6 Ways to Increase Tooling Life & Performance

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There is a gap between cutting tool knowledge and the built-in capabilities of even the most advanced CAM systems. The reason for this is the cutting tool makers know the most about tool performance. CAM systems that incorporate new toolpath strategies that have been proven effective.

Here are some of the strategies for you:

1. Roll In

This first recommendation for improving cutting tool performance via the tool path describes a very simple idea. Carbide milling cutters perform best when the chip thickness proceeds from thick to thin as the cutting edge moves. That way, cutting force is released gradually instead of suddenly. This is the reason to favor climb milling over conventional milling. For this same reason, the tool should not proceed into the material in a straight line. It should “roll” into the cut instead.

In other words, the tool should follow an arc into the material. It should pivot around a point on the circle of the tool circumference, so that the centerline of the tool proceeds through a curve that has the same clockwise direction as the tool’s rotation.

Entering the material this way keeps chip thickness thin at the end of every cutting edge pass, from the very outset of the engagement with the material.

Does taking this extra measure really matter? After all, climb milling will take care of the thick-to-thin requirement for all the rest of the cut. How much impact can the brief duration of entry actually have?

Most of the strain on a tool is not the result of gradual wear, but instead a result of those moments in the cut where the load on the tool dramatically drops off. Carbide inserts that gradually roll in instead of straight lining it have 8 times greater strength and durability.

Rolling in requires the correct direction. Thick-to-thin chips entail climb milling, but also require a “roll” direction that is the same as that of the tool rotation.

2. Ramp Down

Milling away a volume of material in sequential Z-level layers also favors a strategy for keeping the tool engaged. This is true of milling not only down through the layers of a pocket, but also down through the layers surrounding a positive feature. The default programming strategy for machining these layers often has the tool machine a layer complete, retreat from the cut, machine another layer, retreat, and so on. The disengagement can be detrimental to tool life.

Potentially a better strategy is to manually create a tool path that ramps down to the next layer at the end of each set of Z-level passes. If the geometry of the feature permits it, this ramp could be a long, straight descent. Each new ramp down could then lie directly underneath the preceding ramp down, so that the depth of cut remains the same as the tool goes down from one layer to the next. Or, for machined areas that are small relative to the size of the tool.

3. Spiral Out

Inside of pockets avoid the tool wear associated with changing directions at corners is to confine most of the milling to a continuous circular path. This can allow the tool to feed considerably faster and/or last much longer. The tool path follows a growing circle until it reaches far enough out that it finally has to give way to the pocket’s shape.

4. Slice Corners

The spiraling out might use a large tool that leaves stock behind in the corners of the pocket. This is stock that a much smaller tool will have to remove. Plunge roughing may also leave material behind in the corners of a pocket.

To machine these corners with a small tool, the typical approach is to feed into each corner, make a sharp turn and feed out. This approach demands slow cutting. In addition, it might cost considerable tool life because the increase and release of the load subjects the tool to strain.

Each slice is a different tool move that is defined separately. Corner slicing moves with a fixed contour operation and boundaries can be set using the “Fillet” command.

5. Turn Left then Right

Just like milling tools, turning tools also suffer strain when the load on the tool is suddenly relaxed. Using round turning inserts presents particular opportunities for keeping the cutter continuously engaged.

Specifically, for turned features requiring machining with layers. Rather than repeating the same arcing tool path further into the part, change the cutting direction at the end of every pass. That is, the round insert traces the shape of the feature toward the left, then goes deeper to trace the shape of the feature toward the right, and so on until the feature is finished. By going back and forth, the insert lasts longer because it never leaves the material, causing the load on the tool to remain more consistant.

6. Drive the Edge

Accurately removing material around the curvature often calls for five-axis milling with relatively small-diameter tools. Given the combination material and the small tools, cycle times can be long. The slow passes with small tools can at best be like nibbling away the large-diameter parts.

Processes for milling these parts can actually employ much larger tools than shops typically use. The key is to use cutters with round inserts for edge strength. The finish and accuracy of the conic or cylindrical surface is ensured in two ways: (1) by driving the tool according to the leading edge of this insert, where the round insert actually meets the round workpiece, and (2) by carefully managing heights between passes with the large-diameter tool.

Source: Modern Machine Shop