In the business world today it’s all about being productive; applying lean principles such as Kaizen, continuous improvements, 5s, one-piece flow and so on. Most of us have heard or have first-hand knowledge of these methods and how they can improve businesses that are on a journey to become more effective and efficient. By reducing waste and improving processes companies can become more competitive and more profitable.
So it should come as no surprise that many companies are increasingly focusing on how to reduce CNC machining cycle times, particularly through the use of technology. Huge advances have been made in the materials that cutting tools are made from, the coatings applied to improve tool life, and the use of coolants. In addition, many CNC machining centres now feature adaptive feed control to ensure that a constant load is being applied to the cutting tool.
As with all technologies some are very affordable and easy to implement, others require expensive modifications to existing machinery.
This is also true in the world of CAD/CAM where new machining strategies are developed to improve the speed that material is removed or to improve surface finish. The use of adaptive feed control (AFC) is also being applied. This in principle is great, as the end user can now rely on software to consistently control the CNC machining centres, and thereby reduce the cost of applying adaptive feed control across the whole of the machining process.
However, one important element can be overlooked; how accurately does the software-based solution represent the actual machining process? If AFC is applied to code that has not gone through the post processor, then the chances are you’re not going to get the best out of the AFC.
One way to ensure that you are getting the most realistic performance is to use a solution that actually uses the same ISO G-code that the CNC machining centre uses. Vericut is the world’s leading CNC simulation, verification and optimisation solution and is at the forefront of CNC machining optimisation.
Vericut’s optimisation module, OptiPath®, automatically modifies feed rates based on the current cutting conditions to make your programs more efficient, while also extending tool life and improving the quality of the finished surface.
Vericut is a true knowledge-based machining system: through the simulation process it learns the exact depth, width, and angle of each cut – and it knows exactly how much material is removed by each cut segment. With that knowledge, OptiPath divides the motion into smaller segments. Where necessary, based on the amount of material removed in each segment, it assigns the best feed rate for each cutting condition encountered. It then outputs a new tool path, identical to the original but with improved feed rates. It does not alter the trajectory.
Simplified setup and use
A setup wizard prompts the user for cutter settings as the part is machined – essentially, adding intelligence to the cutter – and all the settings for that cutter are stored in an optimisation library. Every time that a cutter is used the results can be instantly optimised. OptiPath also features a ‘learn mode’ for creating the optimisation library with no setup required. For each tool, OptiPath finds the maximum volume removal rate and chip thickness and uses them to determine the best optimisation settings for the tool.
Optimisation for roughing
During roughing, the goal is to remove as much material as quickly as possible. OptiPath keeps the cutter at its maximum safe rate-of-advance into material for the varying cutting conditions. For example, during planar roughing of an aluminium aerospace structural component, material may be removed at a constant axial depth, but the radial width of cut could differ greatly from cut to cut. OptiPath modifies the feed rates to maintain a constant volume removal rate.
Optimisation for finishing
Chip loads typically vary widely as the tool profiles through the material left behind during roughing cuts and over the contours of the workpiece to near net shape. OptiPath adjusts the feed rates to maintain a constant chip load. (Consistent chip loads are recommended by cutting tool makers to reduce ‘chip thinning’.) The results are improved tool life and better finish. This is especially critical when tip cutting with a ball end mill or contouring a surface with a small step-over, such as semi-finishing or finishing in a tool steel mould cavity, for example.
How it works…
As the cutting tool encounters more material, feed rates decrease; as less material is removed, the feed rates speed up accordingly. Based on the amount of material removed by each cut segment, OptiPath automatically calculates and inserts improved feed rates where necessary. Without changing the trajectory, OptiPath writes the updated feed rates to a new NC program. An additional benefit of using OptiPath is that any fresh air cuts encountered are converted into maximum linear feed rates. This alone can reduce a CNC cycle time by as much as 10%. With more time available on the machine, planned preventative maintenance can be implemented.
High speed vs. high efficiency machining
The traditional method of high-speed machining, cutting at high feed rates with very shallow cuts and small step over can actually defeat the goal of reducing machining time. Cutting at greater depths removes material more efficiently. But, the cutter may encounter an overloaded condition causing it to break or exceed the machine’s spindle power. Since OptiPath knows the amount of material removed, it adjusts feed rates accordingly and maintains a consistent chip thickness. This provides more efficient machining while protecting the machine and cutter.
As a general guide, by using Vericut OptiPath end users can expect to reduce their CNC milling times by between 25 – 50% when cutting aluminium or similar materials, 10 -20% when cutting steal and other hard materials and between 5 – 15% when cutting titanium and other exotic materials.
Imagine having an extra 50% machining capacity available. Planned capital expenditure can be reduced on the need for new machinery to keep up with production, projects can be delivered on time more often, direct overheads like shift premiums can be reduced and cutting tools expenditure can be reduced. All these additional benefits will have a direct impact on any company’s profit margins.