When it comes to weld cell issues, oftentimes it is the simple things that are affecting its performance. Being able to know the basics and go through the basics will usually solve the vast majority of your robotic torch performance problems.
Those basics are shielding gas, power (current and voltage), and filler metal. Before going into the basics of troubleshooting, the first step in this process - no matter the issue at hand - is to make sure that all of the proper parts are being used per the manufacturer’s specification. That means all parts are free from defects, parts are tight, and they are installed properly. In many cases this may resolve the issue in and of itself; there are many aftermarket parts out there that may or may not work. These can lead to sub-par welds and poor torch performance.
Having all the parts on hand and installed properly is likewise just as critical. Ensure the torch has a wire liner installed and sized properly along with a neckliner if required. Check to make sure your tip holder is tight, diffuser/insulator is free from spatter and debris, and make sure the tip is clean and sized for the filler metal you are utilizing. These may seem like mistakes nobody would ever make, but you would be surprised at how often the reason a robot torch isn't performing properly is because a very common part was not installed.
Robotic welding torch consumables. From left to right, torch neck, diffusor/tip holder, insulator, contact tip, and nozzle. Some torches will feature all of these components, some less. Make sure they are installed securely and free of spatter bridging and a wire liner is also installed through the torch cable to the contact tip.
Porosity can come from many factors and be difficult to troubleshoot if the right steps are not taken. The first thing to check when porosity occurs is gas coverage. Start by checking the source, generally the tank or bottle, then the flow meter or regulator. This should be set to deliver a set flow rate of gas, and that flow rate should be called out and determined by the Welding Procedure Specification (WPS). If the WPS isn't known at the time, a good rule of thumb is between 30-50 CFH, with 45 CFH being a safe starting point.
The next step in checking gas coverage is to verify that the set flow rate is what you are getting out of the nozzle. If the flow meter is set to 50 and you are only getting 30 at the nozzle, then there is a leak or blockage somewhere along the line. From there, start troubleshooting at the feeder and work your way back up to the welding torch. Check to the make sure the o-rings on the back end of the torch are not dry-rotted and in good condition. Check the hoses on the back of the feeder and make sure they are secured and clamped. Also check that the diffuser/tip holder is free from spatter and blockages, and that the insulator or ceramic diffusor along with the nozzle is free from spatter buildup.
If all of these items are checked out and in working condition, disassemble the front end of the torch - the nozzle, diffusor/insulator, contact tip, and tip holder, and check the gas with a flow meter again. If you still are experiencing significant flow loss, then check the cable assembly for a pinched gas hose. The gas hose could also be split or experiencing dry rot.
It is also important to make sure that the proper gas mixture is being used, this would also be specified in the WPS beforehand. It is also good practice to make sure that proper pre-flows are set up if using a long run of gas hose.
If the above steps are checked and present no issues then look at the wire condition, base metal condition, as well as have the base metal properties checked. If the wire is rusty, oily, or contaminated it should be discarded. Base metal has to be clean and free of paint, oils, or rust to perform as intended with your robot torch.
If during welding, the positive or negative cable gets overly hot there may be an issue with the size of the cable or it may be worn. Evidence of a cable that is not delivering proper voltage and current would be a “ropy” or improper bead shape. Also, the distance from the work piece to power source should be taken into consideration when selecting what size grounding cable. Distance is especially important when utilizing a gantry mounted robot that is very far from the power source. The longer the distance, the heavier the cable needed. The cable manufacturer provides specifications on these distances and amperage ratings.
You also want to check to make sure that the welding torch is set to match the welding being done, a 300 amp water-cooled torch will handle 300 amps at a 100% duty cycle, but if the welding demands are above that rating, it may be a good idea to look at a larger torch.
Issues with wire feeding can also play a major part in welding related issues. In a MIG process the robot torch performance is dependent upon steady and accurate feeding of welding wire. If this doesn’t feed steady and accurately, you will run into issues with tip burn backs, improper weld bead, wire bird nesting at the feeder, and other issues.
The first thing to check is that the proper liner size is used for the size of wire. If your wire is sized for .052" then be sure to use a 52/62 sized liner. Using a liner that is undersized for the wire being used will cause your liner to fail prematurely. Similarly, using an oversized liner for your wire creates a potential cause the wire to fold into the wire liner.
Second checkpoint is that the proper liner material is used for the type of wire (more on that here). For example, on a high heat application you would not want to use a 100% Teflon or PA wire liner because it will melt, it is best to use a combination liner, where a portion of the liner is bronze and can take a thermal load. Also make sure that the liner is cut to the proper length and is free of burrs or sharp edges from cutting. To learn how to properly cut the liner type see the below video (it's for a manual torch, but the premise is the same), or see the operators manual for the welding lead that you are using.
Once proper size and type of liner are verified check to make sure the contact tip is sized correctly to the wire. This can be difficult if not working with a high quality wire. Some wire manufacturers use tighter tolerances than others, and the size of the wire can vary quite a bit and cause issues with feeding through a tip that is designed to feed a specific wire size.
At Binzel, we manufacture standard sized tips along with tighter tolerance tips. An .045” sized standard tip will typically suit many manufacturers of .045” wire. In the case of a tip being “too loose” or the wire having a “wire whip” issue, or there are concerns with long contact tip to work distance (CWTD), a tighter tolerance tip may be necessary.
Other causes of wire feed issues can be a result of improper drive rolls or improper drive roll tension. Many people generally ascribe to the thought that when it comes to drive rolls, tighter is better. This is not always the case. Oftentimes the driver roll tension is tighter than it needs to be or the improper drive rolls are used. If the tension is too tight there will be an issue with pinching the wire, causing it to lose shape and possibly strip off small pieces of wire, like hairs, and forcing it into the liner which will result in a blockage or restriction as it travels through the wire liner and contact tip. This will cause burnbacks and poor arc starts. U-groove drive rolls should be used for solid wires and V-groove or knurled rolls should be used for cored wires. The wire manufacturer or feeder manufacturer can specify this.
Your robotic welding torch should be a reliable part of your weld cell. When it doesn't function properly, knowing where to start can save your production time and headache.