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Tremendous resources for cost cutting in tube sawing

By Peter Sohler, Kinkelder BV

Introduction

In the last ten years, TiN coated sawblades initiated a quantum leap in tool life when cutting most materials but cutting tubes in particular. New sawblade designs together with distinctly different application technologies are now available in the market place. These changes in the "fundamentals" can promote dramatic cost reductions; yet only five percent of the tube cutting companies is realizing the benefits of the technical advances.


Why is the tube cutting industry unaware of these tube cutting benefits?

The tube industry has not yet realized that high performance sawing is now a "technology". In the last few years, great advances have been made with regards to:

  1. NC Grinding New computer driven machines with CBN grinding media have been developed, meaning much greater consistency, greater concentricity, and better surface texture in the profiles of the teeth of the sawblades.
  2. Integral Power blades New sawblade designs, with the aid of special purpose manufacturing equipment, allow much thinner sawblade profiles to be used.
  3. Special purpose sawing machines The latest design of the tube cut off equipment allows for variable RPM of the sawblade during the cut. This allows slow entry while cutting tube, fast feeding through the section and slow exit. This dramatically improves cycle times.
  4. Special coatings The continued development and refinement of the multi-layer coatings greatly increase the life of high speed steel sawblades as well as tungsten carbide tipped sawblades.

Each of the above characteristics contributes toward optimizing performance and cost reduction in the cutting process. The application of these new technologies, however, is much more complex than the "older" cutting applications. Because of the complexities, production managers may not have the expertise, nor the time, to introduce these possible improvements in their production processes as they are nearly always under pressure to reduce the "cost per piece", particularly while servicing the automotive industry. Despite the availability of these interesting opportunities for productivity increase, the tube industry does not appear to be adapting to, and taking advantage of, these important technical advances.

It seems that the path of least resistance is to buy new sawing machines, rather than improving the cutting process on existing machines. Such action/improvements, as mentioned previously, could make purchasing new machines unnecessary.


What is the correct approach to better productivity?

Every improvement starts with analyzing the current situations. For this reason three questions have to be answered:

  1. What is the objective of the improvement efforts?
  2. What is the condition of the existing sawing units?
  3. What are the specific quantities of the tube to be cut?


What are the benefits of new developments?

Integral technology:

A sawblade that has a reduced kerf thickness exactly adapted to the specific need of the application can dramatically reduce vibrations. From this vibration reduction, it is possible to increase the tooth chip load resulting in a significantly higher production output. Examples of tests at a tube cutting company are illustrated below .


Machine: Wagner WA 70 (Table in metrics)

tube

dimension

tensile strength

results - TiN blade

results - Integral blade

output/h

blade life

output/h

blade life

Ø 35 x 3,2

880 N/mm2

600 pcs.

2.600 cuts

1.160 pcs.

6.300 cuts

Ø 27 x 2,6

640 N/mm2

923 pcs.

5.800 cuts

1.333 pcs.

6.300 cuts

Ø 33 x 2,9

570 N/mm2

973 pcs.

6.200 cuts

1.333 pcs.

14.900 cuts

Machine: Wagner WA 70 (Table in Inches)

tube dimension

in inch

tube

hardness

results - TiN blade

results - Integral blade

output/h

blade life

output/h

blade life

Ø 1,38" x 0,13"

126 KPSI

600 pcs.

2.600 cuts

1.160 pcs.

6.300 cuts

Ø 1,06" x 0,10"

93 KPSI

923 pcs.

5.800 cuts

1.333 pcs.

6.300 cuts

Ø 1,30" x 0,11"

87 KPSI

973 pcs.

6.200 cuts

1.333 pcs.

14.900 cuts

The table illustrates that the technical operator can obtain either faster cutting or longer blade life or a combination of both of these characteristics.


Connexxioncut technology (Tungsten carbide tipped sawblades):

Tube hardness of more than 1.000 N/mm2 causes many problems during the cutting process; it is difficult even if only the heat-affected zone of the weld has high hardness. Sophisticated carbide tools with special PVD coatings and different cutting geometrical tooth forms are now available to cope with this problem. A special sawblade on a flying cut off machine can provide major benefits by reducing the cut time to less than one second.


Flying cut off

Flying cut off (Table in metrics)

tube

size

tensile

strength

cutting time

in sec.

blade life

with a coated HSS sawblade

with Connexxioncut Technology

Ø 24 x 2,2

1.600 N/mm2

weld hardness

0,65

270

4.800

Ø 28 x 2,4

1.400 N/mm2

0,80

330

3.900

Flying cut off (Table in Inches)

tube size

in inch

tube

hardness

cutting time

in sec.

blade life

with a coated HSS sawblade

with Connexxioncut Technology

Ø 0,95" x 0,087"

242 KPSI

weld hardness

0,65

270

4.800

Ø 1,10" x 0,095"

208 KPSI

0,80

330

3.900

The productivity increase can be tremendous as the tube mill can run more than ten times longer than with HSS sawblades and much faster. Until now tube manufacturers avoided friction cutting due to the unsatisfactory finish of the cut, the noise and low blade life. With modern carbide tools with sophisticated coatings, combined with high tech machine equipment, it is now possible to obtain both a good finish and an extremely short cutting time (see illustration below).


Flying cut off

Flying cut off (Table in Metrics)

tube size

tensile strength

cutting time

blade life

Ø 55 x 4,0

500 N/mm2

0,60 sec.

4.960

Ø 60 x 5,0

480 N/mm2

0,85 sec.

3.720

Flying cut off (Table in Inches)

tube size in inch

tube hardness

cutting time

blade life

Ø 2,17" x 0,157"

80 KPSI

0,60 sec.

4.960

Ø 2,36" x 0,197"

72KPSI

0,85 sec.

3.720


What are the obstacles in introducing the new technologies?

The lack of awareness of the opportunities to improve the cutting process seems to be an important factor. We also see:

  • Resistance to change.
  • The non-availability of an experienced person responsible for process improvement.
  • The lack of projects group of production, sawing machine manufacturers, and sawblade experts to select/define difficult cutting applications and provide data for optimal cutting conditions.
  • A need for computer software to determine optimal cutting parameters.
  • A system for controlling output and cutting costs on a continuous basis.


Conclusions

  • From our experience > 90 percent of the tube cutting companies perform with productivity rate of 50 80 percent.
  • Even the most efficient companies have room for improvement.
  • Modern technologies can provide the building blocks for the attainment of major improvements. This is most definitely an engineering function as the need for technically oriented personnel is paramount in incorporating these new concepts.
  • Key factors of success are:
    - The definition of the correct tool technology for the application.
    - Using the best cutting parameters, RPM, feeds variable speeds, etc.
    - Each company should try to incorporate a control system for output
    and cutting costs.
    - Productivity improvement should become a "standard process" within the operating conditions of the tube cutting operation.

Kinkelder BV
- Addr: Nijverheidsstraat 2 (industrieterrein Zuidspoor), Postbus 242, 6900 AE Zevenaar, The Netherlands
- Tel: +31 (316) 52 42 42
- Fax: +31 (316) 33 33 46
- WWW: http://www.kinkelder.nl/
- Email:


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