Thursday, October 6, 2011

Why does IHT offer two different height control systems for plasma cutting?

For some cutting applications, the quality of the finished cut is crucial, for others it less important. Therefore the leading manufacturers of plasma power sources have to offer different systems to meet both types of application and in turn IHT offer two types of height controls systems.

Both the C 1000 series and M 4000 ranges have ARC and PCS variants, the main distinction between them being the number of parameters that can be set by the user in order to achieve the optimum cut. The precision and quality of the process flow is identical in both systems.

With the C 1000 ARC and M 4000 ARC, local rotary controls are available for setting the cutting height, pierce height and the pierce time. This simplifies the task for the operator.

For more demanding applications the C 1000 PCS and M 4000 PCS allow more cutting parameters to be set and adjusted. <

This can be done using an operator terminal or there is the possibility to use the optional CUTBUS® interface that allows a CNC system to transfer information and settings direct to the linear drive, useful if numerous changes to settings are required.

Monday, August 15, 2011

Why is earthing so important?

The earthing of a cutting machine is always an important consideration and many users still do not understand its importance. Especially when cutting with plasma, a good earth is critical. Starting with a good connection to the structure of the building, a suitably sized earth cable needs to be connected to each machine.
If this is not done then the reliability of the machine and the cutting quality will suffer. In our installation instructions, you will find all the important information that will help you achieve an excellent cutting result every time.

Tuesday, July 12, 2011

Why is Cutting Height Mode (IHT Mode) so interesting?

In plasma cutting the cutting height is controlled by the arc voltage with the arc voltage being proportional to the distance between the cutting torch and the workpiece. The voltage varies by about 3 volts per millimetre so for example at a cutting height of 3 mm the arc voltage is 9 V. The operating voltage is, however, set at 110 volts. With an applied voltage of 101 volts the torch would touch the plate and with 119 volts the torch would be at a distance of 6 mm .

When you cut, for example, with settings of 100 Amps and 110 volts, the circuit resistance can be shown to be 1.1 ohms using Ohm's Law (R = V / I) . Imagine a cutting operation where one of the following is true; the workpiece is not lying flat on the table, the table is not properly earthed, a worn torch tip need to be changed or the work piece has been already repeatedly cut. All of these will affect the resistance in the plasma circuit. In my example just a change of 0.1 ohms will mean a change in voltage of 10 volts. Practical experience shows that the these variations in voltage can be up to 15 volts. This is where "cutting height mode" becomes of real interest because with this method it does not matter how big the difference is. Here we are setting the height and measuring the operating voltage. It always guarantees an exact cutting height and a consistently accurate cut.

Monday, June 20, 2011

What is Cutting Height Mode?

Cutting height mode, often called the "IHT mode“ is a better choice than the traditional "arc vol¬tage mode" because it is the all important clearance distance between the workpiece and gas nozzle that needs to be maintained not the actual arc voltage. As the nozzle wears, the clearance distance is maintained constant and therefore the clearance for all cuts is identical and the cutting quality is optimised.

It is important to remember that "Cutting Height Mode" also provides protection for your wallet. Because the cutting settings are always correct, the cost of wear and tear on the equipment will be reduced. IHT have already been using this technique in its products for about 15 years, even if others may be claiming it is a recent invention.

Thursday, April 21, 2011

Differing degrees of automation in Flame Cutting in different countries

In certain countries like the USA, China and India the level of automation in the oxy-fuel cutting process is alarmingly low. The lack of automation means that most cutting machine operators are constantly having to adjust the cutting height or modify other cutting parameters. The oxy-fuel cutting process is more complex than most people believe and I estimate that only 10% of all people working with it actually fully understand the oxy cutting process. This is true for both machine builders and end users. Take for example the initial piercing of the metal, I am surprised that how often I see that the piercing process takes too long or that slag is sprayed in all directions. This is often simply due to the wrong gas settings being used.

Thursday, January 27, 2011

What is the difference between capacitive and inductive distance measurement when cutting with oxy-fuel torches?

Both measurement methods can be used to measure the distance between the torch and the work piece. However, there are differences between the two methods and they both have advantages and disadvantages that I would like to briefly explain.

The first question is, am I cutting dry or under water? With a capacitive sensor, I can cut only dry as otherwise it is the distance to the water surface that is measured and not the distance to the workpiece. With an inductive sensor, the water has no effect on the measurement.

A good capacitive sensor (such as one from the IHT range) is both more accurate and more robust than an inductive sensor. Measurement accuracy is higher and the influence of temperature on the measurement is lower. Using an inductive method the cost of additional temperature compensation is very high.

With a capacitive sensor I can automatically prevent a collision of the burner with the workpiece or any slag that has been produced; this is not possible with an inductive sensor.

In summary, both measurement methods have their place but when oxy-fuel cutting, the capacitive method is always preferred. The only exception is when cutting underwater.