Getting straight to the heart of HSM

ANYONE who has ever tried to make something without all the necessary components will know the project is deemed to fail even before it has begun.

ANYONE who has ever tried to make something without all the necessary components will know the project is deemed to fail even before it has begun.

The same principle applies to high speed machining. All the ingredients need to come together to make HSM as efficient and successful as possible.

Suhas Ekbote, GM of DMG says many people have a misconception about what HSM actually is but says high speed machining involves many integral parts to make it work.

“All of the components are very critical to HSM’s success; including the mechanics of the machine, drive technology and the CNC control. External factors such as CAD/CAM software, the tooling and the coolant all play a major role as well,” he told Manufacturers Monthly.

Colin Shennan, engineering manager at Seco Tools says as software improves and the availability of specialist machining strategies increase, machines are now able to produce movements that efficiently feed the tool through complex paths while still protecting the tool from excessive loads.

“When teamed with an agile machine, cutting strategies such as trochoidal or peel milling become a reality,” he said.

“As machine agility improves, high feed cutters (using a similar thin chip thickness approach to high speed machining) are also becoming more widely used but these are more easily programmed with a traditional Z-levelling strategy.

It is often used as a semi-finishing operation for HSM machining,” Shennan said.

“Both methods HSM and HFM (high feed milling) cutters are producing metal removal rates that were previously unachievable using the general or ‘traditional’ machining approach,” Shennan told Manufacturers Monthly.

The price of speed

According to Ekbote, a new development driving improvements in HSM is the introduction of linear motors.

“With this technology we can achieve very high feed rates, up to 90-120m/min,” he said.

“The linear motor works on the same principles as the rotor drive but with the additional benefits of no backlash and higher acceleration speeds.”

Though it is tempting for manufacturers to think faster is better, Ekbote explains that quicker spindle speeds are not necessary the answer to the most efficient HSM.

“There is a fine line between high spindle speeds and how much torque can be generated. The higher the spindle speed, the more strength is applied in the cutting speeds.

“You can cut up to speeds of 24,000rpm depending on what you are cutting, but we find a spindle speed of 18,000rpm allows a wider spectrum of materials to be cut without compromising how and what you want to cut,” he said.

Even though HSM has many potential benefits for manufacturers, it is still a relatively expensive technology compared to traditional methods, and companies are advised to weigh up the initial cost with potential ROI.

Ekbote explains that HSM can be achieved to a certain extent with drives using ball screw technology but says there are limits to it. While these machines can start at around $200,000, those using linear technology and are capable of all axis machining start around $350,000.

However, Ekbote advises manufacturers to look at the overall benefits of using this technology and not just price.

This sentiment is echoed by Shennan, who says companies that are open minded, embrace technology, look at the total cost picture, and not just focus on the cheapest carbide, will move forward and will still be able to compete in a price driven market.

Both men agree that HSM is being embraced by manufacturers in Australia, but say due to cost and lack of volume there is still a limited number of machines sold into the market.

They explain that the more people hear of the successes of HSM and the fact the machines are getting cheaper, the process will be more widely accepted and used.

Increasing spindle speeds, tool life expectancies and improved programming all help provide faster and more efficient HSM, but without collaboration between the different companies involved these would be make redundant.

Communication is the key

Both Ekbote and Shennan acknowledge that communication is an integral part in any HSM operation and say that establishing consistent two-way communication is critical to the success of any project.

Ekbote explains that contribution of the components is not enough.

“The CAD/CAM element might be only 10% of the operation but if one fails the whole thing collapses.

“Working together is an integral part of the process; there cannot be one part without the other,” he said.

HSM was first utilised in tool and die applications and is widely used in the aerospace industry but Ekbote says because it is such an efficient process, it will eventually touch all industries.

“Precision engineering is also starting to adopt the practice as they want to produce parts which have good surface finishes and high tolerances,” Ekbote said.

Ekbote says HSM is still an evolving technology and there is long way to go to perfect the existing process.

“First step is using the linear motor; we still need to implement the technology into all machines first and then move onto the next stage. Unless you finish this stage you cannot move to the next one,” he explained.

According to Ekbote, HSM will develop not so much in area of spindles, but in software and the drive technology.

“Computers are getting faster. Ten years ago, in CNC block processing, 4ms was fantastic. Now you can reach speeds of 0.4ms,” Ekbote said.

Shennan says in the future machines will only get faster and faster and machine agility (feed acceleration and deceleration) will get better.

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