MMSOnline - Optimize Your Machining Process

So, let's take a look at how you can evaluate the factors that drive overall machining costs.

Machining costs are influenced by a range of factors including cutting tools, workholding and measuring equipment, machine tools, workpiece materials, labor and overhead.

Cutting tools and workpiece materials represent variable costs, at 3 percent and 17 percent of total cost, respectively. Fixed costs break out as follows: machine and toolholders (27 percent), labor (31 percent) and overhead (22 percent). Improving any of these variables has a significant effect on productivity and ROI.

The slice for hourly machine burden, reflecting investments in plant and equipment, has grown dramatically in the last ten years relative to labor cost. This is borne out on the shop floor where more and more machines run largely unattended, with one operator running several machines or cells. You may be able to adjust labor to workload through overtime, part time workers or workforce reductions. But once you buy a $500,000 fully featured CNC mill, you can't lay it off when the workload drops. Increasing capital intensity makes it imperative to pay more attention to return on capital and financial performance of equipment in production planning and procurement.

Though tooling represents a relatively small portion of total cost per part—about 2.5 to 3 percent—it can significantly impact total cost per part. The key to optimizing capacity lies in keeping bigticket machinery working, cutting at optimum rates for the material and, above all, in minimizing idle machine time.

Though longer tool life is often touted as a means of improving machine uptime, in reality a 50-percent increase in tool life only reduces total cost per component by about one percent. Compare that to an improvement in cutting para-meters, where a 20-percent increase in cutting speed reduces total cost per component by 15 percent.

Such increases in speeds and feeds are common today with advanced tooling. For example: A switch from a conventional insert to an insert optimized for steel workpieces enabled a hydraulic components manufacturer to increase cutting speed 133 percent on an unalloyed steel cylinder. As a result, productivity rose 40 percent for the process with equal tool life, and the manufacturer gained 642 extra hours per year.

The message is clear. How you tool a new bigticket machine from the outset will make a surprising difference in its productive capacity and ROI. The more expensive the machine, the bigger the dollar difference tooling will make. This may seem too obvious to mention. Yet, when you look at how most new machines are justified, clearly this "obvious" truth is too often overlooked.

The remedy? Consider tooling as you consider the machine itself. Don't separate the two. The choice of tooling, and especially toolholding, will materially affect the productive capacity, and therefore the financial performance, of any new machine.

And, above all, look into modular toolholding for any new CNC milling or turning machine you are considering. The reason is simple. On CNC turning equipment going into medium- or short-run work, modular toolholding will almost certainly increase productive capacity by approximately 30 percent over conventional "stick" tooling. On CNC milling machines, modular toolholding will almost certainly cut your tooling inventory costs by 25 percent over the life of the machine. Milling throughput will likely improve as well, but by less than the 30 percent range typical on turning equipment.

Cases abound in which modular toolholding benefited CNC milling operations in different ways. One heavy equipment manufacturer experienced a 35-percent saving in tooling costs over the life of a new machine by standardizing on modular toolholding from the outset. Where they normally had to buy three full sets of conventional tooling over the life of a CNC mill, now they only need to buy 1.5 sets.

In this case, on a $500,000 mill, an extra $15,000 for modular toolholding at the outset saves $75,000 in tooling over the life of the machine. And since modular cutters become interchangeable, the company also reduced its cutter inventory by 80 percent and eliminated the need for specials. Labor costs also went down for tool setting and repair. And milling throughput improved on the order of 10 percent.

Smaller shops report essentially similar experiences. For example, one small job shop serving a variety of markets commonly faced up to five changeovers per day on a CNC milling center. By tooling a new CNC mill with $30,000 in modular toolholding from the start and retrofitting all the old mills, they cut jobto-job changeover times by 75 percent. And they accelerated the payback from their investment in the new machine by six months.

In addition to tooling cost savings, most modular toolholding users also report at least moderate capacity gains, leading to improved return on capital employed for the machine as a whole. Such capacity gains increase with the number of machines, the variety of jobs handled and the frequency of jobto-job changeovers. The benefit of modular toolholding on milling equipment also increases with the complexity of jobs and workpieces and the necessity for special tools. Buildingblock extensions available in many modular toolholding systems enable handling long overhangs, difficult reaches and unusual cuts. Contrary to expectations, such extension arrangements are actually more rigid and free of vibration than conventional solid tooling.

Modular toolholding is a holding system that provides quick change, interchangeability and positive positioning repeatability for a new cutting edge. As such, it minimizes all production delays for cutting tool edge changes, onmachine test cuts and tool offsetting. By eliminating these time wasters, machine shops typically cut dead machine time on CNC turning equipment by an average of 25 percent. It also enables shops to load any tool into any machine, regardless of which spindle taper or toolholding configuration was built into the machine originally.

A modular tool is a two part component. The back end, or clamping unit, is permanently mounted to the machine. The front end, or cutting unit, holds the cutting edge. The two parts mate quickly and precisely to form a very rigid toolholding structure with the cutting edge in exact reference position within millionths of an inch. The shape of the mating sections is identical for all components in the system so that any cutting unit installs in seconds into any clamping unit on any machine.

Today's leading-edge modular toolholders assure that repeatable accuracy and rigidity are at least equal to—and sometimes better than—conventional integral or solid tooling. Virtually all offer a tool-change speed within 10 to 30 seconds, from the time you shut down to the time you start up again. Some offer the strength and rigidity to take fullspeed cutting loads. You don't have to ease back on material removal rates because of structural limitations in the toolholding system. Some can handle both milling and turning with the same system. The back end of the modular toolholder, permanently installed in the machine, bridges the difference in spindle tapers. It presents the identical coupling geometry for every cutting tool you may ever use.

The Coromant Capto toolholding system provides a good example of the latest in modular quickchange tool-holding. The clamping system is based on a tapered polygon, which provides a very large surface area for transmission of all torque and cutting forces. With regards to accuracy, the system provides 0.000080-inch cutting edge repeatability in length, width and height of the same tool when reclamped. Runout of the system is less than 0.0002 inch per coupling.

Changeout time averages 10 seconds. A half turn of an Allen wrench locks the mating parts to provide positioning repeatability. And the mating parts cannot be clamped together wrong. The entire system includes more than 1,000 standard components today.

By and large, modular tooling will cost 10 to 30 percent more per station than conventional tooling. But let's put it another way. On a new machine, it's generally accepted that conventional tooling represents perhaps 10 percent of the total cost of the package. Modular toolholding, on the other hand, increases the cost of the total package by about 3 percent. And as shown earlier, that extra 3 percent will buy you up to 30 percent greater capacity, lower tooling costs over the life of the machine, and better overall economic performance from the investment.

For these reasons, many companies who have standardized on modular toolholders for new equipment usually include at least part of the tooling system as a capital investment and amortize it over the life of the machine. This makes good sense. After all, the back ends of the better modular toolholding systems are usually dedicated to the machine and will last at least as long as the machine. Moreover, they pay for themselves out of savings in a matter of months and, more important, help improve the earning potential of the machine as a whole.

Other tooling advances can make your new machine more productive, and should be considered from the outset. Advanced short- and deep-hole drills can speed up hole making (often a bottleneck operation) by anywhere from 50 percent to four or five times. Positive rake milling cutters and inserts can speed milling, reduce cutting forces and outlast negativerake milling tools by more than 50 percent on average. Subtle changes in insert geometry nose radius and chipbreaker, such as in new wiper milling inserts, promote a quadrupling of feed rates and corresponding productivity gains of at least 20 percent.

Bottom line, your new machine will perform only as well as its tooling allows. And you can control which tooling goes on that machine. The old adage, "You're making money only when you're making chips," was never truer than it is today. With today's bigticket machines and increasingly capital intensive operating environment, making chips more of the time is even more vital to profitable operation. This is why the tooling choices you make for your new machines are so important—and why tooling should be considered along with the new machine itself.

Tips For Maximizing "Tooling Power"

How can you take advantage of tooling to improve the financial performance of your new machinery? Here are twelve guidelines.

When comparing tooling and toolholding for your new equipment, look at the value provided. Evaluate mainly the improvement in capacity and financial performance it provides for the machine as a whole—not just the cost of the tooling itself.
Include tooling and toolholding as part of your new machine procurement planning.
Consult with a knowledgeable tooling vendor before any new machine decision is made.
Consider modular toolholding. It will almost definitely lower the capital cost of increasing your capacity, whether it's milling, turning or drilling.
Treat at least the back end of modular tooling as part of the new machine price and amortize it over the entire life of the machine.
Select the tooling based on its value in improving the earning potential for the machine tool as a whole. You will find great differences among various tooling and toolholding systems in their power to improve the financial performance of the machines on which they are mounted.
Wherever possible, convert every benefit gained through tooling to improving the productive capacity and earning potential of the new machine. For example, if a new insert outlasts an older one, then push feeds and speeds until the new tool wears out as quickly as the old. More parts in the bin per shift and higher capacity for the machine are much more important than lower tooling cost per part.
Look beyond return on investment for the tooling itself. Look at what tooling can do to reduce your new machine outlays and for the ROI of the machine as a whole.
When you run that new machine, push the tooling as much as possible. Remember, the vendor's recommended machining data for any insert is conservative. Think of recommended settings as a starting point only. A good rule of thumb for optimizing productivity and edge life is to push the tool until it fails after about 15 minutes of cutting time.
When machining stainless steel, run it faster. Stainless steel is probably the most coddled workpiece material being machined today.
When you consider modular tooling, remember you no longer need to compromise cutting rates and repeatability. The best of today's modular toolholding has the strength and repeatability of conventional tooling.
When choosing a modular toolholding system, remember you will live with your decision for years. Regard it as a marriage. Select a modular toolholding system that will cover your present and anticipated needs, including the increasingly popular turn/mill machines.