Robotic Welding Torches: The Definitive Guide

Ideally, you want to get a shift from a contact tip, 2 weeks to 1 month from a nozzle, 6 months to 1 year from your swannecks, and up to 2 years from your torch cable.

This is to say that out of anything in your robotic torch, you will spend more time and money on contact tips and nozzles than any other part of the torch construction. So are you truly taking a close look at your tip life and whether you are extracting the most value out of your process?

Contact Tips

With contact tips, material selection is so important to evaluate and consider because as a torch consumable it’s the last line of conductivity in the welding circuit between the part. The main grade of materials for tips are copper, beryllium, copper zirconium, silver plated, and heavy-duty silver.

Beryllium copper, while being very durable and possessing good characteristics, are considered to be toxic as a consumable to produce. Since it’s not considered a very safe tip to machine, many engineers shy away from using it as a contact tip material.

Another type of contact tip that can be utilized is silver-plated contact tips. With silver-plating the contact tips use a micron silver plating, with the theory being that silver is a very hard but very conductive metal. With silver-coating inside and outside the contact tip, contact tip life can increase by 9x compared to standard E-Cu copper, with lower spatter adhesion and a smoother bore as a result of the drilling process, which can create better heat and current transference.

Drawn vs. Drilled Contact Tips

This is the type of inconsistency that leads to wire flip, where the wire wanders outside the weld joint entirely because of inconsistent tolerances and causes scrap in the part. These types of inconsistencies in the welding consumables lead to poorer arc starts, rework, and losses in productivity.

So, what’s the difference in hardness and conductivity between drawn and drilled tip materials? BINZEL’s contact tips have the following as a point of reference:

• E-CU (Copper): Hardness 110 HV, electrical conductivity approximately 57 m / Ωmm2
• CuCrZr (Copper Zirconium): Hardness 160 HV, electrical conductivity approximately 40 - 50 / Ωmm2
• E-CU Silver-plated: Hardness 110 HV, electrical conductivity approximately 58 m / Ωmm2
• CuCrCz Silver-plated: Hardness 160 HV, electrical conductivity approximately 50 m / Ωmm2
• Service Life:  CuCrCz precision drilled approximately 5x the lifespan compared to a precision drawn E-CU Copper. Silver-plated CuCrZr precision drilled approximately 9x the lifespan compared the precision drawn E-CU Copper.

Nozzles

With nozzles, the most commonplace issue welding engineers will encounter are spatter buildup throughout the process. A bad nozzle will have a lot of spatter build up on it in a short amount of time. As a result of that, you’ll have to go to using your reaming process more frequently.

As an example, when using nozzles that are nickel-plated and coarse threaded running on 400 A at 100% duty cycle for 6 cycles with an air-cooled torch, you can expect the nozzle temperature to remain about 580º C. With a brass or copper composed nozzle material, that same welding parameter would produce a nozzle temperature of 700º C. A temperature difference of 120º C will produce more spatter, force more reaming cycles, and make for a less productive welding cell.

There are two kinds of different nozzles:  slip-on and threaded. Many people like slip-on nozzles because they are believed to be easier to get on and off. The compression ring helps, but they may loosen over time and cause porosity in the weld. Or, if the ring fails completely and the nozzle falls off, the process will incur significant scrap parts. Another downside to slip-on nozzles is their lack of effectiveness for torch reaming. If the reamer blade isn’t sized and optimized for the nozzle, the blade can turn and compromise the nozzle in the reaming cycle, causing it to loosen and potentially fail while in operation.

With threaded nozzles that risk is minimized to non-existent. With threaded nozzles, there are two options:  fine thread and coarse thread. Both styles come with advantages to the slip-on nozzles because they are less likely to fail. Fine threaded nozzles tend to have a difficult time dealing with debris and spatter, and binding within the threads makes them difficult to install and remove. Coarse thread nozzles are minimally impacted by spatter and debris.

• Are my contact tips drilled or drawn?
• What's the hardness and conductivity value of my contact tips?
• What's my contact tip material, and how often am I changing contact tips?
• What's my nozzle material, and how long are my nozzles lasting in production?
• Are my nozzles threaded or slip-on? Are they coarse or fine threaded?
• How often am I changing nozzles, and what is it costing me?

IV. Swannecks: Repeatability, Keying, Construction, and Neckliners and
How They Contribute to Improved Productivity 

Repeatability from piece to piece is always the main thing you want out of your swannecks. Will your torch neck be the same lot to lot and run from run? How well does the swanneck hold up in a crash? Will a minor collision cause your swanneck irreparable damage? Will it sustain a blow without bending? Is the swanneck a single piece or multi-piece design? How does it interface back into the torch module?

The other important item to consider is the keying of the swanneck – is it a single key or double key? This speaks to torch fit. Two keyways locating onto the front module of the robot torch, and where they are located, has a lot of ramifications to the torch neck’s repeatability. Where the wear point is on a robotic torch impacts the durability of the robotic torch. If the wear points – like the soft keyway - are located on the front module of the robot torch – then the integrity of the front module erodes the swannecks durability, and the swanneck will begin to lose its tool center point. The wear points – ideally multiple - should be on the neck. This allows for the piece to be easily removed and replaced in the event that the torch loses its repeatability, as opposed to having to replace the front module if the wear points are located within the module.

Ideally, hard keyways are built into the torch module, which causes rotational movement and wear in the neck. When you remove a swanneck and replace it, you want to maintain a true tool center point (TCP) and not have to continuously touch up your robot to account for TCP variance. That affects uptime, throughput, and ROI in the welding cell.

Construction of the swanneck is another consideration to make when choosing or evaluating your robot torch. A single piece construction of the swanneck is going to be more robust than swannecks manufactured from multiple components. The contact tip holder is another important piece – tip holders are the interface between the swanneck and the contact tip.

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This is especially considered a possibility when the tip holder is also the mounting point for the nozzle. However, this mostly comes down the size of the tip holder. A shorter contact tip holder won’t experience such a problem because the point of bendability is far shorter to non-existent.

Two other areas of the diffusers/tip holder build to be aware of include the gas distribution and the seating of the diffuser. When the diffuser design allows it to sit inside the swanneck end and have support against the outer tube of the swanneck, the diffusers will perform better in crashes and help maintain the Tool Center Point in the event of a collision. The bores along the circumference of the diffuser is another design feature to closely evaluate.

• How many bores are along the diffuser circumference?
• What is the bore size?

Neckliners

Neck (sometimes called jump) liners are convenient and easy to use liners that don’t have as much awareness as they should. While front load liners get all the attention for their convenience and time saving (compared to traditional back load liners), neck liners are even more simple tools that save time and material cost in the replacement and maintenance of liners.  

Typically, a classic wire liner will start from the wire feeder and snake all the way up to the contact tip. Whether handheld or robotic liners, the principle is the same. The advantage of a neck liner for the automated process is that a short liner starts at the torch body and travels all the way to the contact tip. In this type of set up, a standard liner would stop at the beginning of the torch body, and the neck liner connects and houses itself within that standard liner where the torch body starts and feeds the wire through the contact tip.

The aforementioned front load liners use mechanical springs in the back that sometimes don’t perform properly if not installed correct. They are convenient to use, however, because the method to install is just to remove the contact tip and diffuser from the front end of the torch and feed the liner from the front end to the mechanical spring that sits on the back end of the rear retainer nut.

With front-load liners, the trick and key to consider is the length of the liner and making sure it sits correctly on that spring. Front-load liners have to be precisely cut at the length. Otherwise, the liner is prone to birdnesting and will fail more frequently than a standard liner.

When comparing front load liners to a neck liner, for instance, a neck liner would be a quicker more efficient change out, as well as less expensive from both a labor and material standpoint. With neck liners, the engineers or foreman can switch the torch neck out to remove the neck liner, keep production moving with a newly installed torch neck and a pre-installed neck liner, and change the worn liner out of the torch neck offline. Neck liners are very convenient ways to get better production out of your robotic torch because liners are one of the more time-consuming torch consumables to change out in a welding cell.

For liner material, the choices are normally helical versus flat design and steel or metallic versus plastic in material. Flat liners can be less forgiving because they are not as flexible. The biggest consideration and evaluation criteria with liner selection is using the right diameter. There is some thought within the automated welding industry that you can use a larger wire liner diameter than is recommended, but the risk with using an oversized liner is you have too much area around your wire than can cause bird nesting and misfeeding. It’s important to realize your wire only has so much columnar strength to push, so your liner actually enhances the columnar strength of the wire and allows it to push the wire through to the weld piece with less resistance. In short, make sure that you are matching the liner size with the wire size for the best results with wire feeding and liner life.

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Important Questions to Ask About Swannecks

• Is my swanneck single or double keyed?
• Is the wear point on the swanneck or on the front torch module?
• Is my diffuser protected by the swanneck?
• How many bores are on my diffusers? What size are they?
• Am I using neckliners? Where are the wear points on my liners?
• Do my wire size and liner size match?

First, it’s important and obvious to note that there are two types of mounts – over-arm and through-arm. We start with the through-arm mounting setup.

Solid Mounting

Solid mount is the more common setup today because most robots have the ability to detect a collision very quickly, eliminating the need for a shock sensor. In the past, shock mounts had an inherent weakness. When the shock sensor was activated, the repeatability of the tool center point was directly impacted by the way that the operator put the torch back in the home position.

Solid mounting for the robotic welding torch is typically designed as a stack of modules that ideally should secure the cable on top and act as a lock for the torch neck. Swivels or locks can likewise secure the corrugated conduit of the robot torch cable to prevent it from moving excessively during operation, which can cause abrasion and induce premature cable failure. Isolation from the welding current to the arm is another key factor. It’s important to control the conduit so it doesn’t abrade the cable as it moves up and down during operation.

With the torch mount, it’s important that in the event of a crash you can replace the torch neck and maintain the tool center point. For a solid mount through-arm setup, this would often come down to the insulator discs used to secure the mount to the robot. Make sure that bolts are secure. Repeatability is rarely an issue for solid mount robotic torches, unlike with over-arm setups.

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When evaluating a solid mount you want to understand how strong the mount is and how repeatable it is. Do I have dowel pins? What’s the dowel pin size versus its position? Is the dowel pin seated through a stainless sleeve to allow for more strength and repeatability? What is the material? Typically, solid mounts are made from aluminum, but you can use other materials. What’s the construction of the bolt holes?  What is the material thickness of the flange that’s going onto the robot? These are the things you want to consider when evaluating solid mounts.

Over-Arm Mounting

The principle of operation for over-arm mounts are mostly the same for each robot torch manufacturer – using a series of dowels and springs form the basis of a shock sensor. The shock sensor has the ability to take a direct impact in the Z direction. The differentiating feature is how different companies handle the switch that detects the movement in the clutch. Some use a micro-switch, some use a proximity switch, and there are different pros and cons to each. A micro-switch is a mechanical type switch inside the mount; a proximity switch sends an electric signal back to the robot to notify the robot arm that the mount is in the correct position. When the signal is high, the robot knows the mount is in the right position.

Over-arm has the same means of mount – solid mount or a breakaway collision mount. An important feature to verify with direct mount on over-arm is ensuring the robot has onboard collision sensing. The mount patterns for each robot are absolutely essential considerations to make when looking at your mounting options for the robot torch. Once you find the correct mount pattern, you have to make sure the mount matches the torch angle correctly so you have a clean tool center point.

Torch Mount Best Practices: Over-Arm & Through-Arm

When evaluating robot mounts, it’s important to look for mounting accuracy in its manufacturing. With shock sensing, information on its repeatability is another factor to evaluate. How repeatable is it? Ease of installation is another important factor. The faster you can replace a torch mount, the easier it is to use and the faster operations are back to making parts and making money, which is always the most important consideration.

When looking at mounts you really want to see and know how the arm is secured onto the mount and how conducive is it to tool center point repeatability? Something like a tapered pin with a stop on the bottom of the arm would create challenges if the tapered pin doesn’t push in all the way; reason being is that the pin won’t engage properly and you won’t have the same tool center point on your torch neck. This is just one of several mounting designs manufacturers use to varying degrees of success and repeatability.

It’s also paramount to look at how the mount arm clamps to the collision sensor. Is the mount arm bolted on? Is it to a tapered shaft or a slip shaft? What’s the mounting mechanism between the arm and the breakaway, and how repeatable is it? You also want to evaluate collision sensors in through-arm and over-arm for dead zones. Depending on the breakaway mount spring characteristics, the points of pressure applies to the mount may need to be greater to activate the switches or sensors to communicate to the robot. A mount that uses something like a weighted spring that goes 360-degrees around the breakaway mount will not have dead zones in it that can make the damage in a robot crash greater than it otherwise could be.

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For solid mount, look at how or if the solid mount secures the torch cable on the back end of the front module:

Does your solid mount use a clamshell-style or "C" clamp-style mechanism?

• How does it key into position?
• Does it capture the torch cable in a top to bottom style with an anti-rotation key?
• Does it a slip with a rotation key?
• How big are the rotation keys?
• Is it a large slot or a small slot?

In terms of torch mount qualities on both setup styles, look for solid machine surfaces and a minimum number of bolt up components. A minimum number might seem counterintuitive, but the fewer components you have the more solid and repeatable the mounting will actually be (within reason, of course). And, if you have multiple angles that are bolted together, each bolt point becomes a position of tolerance. So, with a solid mount machined out a solid piece of aluminum, you’ll typically get a better part that is less prone to error and experiencing tolerance stack up.

Important Questions to Ask About Torch Mounts

• Is the over-arm mount of torch neck the strong point of my setup?
• How repeatable is the torch neck within the mount and is it secured?
• Does the mount secure my cable?
• Is my strain weight on my breakaway mount correct?
• Are there any dead zones in my collision mount?

Today, it’s not enough to just have an automated welding process. Sure, it saves your production time and money over traditional manpower for those high production applications, but is it producing enough? Just accepting your current automated welding setup as the best it can be – or it not being prudent to look at alternatives – may be selling your companies’ capabilities and bottom line short.

As welding automation continues to evolve and welding equipment manufacturers continue to push to present greater value to welding operations across the world, ask yourself if you’re getting all that you can from your current equipment. It’s too valuable to just rest on the best practices of 10 or even 5 years ago. Manufacturers are moving continuously to make automated welding a more efficient, user-friendly, and profitable operation for you.

Now that we’ve gone through the entire anatomy of the robot welding torch, isn’t it time to take a look at what you’re using and really putting it through the test? The right torch for the right job – using the best practices and materials you can – will always produce the most ROI and create the most value out of your automated welding process. An unshakeable strategy doesn’t shy away from evaluating all the parts of the process and experimenting with new possibilities in the interest of achieving the goal in a better manner.

Finding the value in all parts of the welding torch setup is no exception. By doing so, it means you’re bringing the value back to your company and supporting a cost-effective and time-efficient operation.