Random insights to the world of CNC Cutting Machines.
6/19/15 Making Better Holes with Plasma Cutters on CNC Machines
Making good-quality holes with plasma is easier than ever with Hypertherm’s True Hole technology, but what if you don’t have True Hole? Though not quite as automated, it is entirely possible to make some very nice holes using plasma on a non-True Hole system. Here are some things you can do to get your holes just right.
Pierce height. Set a higher pierce height. The general rule is 1.5 to 2 times the recommended cut height, so if the recommended cut height says .062, pierce at .125″.
Lead in location. Set your lead-in as close as possible to the center of the hole. There are two reasons for this. One, the top of the plate usually contains a slag puddle. If this puddle stays on the radius (contour) of the hole, it will cause the plasma arc to waver and create a divot or ding in the hole. The second reason is that a longer lead in gives the plasma arc time to stabilize (pressure and energy take a while to ramp up), and also allows the height control to index down to cut height before it gets to the contour of the hole.
Lead-out. If you’re using an air plasma system like a Powermax, it is best to have no lead-out. Just let the arc shut off right on the hole contour. Some software has provisions to keep the arc on for a few seconds after the motion stops but on steel under 1/2″ this usually is not necessary.
Cut speed. The advice here: slow down! Cut speed on holes should be about 60% of the speed used to cut the outside contour of your parts. We admit this will create some low speed dross on the bottom of the hole, but the good thing about this is that it will minimize taper in the hole. Some machines will do this automatically on all holes under a certain diameter, such as 1″, while other software may have to have the G Code manipulated to achieve this.
Cut height. If you are cutting a smaller hole (anything under an inch) it is best to disable arc voltage control. Allow the pierce height, allow indexing to cut height, but don’t allow arc voltage height correction. This is because the slower speed used for cutting holes will cause the arc voltage height control to move the torch too close to the plate.
Use mig welding anti-spatter spray. We suggest that you try spraying the top of the plate before cutting. The spray usually makes the top spatter from piercing non -existent, minimizing arc wobble on holes. While you are at it, spray a little on the front of the torch to keep spatter off the shield/nozzle. Do not use the dip type, or silicone or oil based spray. Use a water-based spray instead.
Consumable selection. Use the lowest powered consumable set recommended for your material thickness. Yes, this will reduce your cut speed but its worth it as you will get better results. If you are cutting with a Hypertherm system, use FineCut consumables for all holes on material thicknesses under 3/16″, 40 Amp shielded consumables for thicknesses between 3/16″ and 3/8″, and 60 Amp consumables for thicknesses above 3/8″ to 5/8″.
Consumable inspection. Last but not least, regularly look at your consumables. The orifice shapes the arc and the arc shapes the part you are cutting. just one pierce too close to the plate or on thick material, can affect the shape of your nozzle. The nozzle and shield orifices must be perfectly round with no nicks, dings or craters. (Remember this from our series of posts on consumable wear?) Inspect with a 10x eye loupe. If the orifices are not perfect, take them off the torch and use them for hand cutting or contour cuts that are not as critical.
12/3/14 Classification of Steel
Steels can be classified by a variety of different systems depending on:
-The composition, such as carbon, low-alloy or stainless steel.
-The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods.
-The finishing method, such as hot rolling or cold rolling
-The product form, such as bar plate, sheet, strip, tubing or structural shape
-The deoxidation practice, such as killed, semi-killed, capped or rimmed steel
-The microstructure, such as ferritic, pearlitic and martensitic
-The required strength level, as specified in ASTM standards
-The heat treatment, such as annealing, quenching and tempering, and thermomechanical processing
-Quality descriptors, such as forging quality and commercial quality.
The American Iron and Steel Institute (AISI) defines carbon steel as follows:
Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium [niobium], molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.
Carbon steel can be classified, according to various deoxidation practices, as rimmed, capped, semi-killed, or killed steel. Deoxidation practice and the steelmaking process will have an effect on the properties of the steel. However, variations in carbon have the greatest effect on mechanical properties, with increasing carbon content leading to increased hardness and strength. As such, carbon steels are generally categorized according to their carbon content. Generally speaking, carbon steels contain up to 2% total alloying elements and can be subdivided into low-carbon steels, medium-carbon steels, high-carbon steels, and ultrahigh-carbon steels; each of these designations is discussed below.
As a group, carbon steels are by far the most frequently used steels. More than 85% of the steel produced and shipped in the United States is carbon steel.
Low-carbon steels contain up to 0.30% C. The largest category of this class of steel is flat-rolled products (sheet or strip), usually in the cold-rolled and annealed condition. The carbon content for these high-formability steels is very low, less than 0.10% C, with up to 0.4% Mn. Typical uses are in automobile body panels, tin plate, and wire products.
For rolled steel structural plates and sections, the carbon content may be increased to approximately 0.30%, with higher manganese content up to 1.5%. These materials may be used for stampings, forgings, seamless tubes, and boiler plate.
Medium-carbon steels are similar to low-carbon steels except that the carbon ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. Increasing the carbon content to approximately 0.5% with an accompanying increase in manganese allows medium carbon steels to be used in the quenched and tempered condition. The uses of medium carbon-manganese steels include shafts, axles, gears, crankshafts, couplings and forgings. Steels in the 0.40 to 0.60% C range are also used for rails, railway wheels and rail axles.
High-carbon steels contain from 0.60 to 1.00% C with manganese contents ranging from 0.30 to 0.90%. High-carbon steels are used for spring materials and high-strength wires.
Ultrahigh-carbon steels are experimental alloys containing 1.25 to 2.0% C. These steels are thermomechanically processed to produce microstructures that consist of ultrafine, equiaxed grains of spherical, discontinuous proeutectoid carbide particles.
High-Strength Low-Alloy Steels
High-strength low-alloy (HSLA) steels, or microalloyed steels, are designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition.
The HSLA steels have low carbon contents (0.05-0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium and zirconium are used in various combinations.
Weathering steels, designated to exhibit superior atmospheric corrosion resistance
Control-rolled steels, hot rolled according to a predetermined rolling schedule, designed to develop a highly deformed austenite structure that will transform to a very fine equiaxed ferrite structure on cooling
Pearlite-reduced steels, strengthened by very fine-grain ferrite and precipitation hardening but with low carbon content and therefore little or no pearlite in the microstructure
Microalloyed steels, with very small additions of such elements as niobium, vanadium, and/or titanium for refinement of grain size and/or precipitation hardening
Acicular ferrite steel, very low carbon steels with sufficient hardenability to transform on cooling to a very fine high-strength acicular ferrite structure rather than the usual polygonal ferrite structure
Dual-phase steels, processed to a micro-structure of ferrite containing small uniformly distributed regions of high-carbon martensite, resulting in a product with low yield strength and a high rate of work hardening, thus providing a high-strength steel of superior formability.
The various types of HSLA steels may also have small additions of calcium, rare earth elements, or zirconium for sulfide inclusion shape control.
Low-alloy steels constitute a category of ferrous materials that exhibit mechanical properties superior to plain carbon steels as the result of additions of alloying elements such as nickel, chromium, and molybdenum. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr.
For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.
As with steels in general, low-alloy steels can be classified according to:
Chemical composition, such as nickel steels, nickel-chromium steels, molybdenum steels, chromium-molybdenum steels
Heat treatment, such as quenched and tempered, normalized and tempered, annealed.
Because of the wide variety of chemical compositions possible and the fact that some steels are used in more than one heat-treated, condition, some overlap exists among the alloy steel classifications. In this article, four major groups of alloy steels are addressed: (1) low-carbon quenched and tempered (QT) steels, (2) medium-carbon ultrahigh-strength steels, (3) bearing steels, and (4) heat-resistant chromium-molybdenum steels.
Low-carbon quenched and tempered steels combine high yield strength (from 350 to 1035 MPa) and high tensile strength with good notch toughness, ductility, corrosion resistance, or weldability. The various steels have different combinations of these characteristics based on their intended applications. However, a few steels, such as HY-80 and HY-100, are covered by military specifications. The steels listed are used primarily as plate. Some of these steels, as well as other, similar steels, are produced as forgings or castings.
Medium-carbon ultrahigh-strength steels are structural steels with yield strengths that can exceed 1380 MPa. Many of these steels are covered by SAE/AISI designations or are proprietary compositions. Product forms include billet, bar, rod, forgings, sheet, tubing, and welding wire.
Bearing steels used for ball and roller bearing applications are comprised of low carbon (0.10 to 0.20% C) case-hardened steels and high carbon (-1.0% C) through-hardened steels. Many of these steels are covered by SAE/AISI designations.
Chromium-molybdenum heat-resistant steels contain 0.5 to 9% Cr and 0.5 to 1.0% Mo. The carbon content is usually below 0.2%. The chromium provides improved oxidation and corrosion resistance, and the molybdenum increases strength at elevated temperatures. They are generally supplied in the normalized and tempered, quenched and tempered or annealed condition. Chromium-molybdenum steels are widely used in the oil and gas industries and in fossil fuel and nuclear power plants.
6/3/14 Torches, torches and more torches!
There is no shortage of torches around here. Did you know Hypertherm makes 18 (yes, 18!) different torches for its Powermax systems alone? Why so many torches you may ask? Well, during our travels we’ve watched a lot of people cut with plasma. We’ve seen the many jobs you’re asked to tackle. The torch that cuts perfect parts on a CNC table isn’t necessarily the torch that will work well in a 3D cutting application. For hand cutting, a torch used to cut a flat piece of steel, doesn’t necessarily work for someone trying to gouge out a weld on the pipeline.
Our torch line-up includes Duramax torches. As you might guess from the name, these torches are durable. But more than that, our Duramax line contains patented Hypertherm technology called Spring Start™. This technology (actually found in the electrode) eliminates moving parts in the torch for consistent reliable starting. Our system can also detect when your electrode is about to reach the end of its life, so you can replace it before serious and costly damage occurs.
These torches are made for both handheld and mechanized cutting and gouging, as well as robotic cutting. We have:
– Two options for handheld cutting: a 75° and 15° (which we often call a straight) torch
– Two options for mechanized cutting: 180° full-length machine and mini-machine torch
– Three options for robotic cutting: 90°, 45°, and 180° torches
In addition, to the seven torches just listed, we also have Duramax HyAmp torches. Though these torches work with every Powermax system except the Powermax30 XP and Powermax45, they were designed especially to handle the power found in our Powermax125 system. Torches in this line include HyAmp versions of the seven torches listed above plus four more torches:
– 45° four foot long torch
– 90° four foot long torch
– 45° two foot long torch
– 90° two foot long torch
These torches are all made for handheld cutting. They are great for jobs where you don’t want to get close to the workpiece or for jobs like scrapping or cutting up metal skeletons. These long torches are also handy for cutting up items high above you; in a ceiling for example.
All of these torches come with Hypertherm’s patented quick disconnect feature so you can quickly and easily switch between all the different torches. It’s no harder than plugging a plug into an electrical outlet. Have any of you tried one of our specialty torches, like the long or straight torch for example?
4/10/14 BurnTables Tracer Technology, Measure the Impossible!
BurnTables introduces their exclusive Tracer Technology that allows the BurnTables CNC Plasma, Router, WaterJet Tables to be used as a scanning device. This allows the user the unprecedented ability to scan an unsymmetrical part into the software with ease. The scanning area is the same size as the cutting area of the table which can range from 4’ x 2’ up to 5’ x 10’. Go from scanning a part to replicating it in minutes, not hours.
7/21/13 Versatility is Key!
When choosing a CNC table for your shop or home, it is important to keep versatility in mind. Can the table cut steel, aluminum, wood, plastics, pipe, tube, engraving, etc? Customers tend to think when they are looking at a CNC table that their needs are specific and only need to cut one particular type of material. We have found that most of these customers come back to BurnTables and purchase the additional attachments necessary to cut other types of materials because they have found they are not limited to one type of medium like they first thought.
With the ability to change from several available attachments on the BurnTables CNC Tables, as well as having the software included to perform cutting operations in several different materials from steel to plastics, the BurnTables system is the key to being versatile.
For example, If a customer wants to create a new dining room table, but he wants to be different and unique in its design by incorporating steel, tube, aluminum, and wood. One might think you would need at least 3 different machines to get the job done, not with the BurnTables system.
First the customer would draw his designs in the included CAD software to scale. This is done easily with the fully functioning CAD system that is provided with the BurnTables computer.
Second, in the CAM software, he takes his drawings and applies cutting process to each drawing of his design. In the CAM software the customer tells the machine the thickness of materials he is cutting and with the saved tools, the machine knows what federates and tool specifications to apply to each drawing. This allows the customer to be able to create 3D parts from 2D drawings using the router in woods and plastics.
Lastly, the customer will load his materials on to the table, telling the table where is reference point is. First he would start by putting up his steel and aluminum pieces, as the plasma can cut any material that conducts electricity. After cutting his flat steel and aluminum pieces, he would then load his tube into the tube cutting attachment to cut his bevels and design elements like text into the tube with the plasma cutter. After the tube cuts are completed then he would install is router attachment via 4 bolts to perform his cuts into his wood table top.
In summary, with the right CNC table and right attachments, a customer can perform several different tasks in several different types of materials with one table. With the CNC BurnTables system, you can achieve almost anything.
3/28/13 Its all about the Fixture!
With a CNC WaterJet Table system, Fixturing the work material is high on the list to achieve accurate cuts, and seems to be the most over looked items also. Typical WaterJet systems operate at 60,000 PSI of pressure which equates to a handful of down force, but the problem lies with when the jet enters the tank and reflects off the bottom of the tank and then forces the material in the up direction. This cause movement in all 3 axes directions and vibration in the material, especially thinner gauge material. The idea of good fixturing is to stabilize the material as much as possible which is normally done by clamping the material in to a “square” in the corner of the table to limit it x and y motion of the material. On thinner material, a sacrificial heaver material can be placed on top to reduce vibration in the z direction.
Most WaterJet tables do not come with factory supplied fixturing devices because each customer requirements and types of material being cut differ vastly. because of this, fixtures fall to the operator of the table to design and fabricated fixturing devices that securely hold the work piece with out getting in the way of machine movement.
When making a decision on purchasing a water jet table system, keep in mind the design of the table/tank and motion system. A WaterJet system that has the table/tank separate from the liner motion system as in the BurnTables WaterJet System, is superior to systems that are designed as one piece. With the force of the jet exerting against the tank, the tank itself will flex and vibrate. This vibration in turn transfers to the motion system, if they are connected, and results in choppy cuts. Choppy cuts an also be attributed to flimsy tank design.
3/19/13 Why ATHC is a must for CNC Plasma Tables.
Automatic Torch Height Control, or ATHC (THC) for short, describes a system that keeps the cutting torch within range of its optimum cutting distance from the plate while its cutting. This system compensates for plate warpage and irregular material heights. On tables with THC, the operator can see increase in consumable life, better cuts, less dross, and higher tolerances.
The standard THC system on our tables was completely developed by BurnTables, it is by far the easiest THC system to use, but has all the features that a $5,000 system would and more!
-Adjustable torch height control, pierce height control, pierce delay, anti dive speed, and torch adjustment speed, all adjustable on the fly while cutting!
-All settings are saved, even in the event of power loss!
-Do you only want the system to reference the pierce height, but not use the THC for that occasional odd cut part, yes it can!
-Consumable wearing out but still cutting, but the height has changed because of the wear on the consumable? Don’t change it out, get more life out of your consumables, adjust the torch height by the turn of the knob, on the fly while your cutting!
-Are you getting slag build up on the nozzle? Don’t stop cutting, raise your pierce height with the turn of the knob, save time make money!
-Cutting holes in you part at a slower speed but don’t want the THC to fight you and drive the torch into the material, With BurnTables antidive features, complete adjustable, and you guessed it…. on the fly! Keeps the torch from diving down in corners also, no matter how slow you go!
-Need cut a part out of a already bent part, with the BurnTables z axis ability to travel 6″ and the Automatic Torch Height control, you can cut up to 45 degree bent parts.
-Have a situation that you need to completely turn off the THC, but yet need the functionality of the z axis to raise and lower between cuts, yes it can do that too.
Did we mention that this all Standard on ALL of our CNC Tables!
2/12/13 Oxygen Acetylene CNC Table Cutting.
Some of our customers utilize BurnTables CNC Tables with the available Oxygen Fuel Torch Attachment to cut thicker steel. this attachment can be mounted alongside the plasma torch and lowered down when needed. In comparison to plasma torches, the Oxy Torch has a few more adjustments necessary to achieve great quality cuts. Some being pre-heat time, fuel and oxygen flows, cutting gas flows, time on after cut, heats, tips, etc.
ESAB has a online guide that helps with the adjustments on the torch and regulators, as well as suggested cutting tips and feed rates for table operations.
One of the benefits of the Oxy Fuel Torch Attachment for the BurnTables CNC Tables is the ability to cut thick steel materials with out having to increase the plasma cutting unit amperage, this is a problem for some shops that do not have access to higher electrical supply to support big plasma power units.
A downside to a oxy fuel torch is that the cutting feed rates compared to a comparable plasma cutter for a particular thickness is slower. With increased heat to the part, the time for cool down after cutting is increased as well as clean up time for oxy fuel parts.
1/27/13 Plasma and Thermal Cutting Glossary.
Hypertherm gives some very useful insight to terms in the plasma cutting world:
What does “blow-back” mean? What are “lag lines”? The plasma cutting industry is full of unique words and phrases. Fortunately, our plasma cutting glossary has answers to those questions and more. Read on to learn what they mean. Who knows, you may just shock your friends with your new found knowledge.
AC: An electrical current that reverses its direction at regular intervals, such as 60 cycles alternating current (AC), or 60 hertz.
Angularity: The measurement of the plasma cut angle.
Auto-voltage™ circuit: Input sensing that allows the system to run on a variety of voltages with no rewiring.
Blow-back: Patented technology provides a pilot arc
Boost Conditioner™ circuit: Hypertherm technology that compensates for input voltage variations.
CNC: Computer Numeric Control
Coaxial-assist ™ jet: Patented jet design boosts cutting speed as much as 20% over conventional designs.
Lag lines: Grooves in the cut surface that are the result of the plasma arc.
Dross: The molten waste material created by thermal cutting processes that often solidifies on the top or bottom of the plate. Also called slag, dross is produced in different amounts and can be easier or harder to remove depending on the cutting process that created it.
Dual-threshold™ pilot circuit: Hypertherm technology that significantly reduces nozzle wear by increasing the pilot current precisely when needed.
ETR™ (Easy Torch Removal): A unique connector design that provides easy switching between hand and machine torches.
Heat-affected zone: The part of the metal that has undergone structural changes due to intense heat. Heat-affected zone (HAZ) cannot be seen. Although one of the side effects of HAZ can be a heat tint that is visible, the size of the heat tint is also affected by the surface condition of the plate. Therefore, the size of the heat tint and the heat-affected zone may not be the same.
HyLife® Electrodes: that last longer than ordinary designs by using the same patented technologies developed for advanced Hypertherm mechanized systems.
Kerf: The width of a cut made by the plasma arc.
Plasma: Plasma, sometimes called the fourth state of matter, is a high-temperature, ionized gas.
Plasma cutting: Process in which electrically conductive gas is harnessed and controlled. A torch holds consumable parts, which constrict and control the ionized gas stream or plasma arc for cutting most common metals.
1/3/13 Dry Air is Good Air!
Having dry compressed air for your machine operations, especial for plasma cutters, is essential for proper machine operation and great cuts. There are several intimidate benefits to dry compressed air for plasma cutters especial in consumable life. With just a slight amount of water in the compressed air supply that is introduced into the plasma arc, the water “explodes” and instantaneously erodes the electrode and nozzle. In short time, a $15.00 set of consumables can become trash.
Here at BurnTables, we highly recommend air compressed air dryer for you plasma cutter. In our shop we use the refrigerated air dryer Hankison HIT35 available through retailers like Grainger Industrial Supply. The benefits of refrigerated air driers over desiccant driers is low maintenance cost and longer run times before maintenance intervals with maintenance consisting mostly of cleaning of the cooling coils in the drier. Also with units similar to the Hankison, the air drier comes equipped with automatic drains for the internal water traps. The only downsides are additional energy consumption and higher first cost compared to other driers.
With desiccant air driers, the desiccant medium absorbs water in the compressed air stream and after some time will need to be replaced when its lost its absorbency. The amount of time it takes for the desiccant medium to become saturated is dependent on the humidity in the air of the surrounding environment of the supply air compressor. When the desiccant is saturated there is very little indication other then intimidate loss of consumable life in your plasma cutter which means additional cost to your bottom line. The benefits of the desiccant air filters is low first cost, energy efficiency and small floor print. In drier climates the maintenance cost (over significant time) may be small to not warrant the first cost of a refrigerated air drier, but high maintenance cost in high humidity climates for desiccant dries would out weigh the first cost of a refrigerated air drier.
Compressed air dries are beneficial to other tools, for example the pneumatic air engraver and pneumatic controls on the WaterJet. With reducing water in the compressed air supply, it cuts down on valve corrosion and allows lubricants to have maximum effectiveness in protecting moving pars in pneumatic controls. With either device, BurnTables recommends a compressed air drier for any climate for maximum performance of you cutting table.