations
The fact that the pipe is not completely cut through in the described tear-breaking process means that no internal burr is produced and therefore downstream deburring is generally unnecessary.
Should it nevertheless be necessary to cut the tube completely, this can be switched off directly in the control system of our systems & machines. For pipe end machining, a chamfer can be rolled simultaneously with cutting using a likewise rotating pressure roller.
Further considerable cost savings are achieved by eliminating cleaning processes. In addition to an expensive washing system itself, the associated costly maintenance work, ecological requirements and the purchase and disposal of washing emulsion are also eliminated.
In addition, the elimination of handling and transport times results in capacities that can be used elsewhere.
c) Increase of the tool life
The cutting blades have an excellentlifetime. Depending on the material and use, 80,000 cuts and more can be achieved with one cutting knife. In comparison to the service life of a saw blade (approx. 30,000 cuts), this results in an increase of 166.67 %.
The chipless cutting of pipes using the tear-break process offers decisive advantages over conventional cutting methods such as sawing:
a) High material savings
When processing from coil, there is a considerable saving in material due to the elimination of the gate and remnant piece. Coil material is also cheaper than bar material in most cases. For copper tube alloys, for example, material costs can be reduced by up to 20%.
b) High time savings
In contrast to the processing of bar material, reloading is not necessary. This time saving results in a cycle time reduction of about 10%. In single-shift operation with coil processing, up to 3,000,000 tube sections per year can be produced for copper tube alloys.
c) Low storage costs
Thanks to the compact dimensions of coils, you need less storage space and can therefore reduce your storage costs considerably.
Which materials are processed from the coil depends very much on the tube diameter and the wall thickness.
For the most common tubes made of copper alloys, diameters of up to 35 mm and a wall thickness of 1.5 mm are possible without any problems, but tubes made of aluminium alloys can also be processed from coil. If you want to process steel tubes, especially stainless steels, from coil, this is only possible with smaller tube diameters.
The coil is placed on a driven coiler whose speed is infinitely variable. The pipe is then placed over a pneumatically sprung compensating roller and fed to the automatic pipe cutting machine. The compensating roll controls the interaction of the decoiler with the servo drive of the machine feed and thus ensures uniform decoiling.
In certain applications it can be useful to equip the line with a double decoiler and thus drastically reduce set-up times.
5. Are the diameter tolerances and the straightness of the tube sections guaranteed during coil processing?
The tube coming from the coil is calibrated and straightened by 18 straightening rolls.
After straightening, the diameter tolerances are + 0.05 mm and the straightness is 1 mm per running meter of pipe.
The cost-effective, soft copper pipe is easy to process by means of uncoiling, but a certain hardness of the material is often required. This can be achieved by the straightening process.
The material can be hardened to a yield strength of Re = 180 N/mm2 by the precisely infinitely adjustable straightening rollers.
If the tube diameter is the same from the used and new coil, the coil end and the coil start can be joined together with the help of a crimping tool. The process including the new coil support takes approx. 5 – 7 minutes. The connection point is detected by the feed of the automatic pipe cutting machine and can be cut out there.
For different pipe diameters the collets on the pipe cutting machine must also be changed, the cutting diameter must be set on the pipe cutting machine and the straightening rolls on the straightening roll device must be changed. Adjusting the straightening unit to other pipe diameters is very easy. The straightening rolls can be simply pulled off and the new rolls fitted without loosening lock nuts or locking pins. The adjustable straightening rolls have an absolute scale, so that registered setting values can be set or readjusted without a locking device. The total set-up time is 10 – 12 minutes.