Collision Avoidance or Detection? (Part 2)

May 16, 2012 By jjaje Leave a Comment

Automatic Avoidance is always better than detection.

In the last Blog Post, there was discussion about collision avoidance and detection, especially as automatic avoidance relates to 5-axis machining.

Today we will look at collision avoidance earlier in the process, during roughing.

Difference between Collision Detection and Avoidance.

Collision detection is when your CNC CAM software calculates a cutterpath, which often only takes the tool shape into account, but not the holder or the physical milling machine, then afterwards recheck it for and collisions. If there are any, then manual editing, or some other changes are required to remove the collisions yet still mill the entire part.

Collision Avoidance is when the collisions can be avoided in the first place, during the calculation of the CNC cutterpaths. When roughing, this may include the Tool and Tool Holder, and possibly the spindle.

Mill With the Shortest Tool Possible

You will that mantra from tool vendors all the time, when speaking about performance. Do as much milling with eh shortest tool as possible, and only use a longer tool where necessary, or utilize the short tool at different cutting angles if possible, to maximize performance.

Look at the picture below, in this case we can actually mill out 90% of the material with a very short cutter. We are using the strategy of roughing with a large cutter to take advantage of good material removal rates, and we will use a cutter with a Length/Diameter ratio of 0.9.

Part with tool and holder

Part with tool and holder

In this case, the holder is quite large, so although we can remove the majority of material with this short and sturdy cutter, there will be areas of additional stock to remove.

When you look at the cutterpath from the +Z direction, you can readily see that the CNC CAM  Software automatically limited the cutterpath, taking the tool and holder into consideration, to avoid all collisions, versus just finding collisions after the fact.

Stock Condition after +Z cutterpath

Stock Condition after +Z cutterpath

How the remaining material is removed can be done in multiple ways. Perhaps a different tool or holder from the +Z direction, or if you have the capability to rotate the part, either by a multi axis machine, or simply unbolting it and flipping it on the side, then you can continue to use the same short, sturdy tool to machine the part from other angles, as shown in the picture below.

Roughing with short tool in alternate directions

Roughing with short tool in alternate directions

Other Necessary CAM software Technology

To accomplish multi axis roughing, your CAM software must include the ability to work on a 3D stock model.

To accomplish automatic collision avoidance during roughing, as we did here, then your CAM software must also include the Dynamic Stock Model. Which is a topic for another blog :)

 

 

Filed Under: 5 axis cnc software, CADCAM, CAM software, CAM tips & tricks, NC machining, NC software

CNC – Collision avoidance or collision detection?

April 30, 2012 By cjordan Leave a Comment

For 5-axis applications not only does the CADCAM software have to consider actual collisions with the tool and the tool holder, but also the kinematics of the machine tool itself. For 3-axis machining the concern is mainly the tool length and holder ensuring that it can get into each part of the job without a collision.

For systems with just collision detection, the software tells the user that there is a problem and where the problem is, but the user then has to work out what needs to be done to get over the problem for himself. In some cases this can be very complex and requires detailed investigation of the surface topology of the part.

With CNC software such as WorkNC, users can generate the collided and uncollided toolpaths and get information about the minimum tool length required to finish the job. With this information engineers can cut as much of the part as possible with short rigid cutters and restrict to a minimum, machining with long tools. Best of all, the software does all the calculation for you, so that you can be sure of a reliable, safe and optimized result.

One of the benefits of 5-axis machining is being able to cut much more of the job in one setting with the shortest possible tools, minimizing resetting and secondary operations. If the CAM software just pinpoints where there is a problem, which it will do with collision detection, it is likely that the whole toolpath will need to be recalculated after the problem has been resolved. Producing a useable toolpath this way could take several attempts so at the very least it will be time consuming and tedious. With collision avoidance, the software goes a stage further as it anticipates potential problems as you are programming. Again giving the uncollided toolpath and inserting flip and unwind movements where the axis limits of the machine have been reached.

Having intelligence within the CAM software that provides a solution to potential problems as they occur has got to be a lot better than just letting the user know that a problem exists.

Antonius Köster, who uses WorkNC Auto 5 in Germany, gave this example of one of the problems resolved with collision avoidance. “For an aerospace supplier from the Black Forest, we machined a component which required the tool holder to move inside the part through a drilled hole so that we could mill a pocket at the bottom. Not only was the cutter moving inside the part, but the whole tool holder. This was a really challenging task.”

Filed Under: 5 axis cnc software, Aerospace, CADCAM, CAM software, CAM tips & tricks, NC machining, NC software Tagged With: , , , , , , , ,

The importance of good CAM technical support

February 28, 2012 By cjordan Leave a Comment

Have you ever bought a piece of flat pack furniture and found that there are a few special screws missing? First, you ring up the store and if you are lucky they answer the phone. Next, you talk to someone who clearly knows nothing about furniture and is not really interested in your problem. Finally, you give up and go to the hardware store or rummage in the garage until you find something which will just about do the job!

Imagine if that was your CAM supplier and your machine was stopped and your customer was on the phone – I think I can safely say that this would be classified as a bad day at work and you would probably need a few beers to get over it!

So, getting good support for your CAM system has got to be pretty much top of the list. What you need is a company that is available when you need it, knows what they are talking about, understands your business and your machines and which is enthusiastic about providing a solution. Lots of tools are available now so that support engineers can operate your PC for you, enabling a solution to be achieved in a few minutes. Where this is not possible, you need the engineer to understand the software and the problem so that a viable workaround can be implemented. In most cases, time is of the essence, so this type of quick response can make all the difference.

For customers using the distribution channel for a CAM product rather than the software developer, the local dealer’s knowledge of the system and your application is paramount. Good CAM vendors will make sure that their dealer channel is properly trained, has fast access to extra help for the more difficult problems, and that it can talk knowledgably about local machining techniques in the customer’s own language.

The best CAM vendors will also involve customers in the development process, listen to their requirements and, either create a special application, help them to implement advanced features in the system, or add new functionality into the next software release. Perhaps furniture shops could learn a thing or two…..

Filed Under: CADCAM, CAM software, CAM tips & tricks, NC machining Tagged With: , , , , , ,

Training keeps up productivity

February 8, 2012 By cjordan 1 Comment

To get the best from your CAM system it pays to take the trouble to do the training courses. Some CAM systems are virtually automatic and intuitive, so the training requirement is quite low and users can start producing CNC programs very quickly and easily.

However, every system has its extras that take a little more effort, but which can make a big difference to productivity. Batch processing of programs overnight, setting up sets of standard machining strategies for different types of component, implementation of feature recognition, and analysis of the CAD data to find draft angles and the smallest radius are just a few of the features available in some CAM systems that can produce big benefits. Although not difficult to set up and use, these types of advanced features can be quickly learnt on a training course, saving hours of trial and error experimentation.

Most CAM systems are being continually developed (if yours isn’t you need to look for a new one!) so extra training in the new developments makes sure that your company is taking full advantage of the improvements, helping it to stay at the leading edge in its field. Furthermore, continuous training helps to build up a closer relationship with your CAM supplier, enabling it to develop solutions to your individual problems and to ensure that you are using the existing capabilities in the software to your best advantage.

Successful companies work in partnership with their customers and suppliers so that they can offer a superior service and product. Close collaboration on both sides significantly improves the performance of both parties. Taking advantage of continual training opportunities raises skill levels and productivity making it a very important part of the relationship.

So, when’s the last time you took update training for the CAM system you use?

Filed Under: 5 axis cnc software, CADCAM, CAM software, CAM tips & tricks, NC machining Tagged With: , , , , , ,

Optimizing the post-processed NC code can yield big benefits

January 11, 2012 By cjordan 2 Comments

nc speed toolpath optimization with worknc cadcam I am sure that every CNC machinist would like to chop a further 20% off their cycle times. Well with toolpath optimization you can!

Toolpath optimization programs which sit inside the CAM system and work on the actual post-processed code, which is the ultimate way of making sure that the machine is running at maximum efficiency, can achieve this sort of productivity boost.   The technology uses volumetric analysis to dynamically calculate the amount of material being removed at any instant. That way it knows the load on the cutter throughout the machining cycle and adjusts the feeds and speeds to keep it steady and within the limitations of the cutter. 

Not only does this speed up machining where cutting conditions are good, but for small tools it greatly reduces the chance of a tool shattering when subjected to a sudden shock load. For the engineer, going faster where possible can produce a big reduction in cycle times, while going slower where machining conditions are challenging, increases tool life and eliminates the possibility of tool chatter which will, in turn, make the tooling itself last even longer. 

As well as saving on the cost of excessively worn or broken tooling, toolpath optimization can reduce the chances of producing scrap and also greatly improve the quality of the surface finish. Vibration from toolpath chatter will damage the machine tool itself, and will also adversely affect the finished component through ripples on the surface. 

The optimization process does not stop when the tool is out of the job. By looking at rapid movements and their physical relationship to the job, the system can ensure rapid moves are used whenever the tool is above the workpiece reducing cycle times even more. 

A further advantage of keeping cutter loads constant is that tool deflection is kept to a minimum. The resulting increase in accuracy will make it much easier to produce very high precision parts.

Filed Under: CADCAM, CAM software, NC machining, NC software, Other productivity software Tagged With: , , , , , , , , , ,

CAM software – cheap is not cheerful

December 29, 2011 By cjordan Leave a Comment

In pretty much any walk of life if you buy something cheap, you expect it to have significant limitations or not last very long. I think it is safe to say that this is certainly true in engineered products. Materials are poorer, design is less elaborate and functionality is reduced. A BMW has the same number of wheels as a Lada, both will get you from A to B, so why do people want a BMW? With apologies to Lada drivers, most people can come up with a whole host of reasons.

For CAM software the same principles apply. If you buy a cheap CAM system it may do the immediate job you bought it for, but usually there is no upgrade path so if a job comes along which is too complex, you have to throw the software away and start again with a better system. Not only does that waste money, but you have all the installation costs and the associated disruption of a new learning curve to go through.

Another consideration is the level of support you are going to get with a cheap system. Realistically if there is little or no profit for the CAM system vendor he can’t afford to give proper support. You only have to look at low cost and free software on the net to see that you have to work out any problems you have for yourself. This is fine if you are just typing a document, but if your machine is stopped and the customer is on the phone, all because you can’t get the software going, it can have some very serious consequences.

The same applies to software development. If there is reduced profit for the vendor, development is bound to be slow, software releases risk being inadequately tested, and the system may be full of bugs. The user is certainly not going to be happy if the CAM system causes a machine collision, which can cost more to repair than the cost difference between a reputable CAM system and a cheap one.

Some companies are on a tight budget, so the price of a product is very important. However, if instead of just looking at the purchase price, consider what the lifetime cost of the CAM system might be. This is more difficult to quantify, but elements such as the ability to do more complex and profitable work, less danger of machine damage, more uptime on the machine tool and faster machining cycles will easily outweigh the cost difference several times over.

Filed Under: 5 axis cnc software, CADCAM, CAM software, NC machining, NC software Tagged With: , , , , , , , , , , , ,

Plunge Roughing – Part 2

December 14, 2011 By jjaje Leave a Comment

Previously, we discussed the use of Plunge roughing as an alternative roughing strategy, especially to utilize older or under-used milling machines. What I wanted to do with this entry is provide a few pointers on plunge roughing.

Plunge Roughing – not for all parts.

First, as with all cutterpath styles, you need to match the best cutterpath strategies with the part geometry. Some parts are better suited to a plunge roughing strategy than other parts.

First, consider the amount of material removal. Plunge Roughing works better if removing a larger percentage of material from the original stock, as opposed to a small amount of material. If you only need to remove a small amount of stock from a part, plunge roughing, on a global level, may not be the best choice.

Second, consider the part geometry. Plunge roughing in an automated fashion work best when removing a larger amount of material from larger areas. That is, if you have a whole lot of small pockets, then plunge roughing may not be the best choice. However when you have larger, open, areas for which to rough, it can work much better.

One particular example where Plunge Roughing can be ideal is in hydroform tooling. See the image below of an example of a good part for plunge roughing. There is a high percentage of material removal, compared to the original block of material, and it has larger open areas.

Plunge Roughing example

Plunge Roughing example

Utilizing Finer Control with Plunge Roughing

We saw in the previous post that sometimes the stock condition after roughing is “rougher” with a plunge roughing approach. While a global automatic approach may work in most instances, sometimes a person wants finer control. This may be around certain features in the design, or more often, to mill a larger channel into a part.

In this case, you may make drive curves to follow around particular features, or in a channel. This is shown in the picture below, where we utilize a curve to follow the feature more closely.

Plunge Rough around Feature

Plunge Rough around Feature

Dynamic Stock Model and Plunge Roughing

When Roughing it is important for the CAM software algorithm to know where the tool has been, and where there is stock remaining. This is done via a Dynamic Stock Model, allowing the CAM software to know the condition of the stock at every point in the cut.

This is critically important with Plunge Roughing, because after the plunge cutting motion, the tool steps away from the wall, and off the floor a little before retracting. This keeps the cutter inserts from rubbing along the wall on the way back up. If the CAM software does not know the stock at all times, then that step away can not be calculated safely, and if it were to step awaay into material, it could mean disastrous results for the cutter and spindle.

Plunge Rough Step Away

Plunge Rough Step Away

So in conclusion, plunge roughing works better on some parts than other parts. As always match the CAM milling strategy to the CAD design. Utilizing a Dynamic Stock Model is the only way to ensure the safest Plunge Roughing.

Filed Under: CAM software, CAM tips & tricks, NC machining, NC software

Plunge Roughing – Offers more than many think.

December 7, 2011 By jjaje 3 Comments

Utilize Older Milling Machines

In a previous blog named Concurrent Working Part 2, we explored some ways of doing tasks simultaneously within your shop. One suggestion is to utilize an older, less powerful, mill to do certain tasks, such as squaring off stock, while utilizing the newer, more advanced mills for the 3d Sculpted shape milling.

Another way to utilize older milling machines is to use them for some roughing tasks. While they may not be able to rough as fast or well utilizing the newest high speed tools and roughing strategies, they can often be very good at Plunge Roughing, also called High Volume Roughing within WorkNC.

Plunge Rough Cutterpath on Whole Part

Plunge Rough Cutterpath on Whole Part

Benefits of Plunge Roughing

There can be many benefits to utilizing a plunge roughing strategy, and some of them are:

  • High Metal Removal Rates. Plunge roughing can allow for metal removal rates competitive with newer high performance roughing cutters, running on a machine over a dozen years old.
  • Cutter forces are along the axis of the cutter instead of radially to the cutter.
  • Consistent chip loads because of the algorithms and cutting style.
  • Heat goes away with the chip. You can often place your hand on the material immediately after cutting and it is only warm, but not hot to the touch.

While Plunge roughing does have good metal removal rates, if you are cutting a part with a lot of shape, the condition of the stock will be “rougher” after plunge rouging, with more material to re-rough than other roughing methods. While many may consider this a negative, if one already had to run a re-rough cutterpath regardless, you might as well run one where the tool is engaged in more material. As many roughing tools are designed to remove a larger width of stock, and often have premature failure when the width of stock is consistently narrow.

Result from Plunge Roughing

Result from Plunge Roughing

Have you tried Plunge Roughing? If so, tell us about your experiences int he comments.

 

 

Filed Under: CAM software, CAM tips & tricks, NC machining

Working with lots of different CAD systems

November 18, 2011 By cjordan 1 Comment

Working with lots of different CAD systems – for subcontractors and suppliers this can be a real headache and especially if you are working with automotive or aerospace customers that use some of the high-end CAD packages.

In some cases there is no alternative to actually installing one of these CAD systems and employing a very expensive design engineer to run it, which can be justified if the majority your work is in the one market sector and you have to actively participate in the customer’s design process.

Thankfully for most people, CAD translation has moved on enough to make this unnecessary. For CAM systems neutral formats such as IGES and STEP or direct translators for products like CATIA, SolidWorks and Inventor are very reliable, enabling manufacturers to accept data from many different sources without a problem.

Once you have accepted that translators are OK, you can then choose the best CAM system for your application. Even if you have had to install the high-end CAD, transfer of model data is generally one way into the CAM system, so even for these applications a specialist, best of breed, CAM package will provide the best solution, reducing cycle times, improving quality and reducing tool breakage – real tangible savings.

Filed Under: Aerospace, Automotive, CADCAM, CAM software, CAM tips & tricks, NC machining, NC software, Other productivity software Tagged With: , , , , , , , , , , , , , , , , , , , ,

Are CAM systems really all the same?

November 15, 2011 By cjordan 2 Comments

The answer has got to be an emphatic no!

If you just look at a CAM system’s graphics, it is true that the toolpaths can look similar, but the big difference is what happens when you actually try to cut metal and use the system as part of your daily routine.

Stories abound of companies continually editing programs, suffering from tool breakage, producing poor surface finishes, putting up with long cycle times and extended programming times, and having difficulty programming certain types of component. A good CAM system overcomes all these problems, changing CNC programming from a drama into a safe and fool-proof process.

The other factors to look at, when trying to distinguish one CAM system from another, is what the systems will actually do and how easy they are to use. The system needs to be able to cope with all the types of work your company does, so CAD data translation might be the first hurdle, then it could be 5-axis or 3+2 axis machining, feature recognition when there are a lot of holes or pockets, high-speed machining of molds, or even specialist applications such as dental prosthesis manufacture.

“Ease of use” is a major factor for any CAM system, because if it is difficult to program, not only will it take a lot longer to produce CNC code, but it will reduce the number of people able to handle it. The ability to have more people producing CNC code makes better use of available skills and minimizes the possibility of a programming bottleneck. Are all CAM systems the same in terms of reliability? Certainly not….

So overall, don’t be fooled by fancy graphics and promises, try the system out on your work and machine tools to see what really happens when you press the start button. So, do you believe that there is little difference from one CAM system to the next? Let us have your comments or share your experiences!

Filed Under: 5 axis cnc software, CADCAM, CAM software, CAM tips & tricks, NC machining, NC software Tagged With: , , , , , , , , , ,
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