From Edward. F. Craig
Senior Weld Process Control Eng.

 

 

Frame Robot Weld Report:

For a Tier One Supplier.

Application.

Ford F-150 Truck Frames. 2003

 

 

2003: Summary:

It's the intention of this report to deal with the root causes of the numerous robot / manual weld issues found on the Ford F-150 Frame truck robot line at your facility.

 

At this time your robot frame weld productivity is only 50 % of your goal and your weld repair personnel report that the majority of the MIG welded robot frames require rework. Approx. 60 - 80 welds per frame will have manual weld rework. Of the sectioned welds that daily require macro examination of the weld fusion, an average of 15 % of the welds tested revealed lack of weld fusion. As the photo indicates both the robot / manual weld repairs are poor quality. The numerous weld repairs are providing a patched product, which provides a poor visual weld appearance. Both the in-plant weld process and robot cell equipment decisions are negatively impacting the potential weld productivity and quality potential.

 

 

 

WHERE ARE THE MIG WELD PROCESS CONTROLS?

 

 

The MIG weld transfer mode used for the majority of the robot and manual frame welds is the "globular weld transfer mode". This weld mode produces poor fusion, erratic weld transfer and extensive weld spatter. The traditional MIG process offers short circuit, globular and spray transfer. Modified weld equipment offers pulsed MIG. For consistent weld quality on parts over 2 mm, spray transfer is the preferred mode for frame welds.

Globular and lack of weld fusion

 

 

People Issues: One root cause of the weld process chaos in the frame plant:

While in the plant I had many opinions presented to me on the causes of the extensive robot / manual weld process issues. In the eighteen months since this robot project commenced, the lack of management resolutions for most of the weld issues in this plant comes from the fundamental fact that the majority of the managers engineers and supervisors involved and who provided an opinion (including the plant manager) were simply not qualified on the subject of robot / manual weld process controls.

[a] Report the Problems.

Of the 140 arc welding robots, 88 are dedicated to subassembly and 52 robots make the frame welds. At this time, many of the frame robots average a down time of > 60 minutes per- shift. None of the robot cells have logs to report real world robot down time. The robot weld log is an essential tool for robot PM, robot efficiency and weld process issues resolution. The primary causes of robot down time reported by the shop robot technicians are;

[b] Weld Gaps.

In general and from a robot weld perspective, the majority of frame parts that I have viewed do not have oversized weld gaps. Of concern in the robot cells is the lack of effective robot programmed weld process data that that can compensate for the moderate part gaps.

[c] Unacceptable Weld Joint Dimensions or too many operators making changes to what was once an optimum robot program.

In general the dimensional tolerances were close to acceptable however the ABB robots should have been purchased with the optional Bulls Eye (BE). The BE provides automated TCP control. The BE is one of the key outstanding patented features of an ABB robot. With optimum robot program points established, the BE automatically maintains the programmed points (weld wire position and weld gun angle to work) through control of the robot's tool center point. At this time with no controlled TCP the operators have to resort to shutting down the cells to make what they believe are effective program point adjustments. This manual band aid approach results in extensive manual intervention in the robot cells and less than optimum robot program points that create numerous weld issues that impact both weld productivity and weld rework.

Note: From a product launch perspective. The investment in the purchase of the BE equipment (approx. $2000 - $3000 a unit) makes a lot more sense than the purchase of the 140 Miller Invision "pulsed power sources" As the pulsed arc was found to be unstable the Pulsed MIG is turned off on this application. Frankly if individuals could see through the salesmanship that surrounds the costly pulsed weld equipment they would be aware that it's not been as well suited for high weld speed, steel applications as the lower cost traditional CV equipment. If a Miller, Delta Weld with built in interface had been purchased instead, the savings of approx. $2000 per unit, $280,000.00 in total would have paid for the Bulls Eyes equipment.

Note there was no use of touch sensing or through the arc tracking (TAT) used. Its illogical on some of the weld joints why there was no use of the TAT

[d] Robots / Manual Weld process issues:

The 0.052 (1.4 mm) MIG wire was an incorrect wire diameter selected at the start of the project. This wire requires high spray current, too high for the gage parts. The robot weld data used is therefore in the erratic globular mode, resulting in poor weld quality and excess weld spatter that impacts both the parts and contact tip, (increasing robot down time). This wire selection is a prime cause of your daily process issues.

As extra shifts commence at this plant, and the facility ramps up to attain it's target robot weld production, without a major change to the process and without the implementation of effective management influenced weld process controls, there will be a rapid escalation of in the manual weld rework and an extensive loss of productivity through increased robot down time. The robot down time has the potential to increase to a minimum average range of 90 minutes per shift eventually to a potential loss of weld production from 14 + robots.

[e] Management Engineering driven issues:

From a mechanical weld integrity perspective, the daily over welding that takes place on these frames may today compensate for the inconsistent, unacceptable robot weld quality and productivity, however the frames produced indicate to Ford a lack of management / engineering expertise. Also these parts do not reflect the shop floor employees efforts or the robot's true weld potential

There are many reasons as discussed in this report for the extensive weld issues that prevail. With many robot automotive / truck installations the last thing that is often given consideration for the robot line are the actual welds. After 50 years of use, it's inexcusable in 2003/ 2004 to find the universal MIG weld process confusion and management / engineering apathy that surrounds this simple two-control weld process.

 

With a short course in weld process control training, any of your engineers, technicians or managers should attain the ability to simply look at the part's gage thickness and determine the optimum weld wire diameter. With the wire and thickness determined, the desired weld transfer mode is readily selected. The transfer mode and thickness instantly determine the required wire feed rate, travel rate, weld voltage and the correct shielding gas.

Note: On this complex two control process. Once the weld wire diameter is selected there is only four weld settings to choose from.

My robot / manual process control teaching method provides all the robot control data necessary. The training program enables personnel to instantly set a robot without "playing around with the controls.

Robots do not need the input of skilled welders. Robots do need "correct process data" that is developed from a pre-qualified robot weld process control program, a program. This program is not generally taught in industry or in educational facilities that teach technicians or welding engineers. The refreshing reality for those involved with the robot weld production is when it comes to robot MIG welding there are no gray issues. There is however universal weld process ignorance and process myths combined with the influence of excessive salesmanship. Management and engineers simply have to take ownership of this important process.

Management: Robot / Weld Responsibility.

If you hand over the factory process keys to confident yet untrained workers, inexperienced supervisors or unqualified managers, it should not be a surprise to find that your plant has extensive robot / manual weld process issues.

In any established manufacturing environment it's natural to find on the shop floor great resistance to manufacturing changes. The required changes at this plant have to first be understood, supported and driven by all managers, engineers and supervisors involved. I met with the plant production manager of the robot line that suffers the most weld issues. This man has no weld process experience; he does however have great tunnel vision and a closed mind approach to the required robot weld process issues and the changes required. This is a manager is the classic type A fire fighter, he gave me 30 seconds to tell him the root cause of his problems. Of course if he wanted to know a prime root cause he only had to look in a mirror.

It's important to note that the weld issues at this plant are not derived from the weld shop floor. The weld shop personnel did not select the inappropriate pulsed weld equipment or the incorrect size weld consumables. The robot personnel have no control over the parts or the fixtures. The robot personnel did not turn down the automated TCP equipment or the through the arc tracking option, and the hundred plus personnel that daily make robot weld process changes did not turn down any robot process control training.

Weld best practices and robot process optimization should commence at the design, prototype and launch stage:

At the frame facility, the production pressures and the overall lack of weld process expertise, by many of the key production personnel are causing numerous shop floor moral issues. After 18 months of process chaos you now have a plant in which you have "why change the way we do things mentality". To make changes to an entrenched process in which a daily acceptance for third world weld quality and productivity is now the norm requires experienced management that will guide and support the weld teams. At this time I am sorry to report that management is lacking.

To address the root cause of the primary robot / manual weld issues, all involved have to walk the same production path, agree on the root causes of the issues, the necessary actions, take responsibility for the process ownership and then provide the leadership and time lines necessary to make the weld changes successful.

 

The Weld Resolutions:

Robots: Provide robot weld process control training for all those involved, "including your management and engineers". Change the 052 MIG wire to an 0.040 weld wire. Reduce the CO2 content from 15 to 10% and the robot weld process changes will be easy to implement. The process changes I recommend will increase the robot weld production by 30 to 50%. If you wish I will make the required changes in any of your cells. As I do not play around with robot weld data the changes will be made quickly. The data I provide will ensure you attain your desired production in a consistent manner. The new data will greatly reduce the required weld rework, to less than 5% and reduce the weld spatter by at least 70%. As the new robot weld programs are produced, I will develop 4 simple standard weld schedules that will be applicable to all the robot welds.

Note: Before the ABB robot programs are changed, it would be highly beneficial to get control of the TCP with the installation of Bulls Eyes in the cells

During the new robot programming, it would be beneficial if your key robot personnel and tooling manager worked along side me. The tooling manager understands the parts and fit issues. I would use his expertise to ensure that the process changes made are geared to address the future dimensional issues.

For the manual weld repairs. I would change the wire sizes for the manual welders. Provide them with an 035 or 040 wire and provide them with weld data that is actually designed for manual MIG weld repairs.

The Process Control Training Program.

I provide effective, unique, simple robot weld process control training and have already developed the necessary training resources. Another key issue to the success of the process changes is accountability and responsibility. I would not consider taking on this project unless I was given full responsibility for the robot weld changes.

Obviously the robot process control training is an essential part of this package. Who attends the training is key to the long-term success of this project. I will repeat that it's essential that all personnel including managers, supervisors, QA, engineers and technicians should be given the robot weld process control training. The bottom line with the F-150 frame welds, when it comes to weld decisions that impact the weld production or quality, all the plant's weld decision makers should walk the same process control path.

The large 0.052-weld wire used at your plant may be influenced by the Ford Dearborn approach to welding frames. At Ford the management believe bigger weld wires mean more production. You are likely not aware that for more than a decade every Ford Dearborn built frame has required extensive manual weld rework. Not one single Ford Frame has ever had a 100% optimum weld quality, its simply beyond their grasp.

With robot weld issues when the root causes are not addressed, there is a tendency in the weld shops towards looking for an easy quick fix, or look for a "sales influenced solution" like changing to a more costly MIG power source, try the magic three part weld gas mix or the special coated contact tips, etc. As I sit here writing this report the production manager who does not want to hear about a logical smaller wire size selection or process control training is hinting that he believes changing the weld wire to a "copper coated MIG wire" or changing the gas mix to a three part mix will be a contribution to the plants woes.

 

Note on Ford: In 1997 I was asked by Ford to analyze there numerous (over 160 weld issues) at the Dearborn facility. I not only analyzed all the issues in a 10 day period I had the opportunity on a weekend to set up the future 1998 frame line with my new recommendations for the prototype frames. At the end of that weekend, for the first time in the Dearborn history of the frame line, frames meeting both the robot weld productivity and quality expectations were produced. However due to union issue and management / engineering indifference my changes were never implemented.

A FEW PROCESS CONTROL WELD FACTS:

Weld Wire Size. Here are some welding facts that apply to both copper coated and none copper coated weld wires. The 0.052 (1.4 mm) MIG weld wire selected by your facility is too large for the gage parts welded. To attain stable, minimum weld spatter with the spray weld transfer using the 052 wires requires weld current > 290 amps. Due to the thin gages welded on the frames and to avoid weld burn through, the majority of the robot and manual welds at the plant are welded in the 240 to 290-amp range. Stable spatter free, spray transfer with a 0.045 wire are attained > 250 amps while the 040 wire requires around 230 amps for spray.

As the >290 amps cannot be used with the 052 wires due to weld burn through issues that would occur on the 2 to 4 mm parts, the plant's reactions has been to either lower the weld current typically 240 to 260, lower the weld voltages to 20 - 24 volts or increase the wire stick out which further lowers the weld current. This weld data with an 052 wire results in erratic globular transfer.

With globular weld transfer, the weld produces large erratic weld droplets which cause excess weld spatter and can result in poor weld fusion. However the primary concern for the excess, globular weld spatter generated is on its affects on the fixture equipment, the fixture switches and on blocking the robot MIG gun contact tips and nozzles.

The number one weld process problem at the plant that leads to robot down time is "wire burn back" to the contact tips caused by either inappropriate weld start data, (process training) or the globular weld drops which adhere around the contact tips bore, restricting the MIG wire as it exits the contact tip. As the weld robot weld production increases the globular weld spatter issues will increase becoming a prime cause of robot down time.

The over sized weld wires and globular weld transfer also provide convex welds with poor appearance. Most of the welds are 20 to 30 percent larger than they need to be this requires slower weld travel speeds impacting cycle times. I hope in future that your organization can see the importance of establishing Robot Best Weld Practices before the robot lines are introduced to your plants.

Sincerely Ed Craig:

 

 

 

2006 THREE YEARS AND
MILLIONS OF DOLLARS LATER:

 

E-Mail July 2006

Ed I wanted to send update about that E-Town plant that you visited a few years ago: As you know on your first visit to this plant, our robot lines were producing less than 40 truck frames per-hour and the majority required extensive weld rework. Thanks to your weld process and consumable recommendations the results from our employees are today staggering. Yesterday this plant hit very close to a record of 76 frames jobs per hour. We daily attain our average goal of one frame per-minute. We had two recent weld audits. One weld audit had a total of two failures (one offseam), and the 2nd weld audit was the first 100% pass weld audit in the history of the F-150 line.

Many thanks!

A Grateful Employee
Dana Corporation>


Note from Ed: It's great to hear of a robot welding success like this, especially as the unusual frame weld quality and productivity results were attained with process / consumable logic and spray transfer attainable from any low cost traditional MIG equipment.

The robot process control data I provided this plant is available in my Management Engineers Guide To MIG book and the training I provided is available in a Process Control Training power point presentation, both materials located here. However this site is called Weld Reality, so lets get back on track continue to call a lame duck a "lame duck".

It was 2003 when I delivered the Ford F-150 frame report to Dana corporate management. The report correctly pointed out the root causes of the robot weld issues and provided simple low cost resolutions. The report was not well received by a corporate and plant management unaccustomed to making MIG weld process / consumable changers to existing robot lines. The bottom line, it took over three years for the management to finally agree on process changes that should have taken less than a month to implement. My costs to Dana to fix the weld problems was, less than $20,000. My guess at the costs incurred in lost weld robot weld production and weld rework during those three years has to be somewhere between 10 and 20 million dollars. Who's accountable? Does anyone at the major auto / truck manufactures and the tier suppliers read this stuff? Does anyone see the need to put an end to this ridiculous, common, global loss of profits that occur annually with robots and a simple two control, 50 year old weld process?