Relief Art Mural
From Arc Welded Projects, Volume IVThe James F. Lincoln Arc Welding Foundation
This welding project was prepared by James Cuhel of Ferris State University (David H. Murray, Instructor) in Big Rapids, MI as an entry in the James F. Lincoln Arc Welding Foundation Award Program.
Selecting the Material and Welding Process
The art mural is fabricated from 6061-T6 mill finished aluminum, 0.125" thick. The material was chosen because of its welding properties and its ability to be polished. The TIG welding (GTAW) process was chosen because the welder is able to control the weld puddle with more precision than using other semi-automatic methods such as MIG welding (GMAW). Another welding process used is cross wire welding. The resistance welder is used to weld the 1/8" braze rods together that are found on the bridge. To join the 1/16" braze rod used for spokes on the bicycle, traditional oxy/acetylene and a fluxed braze rod is used.
Starting the Relief Art Mural
After the design was drawn by hand using paper and pencil, a detailed drawing was made using AutoCAD. Using AutoCAD, all the items were drawn to scale and dimensioned. After all the items were drawn using AutoCAD, the file was saved to a DXF format so the computer-controlled plasma cutter could read the AutoCAD file. The file was then transferred to the plasma cutter. Once the plasma cutter was able to read the AutoCAD file and the plasma cutter was set up, the desired parts were then ready to be cut out.
Cutting Out the Parts
To cut the 0.125" 6061 T6 aluminum, the plasma cutter was set up with H35 shielding gas. H35 represents 35% hydrogen and the balance is argon. The plasma gas used is pure nitrogen. The pressure required for the shielding gas is 60 psi. The pressure for the plasma is 36 psi. To get the desired cut quality, the travel speed of the plasma cutter was turned down from the indicated speed. The travel speed used to cut out the pieces is 110 ipm at 100 amps. Instead of cutting the parts out all at once, it was decided to have them cut out one at a time. This was done to help accommodate some of the smaller, more intricate parts. The large backdrop was originally going to be sheared. However, due to the size limit on the squaring shear, the backdrop had to be cut using the plasma cutting table. The backdrop measured 4' x 5' with a 5" radius on the corners.
Cleaning the Parts
When all the parts were cut out, they were taken to a belt sander. All the burrs and sharp edges are taken down. A small die grinder fixed with a scotch bright pad was used on the smaller parts. This helped to reach in the tight corners. In order to have all the individual parts look similar, the edges should not be sanded. It would be impossible to reach inside some of the smaller parts and have them look similar to the other parts.
Locating Parts on the Backdrop
All the parts are placed on the backdrop after all the sharp edges and dross have been removed. This helps to see that the individual parts have been cut properly. It also helped to visualize where they would go. After placing all the parts on the backdrop, the next step was to connect the parts together. Duct tape was used to temporarily join the parts together. Temporary standoffs were made using scrap material left over from the plasma cutter. A hand brake is used to bend the small pieces of aluminum into various-sized pieces of channel. Next, the items plus the standoffs are attached to the backdrop using duct tape.
Most of the changes from the initial drawing were made when the items were temporarily attached to the backdrop. Some of the major changes included the use of brazing rods on a couple of items. The brazing rods are used on the bicycle, bride and tractor. This was done to add color. Also, adding water around the ship helped separate the ship from the tractor.
Welding the Items Together
The GTAW process is used to join the aluminum parts together. The welder used is a constant current AC/DC power source equipped with high frequency starting capabilities. The torch is a water-cooled 300 amp TIG torch equipped with a 1/8" collet and collet body. The ceramic nozzle used is a size 6. The tungsten is 1/8" pure tungsten. To get the desired arc characteristics, the tungsten is sharpened to a point using a diamond grinding wheel. The angle of the sharpened tungsten is 20 degrees.
Compressed argon with a flow rate of approximately 20 SCFH is used as the shielding gas. In preparing the items to be welded, the first step is to remove the oxide on the surface of the material using a stainless steel brush. To weld the members together, ER5356 filler rod in 3/32" size is used. The welder is set up with a max output of 230 amps. The welding machine is equipped with a foot control, allowing the operator to control the arc characteristics and limit the amount of heat put into the part.
Joining the Brazing Rods
After the smaller aluminum parts are welded, the next step is to join the brazing rods together. The spokes on the bicycle wheel are 1/16" thick. The traditional oxy-acetylene method is used to braze the rods together. A number 0 welding tip with 5 lb. of oxygen and 5 lb. of acetylene is used to join them. The brazing rod used to join the spokes together is 3/32" and coated in flux.
The process is called cross wire welding. A press series resistance welder is used to create the heat and pressure required to join the two rods together. The desired length of the braze rods was marked out with a pen and cut on a Beverly shear. Once the braze rods are cut to size, they are then ready to be welded. The two pieces of rod are laid on each other. Using this process saved a lot of time over the traditional oxy/acetylene method. The cross wire welding method does not require any preheating or the use of flux. Because of all the small parts associated with the bridge, a separate table is used to construct it. This helped to see where all the small parts should go and where the best places to weld them together would be.
To connect the braze rods with the aluminum, a unique method is used. Pieces of 1/8" aluminum filler rod are welded to the back of the items. The aluminum filler rod is cut so that they are about 3/4" long. Then the pieces of aluminum filler rod are bent over the braze rod to secure it. Not all of the braze rods are joined at equal distance from each other. As a result, the spacing between the aluminum filler rods is not in identical positions. Using this type of method allowed for greater tolerances when joining the braze rods to the aluminum items.
Putting a Special Finish on the Items
Each item has its own unique surface finish. To create such finishes, Scotch-Brite® pads (made by 3M) fixed to a small die grinder are used. By manipulating the speed of the die grinder and the speed of the die grinder moving across the item's surface, different types of finishes are possible.
Welding Items to the Backdrop
To join the items to the backdrop, the same method is used as in joining the smaller parts together to form the items. However, this time the backdrop has the slots drilled as opposed to the parts having the slots punched. To locate the exact location of the slots, the standoffs are welded to the back side of the items first. Next, the backdrop had to have a finish put on the surface prior to welding. This is done because some of the items would be welded close to the backdrop. There would not be enough space between the backdrop and the items to allow for the dual action finisher. The biggest problem encountered while putting a finish on the backdrop was the water and oil in the air line. The water and oil would get on the backdrop and create smudges. It was very hard to get the smudges out of the finish. Another problem was getting the entire backdrop to look similar. Focusing the dual action finisher in one spot for too long cause the overall look to suffer.
In order for the items to be perfectly level with the surface of the backdrop, pieces of 2" x 2" 16 gauge. square tubing were cut in different lengths. The square tubing was cut in four lengths. The lengths are 1", 3"x 3-1/2", and 4". The backdrop must be laid down so that the items are facing the ceiling. This is the best way of positioning the items up to be tack welded. Unfortunately, it requires that the items be tack welded in a very difficult overhead position. The backdrop was approximately 24" off the ground and resting on two chairs. The GTAW process is used to join the items to the backdrop. The same welding procedure is used as when welding the aluminum parts together. Also, the same procedure is used to remove the oxide from the standoffs and the back of the backdrop.
The first item to be tack welded on was the car. It is in the top left hand corner. After the first item was tack welded, slight warpage was noticed on the backdrop. As a result, the remaining standoffs were tack welded one item at a time by skipping around. A tack would be placed on one item, and then the next tack would be placed on the opposite side of the art mural. The reason for skipping around was to limit the amount of warpage caused by the heat in a concentrated area of the backdrop. There was still some distortion but the majority of it is not noticeable.
The next step is to remove the temporary metal square tubing from under the items. All of the items on the backdrop have different lengths. This was done to give the art project a sense of depth and shadows. After tack welding, the backdrop is carefully picked up off the chairs and leaned vertically up against a table. The welds are made in the horizontal position. Once the welds on the sides are complete, the backdrop is flipped over and the opposite sides of the joints are welded. To limit distortion, the smallest possible welds are made. After all the items had been welded, the remaining standoffs that stuck out past the welds are broken off and ground flush with the backdrop. A 4" right angle grinder is used to take down the remaining welds.
Finishing the Art Mural
The finished art mural must have some kind of protective coating put on it because of the oxidation characteristics of the aluminum. A clear coat type of spray paint can be used.
General Outline of Fabrication Steps
Design using AutoCAD
Convert AutoCAD file to plasma cutting table software
Place a 60" x 120" sheet of 6061 mill finished sheet of 1/8" aluminum on the cutting table
Cut out parts and backdrop using the plasma cutter
Deburr parts using the belt sander
Braze rod for the spokes and bridge supports are cut out using diagonal cutting pliers or Beverly shear
Clean the ends of the spokes and bridge supports with a file or belt sander
Organize parts on the backdrop
Shear out leftover aluminum for standoffs
Duct tape the set offs to the parts to visually confirm correct placement of parts on backdrop
Tack weld standoffs to back of parts
Put a finish on the front of the items using a 4" right hand grinder set up with finishing pads
Weld joining parts together
Put a finish on the backdrop
Weld items to the backdrop
Spray paint with clear coat
It is important to use enough ventilation to keep the fumes and gases from your breathing zone. For occasional welding in a large room with good cross-ventilation, natural ventilation may be adequate if you keep your head out of the welding fumes. However, be aware that strong drafts directed at the welding arc may blow away the shielding gas and affect the quality of your weld. In planning your workshop ventilation, it is preferable to use ventilation that pulls fume from the work area rather than blows necessary shielding gas away.
Remember, electric shock can kill. Wear dry, hole-free leather gloves when you weld. Never touch the electrode or work with bare hands when the welder is on. Be sure you are properly insulated from live electrical parts, such as the electrode and the welding table when the work clamp is attached. Be sure you and your work area stay dry; never weld when you or your clothing is wet. Be sure your welding equipment is turned off when not in use. Note that Lincoln wire feed / welders have a relatively low open circuit voltage and include an internal contactor that keeps the welding electrode electrically 'cold' until the gun trigger is pressed. These important safety features reduce your risk of electric shock during any welding project.
It is essential that your eyes are protected from the welding arc. Infrared radiation has been known to cause retinal burning. Even brief unprotected exposure can cause eye burn known as 'welder's flash'. Normally, welder's flash is temporary, but it can cause extreme discomfort. Prolonged exposure can lead to permanent injury.
Workspace - Protection from Sparks
Before you get started on any welding project, it is important that you make sure your work area is free of trash, sawdust, paint, aerosol cans and any other flammable materials. A minimum five-foot radius around the arc, free of flammable liquids or other materials, is recommended. Extra care should be taken in workshops that are primarily used for woodworking as sawdust can collect inside machines and in other hard to clean spaces. If a spark finds its way into one of these sawdust crannies, the results could be disastrous. If your shop area is too small to allow for a safe radius, please use an alternate area like a garage or driveway.
Cylinders can explode if damaged. Always keep your shielding gas cylinder upright and secured. Never allow the welding electrode to touch the cylinder.
It is also imperative to make sure you have all the necessary safety equipment and that you're wearing welding friendly clothes. You should wear:
Welding gloves - dry and in good condition
Safety glasses with side shields
Protective welding shield with a dark lens shade appropriate for the type of welding you do
Head protection - like a fire retardant cotton or leather cap
Long-sleeve cotton shirt
Long cotton pants
Leather work boots
A fire extinguisher should also be on hand during any welding. Also, make certain no children are in the area when you are welding. They may watch the arc and can experience retinal damage from its intense light. There is also a risk of a child getting burned by welding spatter.
Finally, see the instruction manual for your welder for added safety information.
*This project was published in Arc Welded Projects, Volume IV by the James F. Lincoln Arc Welding Foundation. The material has been edited and some of the drawings improved, but neither the projects nor drawings and instructions have been reviewed for accuracy or safety.
*This project was included because it appeared to be interesting, and in some respects, proposed novel applications. However, since the James F. Lincoln Arc Welding Foundation or the Lincoln Electric Company have not tested the material, nor verified the computations or other aspects described, the Foundation or Lincoln Electric cannot, and does not, assume responsibility for the accuracy of the plans or safety of the project. The project was submitted for such use as may appear feasible, but those making the project must assume full responsibility for the results of their efforts to make or use the project described.