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HOW TO BUILD AN IRON BALCONY PART ONE: CAD DESIGN AND PLASMA CUTTING.

Posted by Pedro L. Sanchez on Feb 22nd 2020

The purpose of this blog articles is to explain how one of our balconies is fabricated.

In the past, wrought iron was only forged by hand with hammers and heat. It was really a skill of Titans.Nowadays the use of modern equipment makes our lives a lot easier. Or no? This first article explains the process of cutting the parts on the CNC plasma starting with the AutoCAD drawing.

The first part is the CAD design.

We first make the drawings on AutoCAD, making sure all the code requirements for a balcony are met. We have a base design that acts as a template for all balconies, and the only thing that changes is the looks.

Many pieces of the iron balcony are cut in our CNC plasma, therefore AutoCAD literacy is very important, because in order to make things work the CAD design has to be perfect. Any imperfections on the drawing will make the machine fail or cut defectively. For instance, if the drafter is not careful and leaves double lines, the machine will stop in the second pass. The plasma has a metal detector, it cannot run on an empty space.It is also important to catch broken lines because they will also make the machine stop or cut defectively. All the drawing has to be “joined”; this is all the lines need to be continuous. It seems obvious, but the cutting area cannot be bigger than the plate size.

Another precaution is to leave enough distance in between pieces, ideally ½ “ is a good gap, but with care one can leave up to ¼ “ in between pieces. Special attention needs to be paid when it comes to narrow pieces, because the may warp during the process and cause “break aways” that would stop production.

Once the CAD drawing is complete, now it is time to put it in a language that the machine can understand. CAD files are normally dwg. files that cannot be read by the machine’s brain. The cutter requires it to be a gm file.Now, dwg files cannot be converted into gms, at least with the software that the machine comes with, therefore the dwg needs to be converted into a dxf. File.

Once we have de dxf file, then we upload the file to the machine software and begin the process of creating a readable gm file. This takes a few steps, which are merely “explanations” to the machine on what needs to be done and the setting of the cutter speed into the program, and to determine the type of “lead ins” and “lead outs”; that is to make the plasma pierce the metal outside the piece and make it approach the cut line in a way that does not damage the looks of the cut, or interfere with other pieces.

Once the gm file has been created, you can transfer it to the machine’s computer via email or simply a flash drive.But after this is done, do not think this is just click and go; a whole set up process has to take place, starting with placing the sheet metal plate on the plasma table. Turn on the compressor, turn on the plasma, turn on the brain, and finally turn on the computer 45 seconds after the brain. Make sure you wait patiently until everything loads up, because if you start hitting buttons like crazy all it will do is freeze the computer.

After that, the machine has to be programed to recognize the position of the plate by moving the torch to its closest corner and hitting “align corner” and then moving the torch to the opposite side and hitting align edge. Now that the machine “knows” where the plate is, we are ready to find our “program zero position”, which is interpreted as the closes point of the uploaded drawing.

When we align the piece, the program zero is set at the very corner of the plate; which is no good, because the torch will start cutting too close to the edge. Therefore it is advisable to move the torch ½” on either axis and then hit “set program zero”. Now the torch can start on the right place.

After the machine is set, we can upload the job from the flash drive. But don’t cut yet! We need to check the settings with the chart provided by the manufacturer, to see if the parameters match the type of material we are going to be cutting.If you are cutting a program that you have not used a while, it is important to check the speed that is set on the program, for it may have been set for a thicker or thinner plate that you are using. The machine has an override that would allow you to reset the speed to the desired position.

Ok, parameters are good, but still there is a precaution that needs to be taken. The torch needs to be inspected to see if all the consumables are in good shape and are the right for the plate type that is being cut. Use a wire brush to clean the electrode and the other parts of the torch, so that they look new and shiny. The air pressure and quality needs to be also checked, for that it is important to purge the water of the air compressor and the filter’s valve.Another important thing to remember is to check the water level on the table, water level needs to be as close as possible to the plate to ensure proper cooling off the pieces being cut.

Last but not least, make sure that the drawing is not bigger than the plate you are using, by moving the torch to the farthest positions. This is specially important when partial sheets are being used. The very last, hook up the ground clamp to the piece. Now you can go back to “program zero” and start cutting.

If all the parameters of the machine are correct for the material, the air pressure and quality correct, and the program is perfect, then the machine will do its job without interruptions, and with great quality.