Rocking the Hard Metal
New bandsaw technology can pick up the tempo of cutting superalloys by as much as 50%
By Dale Petts
Global Product Manager of Metal Products
Due to rising fuel costs, there is a strong trend to manufacture turbines and engines with higher fuel efficiency to meet today’s energy challenges. One approach manufacturers are taking is to design these units to operate at a hotter temperature. In order to accomplish this they must use components made of some of the toughest alloys on earth, creating an increase in demand for difficult-to-cut materials such as Inconel, Hastelloy and René.
As materials get tougher, parting and shaping them to spec becomes more difficult as well, requiring new technologies to meet these challenges. Exotic materials are very expensive, so keeping waste to a minimum is extremely important. Further complicating the process, these materials often “move” when altered due to internal stresses. This can cause immediate and unanticipated dimensional changes. For example when bandsawing, these materials can actually close in on a bandsaw blade, causing it to stop cutting completely and to become impossible to extract, leading to material waste and expensive rework.
New Separation Solution
Bandsawing can be an excellent solution to today’s metal separation challenges, but the right saw blade must be used. Consider using blades with innovative designs and geometry that have transformed how traditional bandsaw blades perform in tough metal applications.
Simonds International (Fitchburg, MA) recognized certain unmet needs for bandsawing applications with challenging materials. When a bandsaw blade’s teeth are in continuous contact with demanding materials, penetration can be difficult, resulting in work hardening and, in turn, rapid blade wear. Simonds decided to re-examine one of their existing technologies, called SiNamic, to further develop it into a custom-engineered solution for specific applications. Simonds’ engineers studied the blade’s back edge in addition to its teeth and material. Born from this research was SineWave technology, which is used on bandsaw blades that are custom-produced based on the contact area of the work, the number of teeth engaged in the cut and the penetrating force available. In most cases, a saw machine requires a lower penetration force with SineWave, while still cutting faster than conventional blades. The technology enables a bandsaw blade to cut tough materials 30—50% faster, significantly reducing cost per cuts, while maximizing sawing performance and providing a better finish.
SineWave is an application-specific solution that produces a unique rocking motion when sawing that forces the teeth to penetrate the work more effectively through a broaching action. To exert more force into the cut without having to increase machine pressure, the blades feature tapered ramps on the back edge of the blade. Ramp customization capabilities optimize the cutting performance of specific alloy cross sections. When sawing, SineWave produces the rocking motion in the cut when the blade is running against the machine guides, creating a self-feeding action that delivers faster cut times and a range of environmentally-friendly benefits and improves productivity. SineWave especially reduces cut times in tough sawing applications.
Compare two methods of parting a large billet of an exotic alloy used for sub-sea drilling components—sawing vs. abrasive cutoff. Abrasive cutting requires a large abrasive cut-off wheel to cut the material. For a 30" (764-mm) billet, a cut-off abrasive wheel exceeding 60" (1500-mm) in diameter must be used. Further, the wheel often exceeds ¼" (6-mm) thickness, thus the width of the cut path being “ground” through the billet wastes a significant amount of material and requires a tremendous amount of horsepower. The machines that are used to perform this often have motors rated at hundreds of horsepower. On the other hand, a state-of-the-art bandsaw machine with a properly engineered blade uses only 30 hp (22.4 kW) or less.
The abrasive cut path also creates a swarf of mixed grinding particulates, with the micro-sized chips being ground out. This is a mixed slurry of materials that are required to go through an expensive energy-consuming process of separation in order to dispose of or recycle them. The alternate method is to dispose of the swarf as an expensive hazardous material. By comparison, bandsawing creates uncontaminated chips of the material being cut, eliminating any separation operations and allowing the material to be directly recycled.
Cutting by abrasive methods also creates heat transfer into the billet. This generates a heat-affected zone on both surfaces of the cut, which also produces a poor surface finish, requiring an extra facing operation that consumes additional time, resources and energy. On the other hand, bandsawing creates a “cool” cutting path. The heat is primarily carried out and away from the cut by the chips. For this reason, there is no additional refacing required, ensuring that the remaining material has not been altered. In some cases, additional face finishing operations have been eliminated entirely.
Due to the high heat created in abrasive cutting, the fluids used for cooling and lubricity are subject to evaporation, which poses a challenge to the environment and increases the coolant-replacement cost. Bandsawing temperatures are only a fraction of abrasive cutting temperatures, so evaporation issues caused by the cutting operation are virtually non-existent.
Less Time, Less Waste, Less Energy Consumed
SineWave’s proprietary design offers several advantages that greatly reduce the risk of costly errors such as crooked cuts, pinching, poor finish and machine wear. SineWave also reduces cut times and lengthens blade life versus traditional bandsawing, leading to substantial savings and labor costs. A review of the benefits include:
- Up to 75% less material waste
- Decreased energy consumption
- Improved surface finish and cut accuracy, reducing the need for downstream operations and face refinishing
- Reduced heat creation within the cut, thus eliminating the creation of waste for cleanup caused by a heat-affected zone
- Cut chips can be immediately recycled without mixing abrasive particles
- Reduced heat creation in the cutting process decreases fluid usage.
This article was first published in the 2013 edition of the Energy Manufacturing Yearbook.
Published Date : 12/6/2013