Cutting tool inserts are expensive. Machines are expensive. Metal stock is expensive. So, too, are time and energy.
Average tool life can affect all these cost centers to varying degrees, so it can easily become a make-or-break factor for machining profitability. It’s therefore important to figure out how you can maximize it.
What steps should you take to ensure you’re getting the longest possible, quality-yielding tool life out of your inserts? And how can you thereby ensure that your shop’s machining operations run as lean as possible?
Today, let’s discuss 5 critical steps you should follow to improve your machine shop’s profitability.
1-Make sure you select the cutting tools that are most appropriate to the jobs.
Different workpiece materials, of course, require different cutting materials (of varying grades) to effectively cut them.
To determine the most effective cutting tool for a particular job, you’ll need to consider:
- The workpiece’s material properties
- The cutting tool’s material properties
- Factors within the cutting zone environment (friction, temperature, coatings, etc.)
A highly abrasive material naturally requires a cutting tool that exhibits excellent wear resistance. Hard material requires an even harder material to score it. Polycrystalline diamond inserts are highly wear-resistant and extremely hard — why not use them for everything?
An experienced machinist can tell you exactly why.
Sure, diamond inserts are hard, but they’re brittle, so they chip easily at high turning speeds. They also decompose easily at high temperatures and will dissolve in molten iron.
Thus, polycrystalline diamond inserts are ideal only for turning non-ferrous materials at relatively low speeds and temperatures. So, if the job is high-speed roughing of gray cast iron in a high-temperature operation, another tool — a cubic boron nitride insert, for example — is a better choice.
2-Pay attention to insert geometry and heat exchange.
The geometry of a given insert will have a significant bearing on the temperature at the cutting interface and on-chip control.
In long-duration, high-temperature turning operations, for example, it’s important to select an insert shape that will not only produce short chips but allow the majority of the heat generated in the cutting zone to be shunted away through the chip itself.
To the latter point, tool geometries that result in excessive heat transfer to the workpiece — or to the tool itself — could lead to cutting defects, or to premature tool wear and failure.
For each material, there’s usually a sweet spot for chip control. Ideally, a good set of parameters for a chip breaker will produce short, segmented chips.
3-Conduct tool life and machinability tests.
Tool life is the length of machining time a new tool can work before attaining a specified limit of wear (or otherwise failing). It’s governed by machining parameters, e.g. velocity, feed, and depth of cut. Tool life decreases (exponentially) for every incremental increase in speed.
Once an appropriate cutting tool is selected for the material you want to test it against, begin with a preliminary tool life test at a nominal speed. Over the tool life test, you’ll make several tool wear measurements at suitable intervals, recording them as “wear vs. time.”
Plot the data points along a curve, like so:
If your manufacturing floor is already IIoT-connected and able to supply your team with a rich data set — and if you have the capacity to run tests in-house without negatively impacting your production schedule — this step should be the simplest. Set your parameters, run your tests and watch the data roll in.
4-Use the data to make informed business decisions.
Let’s look at the example above: tool life vs. turning speeds for Material A and Material B.
We see that our tests revealed Material A can run for 40 minutes at 720 SFM before wearing out the tool. Material B can run for 40 minutes at up to 800 SFM. All other factors held constant, then, Material B causes less wear on the tool than Material A and can run approximately 10% faster.
Now we can make an informed business decision. Our example study has given us:
It may be more profitable to use Material B than Material A if a product made from Material B will provide a comparable function for the end customer.
A suggested course for further research.
A prototype or first article should be produced using Material B, tested for performance in the intended end function, and tested for durability. Results should be compared to existing data on the same product made with Material A.
A contingent action plan.
If performance and durability results are favorable for the product made with Material B, it should be produced and brought to market.
5-Continually optimize your machining process.
Once you’ve used your tool life test to identify more efficient, more profitable means of production, you should continue to refine the process.
Further machinability studies could help you optimize your newfound opportunity and squeeze out an additional return on investment (ROI). In our example case above, for instance, we could conduct additional trials to examine:
- Average tool life vs. cutting fluid or coolant used
- Average tool life vs. fluid flow rate
- Feasible work speed vs. fluid used
- Feasible work speed vs. flow rate
- Average tool life vs. cut depth
- Average tool life vs. feed rate
With each new finding, we could tweak the process to make it more efficient, more profitable, safer, etc. Learning never stops.
Use these steps to improve your machine shop’s profitability.
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