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Turning And Grinding Solutions For Machining Automotive Gears

Turning And Grinding Solutions For Machining Automotive Gears

Innovation in transmission design means that today’s transmissions are generally getting smaller, while simultaneously offering more gear ratios. In what ways have machining automotive gears improved? By Markus Isgro, marketing communications, Emag

The production of a large volume of parts with extremely high quality has been a key feature in the production of automotive transmissions for decades. Developments in both the marketplace and technology, however, are continuing to change production at a very fast pace. For example, the demand for cars has been rising. This Turning And Grinding Solutions increase in quantity is pushing the production volume of gears even higher.

At the same time, the competition from new market participants in Asia is intensifying. What can the transmission builders of OEMs and suppliers do in their production areas to address these developments?

Multifunctional machines that perform an array of hard machining processes on the transmission components in succession are able to provide such a solution. Emag, with expertise in turning and grinding, have provided an option called the VLC 200 GT. This machine was developed for the chuck machining of automotive gears.

Innovation In-Transmission Design

The automobile industry is continuing to spend more money on research, and annual increases of between seven and eight percent in this area have long since become standard. OEMs and suppliers in Germany alone recorded more than 34 billion euros (US$36.5 million) in development expenses in the past year, according to a study by the German Association of the Automotive Industry.

One of the main focal points of this dynamic innovation is transmission design. Today’s transmissions are generally becoming smaller (and therefore lighter), but can simultaneously offer more gear ratios and therefore have more gears and gearing components. This produces optimum speed ranges and reduces fuel consumption.

Each individual gear must be manufactured extremely quickly and very precisely. Given the high unit volumes, the production technology is virtually always a concern for production planners. They try to find solutions that reduce processing time and unit costs, while still continuing to increase the quality of the parts.

Nearly 20 years ago, the first pick-up machine for the combined turning and grinding machining of chucked parts was developed. Its key feature was the combination of the two machining processes in rapid alternation, based on the shape of the workpiece and the quality required.

Building on this, the VLC 200 GT has focused on enhancing productivity, especially in the machining of automotive gears. Guido Hegener, managing director of Emag, explained the approach: “The high unit volume and quality requirements of gears make them ideally suited to our approach.”

Complete Process, Including Dressing

To start, the machine is loaded at high speed by the integrated pick-up spindle. Once the spindle with the part reaches its machining position, the process starts with hard pre-turning of the shoulder and the bore hole in quick succession.

Only a few micrometres of material are then left to be removed from the gear. That means the subsequent grinding process, using either aluminum oxide or CBN grinding wheels, takes significantly less time.

Meanwhile, the machining quality also benefits from the combination of turning and grinding: when there is only a small amount of material remaining to be ground away after turning, the specifications for the grinding wheel can be based more precisely on the end quality required. As a result, surfaces with an average peak-to-valley height Rz of less than 1.6 micrometres can be created.

In addition, this multifunctional technology offers users a multitude of possibilities, such as internal and external grinding spindles, scroll-free turning tools, block tool holders, and a 12-station tool turret, which can all be installed as required.

Tool Cost Savings

There is an additional advantage in terms of tool costs because during this process the grinding wheel wears down more slowly and therefore does not need to be dressed as often. When it does need dressing, the machine has a separate diamond-coated dressing roll designed specifically for this. To ensure sustained process reliability and high machining quality, the integrated measuring pin is used to check the diameter and length of the clamped component at the end of the process.

Operator comfort and ease of access were also important priorities, so large doors allow easy access to the machining area. The tools and clamping devices are easily accessible and can be changed quickly and conveniently.

Automated Option

With a small footprint and the ability to flexibly integrate into interlinked factory systems, the machine can be incorporated into a plant’s production system with the aid of a variety of automation systems.

One option for this is the TrackMotion system. This automation system handles the transportation from machine to machine with functions such as part gripping, positioning, and flipping of the workpiece.

“On the other hand, there is also the option of using the machine as a stand-alone machine with simple O-belt automation. This is an appealing alternative for many customers in the Asian markets especially,” Mr Hegener added.

The VLC 200 GT uses a variety of process combinations for the hard machining of checked components

The VLC 200 GT uses a variety of process combinations for the hard machining of checked components.

Dr Guido Hegener, managing director of Emag.

Dr Guido Hegener, managing director of Emag.

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Quality Is Profitable: Faster Machining Time With Tool Holders

Quality Is Profitable: Faster Machining Time With Tool Holders

In order to increase the productivity of the milling process in a die and mould company, one cannot concentrate only on the high-performance Faster Machining centres. Contributed by Haimer

Die and mould company Langer GmbH & Co found out that proper usage of tool holders could reduce the total Faster Machining times on several applications almost in half.

The company, located in Illmensee, 17 km north of Lake Constance in Germany, is a die and mould producer with approximately 140 employees. The services that they offer include the development and production of prototypes of serial tools for injection die moulding, up to the sampling of pre-series and small series production.

Injection Die Moulding

The die and mould department’s 60 employees focus on finishing the tools for injection die moulding in the quickest possible time while reaching the high-quality requirements of the automotive industry.

The data to be transcribed out of the design department into high-quality tools out of aluminium-wrought alloy or profile steel of type 2312 and 2767 is the job of the company’s NC Machining team. Their team leader, Jörg Lehmann explains that along with the machines, tool holders and tools are the main factors that affect machining times. In his department, there are six modern, three to five-axis machining centres from DMG, Mikron and Hermle.

Langer was not satisfied with the current shrink fit chucks they were using, however. After a few shrink cycles, those shrink fit chucks were no longer giving the required clamping forces.

Theory And Application

An important feature of shrink fit chucks is a tight-fitting bore that holds the tool in the longest range possible. The entry chamfer of the shrink fit chuck plays a very important role, as this is where the protruding length and the rigidity of the tool are decided. Shrink fit chucks from various producers allow the entry chamfer to be five to 10 mm long.

As a result, there is often no clamping in this position, and the protruding length of the tool is unnecessarily increased. This can also similarly happen on the back end of the fit, where the chuck often has too much material turned out. There are also no clamping forces that hold the tool here. Due to these factors, the range of the fit is relatively short.

Mr Lehmann Faster Machining tried the chucks from Haimer and shared his observations. “The chucks offer a lot of mass in the upper range, which reduces vibrations and the slim form in the lower range enables machining in tight contours,” Mr Lehmann said.

Made For Mould & Die

The company Faster Machining developed the Power Mini Shrink Chuck especially for the requirements of five-axis milling in the mould and die industry, where they are suitable due to their special combination of a slim tip and strong base.

A prominent feature of the chuck is the slim outside three-degree angle contour, which is the draft angle that is used in injection die moulding. The chuck has a strengthened contour at the bottom end of the chuck. Due to this, the shrink fit chuck can cut in deep mould cavities but is rigid enough to absorb heavy side forces occurring at five-axis machining.

“We can go for much higher cutting values and save time with pre-work, for example, groove milling in steel. Here we use a two mm diameter ball cutter to pre-finish first to 1/10 of a millimetre. We can reach the desired result in one finishing pass. The machining time is then reduced by up to 50 percent,” said Mr Lehmann.

Optimal Surface Finishing

Faster Machining Mould and die makers often use high rpm in order to achieve optimal surface finishes. When milling in deep cavities or pockets however, it is important that the chips are properly washed away. That works only when the coolant stream hits the right point with high pressure.

Haimer recognised this problem in its production. The company’s previous solution was the Cool Jet System, which integrated coolant bores into shrink fit chucks and other tool holders. Through the use of two or three nozzles, the coolant is transported directly onto the tool cutter.

The company used this approach to develop the Cool Flash system, which can be integrated into shrink fit chucks. At the top of the shrink chuck, a disc is inserted onto the Cool Jet bores, which has a small ring gap left open with slots opposite to the tool shaft. The coolant is not fed through points but is transferred in a ring form to the cutter and can lie around the tool like a coating. The coolant then clings and slides on the miller shaft, also at high rpm, as a coating over the chip flute to the cutting edge. The shrinking process is not an issue and the system does not involve any assembly.

Faster Machining  High-Speed Cutting

In order to have high-quality finishing results, the milling cutter must be cooled externally to flush chips out of the way, but many milling cutters may not have an internal bore for the coolant due to stability reasons.

In Langer’s testing of the new system alongside the typical flush cooling from the coolant hose, Mr Lehmann said that the system has allowed for speeds of 20,000 rpm, compared to previous tests which started to have wide dispersion at 6,000 rpm.

“Where we used to have to decrease feed rates by critical operations such as pocket milling, we can now work in normal speeds. There aren’t any chips that get stuck and the millers do not break. In addition to the Faster Machining increased process stability, we also save on coolant usage compared to the flush cooling from outside,” said Mr Lehmann.

The Faster Machining proper shrink fit machine is also required for the shrink fit chucks. An inductive shrink fit machine can be adjusted to the length and diameter of the chuck. Due to this only the clamping range of the chuck is heated, which considerably reduces the cooling time, among other things.

The proper shrink fit machine is also required for the shrink fit chucks. An inductive shrink fit machine can be adjusted to the length and diameter of the chuck. Due to this only the clamping range of the chuck is heated, which considerably reduces the cooling time, among other things.

Faster Machining From left to right: Joerg Lehmann, team leader NC machining, Langer,and Oliver Lechner, Haimer.

From left to right: Joerg Lehmann, team leader NC machining, Langer,and Oliver Lechner, Haimer.

The Faster Machining finishing was made in one pass and met all quality requirements.

The finishing was made in one pass and met all quality requirements.

The Faster Machining Cool Flash System enabled cooling and chip-removing effect up to 20,000 rpm.

The Cool Flash System enabled cooling and chip-removing effect up to 20,000 rpm.

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The Macro Economics Of Optimal Material Removal

The Macro Economics of Optimal Material Removal

Many CNC parts manufacturers, as well as production and job shops, could reduce their overall production costs 15 percent or more by leveraging existing CAM technology that is readily available. By Stas Mylek, applications advisor, CNC Software Optimal Material Removal

Typically, production cost centres are Optimal Material Removal often evaluated independently, whether they be tool costs, raw materials, capital equipment, manpower, or production costs. However, incremental savings in each typically do not add up to significant gains overall.

Our Optimal Material Removal contention is that the areas of cutting tools, CAM, and production, particularly the newer toolpath technologies, along with machine capabilities and investment, be looked at concurrently with the goal of optimisation as they relate to each other. What we are looking for is hitting the optimised sweet spot of all three, referred to as machining effectiveness, to gain significant production cost savings.

Machining Effectiveness

Adoption of this approach pursues a very simple formula:

  1. Select optimal cutting tools for the part. This will often be high-quality Optimal Material Removal carbide, but can be ceramic, insert tooling, or any other type of tool. The key is optimising to the chosen tool(s).
  2. Based on the cutting tool manufacturer’s recommendations, import the correct parameters for consistent chip load machining into toolpaths having this capability.
  3. Optimise the cut parameters, if necessary, to match the full capabilities of the machine the job is running on.
  4. Repeat for every toolpath process you create using CAD/CAM software where the same tools, material, and machine are used.

Everything begins with the tool, and the calibre and quality of carbide, advances in new ceramics, new grades, coatings, tool geometries, and the design engineering going into today’s tools are far different and more capable today than what was available just five years ago. Full slotting tools capable of going up to four times deeper in not only hardened steels and stainless, but super alloys was unheard of even a short time ago.

Today, it is much more prevalent. These tools promise huge material removal gains, yet also require exact adherence to recommended cut conditions and chip load to gain optimal performance and predictable tool life to address machining effectiveness.

New Toolpath Strategies

Optimal material removal and cutting tool performance occur when CNC machines are programmed using newer, readily available CAD/CAM software technology (Mastercam’s Dynamic Motion technology is one example). This technology continually maintains the cutting tool manufacturer’s recommended cut conditions and chip load, regardless of part geometry. Significantly higher material removal rates, with more predictable and extended tool life, translates into the higher reductions in cycles times and production costs necessary for achieving machining effectiveness.

And the machining effectiveness of the newer toolpath strategies are not limited to just the new breed of cutting tools; improved material removal rates and tool life can be realised with virtually any tool since these newer toolpath strategies are based on consistent cut conditions.

Over the better part of a decade, since these new toolpath strategies have been available, manufacturers of all types typically report CNC machine cycle time reductions for their roughing operations of between 25 to 70 percent—sometimes much more. Recently, a manufacturer reported that apart with a machine cycle of 32 minutes had been reduced to 12 minutes by implementing a machining effectiveness mindset.

Matching Machining Capabilities

Optimal Material Removal Machining effectiveness gets another cost savings to boost when you begin to match machine capabilities to cutting tool performance potential and toolpath strategy.

With a toolpath that always keeps the tool in a safe, cutting condition and does not violate the tool manufacturer’s recommended chip load specs, CNC programmers can apply different methodologies. On faster machines where work holding might be lighter and cutting tool selection more traditional, users might opt for a higher feed rate and small step-over approach to maximise material removal rate and to lower cycle time.

If set up is on a higher horsepower machine, that tops out on feed rate yet where the work holding can be locked down, a company might run the newer, full slotting-capable tools. Matching tool to machine to cutting tool capability, they could run heavy step-overs of 65 to 80 percent at 2x to 3xD or more and see material removal gains increase well beyond 70 to 75 percent over traditional toolpath strategies, resulting in a huge production cost savings. All this is feasible once companies put machining effectiveness into practice.

Time To Adopt

However, adoption of these newer strategies and embracing a machining effectiveness mindset has been slow, yet there are signs they are finally beginning to take hold. Straw polls of CAD/CAM users and industry event attendees indicate that 30-40 percent of programmer/machinists are using these new toolpath strategies with increasing regularity.

But what about the other 60 percent of CAD/CAM users? They frequently report not looking into it because, honestly, they have not had the time, nor given approval to do so.

Exactly how much time are we talking about to implement a demonstrably better cost cutting methodology? Actually, very little. Tool manufacturers’ recommended cut parameters are often provided in available tool libraries and easily imported directly into toolpath operations of the CAD/CAM system when selecting a tool and material. Adjustments are made based on tool capabilities such as whether to use a small or large step-over approach and what limits need to be applied to depth cuts based on the type of tool.

Utilising Your Machine’s Potential

Machine limits relative to spindle speed, feed rate, and horsepower are also considered prior to processing the program. Using toolpaths that maintain consistent chip load and safe cutting conditions, it is simply a matter of taking the program out onto the machine. Machine performance is validated relative to holding the programmed feed rate, ensuring the right workholding setup is in place for strategy, and that spindle load is maintained under the set requirements.

Once the program is running on the machine, it may be necessary to make some minor adjustments to toolpath parameters to make sure the software is taking full advantage of the machine’s capabilities.

Conversely, some machine controller settings may need adjustment to take full advantage of the toolpath. Very often, cutting tool vendors, CAD/CAM resellers, and technical specialists are happy to help you maximise performance and prove out the application.

Cutting Chunks Off A Cycle

Once the process and strategy is validated, the approach can be applied every time that tool is used to machine a part made from that material. Benefits can be seen in everything from simple to extremely complex, aerospace and thin wall parts, and more easily machined materials to super-alloys.

For example, a job shop recently took six hours off of a 24-hour cycle for an aerospace part by adopting machining effectiveness methodology. This conversion paid for itself immediately after the first part was produced. Better still, the company had a contract to make six more of them. So the benefits multiplied quickly.

The bottom line is that many manufacturers in many industries are operating far less efficiently than they could be and leaving money—lots of it—on the table by not optimising cutting tool, toolpath, and machine performance and viewing them in an integrated relationship. Cutting costs is necessary to compete and remain profitable. However, there’s a lost opportunity cost for companies, and possibly for entire manufacturing sectors, that don’t leverage everything they can get from inter-related technologies.

Significant Gains

By aiming at that optimised sweet spot called machining effectiveness, the gains company-wide or even for industry, can be significant. By that, I mean millions.

This seems like a pretty outrageous claim. Can it be justified? I think so. Cutting tool manufacturers are very confident that their best route to justify the benefit of higher quality and cutting tool performance is to show new users improved productivity.

For example, Tom Raun, national milling product manager of Iscar Cutting Tools, maintains that the cost of the tool is really insignificant compared to the benefit of improved machine cycles. Cutting tools amount to about three percent of a typical CNC shop’s total costs. If tool life can be doubled, then that ROI amounts to less than 1.5 percent of the shop’s total costs for cutting tools. Even so, if a shop realises it can reduce its tooling costs by a million dollars by making a simple purchasing decision, it will jump on that opportunity in a heartbeat.

On the other hand, experience has Raun convinced that a 20 percent improvement in material removal efficiency can yield a 15 percent improvement in manufacturing costs per unit.

Think about it: A shop with US$100 million in sales could realise a US$15 million gain by making an average 20 percent across-the-board improvement in machine cycles using mostly existing equipment and software. If parts manufacturers in just the automotive, aerospace, and energy industries embraced this idea, the savings would easily be billions.

Embracing The Effective Viewpoint

So why are we not doing it? It all comes down to a change in viewpoint, finding the time to save time, and making a commitment to get better. Production deadlines are always looming and we all get comfortable with current processes, whether we’re managers or programmers. It takes valuable time and resources to test and evaluate new technologies and methods, or to experiment with the outer boundaries of what is possible.

Yet, with the potential payback and production costs savings of 15 to 25 percent or more, isn’t it worth it? The pressure of a tight deadline could be loosened by the opportunity of getting jobs done faster and with fewer issues or setbacks.

What is needed is a little bit of planning and optimisation targeting better machining effectiveness up-front. This can lessen the impact of tight deadlines as well as downtime incurred due to lack of efficiency. It is not uncommon to find initiatives of this sort yielding total manufacturing process cost reductions of 15 to 25 percent or more.

Savings of this magnitude could be used to achieve such worthy objectives as improving profits, capturing more business, and doing the modest amount of training required for more robust workforce development and continuous improvement.

People who are in charge of the day-to-day operations at machine shops are frequently under too many pressures to take the lead in initiating the sort of changes that are required. That sense of urgency also needs to come from the top.

Optimal Material Removal Manufacturers need to evaluate their tool efficiency to achieve maximum output.

Manufacturers need to evaluate their tool efficiency to achieve maximum output.

Optimal Material Removal Cost breakdown of the manufacturing process

Cost breakdown of the manufacturing process.

Optimal Material Removal Stas Mylek believes the right tools are essential in increasing revenue for manufacturers.

Stas Mylek believes the right tools are essential in increasing revenue for manufacturers.

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