Controlling costs as a manufacturer is essential to remaining competitive in any market. One of the key areas in which cost reductions can be achieved is in regards to tool life. PCD tools are versatile cutters that can dramatically decrease tooling costs and deliver better surface finishes for parts. However, they are also brittle and susceptible to chipping and cracking if mishandled. As well as knowing the best way to store tools, optimising their use during machine operations is key to maximising tool life. This article will serve as a tool care guide that discusses several ways to ensure you get the most out of your tools, PCD or not, and maximise your return on investment through proper usage and care.
How do I increase my tool life in milling?
Long production runs, incorrect feed and spindle speeds, deep cuts, and improper handling are all sure-fire ways to dramatically decrease tool life or break tools prematurely. However, there are five main ways to reclaim control over manufacturing costs and maximise tool life.
1. Reduce Ae/D ratio
As it relates to cutters, ‘Ae’ is the cutter’s radial depth, or how much the cutter is stepping over into the workpiece. Ae is also referred to as ‘step over’ or the ‘cut width’. On the other hand, ‘D’ is the diameter of the cutter. By reducing the cut width to diameter ratio, tool life can be greatly increased. When the ratio is large, chatter can begin to occur – if too much chatter is present, the tool’s life is significantly reduced and breakage can even occur, much faster than expected. Reduce this ratio to help maximise tool life.
2. Use shrink fit or hydraulic holders
Another way to increase tool life in milling is to use shrink fit or hydraulic holders for tools rather than those that simply use a set screw or collet chuck. Shrink fit holders have a diameter slightly smaller than the shank diameter of the tool. As the holder is heated, its diameter increases and the tool can be inserted. As the holder cools back down, it shrinks and tightly grips the shank of the tool. Hydraulic holders use an internal piston with pressurised hydraulic fluid to grip the shank of the tool.
Both shrink fit and hydraulic holders can increase tool life through an extraordinarily tight grip that increases concentricity and reduces chatter, leading to better surface finishes and longer tool life. Though using these holders can be expensive, their ability to increase tool life can justify such a purchase.
3. Ensure tool assemblies are balanced
Two factors that can influence tool life negatively are improper tool set-ups and tool paths. These two things inevitably lead to excessive vibration and chatter. Unbalanced tool assemblies are no different. Before starting a job, machinists need to ensure tool assemblies are balanced based on the RPM they expect to run – if not, the tool becomes susceptible to chatter, which decreases the tool’s life and worsens part quality. However, with balanced tool assemblies, tool lifespans are increased and part quality is improved.
4. Use recommended cutting data
In machining, it’s important to keep cutting parameters within the recommended bounds described for the material and the recommended bounds for the machine as stated by the manufacturer. Depending on the workpiece material, hardnesses can significantly differ. Likewise, the hardness of different cutters can also differ. Therefore, it’s important to stay within the recommended range for feed speeds. Not doing so can result in chatter, broken tools, long lead times, and quality defects.
5. Use appropriate work-holding methods
The life of a tool and part quality are heavily influenced by the work-holding method chosen. It’s important to pick a method that will ensure the workpiece is securely clamped and will not move during machining. If not, the workpiece will vibrate as the tool cuts into the part. These vibrations are then transferred over to the tool and lead to chatter. Pick a work-holding method that adequately holds the workpiece down, and tool life will be maximised.
Tools that break prematurely can cause disruption – not just to your productivity, but also to your bottom line. Simply knowing the best ways to store tools is not enough when it comes to tool life. Consider this article and the five methods described as a tool care guide to maximise your tool life and subsequently save on having to buy replacement tools. Contact an Exactaform representative today to discuss how we can assist you with your tooling needs.