Understanding MQL

Minimum quantity lubricant can save money, improve tool life and improve the part finish. But it may involve changes to both the equipment and the processing strategy.

Article From: Modern Machine Shop, Ron Quaile 

Posted on: 12/13/2004

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In a machine designed for MQL, the dosing system is integral to the spindle.

Controlling heat is an important consideration in MQL, and the process may have to be redesigned to achieve this. When this steering knuckle is machined through MQL, the part is quarantined before machining until it has sufficiently cooled.

We have all been conditioned to keep cars cool by filling the radiator with coolant. Much the same preconditioning has been applied to manufacturing, where coolant is routinely used to address the thermal stability of the machine tool, cutting tool and workpiece, and also to remove chips. But is coolant as essential to every machining process as it is to a car?

The cost of coolant is approximately 15 percent of the life-cycle operational cost of a machining process. This cost continues to rise. It includes the costs associated with procurement, filtration, separation, disposal and record keeping for the EPA. Already the costs for disposal of coolant are higher than the initial cost of the coolant, and they are still rising. Even stricter regulations are under consideration for coolant usage, disposal and worker protection. As a result of all of this, coolant in wet machining operations is a crucial economic issue. An alternative, machining with “minimum quantity lubricant,” or MQL, is gaining acceptance as a cost-saving and environmentally friendly option in place of some wet machining processes.

MQL permits dramatic cuts in coolant costs, while protecting workers and the environment. It also delivers improved tool life and surface finish—even though tool life is often the reason why wet machining is applied. MQL can deliver better life for two reasons: (1) the optimum concentration of lubrication can be specified for a given operation, and (2) silicon particle contamination suspended in the cutting fluid is eliminated.

MQL machining processes can be adapted for cast iron as well as aluminum. Challenges (all covered below) include precisely controlling lubricant mixing systems, maintaining thermal stability, choosing the appropriate cutting tools and removing the chips.

Control of Lubricant

Control over the amount of lubricant dispensed is important because different processes require different amounts of lubricity. For example, milling is a surface operation, and it requires a minimum amount of lubricity. Deep-hole drilling is a different operation requiring a different level of lubricity. And yet a third level of lubricity is required for tapping and thread cutting operations because of their high surface pressure.

The objective of an MQL mixing system is to deliver a precise amount of aerosol. That is, the diameter of the aerosol particulates is held to a precise tolerance to maintain optimum wetting and lubrication properties. In machines designed for MQL, lubricity can be controlled using a parameter in the part program that varies the aerosol’s amount and duration. Early attempts to apply a mixture of oil and air in this way failed because demixing of the oil and air occurred at high speeds. However, new systems have proven as effective as wet operations at maintaining lubricity. One example is Cross Hüller’s “Specht Duo,” a two-spindle CNC production module built for wet or MQL operations, which features a precision dosing system. The dosing system is integrated into the motorized spindle housing.

The CNC program controls the dosing valve that provides the precise amount of lubricant. The lubricant is mixed with air to form the desired air/oil aerosol mixture. It is then fed to the cutting edge through ducts in the tool. Because of the short distance between the aerosol generation point and the cutting surfaces, optimal cooling and lubrication conditions for a given machining process and cutting tool can be achieved and maintained. The aerosol is switched off as the spindle traverses from the position of one machined hole to another. This eliminates oil buildup on the workpiece and on the surface of the machine, minimizing the need for operator intervention to clean the machine. Because the chips produced with the MQL system remain essentially dry, the need for time-consuming and costly coolant recovery operations is eliminated.

Silicon Contamination

Along with the ability to control lubricity, MQL improves tool life and surface finish by eliminating abrasive silicon particles suspended in the coolant. Aluminum workpieces contain approximately 13 percent silicon, which reduces tool life and leads to poor surface finishes. Fine aluminum/silicon particles can become suspended in wet machining coolant. While filtration systems eliminate 40-micron particles, particles smaller that 40 microns pass through the system to get recycled with the coolant.

Thermal Stability With MQL

When employing MQL, the strategies for maintaining thermal stability and part tolerances include minimizing the amount of heat introduced and compensating for thermal growth.

Changing the sequence of machining operations can minimize the effect of introduced heat. In wet machining operations, a part is normally rough machined, then finish machined. Rough machining of pockets and cavities, as well as threading and tapping operations, are all done early in the process, and then the finishing operations are run. But in MQL machining, rough machining is reduced to what is essential to distress the part. The part is finish machined before it heats up. Typically, bearing bores and dowel holes with a tight positional tolerance will be finished relatively early in the process. Then miscellaneous operations not affected by thermal aggression, such as drilling and tapping, are run after this finishing is done.

A related MQL strategy is to quarantine incoming parts until their temperature is stable. One machining process involving aluminum wheel knuckles provides an example. For this process, the parts are received directly from an adjacent foundry. A temperature probe measures the incoming part temperature. If it is too high, the parts are quarantined in a queue until they are cool enough for machining. Once the knuckles reach the desired temperature, they are loaded with the use of robotics into the machine tool for cutting operations.

If inventory is too small for quarantining of parts, an alternative is to develop a proprietary temperature compensation algorithm for a specific part. A part-specific algorithm is needed because a complex part may not expand uniformly when heated. In one example, a cylinder head was artificially heated to determine how it would expand. A lookup table was developed from this experiment and included with the part program. Based on the temperature determined by a probe, an automatic compensation was made to the position of the feature machined.

Cutting Tools

MQL processes for milling, drilling, tapping, finish cam boring and finish machining of valve seats and guides all require a lubrication duct in the cutting tools. The duct allows the dose of aerosol lubricant specified by the part program to reach the cutting edge of the tool.

As the aerosol is pumped into the ducts of the tool, any abrupt changes in the diameter of the passageways, or any blind endings, will inhibit the ability to flow freely. The aerosol will reclassify itself as a larger globule of oil, and the lubricity properties of the aerosol will be lost.

Therefore, a cutting tool used in MQL machining must include a transition for supporting the flow of MQL from the spindle to the cutting tool. The route of the duct (its branching and its changes in direction) needs to facilitate flow conditions, while the location of the duct outlet ensures that lubricant reaches the cutting edge of the tool.

Chip Disposal

There are a variety of techniques for effectively removing chips without the use of coolant. For example, stainless steel chip sheds with a steep angle eliminate chip nests; a vacuum system can recover fine mists and dust; and chip conveyors can evacuate chips from the machine. Contamination of the machine is controlled by using a responsive mixing system. This can avoid the need for manual intervention to clean chips sticking to the walls of the machine.

Implementing MQL

Removing coolant from machining presents challenges related to heat, tool life and chip removal, but certain systems and strategies can address these challenges. Heat dissipation without coolant requires a different approach to processing the part. Special tooling using lubricant ducts (as well as high-performance coatings and heat-resistant materials) is also required. Chip evacuation systems must be used as well.

In addition, optimum implementation of MQL requires an appropriately designed machine tool. Such a machine can allow the same feed rates and speeds to be used as in wet machining processes. Tool life is unchanged from wet machining. And as long as the mixing and dispersion of oil is precisely controlled, part quality is as good as or better than wet machining processes. In the final analysis, MQL machining provides an economically and ecologically reasonable alternative to the traditional wet machining process.

About the author: Ron Quaile is vice president of Cross Hüller North America (Sterling Heights, Michigan).

SolidCAM Xpress Review

SolidCAM has built a reputation on providing single window integrated CAM for the SolidWorks community, but how can it address those first dipping their toes into CNC Machining? Al Dean finds out

With today’s trend towards outsourced manufacturing, it may come as a surprise that many design and engineering houses are looking to bring their machining operations back in house. Or indeed, to establish them for the first time.

SolidCAM is integrated directly into the SolidWorks users interface, so geometry manipulation and selection will immediately be familiar to any users

Many are quoting a level of frustration and lack of control over outsourced operations, while others see producing locally as much more sensible. Alongside this, economic downturns often have the effect of spurring on displaced staff from larger companies setting up on their own and that’s no less true than in manufacturing. So, we have a situation where machine tools are being installed into new environments.

While it’s perfectly possible to program these machines manually, a much more appropriate method is to use a CAM (or Computer Aided Machining or Manufacturing) system. This lets you work off your 3D CAD geometry and create toolpaths that should be efficient and much less error prone than doing it manually.

The problem is often that the CAM system costs can greatly add to the capital costs when buying machine tools. With this in mind, the team at SolidCAM has introduced SolidCAM Xpress, which brings the basic functionality from its full blown product to market at a much lower cost.

So let’s explore what you can actually do with it.

Benefits of CAD integration

SolidCAM is built directly into SolidWorks’s user interface. While there’s the usual pulldown menu addition, the majority of functions are driven from the SolidCAM PropertyManager and machining tree structure that stores all of the set-up and operations.

Just as with the full product, all the modelling and editing operations that are part of the SolidWorks toolkit are at your disposal. A perfect example is the set-up for a machining job. SolidCAM uses assemblies as the basis for part programming. That gives a couple of advantages. Firstly, because the part being machined is disconnected from the originating part file, the user has the ability to adjust its orientation and set-up the datums for machining without having to adjust the native part. It also means that part geometry for fi xtures can be brought in so they can be avoided where required.

Alongside regular 2D machining,SolidCAM Xpress also supports basic forms of 3D feature machining, allowing you to handle features such as this fillet

Once the datum is set-up and any fixtures are in place, the part programming process can begin. First task is to define the stock for the part. This can range from a basic billet size (which can be auto-sized), use a configuration of a part (for those parts with machining stock added) or you can even import an STL file for castings and forgings.

As we’ve already discussed, SolidCAM Xpress is a reduced functionality version of the full system. The system is supplied with basic 2D machining operations that can handle face and pocket machining, profiling and drilling. It’s also worth noting that the team at SolidCAM has chosen to provide a basic 3D surface machining operation into the Xpress version too. The rationale is that it’s very easy to define 3D surfaces within your CAD system, so they’re giving you the chance to machine those forms in this lower-cost product.

The process for defining an operation is pretty simple. Taking the example of creating a pocketing operation, you select the geometry for the boundary (and the depth), add the operation from the menu
and define the parameters. SolidCAM Xpress shares the same cutter database with the full system, so you have the ability to select from a pre-defined list of cutters either per machine or across your
machine shop.

As you’d imagine, feeds and speeds are derived from the cutter and the material and the depth is typically derived from the geometry. A point worth noting is that the system flags up whether the parameters are automatically stripped from your geometry (flagged with a red colour) or if you’ve overridden them. The system also gives support for all the usual high-speed machining aspects such as entry and exit options. Once done, the system allows you to simulate the material removal as a sanity check before you commit.

SolidCAM Xpress has the full intelligent cutter/tool libraries from the full version

The other operations follow a similar process. Drilling will allow you to either pick up the hole definition from the SolidWorks model (assuming you’ve defined it using the intelligent hole wizard tool) or allows you to define a number of cycles to create the holes you need, in the manner you want.

One thing worth discussing a little more is the surface machining operation. This gives you two operations, either a constant-Z or waterline or a parallel or zig-zag strategy. It’s pretty basic, but the ability to machine these more complex forms, at a low cost, is very handy indeed.

Once your list of operations is complete, you can generate the g-code. Again, the system includes all of the post tools from the full blown product. It’ll also output setup sheets with all the datum locations, tool set-ups for use on the shop-floor.

In conclusion

The machining world is changing. Machine tools are dropping in price and there’s also this vaguely counter intuitive trend towards new machine tool adoption. As a result, having a CAD integrated CAM system that’s low cost makes perfect sense to me.

The system includes full workpiece and cutter simulation

While I’m sure the die hard machinist will scoff at the reduced set of functionality, that would be missing the point entirely. There’s a whole raft of users and organisations that are carrying out machining for the first time that simply don’t need those advanced tools.

That might be a start-up producing components for the first time. It might also be a team running a smaller scale machine tool in a prototyping workshop. It’s these users that can derive huge benefit from using CAD integrated CAM, but typically can’t afford it or justify the considerable costs.
solidcamxpress.co.uk

Whats is Post Processing - CAD-CAM

What is Post-Processing? 

In the early days of post-processing, a post-processor was considered an interface tool between computer-aided manufacturing (CAM) systems and numerically controlled (NC) machines - a mere translator, reading the manufacturing instructions issued from a CAM system and writing an appropriate rendition for a target NC machine. Today however, post-processing has evolved to include a dynamic range of code optimization tools which are responsible for outputting the most efficient and productive machine tool code possible.

NC post-processing is responsible for joining two very different technologies, and it often serves to compensate for weaknesses on either end. Therein lies the crux of the issue: a post-processor can enhance technology, or it can inhibit it, depending upon its application.

To understand how a post-processor can enhance technology, it helps to understand how and why post-processing evolved, how it has been traditionally applied, and how the emergence of advanced post-processing systems has changed the way it is used today. This article will show how post-processors can be used as key components in factory automation

What is a Post-Processor?

Most CAM systems generate one or more types of neutral language files containing instructions for a CNC machine. These are either in a binary format called CLDATA or some ASCII readable format tailored after the APT language. APT is an acronym for "Automatically Programmed Tools," software that accepts symbolic geometry and manufacturing instructions, and generates CLDATA describing the manufacturing operation in absolute terms. Some CAM systems provide a large degree of flexibility, allowing just about anything to be included in the neutral file, others are quite strict about what can and cannot be included.

At the other end of the equation sits the NC machine. It requires input customized for the controller being used and arguably to a lesser extent, the operator running the machine. Most important, the NC machine must be driven in a manner that satisfies shop floor criteria, which are primarily based on safety, efficiency and tradition.

Between these two lies the post-processor. The post-processor is software responsible for translating neutral instructions from the CAM system into the specific instructions required by the NC machine (Figure 1). This software responds to the unique requirements and limitations of the CAM system, NC machine and manufacturing environment. Therefore, post-processing is an important part of factory automation, as is anything that lies on the critical path between the design engineer and the shipping department.

A Historical Perspective

People often ask if post-processors are really needed, wondering if perhaps the whole issue has been perpetrated on the unsuspecting by unscrupulous software houses! In fact, there really isn't a conspiracy, just a lot of practicality. International standards (ISO) as well as national standards (ANSI, EIA) define both an output format for CAM systems and an input format for NC machines. These two formats, output and input, differ significantly.

Why not one standard, one format? Standards are more often than not based on existing practice. They serve to define a single method from a host of possible choices, all of which are generally rooted in actual practice. Standards that go against common practice do appear from time to time, but they are hard to justify, difficult to create and slow to be accepted. They also require a lot more dedication and effort than most people are willing to volunteer.

So when the proliferation of competing APT systems warranted a standard to help define and control the format of its inputs and outputs, standards were created defining the core elements required for manufacturing. Similarly, the proliferation of controllers also demanded some uniformity, and NC control language standards were created defining the core practices of industry.

What Might Have Been

But let us suppose for a moment that a single unifying solution had been created in a reasonable time frame, and that a significant number of CAM companies and NC controller manufacturers agreed to do things differently for the common good. What then?

Time passes and CAM and NC vendors soon realize that a single unifying solution does not account for competitiveness. There are at least three ways a new feature (such as probing) can be brought to market in this environment. One is to revise the standard first, then provide this feature to customers at a suitable point after the standard is next published. The second is to provide the feature to customers first, then press for standardization later. The third is to ignore any effort to standardize company proprietary information and get the feature to market as quickly as possible.

No contest. The feature goes to market as quickly as possible.

Now things get a little more complicated. If the feature is an NC one, how will the customer's CAM system access it, and vice versa? The standard has to be extended on both sides of the interface to make the feature work. The CAM and NC vendors must both agree to incorporate nonstandard functionality to allow access to this new feature. Who will profit? Will both profit equally?

It would be more likely that some sort of pre-processor would be required to change the output of the CAM system to satisfy the input requirements of the NC machine. Besides, a pre-processor is probably already needed to handle binary format conversions between the CAM system computer and the NC controller. Initially the conversion will be simple, but as time goes on and deviations from the standard continue, the conversion will become more complex, perhaps to the point where different pre-processors might be required for different NC machines.

Who will provide the pre-processor, especially if both the CAM system output and the NC machine input contain extensions to the standard? What happens when a revised standard appears, or a CAM vendor leaves the market, or the computer manufacturer tells you that the computer you are using is obsolete and not object-compatible with the newest model?

Is this all starting to sound familiar?

It really makes no difference if the interface between CAM and NC is unified or not. Market pressures will ultimately create incompatibilities, and software will be necessary to bridge the gap. The only question left to answer is, what software?

Enter Post-Processing

Post-processors can do many other things besides translating CLDATA to NC machine codes. For example a post-processor may summarize axes travels, feed and speed limits, job run-time and tool usage information, which enables better selection and scheduling of resources.

More sophisticated post-processors may validate the program before it is run by the machine tool. There are many simple rules that a post-processor can follow, with warning messages displayed when these rules are violated. Some examples: Noting if a tool is not selected near the start of the program, warning when motions at feed rate are done with a stopped spindle, flagging long series of positioning moves, or conversely, flagging feed moves at or above the program clearance plane, or noting if diameter or length compensation switches are not changed when a tool is.

Beyond simple validation comes correction. There are many situations where a post-processor can detect an error and correct it. Examples include: cycles left active during a tool change (they should be temporarily cancelled), selecting an incorrect or nonexistent spindle gear range (the post-processor should select a range that supports the speed), or specifying an unavailable coolant type (the post-processor should select the next best type).

The best post-processors maintain a global picture of the entire job at all times, using upcoming events to help make decisions about current ones. The NC programmer uses this information to optimize the job without intervention. For example: pre-selecting the next tool as soon as physically possible, segmenting a tape at a tool change if the entire upcoming tool path will not fit on the current reel, selecting a spindle gear that best fits the current and subsequent speed requirements, or switching intelligently between parallel axes (Z and W) based on the types of upcoming operations and available travel limits.

Post-processors can also work around limitations and bugs in the CAM system or in the machine tool. It is generally far easier to change the post-processor than it is to get a new revision of the CAM system, or a new executive revision for the NC controller.

The important point to be made here is that the NC programmer should not be concerned about machine tool or machine operator idiosyncrasies that do not directly affect the production of a job. Wherever possible, good post-processors should hide these details within.

Standard CAM systems, standard NC machines, standard CLDATA and standard post-processor vocabulary can not all be mixed together to instantly produce a working system. There are too many variables in the real world, and standards are too restricted in scope, to achieve integration with off-the-shelf components.

Post-processors tie it all together, and good post-processors can do this with a minimum of effort.

Post-processing works best when it is "transparent," in other words the best post-processors are those that the user neither knows about nor cares about.They quietly go about their work, only raising an alarm when warranted.

Source : ICAM,Canada.

iMachining

iMachining is a giant leap forward in Tool-Path technology reducing cutting times by up to 70%. iMachining achieves this by optimizing tool engagement and cutting feed through the entire tool-path therefore allowing much deeper and more efficient cutting. 

iMachining is driven by a knowledge-based Technology Wizard, which considers the machine being used, the material being cut and the entire geometry and material of the cutting tool. This ensures the tool load is constant which in turn increases tool-life and makes it possible to machine with the full length of the cutter.

Most conventional CAM software will cut deep features in small steps to ensure the tool is not overloaded and to minimize the impact of over-engagement. With iMachining, programmers can confidently cut to the full depth of the tool in a single pass, as cutter engagement is completely controlled by the technology wizard generating smooth morphing tool-paths. Furthermore, the software automatically avoids sudden direction changes and sharp corners, eliminating shock loading on the tool, and enabling the maximum volume of material to be removed in a single pass.

iMachining optimizes the feeds and speeds through the technology  wizard for each individual component and setup taking into account all the machine specifics (Spindle power, max feed / speed etc.), all the cutting tool data (number of teeth, helix angle, cutting length, tool material etc.) and all the material properties By combining all this information and then selecting the level of aggressiveness for machining - matching it to the rigidity of the setup - iMachining produces a safe and smooth tool-path which will routinely halve machining times.

Algorithms within iMachining eliminate air cutting thus concentrating on areas where excess material is located keeping the tool in contact with the work-piece at the maximum. iMachining has the ability to subdivide pockets into areas that can be cut with iMachining’s morphing tool-paths. The intelligent separation routines use iMachining’s unique channeling tool-paths to divide the pockets up into areas that can be efficiently machined using the standard imachining morphing tool-paths which smoothly remove the remaining material.

iMachining also includes ‘rest’ and ‘finish’ operations to remove uncut areas left by the larger roughing tool, both strategies utilize the intelligent morphing technology which completely controls the cut at every position.

By considering every aspect of the machining operation, the intelligence and technology built into iMachining enables parts to be cut in a fraction of the normal time by making full use of the capabilities of cutters and by generating a smooth and safe toolpath. This produces very significant savings in cost and time on all material types and is particularly effective on hard materials.

About SolidCAM

Founded in 1984 by its Managing Director Dr. Emil Somekh, SolidCAM provides manufacturing customers a full suite of CAM software modules for 2.5D and 3D milling, high speed machining, multi-sided indexial 4/5 axes milling, simultaneous 5 axes milling, turning, turn-mills up to 5-axes and WireEDM. SolidCAM is the Gold-Certified integrated CAM engine running directly inside SolidWorks software and provides seamless, single-window integration and full associativity with SolidWorks software including parts, assemblies and configurations. Today, SolidCAM has more than 13,500 seats installed in industry and education. SolidCAM is sold by a worldwide reseller network in 46 countries. SolidCAM has been on a very rapid growth path since it implemented the SolidWorks integration strategy. In the CIMdata NC Software Market Assessment Report V17, CIMdata named SolidCAM as the consistent growth leader in CAM worldwide over the last 5 years, with annual growth rates in the 30% range.