Jun 9 2016

Acrylic Glass Routing (Plexiglas)

admin

Acrylic Glass Routing (Plexiglas)

Routing acrylic materials (Plexiglas, Lucite, Acrylite, Perspex, etc.) is one of the most popular methods used in the fabrication of this type of material. A high quality standard kept for the material regardless of how it will be used is routing the product with a fine finished edge, eliminating the need for finishing the item after it has been routed. There are a number of key factors you will need to take into consideration to keep your finish high-quality, two of the most important factors being tooling and programming.

CNC acrylic

CNC acrylic

There is a lot that could be said about tooling if we were to get into specifics but there are some more basic guidelines you can follow for acrylic routing. When you are choosing which tool to use the first criteria that affects your choice should be diameter. On a lot of jobs clients commonly have requests that will require you to use tools that are 1/8” to 1/4″ in size. Using larger tools, from sizes of 3/8” to about 1/2″, will result in consistent surface finish results that are superior to smaller tools. The increased stability and flute depth of tools with larger diameters cause the increase in quality. Any tool that is larger than 1/2″ will only improve your results slightly and as you use larger and larger tools the size increase will eventually do more harm than good. Using anything bigger than 1/2” is unnecessary. Additionally, your cut depths should not exceed 2”. Once you have selected your diameter the next thing to choose is cutter configuration. Generally speaking, the smaller the diameter of your cutter the more likely it is that a spiral configuration will leave a good finish. When you use larger tools (3/8” and up) a straight flute works better. If you are using a tool that is 1/4″ or smaller a single edge spiral O-flute will give the best finish. At larger sizes low helix multi-fluted tools work better (the exact type of tool you will need depends on if the acrylic is cast or extruded and on any fillers that may have been used in the material’s manufacturing). These are the sizes where you will want to use double edge straight tools. O-flutes and V-flutes can both work well when using tools of these sizes. In addition to these conventional tools there are also some specialty tools on the market for this kind of work so it does not hurt to do a little research and see what is available.
When you are programming it is key to select the correct cutting methods and cutting parameters. Every different combination of material and cutter will have its own “sweet spot” that you want to hit for ideal machining. Your feeds and speeds are going to be the most sensitive parameter while you are programming. Acrylics (and other plastics) have a very small chip load range that you need to find in order to maintain a sufficient finish. Each cutter is going to have its own optimum chip load for every different type of material. You need to look up the feeds and speeds that you will need or, if that is not possible, experiment until you find the right configuration. Once feeds and speeds are settled you will select your cutting method. Conventional and climb cutting are both good but tools with larger diameters work better with conventional cutting. With smaller diameters the cutting method you need will depend on the material; you will have to do some trial-and-error work to figure out what works best. If you are new to working with the type of acrylic you are using some trial-and-error experimentation will be necessary to figure out a lot of parameters like finish passes, depths of cut and entry points. There is a lot to learn about this type of work but with time and practice you will get the hang of it and be machining like a pro in no time.


Jun 2 2016

Aluminium Cutting and tips for cnc routers

admin

Aluminium Cutting and tips for cnc routers

Some hobbyists may ask if a CNC router can cut aluminum(Aluminium Cutting) since you most often see other users cutting wood or plastic. You can use your CNC router to cut aluminum if you know how to do it right. Aluminum (and other metals) are different to cut compared to wood or plastic. They have a smaller “sweet spot” for optimal cutting. If you leave the sweet spot your cutter will start breaking and wearing out faster and the surface finish will not be very good. Another thing to keep in mind is the “stickiness” factor (this applies to some other metals too). Aluminum wants to stick to your tool. It will do this to the point where it welds itself to your tool(tools). When sticky bits of aluminum have clung to your cutting edges your tool is not going to have much more life in it. Even though it is challenging you can cut aluminum on almost any CNC router. This article will give you a few tips to make sure you stay on track doing that job safe and proper.
While a CNC router can cut aluminum it is not the best tool for big parts, like vehicle parts. To cut successfully you need to do the job slowly. Just let your machine do its job and do not be in a rush. Cutting aluminum is not easy and will probably push your CNC router to its limits(Aluminium Cutting). Use a Feeds and Speeds calculator to optimize your settings so that you are not dodging the tip of your cutter that broke off and is flying across the room. Ideally you want to use a calculator that takes minimum RPM, CNC router cutter types, deflection, rubbing warning and chipping thinning into consideration. Your first problem will be recommended RPMs being too low. A CNC router cannot always go as slow as you want to go for cutting aluminum but there are ways to bump you’re the recommended RPM and fix this problem.

CNC router cutting aluminum ((Aluminium Cutting)

(Aluminium Cutting CNC router

The first tactic is to user cutters that are good at high speeds. The measurement to look for is Surface Speed which is high is carbide cutters. Cutters like HSS and Cobalt will be too slow so look for carbide TiAIN coated cutters. They cost a bit more but the improved results of your project will be worth it. Say you were using an HSS Endmill and the recommended RPM is 5877. Your CNC router’s spindle may have a minimum speed of 20,000 RPM (this is a very common minimum speed for routers). A TiAIN Carbide Endmill may have a recommended RPM of 16,897, putting it much closer to your machine’s minimum RPM. For aluminum try to get as close to 20,000 RPM as you can and you should be fine.
Another way to increase RPM is using small diameter cutters. The largest cutter you want to use should be ¼” but go smaller than that if you can. You will most rigid cutters to stop tool deflection from being a problem (this is where having tool deflection on your calculator becomes important). The smaller your cutter is the closer you can get it to 20,000 RPM. Be extra careful about clearing away chips. Recutting chips is an easy way to break a cutter. Be paranoid about this and do not just assume that your dust collection system is good enough without testing it for this first. It will be harder to get chips out as you cut deeper. Make more passes to cut down as far as you need to and you will open up shallower depths for better access. Lubricate your tools that that the chips will not stick to your cutting edges. The best way to do this is with a mister if you can set one up.
Now you need to think about avoiding tool rub. Going too slow with your federate can cause this to happen. Using your calculator should let you dodge this but be careful because the high speeds of your CNC router can result in tool rub happening easily. It can even start to happen while you are unaware that it is going on. If you cannot feed fast enough use fewer flutes. You should use a maximum of three flutes at once regardless. Using few flutes is good and is the reason 1 flute cutters are sold. There is a lot to remember when cutting aluminum but once you know what you are doing you should be able to use your CNC router for aluminum projects safely and accurately.


May 26 2016

Aluminum Types

admin

Aluminum Types

Aluminum is a metal commonly used for milling but there are multiple types to choose from, each with different uses that make them best suited for a variety of projects. 1100 (also called pure aluminum) resists weather and chemicals and is low cost and easy to weld. It is commonly used for chemical equipment, fan blades and sheet metal. 2014 is used for structural applications like parts on planes, trucks or other vehicles as well as other machines. 2024 is also used structurally and has high strength and workability while also resisting corrosion. These traits make 2024 aluminum ideal for large pieces of equipment like truck wheels and recreation equipment as well as small items like rivets and screws. 3003 is a general purpose material with the same capability for welding and formability as 1100, but it is stronger than 1100. It is used for many of the same things as 1100 along with seeing use in making more everyday items like cooking utensils. 5052 is even stronger than 3003, allowing it to be used in marine environments while still having all the uses of weaker aluminum alloys. 6061 has good weld-ability, formability and corrosion resistance on top of its impressive strength. It is used in the construction of vehicles, furniture, architecture and even basic sheet metal, amongst other things. While there are many more types of aluminum available than the ones mentioned here these are some of the more common varieties that millers may find themselves using.

Badog Aluminum

Aluminum

Machining aluminum can be a tricky task but there are some things you can do to make sure the process goes smoothly. There are cutting tools that are made and sold specifically to cut aluminum and these are the ones you want to use. Aluminum is a soft metal and becomes very sticky when you are cutting, clinging to your cutting tool and gumming it up. The tools built specifically for aluminum cutting are made to counter this effect. To separate a chip from the rest of the material you are going to want high rakes angles. Using positive rake angles up to 20 degrees axial and 25 degrees radial is a common practice. Having a high helix angle (at about 45 degrees) is also a good idea. Keeping the helix angle this high will help to move chips out of your cutting area and will give you a good surface finish while softening the impact when you start to cut as well. Using a two- or three-flute end mill will allow for larger flute areas. A core diameter just below 50% of the cutter diameter also helps the flute areas. The use of an open flute design will further help in getting chips out of your cutting area. Aluminum likes to stick and the hot chips will try to stick to your otherwise smooth surface area so keeping them out of the area is important. Chips can also be kept out of the flute area with the use of coolant, which you will also need to keep your tool at working temperatures. An air gun spraying a mist is a common choice for coolant but flood coolant can get chips out of the way if the pressure is high enough. Using an air gun should be satisfactory is your tool is coated. Slick tool coatings on your equipment will help to reduce friction on the flute surface. The three big things to remember when preparing to mill aluminum are to use a cutting tool specifically designed for aluminum, use a machine with speeds and feeds that are high enough for aluminum and make sure you can get chips out of your cutting area while working.


May 19 2016

Precision Machining CNC

admin

Precision Machining CNC

When you are programming your code into your CNC machine the software can assume that your machine is always going to be perfectly accurate(Precision Machining). In practice this is not always the case. Backlash often undermines the accuracy of your machine. A machine with backlash can still be precise if your machine is cutting from only one direction and all the drive systems are tightly pressed together in that direction. But in a lot of cases a combination of backlash and a dull tool can cause gouging on your project. Backlash can also throw off precision during axis movement reversals, like when you are cutting a circle. Backlash is the enemy of any CNC machine user and you need to do what you can to minimize it.

Precision Machining CNC

Precision Machining CNC

To keep your backlash at minimal levels you will need to adjust the backlash parameter values on your machine. If you do not know how to do this and are having difficulty figuring it out there are technicians who offer the service of doing it for you. You should check the values once every 3-6 months minimum. Checking your machine and making adjustments is not a long process; it should only take you a little over an hour once you have programs for checking your machine set up and ready to go. You can also potentially find other issues with your machine by checking the backlash. If you find that backlash is increasing very quickly you could discover that there is an issue with your chip build up (or some other problem) and then you can fix that before it leads to a larger complication. All machines, even brand new factory-made ones, have some backlash adjustment. As wear starts to take its toll the value needs to be increased to compensate. Normal wear usually calls for you to adjust a ballscrew anywhere from .005” to .010”. If you have to make an adjustment greater than .010” there could be a greater problem with your machine that you need to address. When you do make your adjustments be sure to closely examine the screws; some areas of the screw could wear faster than others. For example, if you always have a vice or fixture mounted in the same spot your wear is confined to that one area. Move your fixture or vice around at least once every few projects, if not every project, to spread the wear around evenly. Doing so will make your equipment last longer.
Start checking your backlash by writing down the current parameter value and then clear it (set it to zero). Have your machine move through memory mode and look for discrepancies between memory mode and the machine’s handle. Remember that backlash is the amount of wasted motion you see when an axis changes direction. If you are checking a lathe you should check the backlash at various distances from the chunk. Finding different values in different areas means that part of the screw is worn while the rest of it is fine. If the differences are significantly big you may have to replace a screw instead of just adjusting it.
One of the main advantages of CNC machines over manual machines is their precision. Machines are capable of doing work in far greater detail, at great speeds, than a person. Making sure your CNC machine can maintain this feature is key because any CNC machine that cannot do work accurately is not worth the time, money or effort of maintaining. If you want a tool to keep doing its job you have to make sure that it is well maintained and in this respect a CNC machine is no different from any other tool.


May 12 2016

CNC machine types what are the differences?

admin

CNC machine types what are the differences?

Numerical control (NC) refers to automated machine tools. That are controlled with pre-programmed computer commands. As opposed to machines that are operated by hand. Most numerical control today has evolved into computer numerical control (CNC). The difference from NC being the large and important role computers play in the system. With the computers modern CNC systems use computer aided design (CAD) and computer aided manufacturing (CAM) software to run. This article will highlight several different types of machines that can use this type of set-up and software.

CNC ROUTER MACHINE

CNC ROUTER

CNC mills use rotary cutters to remove excess material from raw material that are “fed” into the machine at an angle with the axis of the tool. These machines can be used on small individual scales or for large heavy duty operations. Milling is one of the most common methods used to machine precision parts today. The computer controls on the machine are used to translate programming into various locations and depths that the machine can follow. G-code, the standard programming language on CNC machines, is used most often but some machines have their own languages created by machine manufacturers. Custom languages can be easier to learn than G-code but have the downside of being unusable on other machines.

LASER CNC Machine

LASER CNC Machine

Lathes are machines that rotate workpieces on their axis, allowing the user to perform tasks such as cutting, sanding and drilling. This allows the finished project to be symmetrical along its axis of rotation. They can be used for a variety of differing projects like woodturning, metalworking and even glass-working. They can also be used to shape pottery (a potter’s wheel is a type of lathe). CNC lathes can make fast, precise cuts using indexable tools and drills using their computer programmed commands, allowing them to create items that could not be made on a manual lathe. The CNC versions usually have tool holders and coolant pumps to reduce wear. Controls on a CNC lathe are similar to a CNC mill. Like a mill they can usually read G-code and the custom language of the manufacturer (if applicable).
Plasma cutters use plasma to cut material, commonly steel and other metals but other materials can also be used. Gas, such as compressed air, is blown out of the nozzle at high speeds while an electrical arc is formed through the gas as it comes out of the nozzle to the surface of the material being cut. This turns some of the gas into the plasma used for cutting. Plasma is so hot that it melts the material being cut and it moves fast enough to blow molten metal away from the cut. Plasma cutters are used to cut metal as frequently as mills are used to cut wood, giving them an alternate specialty compared to other machines that can do similar work. Like other CNC machines they can be programmed with G-code but also sometimes have a manufacturer-designed code available as well.
Water jet cutters (frequently just called water jets) use an extremely high pressure jet of water (or a mix of water and an abrasive substance, such as sand) to cut materials. The term pure water jet (or water-only) refers to a water jet that cuts without abrasives and is usually used on soft materials like rubber or wood. Machines that use an abrasive and water mix are called abrasivejets and are used for cutting hard materials like granite or metal. Water jets are common for cutting machine parts and are used for parts made from materials that are too sensitive for the high temperatures used in other cutting methods.