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: , , , , , , , ,

Extremely Automated CAM – Dental edition

February 16, 2012 By jjaje Leave a Comment

Automating CAM Software

Through the use of sequences, templates and other time saving devices, it can often be possible to automate much of the manual input and programming of CAM systems.

For example, one might make a template for roughing hard steels, larger than 24 inches, and another for hard steel between 12 and 24 inches, and a third for parts smaller than 12 inches. Similarly, they could have templates (we call them sequences) for other materials, such as Titanium or Zinc, or for other operations, such as finishing or semi-finishing.

Similarly, this approach can be used to automate processes in specialized fields, like Dental.

Dental CAM Milling

First, let us say right off the bat, this works best with open systems rather than closed systems. Not sure what the difference is between an open or closed Dental milling system? We made a small document/presentation outlining some of the differences between an Open Dental CAM Milling system, a Closed Dental CAM Milling system and those in between.

This document can be found at the link here.

Next, you can virtually completely automate the CAM milling process for similar parts, like dental parts, via pre-planned sequences. Simply select a material, select a machine, load parts to mill, locate parts, add support structures and calculate the CAM cutterpaths. If only all CAM programming were that easy.

Why are we bringing this up here you ask? One, all programmers could benefit from some additional automation. Two, Sescoi not only has a WorkNC product for general machining, but also a product specific to dental machining, WorkNC Dental.

In dental machining, you can mill relatively soft materials like Zirconia or Wax, to very hard metals like Chromium Cobalt and Titanium. Parts are usually very small, and often several parts are nested into one block of material.Parts being machined are often scan data, with thousands of points and facets.

In dental machining, finish is important in that you can not have sharp corners and burrs that could cut into the soft tissues of the mouth. Also, of critical importance is what is referred to as the margin. The margin is where the dental prostheses mates with the existing tooth material. This margin must allow for a perfect match else bacteria will get inside and cause decay. Thus the machining must also be accurate, as well as smooth.

The dental industry is often looking for skilled programmers with machining experience. If that’s you, check it out.

Below are some pictures of parts. Leave comments on your automation stories, or if you have dental CAM experience.

Filed Under: 5 axis cnc software

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: , , , , , ,

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: , , , , , , , , , , , ,

dramatic toolpath calculation time savings using task threading and parallel processes on multi-core processors

December 2, 2011 By cjordan Leave a Comment

In this post I want to share some of benefits of CADCAM software that enables “task threading” and “parallel processes” on multi-core processors , but first a quick explanation of those two terms:

* Task Threading: certain cutterpaths run multiple threads. That means individual portions of the cutterpath will be calculated at the same time. Computers with multi-core processors will run those threads individually, on separate cores, decreasing calculation times. It is not just cutterpaths that can be multi threaded, but other calculations as well.
* Parallel Processes: multiple cutterpaths in the workzone can be run simultaneously, as long as one is not dependant on another. For example, Planar Finishing in the WorkNC CADCAM system can run at the same time as a Z-Level Finish, since one is not dependant on the other. However, a Global ReRough may need to wait on a stock model update before calculations start. Parallel processing will allow you to calculate more cutterpaths faster than ever before, taking advantage of multi-core processors.

We tested the new version of WorkNC CADCAM software with task threading and parallel processes (Version 21) on some typical customer parts.
The same toolpaths were calculated in WorkNC Version 20 and then in WorkNC Version 21 with one CPU, followed by WorkNC Version 21 with 2 CPUs.

The results are as follows:

WorkNC CADCAM customer part 1 Part 1 with 4 roughing and 4 finishing toolpaths 

Calculation times:
2h 09 min  V20
0h 37 min  V21 one CPU
0h 29 min V21 two CPUs
WorkNC CADCAM customer part 2 Part 2 

with 4 roughing and 4 finishing toolpaths

Calculation times:
1h 30 min  V20
0h 33 min  V21 one CPU
0h 27 min  V21 two CPUs
WorkNC CADCAM customer part 3 Part 3 with 2 roughing and 5 finishing toolpaths 

Calculation times:

0h 49 min  V20
0h 24 min  V21 one CPU
0h 13 min   V21 two CPUs
WorkNC CADCAM customer part 4 Part 4 with 8 roughing and 9 finishing toolpaths 

Calculation times:
2h 11 min  V20
1h 13 min  V21 one CPU
0h 39 min V21 two CPUs
WorkNC CADCAM customer part 5 Part 5 with 4 roughing and 11 finishing toolpaths 

Calculation times:
1h 41 min  V20
0h 44 min  V21 one CPU
0h 22 min  V21 two CPUs

Using 2 or more CPUs leads to a significant savings in CNC toolpath calculation times.

Dramatic reductions, but as the examples show, the toolpath calculation time savings for parts having a high proportion of roughing toolpaths is, due to the interdependent toolpaths, less important than for parts with a greater number of finishing toolpaths.  Interesting stuff.   If you are using CAM software that supports parallel processing, what are the most dramatic toolpath calculation time savings you have seen?

Filed Under: 5 axis cnc software, CADCAM, CAM software, NC software, Parallel processing 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: , , , , , , , , , ,

Concurrent Working

November 2, 2011 By jjaje Leave a Comment

Concurrent working  – Multitasking

What is that I hear you ask? Put simply, it’s doing several tasks at the same time, often referred to as multitasking when dealing with one individual. When you are manufacturing or designing a product there are several steps required, design, costing, market research, product literature, handbooks, quality assurance, tooling, fixtures, machinery, suppliers etc.

You could do all this in order, one thing after the other, but it is pretty obvious that some things can be done alongside others greatly reducing the overall lead time. The problem is what level of concurrent working is reasonable and possible. For the most part, the limiting factor is being able to share the latest information. Software for viewing analyzing and marking-up CAD data can make sharing this information much easier. Designers can come up with a concept and even in the very early stages, marketing can look at the customer’s reaction, manufacturing can check for difficulties during production, while preliminary costings can be done to arrive at a price. By feeding back comments, the design and manufacturing stages can all be telescoped by doing far more tasks in parallel.

So to sum up, effective communication software which enables economic sharing of design and manufacturing data can cut lead times by getting all those involved to work concurrently as much as possible. In our next blog, we will look at how this can apply to CNC machining, so stay tuned.

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How good is your postprocessor?

September 20, 2011 By cjordan 5 Comments

For most CAM systems, the basic functions of a postprocessor are pretty reliable nowadays, generating NC code that requires no editing. If you do need to edit the code, it’s time to get a new CAM system!

However, CNC machining is becoming more and more demanding, and machine tools are getting more sophisticated, so postprocessors have needed to get cleverer too. Certain toolpaths such as 4 or 5-axis can only be used on particular machines, and within that there are even more limitations according to how far an axis will tip or rotate, the angular increments possible, and the need to unwind when limits are reached.

To try and solve these types of problem manually is virtually impossible, so engineers have to have absolute confidence that their CAM system will do it for them. What they need is information about which postprocessors can be used for a particular toolpath, and checks to stop them inadvertently picking the wrong one.

Collision avoidance is a crucial element in 4 and 5-axis postprocessors. The geometry of the machine, the tool and its holder all need to be considered so that the part gets completely machined, without resulting in a collision.

The quality of the surface finish can also depend on the postprocessor. On very large components, some systems don’t produce enough data resulting in waves and flat spots on the finished part. High accuracy in the CAM system and in the postprocessor will eliminate problems like these. So spare a thought for your postprocessor and if it can do all this reliably and with the minimum of fuss then it’s going to make your life a lot easier, make tools last longer, avoid damage to the machine and ensure parts are made right first time.

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

What’s next for CAM software?

September 7, 2011 By cjordan Leave a Comment

Automated 5-axis machining and automated 3+2 axis machining are just two of the major steps forward in CAM software recently. The latter is geared towards all those companies that have multi axis machines which operate best in 3+2 mode and not continuous 5-axis.  If your goal is to use shorter tools, milling deeper pockets and reducing the need for EDM operations, these technologies can be very helpful. WorkNC’s auto-5 and auto 3+2 do this by converting a 3 axis cutterpath to either 5-axis or 3+2 axis automatically allowing the use of short tools, with collision avoidance.

Speed has also been addressed with multi-threading and parallel processing used to reduce calculation times by up to 70%. Hybrid modeling makes it easier to manipulate imported CAD data and automated routines take much of the decision making out of CNC programming.  Hybrid modeling also enhances manufacturing with custom functions such as electrode extraction routines.

Are  niche applications and functions going to be the way forward? I can visualize a special application just for particular types of mold tool. Vacuum forming could possibly benefit as shapes are relatively similar without complex slides. Part trimming could be incorporated as a downstream process, automatically programmed at the same time as creating the tool.

Could this all this a stage too far for engineers that like to have full control of the metal cutting process? We would love to hear your views and suggestions.

Filed Under: 5 axis cnc software, CAM software
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