Examining roll forming machinery, tooling, and lubrication
Given the problems in your roll forming operation aren't attributable to material, you may want to look into machinery setup and especially your lubrication situation to uncover the real culprit.
Last time around we took a closer look at problems in the roll forming process and found that work material generally is not the culprit.
If material is ruled out, what can the problem be? No changes have been made, and the operator and setup people claim that they have done nothing different. Hmm ...
Machine Setup Check Points
In most cases the problem can be traced to a machine setup, maintenance, or electrical problem. Here are some items you might want to have on a checklist:
- Check if roll forming coolant has not been applied or has been turned off in critical forming passes.
- Check uncoiler for break pressure and a free-spinning reel. Make sure material is not jerked back during the run.
- Check roll setup against your setup chart.
- Check tooling records.
- Check punch tooling for free movement over material.
- Check entry equipment line-up and material guides in the mill.
- Check forming gaps with wire, or check applied pressure against your setup chart.
- Cut section samples coming out of the mill and check (use a template for critical passes).
- Check electronic sensors' function and location.
- Check punch press program.
- Check condition of the mill; ensure proper shaft alignment within the pass and between passes.
- Check drive components; worn belts often are overlooked.
The Machinery-Material Connection
It might come as a surprise to you that most material problems are related directly to a machine problem or faulty setup in the roll and punch tooling. Ensure that operators and setup personnel on all shifts keep and maintain good set-up charts.
Do not tolerate those infamous, secret setup pocket books! It is very costly to troubleshoot opinions, especially those about tooling and machine setup.
Now let's talk about the hardest roll forming problem to troubleshoot -- lubrication. You want to eliminate lubrication problems permanently, because in most operations, you will find the purchasing department in control of this aspect of roll forming.
Normally this is, besides material, the line item the red pen strikes first. But wait a minute! Why is it necessary to apply any sort of lubrication and then take it off? Why would anyone spend time, effort, and money on this? And then, why are we spending all our hard-earned dollars on special lubricants?
Steel mills usually coat coil with some sort of oil to prevent rust. However, this oil was not developed for forming.
Physics Brief. Visiting the physics of material surfaces briefly, we know that the surface of metal is quite rough, even though it appears smooth to the naked eye.
Picture peaks and valleys to get a good understanding of how a polished surface looks under the microscope. We also know, based on the formulas of Hertz in regard to pressure between elastic bodies, that harder materials penetrate softer materials. Add friction to the equation, and you get a shear force to your peaks.
Over time the peaks erode as they break off and get pressed into the coil material. The effect, as you probably already know, is that material is deposited on roll surfaces, especially on the high-wear grooves. It is obvious that this has an effect on product quality and tool life.
Heat. In addition, the roll forming process generates heat from friction and forming energy, which does not affect the material's microstructure; but in some cases, as in line welding, heat can introduce shape variations and other issues to a cross-section. A liberal amount of roll form lubricant acts as a coolant.
The point is to control and manage the impact of these effects. To review, roll forming lubricants:
- Reduce friction.
- Reduce heat.
- Remove contaminants on strip and rolls.
- Establish and improve corrosion resistance of finished products.
- Extend tooling life of punches and rolls.
However, if you select the wrong roll forming lubricant, you might encounter:
- Corrosion (red or white rust) on the finished product and equipment.
- Paint stripped off of equipment.
- Lubrication washout of bearings and glide surfaces.
- Inability to remove lubricants with existing coating line.
- Incompatibility with welding, adhesive bonding, material handling, or mechanical fastening.
- Slippery tooling from too much lubricant (not enough friction).
- Environmental, health, and fire hazards.
- Discolored product after roll forming.
Considering the Final Product. You must take the finished product and its application into consideration when selecting roll forming lubricants.
A light wax residue might be acceptable on a hidden part, but what will happen if you use the same lubricant on roofing applications? Your credibility will drop, that's what. It's best to discuss the application with an expert and to remember that the right lubricant can provide substantial benefits; however, the wrong lubricant can cost you dearly, in more ways than one.
Creating a Waste Management Program. In addition, you should consider lubrication as an entire system. This means that you need to consider environmental, OSHA, and local regulations to obtain the lubricant's benefits and to steer clear of trouble.
Above all, you need to establish a waste management program. This program not only ensures that you comply with the law, it improves process efficiency. Take a look around next time you walk through your plant. You might find some of the following:
- Plant managers who take it for granted that waste prevention is being implemented because of high waste disposal costs
- Purchasing agents who order too much product, with the unused material becoming obsolete in the plant
- Production employees who mix the wrong materials together
The point is that your efforts to improve and maintain your roll forming operation need to extend to lubricants. Do not forget to look at the maintenance aspect of lubrication—the continuous use of forming lubricants and their proper disposal or, even better, recycling.