I Choose That Welding Torch, Please

Would you let someone else pick out your spouse for you? Then, why in the world you let someone else pick out your welding torch for your robot?

I draw the comparison in fun and, because, a welding torch can be a lot like a spouse. Perhaps you got a good one and life is just peachy for you; production is smooth sailing. However, for those robots that were not so lucky and have a “high maintenance” torch, your life can be miserable.

Furthermore, just like marriage, divorcing your current welding torch will take a lot of effort and will cost you a lot of money! So choose wisely. Let’s pose some thought-provoking questions:

• How readily available is another new torch, same make and model?
• What’s its lead time?
• Do you have extras on your shelf? (You should.)
• Does your welding distributor have spares on its shelf? (They should.)
• Do you have a torch straightening jig to straighten your bent torch after a crash?
• Have you noticed if your welding torch has “play” in it because of crashes?
• Is your welding liner all the way to your diffuser? (If not, it will cause wire feeding and welding problems.)
• How much do your contact tips, diffusers and gas nozzles cost?
• Have you added up how much your company spends on contact tips and other consumables per year?
• What can you do to cut your consumables cost in half?

First of all, how long does one contact tip last you in production? If your answer is less than four hours, then you have a problem with feeding or lack of cooling. Are you welding over 200 amps? Typically, anything over 200 amps you want to be careful. How long are your welds? Yes, there are air-cooled 400 amp and 500 amp guns that will work fine as long as they have some idle time to cool down.

Now, please pay close attention to what I’m about to say: If you are continuously welding (usually six minutes or more), it is possible that you could have a situation where the welding torch can take the heat, but your welding wire cannot.

If the cumulative temperature at the contact tip exceeds the melting temperature of your filler wire then a droplet of metal will form and eventually disrupt your wire feeding. The torch is unaffected, but your welding wire melted at the end of the contact tip.

Honestly, most people misdiagnose this as being a wire feed problem when, in actuality, it’s a heating problem or lack of cooling, if you want to look at it another way. I have seen this happen with solid wire and cored wires. As for cored wires, they seem more sensitive because of the thinner metal sheath has less mass and, therefore, is more likely to melt.

An easy way to test if you are over heating your welding wire is to send the torch to the reamer after every four to six minutes of welding. Let it sit there for two minutes to cool down, then continue welding. Repeat this cycle as necessary until your part/parts are completed. (Remember this is only a test. Don’t leave your production set up this way.)

Now think about it. If your production runs all day without burn backs with the added two-minute cooling every four to six minutes, you have found your problem. Your choices are to switch to a heavier duty, air-cooled torch or to a water-cooled torch. Try to select a torch that has the same TCP (tool center point) as your original to minimize touchups.

If you go the water-cooled route, make sure you add the correct type of water as recommended by the manufacturer, along with the recommend type of bacteria inhibitor and ice preventer if you’re in a colder climate.

Do not underestimate the importance of following the manufacturer’s recommended maintenance of your water cooler. You do not want it to become the “Achilles heel” of your half-million-dollar weld cell. Never let a low-dollar item stop production on a weld cell. That’s never good!

In the past, I have seen instances where people program the robot tip and nozzle too close to the part. You must consider that the power source must increase the welding current in a CV process to maintain a consistent arc voltage (more heat) then add in the reflected heat from the arc – ouch!

Step back and look at what’s going on. Try some simple logical tests. The outcome of your test just might save your company a ton of cash, increase production and improve quality.

My humble opinion is that most robot users do not put enough thought or care into selecting what welding torch they are going to be “married to” for the rest of their robot’s life. Keep in mind this simple tool is doing some serious grunt work.

Select the torch that’s going to fit your current production along with any future parts you company may be welding. Put some effort into your selection. Get the one that’s going to give you the least amount of problems.