Miller recently released the Millermatic 255, the latest in a long line of industry-leading MIG welding machines. Theres big news this machine incorporates pulsing, something I have been eager to try on a MIG welder for some time. The machine runs on 240V, single-phase power. Its housed in a compact cabinet with a large, easy-to-read color LCD display, and is available with running gear that holds a gas bottle, making the outfit easy to move. The running gear also has a handy storage compartment, which is great for storing consumables, safety gear, and other accessories. No tools are required to secure the machine to the running gear. Theyre joined by clever fasteners, which can be set or released in seconds. The machine ships with Millers new 250-amp MDX gun, which is very ergonomic and feels just right in gloved hands. The standard length is a generous 15 feet, which is more than sufficient for the work I do. The power switch is right on the front panel; a detail I like very much, so you dont need to grope around to find a switch concealed in the back. Once the power is switched on, the bright LCD display is illuminated. This machine has the Auto-Set Elite feature, which can automatically set the welding parameters based on the wire type and diameter, material thickness, and welding gas. Auto-Set has worked so well for me with my other Miller machines that its been years since I used a lookup chart, but there is a chart inside the hinged cover should you need it. This is the new Millermatic 255, an extremely capable machine that incorporates pulse welding. I really like the control panel on this machine; its simple, un-cluttered, and easy to understand. Seven buttons and two knobs are used to make all the possible adjustments, while the large color display shows exactly what your settings are, and makes it easy to change the parameters, even displaying pictures when appropriate. After the machine is turned on, the first step is selecting the process with the top buttons. The left button toggles Auto-Set on and off. When its on, the button is illuminated, and when its off, the machine is in MIG mode with manual settings. The top right button toggles the pulse function on and off, and its illuminated when pulsing is enabled. When manual mode is selected, MIG is displayed at the top of the screen. The chart inside the machine lists the recommended parameters based on the type of gas and the material, wire diameter, and material thickness. The voltage is adjusted with the left knob and the wire speed is adjusted by the right knob; the selected values are displayed on the screen. Pressing the bottom left button allows you to scroll through the selections for gas and wire type. To set up the machine, the gun is fed through the face panel and connected to the drive mechanism inside the welder. I almost always use the Auto-Set feature; its quick and easy and usually hits the sweet spot with the parameters. Auto-Set MIG is displayed at the top of the screen when youre in this mode. The two buttons on the bottom left cycle through eight available wire types and gases. Pressing the middle button toggles through the wire diameters, from 0.023 to 0.045 inches, the screen displays the selected size. The bottom right buttons cycle through the material thickness selections; from 24 gauge to 1/2 inch. The screen shows the thickness thats selected. Once youve made these selections, the machine automatically sets the parameters; displaying the voltage on the left of the screen and the wire speed on the right. These settings can be tweaked for particular processes or operator preferences by using the knobs on the left or right side of the face panel. The display shows a bullseye when youre at the recommended setting, but you can fine-tune the parameters within a defined range. A spool of wire is installed on the spindle inside the machine. This is a 10-pound spool, but smaller ones will fit, too. Pulse can be used with Auto-Set, too. The screen displays Auto-Set Pulse MIG when in this mode. Note that you must use C-10 gas when in pulse mode on steel (90 percent argon, 10 percent CO 2 ). The voltage reading is replaced by Arc Length when in pulse mode, with 50 being the default. When in pulsing, the machine constantly adjusts the voltage in relation to the wire speed. You can use the pulse mode when using the manual setting, too. When in this mode, the screen displays Pulse MIG at the top of the screen. The bottom left button is pressed to enter the setup mode, where you can use the left and right knobs to select the wire and gas types and the wire diameter. The recommended wire speeds are listed on the chart, based on the material type and thickness. So what is pulsing for a MIG welder, and how is it beneficial? When in pulse mode, the machine automatically cycles between a hot (peak) setting and a cooler (background) setting. There are several benefits to this, including high deposition rates, good penetration, good weld appearance, and little spatter. There is less heat buildup in the part being welded, which minimizes distortion and warping. Pulsing provides a wider operating range for a given wire diameter, so you can weld a broad range of material thicknesses without having to change the spool of wire. These are the drive rolls that feed the filler wire to the gun. There are several different sizes and styles, and its important to select the ones designed for the wire youre using. So how does this magic happen? The conventional MIG process uses short circuit transfer. When you pull the trigger on the gun the wire automatically feeds toward the base metal. As soon as it touches the wire heats instantaneously and forms a globule, which pinches off, flowing into the puddle and creating a small gap between the puddle and the wire. As the wire continues to feed it touches and pinches off again. This process repeats very rapidly, and thats what causes the distinctive frying bacon sound associated with MIG welding. In heavy industry, spray transfer MIG welding is sometimes used. This allows high weld deposition rates but it puts a lot of heat into the base metal. Spray transfer is recommended for flat and limited horizontal positions. Pulsing is essentially a modification of the spray transfer process, designed to eliminate the disadvantages. Pulse MIG is a non-contact process, which means the welding wire never touches the puddle. A droplet of molten metal is formed at the end of the wire, then the current cycles up to push that droplet through the arc into the puddle. The current drops when extra power is not required, providing a cooling period in the cycle, which lowers the heat transferred to the base metal. Pulse MIG works well for welding in all positions. The machine ships with the new Miller MDX 250-amp gun. Its robust enough to weld anything up to 1/2-inch thickness. I decided to test this welder with some tasks that a typical car builder might encounter. I started with 18-gauge steel. I used 0.035-inch wire diameter and C-10 gas for all my pulse welding. I did a butt weld first. I tacked two pieces of metal together and then made a pass from end to end. The weld was quick and easy, giving me excellent penetration and good fusion, and the appearance was excellent. Next, I did a fillet weld with 18-gauge steel. I cut one piece of metal 2 inches wide and a second piece 1-inch wide and fitted them together like an inverted T. Again, I tack-welded the pieces in several places, then made a pass from end to end. Its easy to blow through the vertical element when making a weld like this, but I found the arc very easy to control, and by favoring the baseplate slightly more than the vertical piece I was able to get a weld that flowed in nicely into both pieces and had excellent penetration. I welded 1/8-inch steel next. This is a common thickness for chassis components, and I had a few 23 bends left over from a previous project, so I tacked a few pieces together to simulate a chassis kickup. As always, I tack-welded the pieces first, being careful to align everything properly, and then I finish-welded the joints. In the photos, you can see how well this came out. When welding steel in pulse mode, C-10 gas is recommended. Thats 90 percent argon, and 10 percent CO2. I wanted to try a corner weld on 1/8-inch material, so I mocked up a Model Astyle framehorn. Just like before, I tack-welded the pieces, making sure the fit-up was good, and I got excellent results with the finish weld. I really appreciate welding that has minimal spatter; it makes a better-looking weld and the clean up is much faster and easier. I did a butt joint and a fillet weld on hot-rolled 3/16-inch material. While its always best to weld on metal thats squeaky clean, MIG welding can tolerate a bit of the mill scale on hot-rolled steel. I cleaned the parts with a degreaser to remove any oil, but left the mill scale, and I got very good resultsas you can see in the photos. Next, I welded a piece of 1/4-inch wall tubing to a 3/8-inch plate. After tacking, I welded one face of the tube at a time and got a beautiful fillet weld. The Millermatic 255 can weld up to 1/2-inch material, but thats thicker than I normally use. All in all, I really like this machine. The setup is quick, and its easy to make top-quality welds. This is a full-featured, state-of-the-art machine, capable of high-output welding for extended periods. It can be outfitted with a Spoolgun or a Push Pull gun for welding aluminum, and there is a Multimatic version that adds the capability of TIG and Stick welding, too. The control panel is extremely simple and easy to use. The top two buttons toggle the Auto-Set and pulse features on and off. The text at the top of the display shows what mode youre in, and the buttons on the bottom and knobs on the sides allow you to quickly cycle through all the possible settings. The Auto-Set feature very quickly adjusts the parameters to the recommended settings, but its easy to tweak them to your liking. For those who may want to set the parameters manually, there is a comprehensive chart inside the hinged door on the side of the machine. My first test was making a butt weld on 18-gauge sheet steel. As you can see, I got excellent results with virtually no spatter. This is one of the great benefits of the pulse feature. Next up was a fillet weld on 18-gauge steel. This is a more challenging joint, since the vertical piece can have a tendency to burn through. Another benefit of the pulse feature is minimizing the heat that is transferred to the metal. To test the machine on 1/8-inch-thick material I worked with some 23-inch tubing. Im tack-welding the joints here in preparation for the finish welding. Here are the joints after being welded. Note the cleanliness of the weld, and the uniform, slightly rounded bead. You can see that the toes or edges of the bead have good fusion with the base metal. I decided to do a corner weld on 1/8-inch-thick steel, so I mocked up a Model A framehorn. Im tack-welding the pieces together here. Here is the framehorn after being finish welded. These welds will be easy to clean up by sanding. Note the complete absence of porosity or voids in the welded areas. I used 80-grit sanding discs to smooth the welds, and Im going over the surface here with a Clean and Strip disc to get a uniform surface. Next, I made a butt weld on two pieces of 3/16-inch hot-rolled steel. Sometimes the scale on hot-rolled material makes welding difficult, but it didnt slow down the 255 at all. This is a fillet weld on 3/16-inch hot rolled steel. Again, you can see how uniform the weld bead is, and how well the toes of the weld blend in with the base metal. For my last test, I welded a piece of heavy wall tubing to a plate of 3/8-inch steel. It takes a lot of power to weld metal this thickness, but this is no problem for the Millermatic 255, which can handle material up to 1/2-inch thick. The post The New Millermatic 255 is Weldings Latest Innovation appeared first on Hot Rod Network .