Sep 22 2016

Pocket Milling

admin

The combination of CNC machines and CAD/CAM software allows machinists to cut materials faster and more accurately than what is possible when cutting by hand. One of the most common types of cutting is pocket milling (or pocketing), which sees extensive use in the aerospace and shipyard industries along with the uses a hobbyist has for the technique. Pocketing milling can be used with 2D or 2.5D projects and roughly 80% of all mechanical parts can be created with this kind of toolpath. Using this type of toolpath can make a big difference in the quality of a finished project.

Pocket milling

Pocket milling

Pocket milling allows you to use an end mill and machine away large parts of your raw material in a roughing process prior to finishing your project. This process allows you to save time and money while maximizing the amount of material removed. There are several styles of pocket milling such as traditional lace or zig-zag, concentric or offset In/Out and high speed cutting paths. The type of toolpath you pick can be categorized as linear or non-linear and there are parameters that can be set in many CAD/CAM software programs to control the pocket milling process.
Linear tool paths are unidirectional and the two major types are zig-zag tool paths and zig tool paths. Zig-zag milling causes the tool on your machine to move back and forth while removing material. Cutting is done with and against the rotation of the spindle. This method makes machining faster but also increases tool wear and machine chatter. Zig milling causes your tool to move in only one direction which results in better surface quality. However, you will have to lift and retract the tool after each cut so it takes more time to finish machining.
Non-linear tool paths are multi-directional with contour-parallel tool paths being an good example of this type of tool path. Contour-parallel tool paths use the pocket boundary to derive the tool path. Using this method your cutter is always in contact with your material, allowing you to eliminate time that would be needed to position and retract your tool using other methods. This method is used frequently for large-scale material removal and there are two different approaches that can be classified as contour-parallel tool paths. Pair-wise intersection approaches bring the boundary of the pocket inwards in steps. Offset segments intersect at concave corners and intersections are trimmed off to obtain the required contour. Voronoi diagram approaches segment the pocket boundary and the voronoi diagram is constructed for the entire pocket boundary. Voronoi diagrams are used to generate tools paths and this method is considered to be efficient since it avoids the topological problems machinists can run into using traditional offsetting algorithms.
Toolpath parameters for pocket milling in your CAD/CAM software will include data about roughing and finishing tools, pattern selections, cutting direction options (climb vs. conventional), toolpath cutting angle and step over % input fields. There should also be data that allows you to control side and bottom allowances for finishing as well as depth controls for single or multiple roughing steps. Many CAD/CAM software programs allow you to define single, even cutting depths based on the overall depth and define or force depths. Finally, there should be lead-in and lead-out options to control how the tool enters and exits the cut. Some CAD/CAM software programs will offer all or at least some of these options and some will not; it will depend on what software you are using. There are CAD/CAM programs that offer explanations and tutorials on pocket milling and these programs are usually the ones that are well equipped for pocket milling operations. Examples include BobCAD-CAM, CIMCO CNC-Calc and SimCam (CNCSimulator Pro).


Sep 8 2016

Europe’s Best Hobbyist CNC Machines

admin

When a hobbyist is selecting a CNC machine to build or buy one of the biggest factors can be location. You may be able to find a good machine at a reasonable price somewhere but realize that importing it would cost so much that the “reasonable price” will now cost you an arm and a leg. Budget is often one of the key deciding factors when a hobbyist is selecting a machine so looking to buy locally is not only smart but often necessary. This article will review some of the better European-made machines on the market for our European readers who find themselves in this situation. Readers who are not European but do not mind the cost of importing may also find this article useful; one of these machines could be exactly what you have been looking for.

CNC-Step CNC router

CNC-Step CNC router

CNC-Step is a German company founded in 2005 that has grown into an extremely successful business. They produce a series of CNC routers called the High-Z, of which there are three main models, each with their own sub-models. The original, and most popular, machine they offer is the High-Z S-Series which comes in three varieties: the S-400, S-720 and S-1000. In terms of functionality these machines are all perform the same. As you go up in model number the size, weight and price of the machine increases so you can select a machine based on how big of a workspace you will need. The S-400 sells for €2.237,00 while the S-720 sells for €2.793,00 and the S-1000 sells for €3.343,00. The next step up is the High-Z T-Series which features ballscrews. The smallest version of this machine, the S-400/T, is actually a bit cheaper than the S-1000 so if space is not an issue this can be a powerful machine that you can purchase for a fairly reasonable price. Other machines are offered by CNC-Step but their remaining machines are more heavy-duty, better suited for professional machine shops than a hobbyist’s work area. Full details on the company and their products can be found at http://cnc-step.de/en/.

BZT CNC Router

BZT CNC Router

BZT is another German company that makes excellent CNC mills on the hobbyist and professional levels. While they have only been making CNC machines since 2006 the company has been around as a machining company for 30 years. They offer a large number of machines in a variety of series for customers with various needs and differing levels of skill. One of the best series for starting hobbyists is their PF series. All machines in the PF series are 3-axis machines that use 16mm ballscrews and the most basic machine, the PF 600-P, can be purchase for €2.201,50. Like other CNC machines that are sold in a series the higher model numbers tend to have the same mechanical performance but a larger work area and higher cost. BZT offers over a dozen different series of milling machines; you would be hard pressed to look at what they offer and not find a machine that can suit your needs. They also sell software, parts and even cheaper used machines in addition to the new mills they produce. To see all of the products BZT offers firsthand take a look at their website at http://www.bzt-cnc.de/en.

Badog CNC router

Badog CNC router

Badog CNC although is one of the smallest boasts a service helpline that can not be ignored. It seems that when you ask for help you don’t just get the usual any answer runaround but instead a Swiss accredited engineer actually answers your question. They even go so far as to offer free services of project development and free translation off digital files. The company started in 2008 with a lean management system but has sold over 600 machine products in Switzerland alone. Obviously one of the big up and comers in the milling machine market. See here http://www.badog.ch
There are certainly many other options for CNC machines if you live in Europe but these three companies are good starting points. Maybe you do not want to buy a new machine and are trying to build one instead. You could at least use these organizations to look for some of the parts you will need so even if you are building instead of buying these companies can still be useful to you. Not every company you look at has to be a large organization either. Try looking for local businesses as well; you never know what you may find.


Aug 18 2016

Do I Need a Formal Education to use a CNC Machine?

admin

CNC machining is a hobby to many people but it is a profession to other individuals. There are classes and schools dedicated to teaching people about CNC machines. You may ask yourself whether it is necessary to get a formal education regarding CNC machines in order to use one. While it is not necessary, it certainly helps. Operating any CNC machine is by no means self-explanatory and professional CNC technicians are required to go through training. Hobbyists can and often do figure things out on their own but if you have the time and budget to take a few classes they will certainly increase your knowledge of CNC machines.
There are a lot of technical schools out there but not all of them will offer training with the type of CNC machine you want to use. Most schools that do offer training programs will not train you in a single classes; multiple classes are taken to break the training process up into several sections. Beginning classes may not even offer any hands-on training with the machine; actually working with the machines can be reserved for later classes in the training program.

CNC router machine

CNC router machine

Beginner classes will teach students about the basic concepts of CNC machines. Remember that even if you know a bit about CNC machines the same may not apply to everyone in the class. Just because the information the class is going over is not benefitting you does not mean no one in the class needs to learn that material. It may be boring at first but you have to get past the basic courses before you can move onto the real fun stuff. These courses will frequently cover the limitations of CNC machines. You will be taught to consider factors like tool selection, spindle speed, cutting sequences and clamping and positioning before you turn your machine on. Reviewing the function of G-code and how it interacts with a CNC machine is also commonly covered. Examples of coursework in beginner classes includes establishing how you will choose the right tool for a project (considering factors like safety and efficiency), installing handling devices and tools, loading G-code into the machine’s software and producing sample parts to make sure they match specifications and operation instructions given to you.
Advanced classes are where you start to really use the CNC machine, now that the beginning classes have taught you the basics of how to operate it. Initial advanced classes tend to start with reading, comprehending and making CNC programs for basic tasks like drilling, threading and turning. Later classes will cover more complex tasks like machine adjustments, program editing and creating new command syntax. Coursework in these classes may involve things like comparing test results to identify editing needs, regulating and adjusting coolant flow, repairing or replacing damaged tools and taking steps to prevent damage to tools, the CNC machine and the material being used for your projects.
These are generalizations of how a CNC machine training program is run and each institution may do things a bit differently but most places will do something along these lines. For a hobbyist it is not 100% necessary to take classes for CNC training but you will learn any subject faster when it is taught to you, compared to just figuring things out for yourself. Even if you do not have the time or budget to attend formal training at a school you should still look up tutorials and other help videos online to get a better idea of where to start and what to do. Everyone was a beginner at some point and they all had to learn somehow; determining the most effective and efficient way of learning is up to you.


Aug 11 2016

CNC machine Attachments

admin

When you first buy (or build) a CNC machine your primary concern when working on your budget is likely going to be figuring out what the best quality parts you can afford are. Every machinist, from professionals to hobbyists, wants to get the best CNC machine that they can in order to make machining processes as smooth as possible. While you should certainly concern yourself with the necessary parts of the machine first, so that it can actually run, there are additional considerations you can take. Attachments (or accessories, add-ons, or whatever you wish to call them) may not technically be essential to the running of a CNC machine but once you start using them they can be so beneficial that they will certainly start to feel like necessary components.
Some attachments are so common that many machinists would likely argue that they are essential components to any CNC machine. Ruin boards are a great example of an attachment that fit into this category. Image that you have your CNC machine set up and you are ready to machine your first project on your nice, new t-slot table. With what you just paid for that t-slot table you can picture what a nightmare it would be to accidently cut right into the table and destroy it. Keeping a ruin board between the table and your material should stop this from ever happening. Ruin boards do not need to be too thick; usually something between ⅛” and ¼” will work fine. New machinists may want to use a thicker board to leave more room for error.

CNC machine clamps

CNC machine clamps

Clamps are another great, yet simple, attachment that most basic CNC machines should include. Any level of precision machining will require you to hold your material still. There are a lot of ways to do this and clamps are one of the easier and more cost efficient methods. Sometimes you may have other methods available; t-slot tables utilize t-slot nuts, step blocks, step clamps and other implementations but it can be a hassle to find pieces that fit the specific table you are using. Making a clamping system of your own can be much more effective. Be creative and try to develop an easy-to-use system that works well with your equipment and set-up.
In some cases clamps may not be a good hold-down method because the item you are machining is too small. When you find that your clamps are too large, a milling vice is an excellent alternative tool. While a regular vice could be jury rigged to your table, a milling vice is designed specifically to work with a CNC machine table and they tend to be extremely precise. There are many different types and brands of milling vices in many different sizes so determine your needs and do a bit of research before committing to anything expensive.
Once you have a hold-down system in place you can start actually machining. On any project you want to make sure that everything has been machined accurately and there is no set of tools better for this than a pair of calipers. Digital calipers are the way to go for their extreme precision; 0” – 6” calipers will work fine for the vast majority of measurements you need to take while examining the finer details of projects. Cheaper calipers work fine but like any other tool you will want to go for the higher end of tool quality and price range as your budget allows.

 air sprayer for cnc machine

air sprayer for cnc machine

During and after machining, chip evacuation will be one of your primary concerns. Using an air sprayer is the best way to clear out chips while your CNC machine is running. Any standard air compressor with a trigger nozzle can do this well. Clearing away chips during the cutting process is often a critical procedure. After your machining has been completed you will want to use a shop vac’s powerful suction to get all of the chips out of your work area, leaving everything crisp and clean for your next project. Any time you are working with chips, and when using a CNC machine in general, always remember to wear safety goggles.


Jul 28 2016

Plastics routing

admin

Modern plastics vary greatly throughout their manufacturing processes. The differences between various types of plastics and the different uses machinists will have for their materials cause problems for some people. A good machinist, whether you are a hobbyist or a professional, should be aware of the problems you could run into and steps you can take to get around those problems.
Not all plastics are made equal, not even plastics that share the same name when you are purchasing your raw materials. Something as simple as a change in color can alter how one plastic cuts compared to another. You need to be able to recognize and classify what kinds of categories plastic falls under when you are working with it. To start, determine whether you are working with hard or soft plastic. This is easy to determine; you can check this by seeing how rigid or flexible your material is. Alternatively you can see what type of chip is produced when the material is cut. Soft plastic chips will curl while hard plastic chips retain their solid shape. A single type of plastics is not always universally hard or soft; some plastics can be hard or soft depending on how they were manufactured. Knowing the geometry of your cutting tool is the second step to success. Tools that are best suited for cutting plastic have high rake and low clearance. These days there are thousands of different tools made for plastics cutting that you can choose from. Soft plastics tools have “O” shapes and are usually straight or spiraled in shape. Hard plastics tools can have an “O”, spiral shape or a “V”, straight shape.

Routing plastics

Routing plastics

One of the most irritating problems you can run into is the plastics material welding. This problem can happen due to the direction of your cut, using a cutting tool that is too small or having a chipload (the thickness of a chip) that is too large. Chipload is the most common cause of this problem. Your chipload is determined by your spindle speed, feed rate and the number of edges on your cutting tool. In plastic routing you want your chips to be just the right size to distribute heat correctly. Another potential problem is your finished project having poor finish. Having good finish is extremely important on plastic items, especially ones that are made to be put on display somewhere. The quality of your finish is going to be heavily affected by your chipload. Problems aside from chipload tend to come from the condition of your CNC router. You want to make sure that your CNC router is up to speed on maintenance and performance at all times. Learning to work with plastic correctly is a matter of practice and with time you will become experienced enough that you will run into these problems less and less, until you stop running into them almost altogether.
Making sure you have the right bits for plastics is one of the most important parts of preparing for projects. Your best option for hard plastics is a solid carbide router tool. If you cannot get one of those a carbide tipped tool is a good second choice but they will not perform as well as a solid carbide tool. You can use the same kind of tools on soft plastics but high speed steel tools will also work well on these softer materials. Your CNC router should be capable of speeds of at least 15,000 RPM to work on plastic. A CNC router is the best type of CNC machine for working on plastic, being the machine that is best suited for working at the high speeds your projects will require. Ideally you want to be working at 18,000 RPM, if your machine can operate at that speed, at a feed rate of 200 in. per minute. This is a general figure for plastics in general and the exact speed and feed rate you should use will vary a bit between different types of plastic.