Robotic Technology

Get into the mix

By Nick Wright

Above: The WolfPack line of modular systems (welders plus positioner) can be customized for a high-mix/low-volume production cell.

Automated robotic welding gains traction as shops look to run lean with high-mix/low-volume manufacturing

April 2013 - When shopping for a new car, it would be great to find one that seats five adults, tows an RV, gets 55 mpg and accelerates 0–60 mph in 5 seconds. But in reality, your best bet is to pick two or three of those capabilities to narrow down a viable set of wheels.

Setting up an automated robotic welding solution for high-mix/low-volume (HMLV) processing calls for a similar approach: Pick an optimal, mixed range of parts and automate them for cost efficiency.

In the last few years, HMLV has grown among manufacturers that need more flexibility with their automated setups (in this case, welding). The goal is to accommodate a big catalog of parts efficiently—whether the production quantity is 10 or 1,000—in the name of improving quality and increasing production, says Chuck Boyer, marketing coordinator at Wolf Robotics, Fort Collins, Colo. The company customizes automation solutions for fabricators, manufacturers and large OEMs.

“High-mix/low-volume fabricators, like most fabricators, are faced with the problem of finding qualified manual welders,” he says. This is just one factor fueling the HMLV automation trend, although a lack of workers on the factory floor highlights the human element. Robots still need people to program and service them.

There’s no secret formula for making an HMLV production approach cost-effective. It varies, depending on the company and its catalog of parts. In extreme cases, some companies define “high mix” as one crucial part they need to produce once a month, which would certainly qualify as low volume.

Drew Akey, project manager at Wolf Robotics, says he considers a high-mix system at least five parts, for example, even if two or three of those possible five only are being made in a production cycle. It doesn’t have to be hundreds of parts; every manufacturer has different scales.

Other factors hang in the balance, as well. Tooling switchover time, production scheduling, part programming and part size, for example, are all taken into account for an HMLV diet.


Tackling obstacles

Whether a manufacturer already automates an aspect of its process or it’s completely new to automation, there are inherent limitations to applying HMLV. This is where integrators like Wolf Robotics come in.

From Akey’s viewpoint, the toughest cases are companies with parts that have never before been automated. 

New customers tend to have parts that are designed for manual operations. Getting them redesigned for robotics generally can be difficult in just getting the product to work. With existing customers, it depends on the family of parts, referred to as a grouping. They may want to capture small and big parts all on the same system. 

“It’s a challenge to develop a solution that works with all part ranges,” Akey says. 

Say a company makes 100 different steel parts that get welded. A select two-thirds of those parts might get welded more often than the other third, even if in small quantities. The HMLV approach finds the optimal combination of robots and processes mainly based around the two-thirds segment. Batching parts for HMLV also is called product segmentation.

“One part can make or break whether you’ll have an effective segment of parts you’ll be able to achieve, depending on part characteristics,” Akey adds.

In any case, part fit-up and the end-user’s technical expertise must be assessed when shifting production methods. The capabilities of adaptive welding for robotics and automation has improved, explains Boyer. This means parts that weren’t candidates for automation 10 years ago can be welded with a robot today. However, there are still limits to how much variation can be tolerated.

As with any material handling aspect of manufacturing, there can be handling and tooling limitations when there’s a high weight mix.

“If you want to clamp a part that’s a really small, lightweight part, but you need the force to clamp something 10 times its weight, you need a variable adjustment with that securing force,” Akey says. “This is so you don’t crush the smaller part if your clamping force for the bigger part is that much stronger. If the parts are in the same family, in terms of weight and raw material size, then you can usually get the mix to work together.”

Other challenges of adopting an HMLV approach relate to planning and scheduling. It’s not unusual to have several weld stations manually producing a variety of parts at a given time. Welders select a part and weld until it is finished, which could take minutes, hours or days.  

When shifting from a manual process to robotic welding, planning is vital. For example, production with a robot in a single-weld station typically reduces production time to 20 percent to 50 percent of the manual production rates.

“This means that the end user needs to have a process in place to manage incoming parts to make the robotic weld cell most efficient,” Boyer says.


Smart solutions

Now, those challenges might sound cumbersome, but integrators like Wolf Robotics make the transition relatively painless. Operating as Wolf Robotics since 2003, the company is seasoned in decades of robot experience. It originally sold robotic welding equipment when in started in 1978 as ESAB Automation, and later, as ABB’s welding systems division. 

From a design standpoint, offline part programming has become a huge enabler for HMLV production, says Boyer. Before, the time required to program a part would be a real barrier to robotics because programming would mean taking the robot out of production to add the new part.  

“Now, with offline programming, programming new parts often can be done on a PC while the robot remains in production,” he says. This calls for the end users to develop expertise they might not have.

By using the customers’ CAD drawings, offline programming lets the robot keep running in production while a new part gets programmed. The program is downloaded when complete. The programmer might make a few touch up points prior to production. 

“The customer can either purchase the software for their own use or they can hire Wolf Robotics to do the programming for them,” Boyer says. Wolf Robotics has successfully transferred programs offline for customers in the energy, oil and gas, mining and structural steel industries. It recently did the first part on a new installation with zero robot weld defects for a major U.S.-based OEM. 

When it comes to hardware, Wolf Robotics integrates ABB and Fanuc robots into standard modular robot welding cells and systems that incorporate Wolf’s robot carrier tracks, towers and welding positioners with capacities up to 100,000 kg (about 220,000 lbs.).

Akey says the most flexible solution is two robots: a handling robot to present parts to the welding robot. A single robot can do multiple processes, too. In some applications, a robot may prep or bevel a part that it will then weld. That a robot can make multiple sizes or numbers of welds, offering a high flexibility of process, complements the HMLV solution.

“It depends on what capacities exist at the weight scales,” he says. “Smaller parts can be batched on a high flex system that presents and welds them, although those can be challenging programming-wise to be efficient.”

Lean playbook

Product segmentation, or the batching of part families that share a common platform, borrows from the canon of lean manufacturing. By pushing automated systems to their full potential with groupings, HMLV reduces material handling, machine movement and possible defects associated with manual welds. Akey explains that because HMLV demand is rising, the applications are growing in complexity. Job shops and large manufacturers alike want solutions that work with HMLV parts, but the setups aren’t set in stone.

“We want to be able to adapt the systems, but at the same time, if companies have a critical part come through the line, we’ve got to throw it in,” says Akey.

For example, to optimize tooling and part changes, Wolf Robotics has developed a way to mount a tacked part to a grid plate that can be quickly attached to the manipulating positioner.  

“The robot then senses three points on the plate to determine the layout position and can start the welding process. This permits high load capacities (100,000 kg) with a low profile for simple loading/unloading of unique shapes and sizes,” says Boyer.

The manufacturers for which Wolf Robotics has integrated automated robotic welding systems are, on the whole, finding them effective. But HMLV solutions are only as good as the minds behind them.

“I would say that systems that are implemented in high-mix/low-volume environments are normally very successful,” adds Boyer. FFJ

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