Wire feeding is a critical part to your automated welding process. Without functioning wire, this multi-layered, complex process would not deliver optimal performance. This could lead to complete failure of your process. Challenges can arise due to wire feed speed, wire feed distance, and friction within the system causing a host of problems throughout your process. As you continue to understand your robotic welding cell, it is important to evaluate your wire feed practices.
What Does an ARC Process Look Like?
For starters, it is crucial to understand the basics of a typical ARC process in automated applications. On the end of the robot, you will have the robotic welding torch. Wire travels out of a contact tip in the front of the torch, through the back where it is pushed from a wire feeder connected to the back of the robot. Drive rolls will be found in the wire feeder, which pushes the wire up to the torch. Typically, that wire can either be taken from a spool or a drum depending on your setup. Your robot controllers will send a signal to the power source telling it how to manage the speed, amperage and voltage of the wire. In some automated systems, you will have a cooler connected to your system to take heat away from the contact tip.
Drum Fed Wire vs. Spool Fed Wire
Just like most things in life, there are pros and cons for each system. Drum wire delivery systems, which can weigh in at a few hundred pounds, allow for more wire due to their size. This results in a less frequent change. For operations using more wire, it may make more sense to opt for this system as you will not need to stop production as often to change out your wire. The spool wire delivery system is much easier to manage, in terms of size, but has limitations with the amount of wire it can hold. In relation to the drum, a spool is often times no more than 30 pounds. More frequent changes will need to be done using this system.
Another pain point to consider is the way the wire moves. With a drum, you will have to deal with helix of the wire. The way the wire is tightly wound can cause helix of the wire, allowing the wire to twist. When comparing to the spool, you are typically only dealing with the cast of the wire. This is easier to control as you will have a more consistent, straight feed.
From a material handling standpoint, a drum is much harder to handle due to its weight. Out in the field, we often see this equipment picked up by a forklift and brought over to the cell itself. The constant shift in movement can cause problems inside the drum, mainly disrupting the way the wire is wound inside the barrel. With a spool, the handling is much easier to move back and forth.
Properties of Welding Wire
Understanding the cast and helix of your wire is another important aspect to take into consideration. If you were to pull out several feet of the wire from a drum or a spool, and let it rest naturally on a table, you can see the helix and cast. The cast is the diameter of the wire as it naturally sits and the helix is the vertical height from the flat surface. Both can have a negative and positive effect to the wire feeding process.
With a drum, the cast is often times fairly constant. This is because the drum has a wider diameter and the wire is wound up consistently along the entire barrel. With a spool, the wire is wound up starting at a smaller diameter and gradually gets bigger as more wire is spun over itself. You will see varying cast with a spool feeder, but constant helix. Like we stated before, a drum can lead to helix in the wire as it twists. If the helix exceeds normal limits, you can experience tangles within the drum causing wire to get stuck.
Wire Feed Peripheral
Additional wire feed equipment can be added to the operation to help alleviate pain points. Wire boosters and wire straighteners are most commonly used to advance your operation. Wire straighteners are added to your process to help address cast and helix issues that can impede smooth feeding. In a perfect world, we would have a straight wire than feeds through the system without any bends, but that’s just not the case.
Wire boosters are utilized to help support pushing wire over longer distances. As you start to get into the 12-15 meter range, you will want to consider adding a wire booster to your process. These can range from simple pneumatic to advanced electronic controls and recording. Pneumatic boosters have been around for years and typically mount to the top of the drum. While adequate, they often can create other issues such as marring of the wire, addition of oil, and surplus of other contaminate due to usage of air. The electronic boosters provide a much more precise support to feed ability and are significantly cheaper to operation. These systems allow for data collection, where you can gather and utilize information around length of wire used, productivity/uptime, and even support calculation of wire left in the drum with alarms to notify when certain levels are hit.
Wire Feed Options
When it comes down to your wire feed system, you can choose between working with a main wire feeder, known as a single drive, or you can combine that system with a support feeder, creating a dual drive. Whether you use a single or dual system will depend on the wire material you are using in your operation. When using softer material, such as aluminum, you will look to a dual drive system, with the secondary support feeder being as close to the process as possible.
Wire Feeding Conduits
This area is one of the biggest issues we see in automated applications. The straighter you can keep your wire conduit, the more accurate and robust your wire feeding process is going to be. There are two types of wire conduits, a standard wire conduit and a MasterLiner (also known as a roller liner). Typically, a standard wire conduit can be thought of as a tube, where the wire enters one side and exits out of the other. Ideally, you will want your wire to flow smoothly through the tube. The motion of the wire rubbing against the inside walls of the tube creates an increase in friction. This is something you will want to avoid.
When you run into issues with keeping your wire and wire conduit straight, the MasterLiner can be a better solution. This process involves four rollers, which have a stainless-steel axel going through them which prevents moisture from getting inside. The wire travels through the middle and every time it touches a roller it spins, causing much less friction. MasterLiner's are best used when bends are prominent, especially going up the side of the robot. Ultimately, the goal is for the wire to be fed with less friction in order to achieve longer distance in your operation and the ability to use only one wire feeder.
A good way to determine the status of your wire feed system is to open up the drive rolls and bend the wire into a hood shape at the contact tip. Using a standard fish scale, pull the wire directly in line with the tip. The pounds of force required to overcome pulling the wire, provides you a quantitative number on which to set your goals. It is not uncommon to see 25-30 pounds or pull required to move the wire. In cases where we have applied the MasterLiner, we have been able to reduce it to well below 10 pounds - sometimes under five.
As shown throughout this blog, wire feeding plays a significant role in the overall performance of your automated welding application. Proper wire feed techniques and equipment are necessary to result in a successful process. Understanding how your complete system operates, while learning what equipment creates more benefits than others will greatly reduce problems while welding. Each operation is different, which is why options are available. With this information, you may be able to avoid trial and error, but of course some wire feeding systems may work in differently depending on your setup.