We often have customers thinking of upgrading to a new machine or just looking into what machine could possibly suite their profiling needs. We decided to put together a list of frequently asked questions and provide some short and concise answers. We hope that this FAQ may help you to quickly ascertain some of the basics involved when looking into a profile machine purchase.
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Photo: Contemplation (Sculpture by Jean Proulx Dibner)
Plasma is the fourth state of matter along with solids, liquids and gases. Plasma is a jet or beam of ionised gas capable of conducting electricity. This ionized jet or beam produces extreme heat of around 22,000o C.
CNC stands for Computed Numerical Control; a CNC Machine is a machine which is controlled by a computer through a numerical program, this program is often in a format called G-code. G-code is also used on a wide variety of CNC machines such as Lathes and Mills. 2D profiling CNC machines can use Plasma or Laser to sever material into almost any 2D shape by melting or vaporising the material. This type of 2D profiling has been done by CNC machines in industry for over 25 years.
Photo: CNC driven Cutting machine by IDA Control
High Definition Plasma is the same process as plasma cutting but the plasma beam is delivered through a much smaller nozzle orifice at higher velocity and results in more accurate profile cutting. A shield gas is also used to swirl around the plasma beam to constrict the beam and keep the cutting beam straight resulting in a square edge on the cut parts and better cut surface quality.
Photo: Cut surface quality with High Definition Plasma
No, unfortunately this is impossible! The machine needs a thorough adaptation, or we won't have the best cut quality possible. It is not enough to replace just the torch, to achieve an upgrade of the cut quality. For more details, please refer to our relevant High Definition Plasma text in our Support section.
A virtually dross free finish means that the cut edge finish is almost totally free from any molten remains of material still stuck to the underside of the part. A virtually dross-free finished edge will be able to be handled without any other de-burring process being necessary. Virtually dross-free edge finish is the goal of High Definition systems and machines and it shows the degree of the correctness of the cutting process fine-adjustments.
The photo on the right, shown in rocknfish.com, is an example of what Dross-free finish is NOT!
Dross depends on many variables: Machine variables such as Feed Rate (Torch Travel Speed), Current amperage and voltage, Torch Height and quality of consumables and material variables, the most important of which are material type (chemical composition, grade, flatness, surface condition), material sheet thickness and temperature changes. The three most critical variables, though, are cutting speed, amperage, and torch height.
When the cutting speed is too low, the plasma column heats the material too much and a larger quantity of metal is melted and blown away. As a result, we get a wider kerf and some of the molten droplets of the metal are not ejected away by the plasma jet. These droplets accumulate along the bottom edge of the cut forming thicker globules; this is what we call low speed dross. It is caused by too much energy absorption by the material. Similar conditions are created when we work with increased amperage or decreased torch height and the dross formed has the same characteristics as the low speed dross.
1. Increasing the cut speed in 10-12mm pm (5 ipm) increments
2. Increase the standoff in 1.5 mm (1/16 in) increments or 5 volt increments
3. Decrease the amperage in 10 amp increments
4. If none of these measures improve the cut, consider a smaller nozzle size
If the cutting speed is too fast, the arc begins to lag back in the kerf leaving a small hard bead of uncut material or rollover dross along the bottom of the plate. The predominant direction of molten material flow is to the sides of the cut rather than in front of it and down blown away by the gas flow. This type of dross is difficult to remove. If the speed gets excessively high the arc becomes unstable as it is more and more difficult to raise the temperature of the material to ensure the process's continuation. At very high speeds the arc cannot cut deep into the metal, if it can cut at all and it is not extinguished. High positioning of the torch or low current can have similar results as far as dross forming and cut quality is concerned as they cause reduction in the energy of the plasma jet.
1. Check the nozzle first for signs of wear (gouging, oversize or elliptical orifice)
2. Decrease the cutting speed in 5 ipm increments
3. Decrease the standoff in 1/16 increments or 5 volts increments
4. Increase the amperage (do not exceed 95% of the nozzle orifice rating)
While cutting, metal droplets are sometimes sprayed on the top of the cut pieces, where they solidify. We call this top spatter and it is easy to remove. The reason may be a too fast cutting speed, worn nozzle or high standoff of the torch. If, due to these problems, the plasma jet swirling flow is not optimally directed, the molten material is flung out in front of the kerf rather than down through it.
1. The nozzle must be periodically checked for wear
2. The speed should be decreased in 12mm per minute (5ipm) increments
3. The standoff should be decreased 1.5 mm (1/16 in) increments or 5 volt increments
Surface finish roughness is best described in the drawing to the right (shown in esabcutting.com).
Cut face roughness can be consistent or inconsistent and a result of wrong configuration of the machine, badly serviced machine or worn consumables. Please check:
1. Incorrect Shield gas mixture
2. Worn or damaged consumables
3. Too high Oxygen flow
4. Machine faults like dirty rails, wheels and/or drive rack/pinion. (Refer to maintenance section in machine 'Οwner's Μanual')
5. Carriage wheel adjustment
We can supply our Plasma Cutting machines with water tables, if the customer so wishes, because such a table has some advantages:
a. water muffles the sound of the plasma cutter,
b. parts can be kept cooler and will not distort,
c. fumes are pushed into the water rather than the atmosphere,
d. less power is needed compared to a fume extraction table,
e. the table is silent except for when it's raising or lowering the water and
f. there is no need to purchase an expensive fume extraction system.
There are also disadvantages with such a solution:
a. Good plumbing installation needed and easy access to water
b. The user has bad or no optical control of the cutting process
c. Some delay in the process because of the time needed to low and raise the water level or the cutting table
d. (And most important) Cut quality is noticeably lower than the one of cuts made by the same machine in the air
Many different industries use Plasma for cutting, for example because of its bigger thickness cutting capabilities. Many companies in the heavy engineering sectors use plasma to efficiently cut thick steel plate that would not be suitable for Laser.
2D profile cutting industry makes good use of both cutting disciplines and both excel in different jobs. Lasers are best for thin gauge material whereas plasma cutters are best at cutting thicker sheets. As Laser resonators are getting more and more powerful and High Definition plasma systems cutting gets better and better there is now a large cross over between the two. The best way to see which technology is right for your company is to talk with an expert in both fields (that is, IDA Control!) about the thickness of material needing to be cut, the amount of work needing to be processed, the finish and accuracy needed and the rough budget for the machine.
A Plasma cutting machine is capable of cutting material much faster than oxyfuel, but plasma is only capable of piercing material up to 50mm thick. Plasma is also able to cut a larger range of material and transfers much less heat into material than oxyfuel. Often plasma cutting torches and oxyfuel cutting torches are mounted on the same CNC cutting machine to give the machine a larger range of processing thicknesses, for example 3mm - 150+mm. For most work Plasma is more efficient than Oxyfuel as 90% of steel cut is less than 50mm thick and if you were to compare some suitable Plasma Cutting system to an oxyfuel system it would process 50mm mild steel more than twice as fast.
Plasma Cutters are able to cut many conductive materials including Mild Steel, Aluminum, Copper and Stainless Steel. The most popular material cut in the industry is mild steel which also gives the best cutting results.
Generally Plasma is used to cut mild steel between 3mm - 50mm thick, though there are many customers in the industry cutting both thinner and thicker material.
The new FineFocus 1600 by Kjellberg now provides the greatest range of processing from a high definition plasma system. The FineFocus 1600 by Kjellberg is capable of cutting 0.3mm mild steel at 30Αmps and still able to cut 110mm mild steel at 400Αmps. Cutting thickness can reach 160mm, but in this thickness range we understandably get inferior cut surface quality.
Plasma cutting machines are a very affordable way to 2D profile steel parts and good quality plasma machines require little maintenance. Most of the cost incurred while cutting comes from consumables such as Gas, Electrodes and Nozzles which are relatively cheap in comparison to the amount of cutting they can produce. IDA Control systems use the best technology available to maximise consumable life and therefore minimise the cost of cutting for the end user. When purchasing a machine make sure the manufacturer can provide you with a good and timely supply of well-priced consumables.
For most simple 3 axis cutting machines, operators with no experience can be trained in a couple of days to be a successful operator. With the machines and cutting equipment technology increasing all the time the modern machines are equipped with some degree of automation which makes cutting easy. The machines run in auto mode anyway, even when experienced personnel are available, because of their high level of complexity; manual running could result in serious damage to the work or the machine. Manuals can be available in advance, so that the users begin learning about plasma cutting and the machine operation before the machine even arrives at the customer's premises.
Although what we have already said is true, it is also true that experienced operators could take better care of the equipment in cases of emergency, better understand the whens and whys for the machine's need for service, pay better respect to Warning and Hazard procedures, and make better use of your consumables. Experienced personnel are not a must, but they can always help run things better.
Fortunately, this is a problem that can be solved easily.
It is pointless to buy a machine that would not cut the specific thickness of the specific materials we use, at least the ones that our main workload consists of. On the other hand, it would be a pity to be unable to undertake a job just because our machine cannot cut the material sheet required. Luckily, if we go into buying a machine that can cut through material much thicker, we do not just make a profit whenever such a job knocks at our door; we gain every time there is a cutting job to be done, because cutting speed and quality are higher for higher power of the cutting machine. Higher cutting speed results in shorter cutting time; high quality and high precision cutting while working on any part affects part quality and makes further secondary operations unnecessary, resulting in shorter manufacturing time; If time is money, we have earned already enough time to pay for the extra charge on the more powerful machine.
High definition Plasma cutting technology provides better focussed arc offering cleaner, smoother, straighter cuts with a narrower kerf, only second to Laser Cutting in quality, but Laser comes at much higher prices. Nevertheless, there is a good margin between the price for a good old-fashioned Plasma cutter and a new High definition one: we should not pay that extra money unless we actually need the extras offered by the latter.
This technology puts a lot of strain to manufacturers who do not have the “vertical” know-how required to incorporate into their production the best of electronics and software indispensable for the state-of-the-Art Ηigh Definition Technology. Our oppinion is that one should not invest in a High Definition Plasma system manufactured by anybody who relies on outsourcing for electronics and software; even the best outsourcing demands an expert embodying and fine-adjusting into the system, and if that expertise existed outsourcing would be rejected in the first place, as it would be much easier (and much less expensive!) to produce the automation in question in the premises!
Do you belong to the group of consumers who accept the picture of counterfeiters as latter-day Robin Hoods, working for the good of consumers who have fallen foul of profiteering companies? Well, what would you say if you knew that often the price of fake products is only slightly below the cost of the real thing. Even when this is not the case, there are very few consumer benefits cost-wise but the fraudsters are making big profits.
As a rule, third party no-name consumables are cheaper than the genuine ones, but are their prices cost-effective? The answer is no! Always purchase the recommended consumables for your machine. Cheaper consumables will not last as long nor will they provide the same high-quality results. Even if these parts cost one fifth of the price, they will also last for one fifth to one tenth of the cutting time, resulting in being more expensive in the long run, not to mention the inferior quality of the finished product all the way.
Please remember that most manufacturers consider the use of fake consumables a factor important enough to waive all of their Warranties towards the customer.
We would bring coal to Newcastle if we said that this depends on the manufacturer! The best machines are carefully designed to meet the workload requirements and are built to meet very high quality standards. Machines need to be strong, heavy duty and able to work for a long time and in the most adverse environment. They should be able to handle heavy loads and maintain their cutting accuracy; due to their sturdy construction they should promise a long and productive life, and keep this promise!
However, customers have been spoilt by manufacturers to believe that (especially their own) machines never fail; we should rather stick to the rule that anything made from more than one parts is likely to some time, somehow have some problem. A good PM (Preventive Maintenance) contract is always the best way out.
Since cutting machines usually are in the first stages of your production line, a temporary failure of the machine puts a temporary stop to all stages of your production and the more workers you employ, the more people will go around having very little to do. If you cannot afford this unavoidable stop, buy two machines and keep one for emergencies! Otherwise make sure you buy your machine from some manufacturer who can promise and provide maintenance and repair services on a basis that meets your production needs. A provision for a good maintenance schedule, before your machine fails, will ensure a longer and problem-free performance. In other words, you will also need the machine manufacturer’s advice and help AFTER you have paid for his machinery, whatever this entails.
