Multi-tasking machines and high speed machining is putting new demands on cutting tools. Katherine Crichton looks at some of the latest developments keeping tools in their place.
IN the last 15 years, toolholders have changed significantly with more accurate methods of toolholding such as shrink-fit holders, hydraulic expansion chucks and hydro mechanical tool holders.
Benefits include more consistent and longer tool life, higher speeds and feeds, shorter cycle times and all round improved productivity.
Jeff Boyd, key market manager with Sutton Tools says in addition to the above, machine producers have really improved operations like tapping cycles to the point that the A and Z axis on the machines are very close to being truly synchronised to each other.
“Prior to this technology, tapping tool holders with axial and/or radial float were used, which had an element of inconsistencies in high performance production of internal threads, particularly in difficult materials or applications greater than 1.5 X D in depth,” Boyd explained.
“Previously, the tool geometry was commonly the main feature of the cutting tool, as it was the tool that was expected to produce stable cutting.
“However, today, the tool holders and machines operate a great deal more accurately, therefore the tools are optimised to specific applications and material groups,” he said.
According to Boyd, a common challenge for manufacturers is the variety of toolholders on offer.
“Careful consideration of the most suitable holder for your application is extremely important to ensure the optimal efficiency in machining operations,” he said.
Jason Theobald from Sandvik Australia agrees and told Manufacturers’ Monthly developments in toolholders such as hydraulic, shrink fit and hydro mechanical holders have resulted in a smaller run out capability.
“Older styles of toolholders relied on clearance fits to work, so you would have a smaller diameter tool inserted into a larger diameter toolholder.
“As a rule of thumb, with certain carbide cutters, any run out above the holder of 10microns can half the life of a tool. Most precision chucks are under 6 microns, so if you go from a side lock holder to a precision style holder you can double your tool life,” he said.
Theobald also said that one of the benefits of using a hydro-mechanical style toolholder in machining applications is the fact you are not relying on hydraulics to keep the tool locked.
“When you have mechanical type of clamping system you can do from roughing to finishing cuts as it is more rigid than hydraulic chucks ,” he said. “With most hydraulic chucks you are limited to finishing cuts.”
Advances in toolholder design are also allowing manufacturers greater accessibility in machining operations.
“Some toolholder designs are now slimmer and longer allowing greater accesability, which is particularly useful in aerospace and mould and die applications,” Theobald said.
“Tool holders available in modular designs, also allow greater flexibilty with tool length and adaptability to different spindle and tool changer types.”
The right fit
While new toolholder technologies can offer manufacturers many benefits, there are still some limitations to be considered.
Even though shrink-fit holders for example can offer improved accuracy and greater cutting speeds, they do so at a price, Theobald pointed out to Manufacturers’ Monthly.
“Using shrink-fit holders requires a heating/cooling unit. You can get less sophisticated units which just heat the toolholder but then a waiting period is required to let it cool down before use,” Theobald said.
“They can reduce cycle time in clamping/unclamping the tool but it’s a more elaborate and complicated system compared to other holders.
“Another disadvantage with shrink-fit systems is the specific size requirements they have. For example if you have a diameter 12 holder, you can only put diameter 12 tools in it.
“With other systems such as hydraulic, hydro mechanical and collet chucks, you have a wider range of tool diameters that can be placed in the holders,” Theobald said.
Both Boyd and Theobald stress the importance of choosing the correct toolholder for the application.
“Manufacturers need to look at their physical requirements, such as spindle interface and pull stud specifications and required length of holder i.e. short rigid or long reach?” Boyd said.
“They also need to look at operation type – drilling, milling, tapping, cutting – tool geometry and machine capabilities – HSM or conventional?”
Theobald also advised that manufacturers need to consider the amount of moving parts of the toolholder that can be damaged if operators are heavy handed.
“The point that we try to get across to people is that they spend a lot of money on their machines but tend to have less consideration for the aquisition of tooling systems.
“If they are going to spend months deliberating on the right machine, they should also be making informed decisions about toolholders and cutting tools,” he said.
Boyd says with Australian manufacturer constantly under pressure from the threat of business being lost to overseas competition, investment in solutions such as high performance cutting tools and toolholders can help give them an edge in the global marketplace.
“This will also ensure that products made locally are manufactured at the lowest cost with the highest quality. Also, in addition to this, I would consider buying Australian made products wherever possible to support the local manufacturing industry,” he said.
For information email
Sandvik Coromant – firstname.lastname@example.org
Sutton Tools – email@example.com.