Precision TIG Series 5: Design, Construction

In this the last article of our TIG welding series, we turn our attention to the design, construction and testing of Lincoln Electric's Precision TIG® 275 and 375 welding units. Lincoln Electric's exacting standards ensure a machine that is rugged, built to last and loaded with high-quality components.  

Add Lincoln Electric's superior design process to the long list of items that we have covered in previous articles - and the Precision TIG is a must for every shop. These attributes include: 

     Superior arc performance
     Better output with lower input current draws than the competitor
     Easy set-up
     Lower price than the Miller Electric® Syncrowave®
     Innovative features not found on any other TIG machine


Many attributes of the Precision TIGs are readily apparent just by looking at or welding with the machines. Today, we examine some of the less 'obvious' items on the unit - things that may not be seen at a glance, but make a difference in the overall reliability and service life of the product. This attention to detail is just another example of how Lincoln Electric carefully addressed each aspect for these new TIG welders.

Not only did Lincoln Electric pay attention to details; the company also paid attention to the customer! Interviews with TIG operators, distributors and sales personnel revealed that having a rugged machine that could stand the test of time was an important factor in purchasing decisions.

By utilizing outstanding design and construction techniques in adherence to ISO 9001 certification procedures and conducting a variety of tests to ascertain the quality of the design, Lincoln Electric delivers a machine that fits in with the company's mission statement of providing products that exceed customer expectations.


Reliable and Innovative Features
Built into the Precision TIG® 275 and 375 are features that consumers will not find anywhere else:

When the user strikes an arc with these Lincoln TIG units, the fan automatically turns on, runs during the entire welding period and then shuts off after a specified time delay for appropriate cooling when welding is completed. The Fan As Needed feature maintains a relatively uniform temperature on critical internal components, minimizing thermal stress cycles that can reduce the service life of those components.

In contrast, the Miller Syncrowave uses a Fan On Demand™ system that is tied to a thermostat found in the transformer windings. When the temperature rises to a preset rated temperature level of the machine, the fan turns on. The problem with this technique is that the machine is constantly going through rapid heating and cooling cycles during welding - even when not welding at the maximum rated output level of the machine. This repeated thermal cycling stresses the unit's internal components.

Air Flow Design
Lincoln's innovative design for its Precision TIG models uses only rear air flow louvers that bring clean air in from the top of the unit and exhaust it out the bottom. In this way, less dirt is drawn into the machine. To further minimize dirt contamination and build-up, Lincoln uses an air pattern inside the machine that creates a higher velocity horizontal flow over main power components that require cooling, such as the transformer, choke and rectifier. The benefit to users is that this airflow provides for better cooling and higher ratings than the competitor's unit. Compare this clean environment to Miller's Syncrowave, which intakes air through base louvers next to the shop floor, drawing in dirt and debris in a manner similar to a vacuum cleaner.

Separate PC Compartment
Precision TIG® 275 and 375 PC boards are housed in a separate compartment that keeps contaminants out and provides shielding from disturbances of TIG high frequency. The control leads entering the board are also shielded from electrical noise. And if that's not enough, the board is selectively potted and dipped in a environmental sealant to further protect it.

But don't think the separate compartment of the PC board makes it difficult to access. By simply removing two screws on the front panel of the machine, the operator can easily get into this area if required - there is no need to remove the sheet metal case.

High Frequency Arc Starter Compartment
From talking with customers and maintenance personnel during the development of this unit, it was noted that the number one maintenance item on a TIG machine is cleaning and adjusting the spark gap. So, to make this task easier, Lincoln developed a compartment to house the high frequency arc starter. Located at the side, it is easy to access with a removable panel that eliminates the need to remove the entire case side. Also, this isolated and shielded compartment minimizes the high-frequency arc emissions from getting out of the spark gap area and into other areas of the machine. Furthermore, the separate compartment helps protect the High Frequency spark gap from dust and dirt. Miller's TIG units have an access panel but do not have separate compartments for the arc starter.

TIG Torch Connection BoxPrecision Torch connection
Another separate compartment that the Lincoln Electric Precision TIG® has built in for convenience and reliability is a TIG torch connection box. This box, located at the side of the machine, helps operators make connections easily in a standing position, but also isolates water lines from the main transformer compartment should a leak ever develop. Making the connections is a simple, intuitive process. The operator connects the color-coded input water and gas fittings at the back of the torch connection box. TIG torch connections are made at the front, or output side, of the connection box with convenient wrench access.

Precision Torch connection on the Precision TIG's optional cooler is housed in a slide out drawer under the unit that makes it easy to service and maintain. It also uses a Pro-Con® brand water pump with a heavy-duty motor. Pro-Con® is widely recognized as a leader of reliable pump components in the cooler industry.

Construction Highlights
Not only do the Precision TIG® 275 and 375 machines offer innovative design features not found on competitive units, but these TIG welders are also constructed to exacting standards so that purchasers can expect long service life out of the machine. Here are some of the construction highlights that set them apart:

Durable Switches
Precision Torch connection Lincoln's design ensures the best possible electrical connections. To do this, the company uses durable switches that make positive electrical and mechanical contact. The operator switch leaves no question whether the switch is in the correct position. This also reduces intermittent electrical contact that can cause switches to fail.

No Direct Mechanical Connections of Aluminum to Dissimilar Metals
Lincoln Electric's stringent design standards specify that there are no connections made to dissimilar metals such as bare aluminum to copper, without plating the connection. In contrast, the Miller Syncrowave makes a connection of bare aluminum from the high frequency transformer to bare copper at the output stud. However, aluminum to dissimilar metal connections can promote the formation of aluminum oxides, which act as an insulator and reduce electrical conductivity. Miller also falls short by using input lead connections made of aluminum - for customers who typically use copper wire to connect power to the machine, this also could lead to the formation of aluminum oxide.

Mechanical Crimping and Soldering
Precision output studs Heavy current carrying connections and power lead lugs in the Precision TIG® units are mechanically crimped and soldered. Additionally, care is taken to be sure lugs are not crimped over the top of the insulation; all leads are stripped before they are crimped. These leads are also routed neatly through the Precision TIG machines and fastened securely so that the leads cannot loosen over time and come in contact with hot surfaces over time.

Secured Sleeves
Lincoln Electric provides secured sleeves for bundles of leads. The sleeves are mechanically secured so they will not loosen over time. These measures also ensure the leads are not subject to abrasion against sharp components or insulation inside the machine. Miller's competitive machine has SCR gate leads that are not secured and may come in contact with the main transformer coil. To alleviate high frequency leakage, Lincoln provides insulating sleeves for the high frequency circuit leads, which Miller does not.

Adequate Electrical Spacing
The Precision TIG® 275 and 375 units use a transformer construction that maintains adequate electrical spacing and tracking distances between transformer windings and lamination. To do this, molded insulated coil spacers are used.

By comparison, Miller Electric's comparable machines use wooden spacers wedged in between transformer windings and lamination. Wooden spacers are subject to swelling with moisture, and subsequent shrinking as they dry out. Over time, this can cause the spacer to loosen, thereby introducing the possibility of vibration, electrical shorting and more serious transformer failure.

Mechanical Fastening
To avoid, the Precision TIG® 275 and 375 units have mechanical locking tabs on the electrical PC board connectors, which are specifically designed to eliminate mechanical loosening that can, in turn, be a cause of subsequent electrical failure. In addition, the pins are treated with corrosion-resistant grease. The Miller unit uses no independent fastening and relies on the engagement friction of the connectors.

Not only do Lincoln Electric's innovative design and construction practices make the Precision TIG® 275 and 375 stand apart from the competition, but rigorous testing conducted before the machines are put into production ensure the utmost quality. Some of these tests include:

Drop Test
The TIG units are dropped at different orientations to a flat concrete floor from a 12 inch height.


Jerk Test
The integrity of the lift bail designed for overhead crane lifting is checked by dropping the machine 12 inches and then stopping it in mid-air. This test is performed multiple times to look for signs of damage to the structural integrity of the lift bail assembly.

Vibration Test
As part of the regiment of stress tests, the Precision TIG® unit is put on a vibration table to test its ability to withstand vibration. This test is meant to simulate the vibrations of common use over the intended life cycle of the product as well as the vibration generated by transport over various road conditions, as might be experienced during shipping.

Environment Test
The machine is put in a chamber to test if malfunctions occur when exposed to extreme conditions, as might be experienced in the real world, including abrasive and conductive dust, humidity, moisture and fluctuating temperatures.

Undercarriage Test
At the job site or in the fabrication shop, the machine may be moved from location to location as projects and plant layouts change. Considering this type of use, Lincoln engineers determined to test the stability of the machine when fully loaded with its typical accessories. For example, in this case, Lincoln adds shielding gas bottles and, with a variety of repeated stress test conditions, takes it up and down obstacles at different angles to verify stability and integrity of the wheeled undercarriage.

Shipping Test
Lincoln tests the integrity of the packaging to International Safe Transit Association (ISTA) standards so consumers and distributors can be sure they will receive an undamaged unit.

Life Testing
After the machines have survived the above battery of mechanical stress tests, Precision TIG units undergo cycling tests at full capacity and maximum load for an extended period of time to verify continued functionality.

Electrical Stress Testing
This testing checks for proper functionality of the Precision TIG when exposed to high voltage surge pulses on the input lines. Also, tests are run to check immunity to various types of electromagnetic interference (EMI) and RF, as well as how much EMI the machine itself emits.

Field Testing
Before selling to customers, Lincoln put several Precision TIG machines into 'real world' field testing for a six month period. To do this, key customers weld with the new unit for an extended period of time and report their findings back to the Lincoln design team. These "testers" look at such things as performance, design and reliability.


A rugged, reliable design, serviceable features, outstanding construction and strigent testing that goes beyond the norm - Add these to the long list of other attributes such as superior arc performance, value added features, easy set-up, more power and output range delivered at a low price and now you have the full story of how the Precision TIG family gives you the Power to Perform.