Metal forming is an essential manufacturing process, which can take raw materials and create components using various forms of shaping such as stamping, bending, and deep drawing.
Though straightforward in nature, small errors can turn into large problems escalating to scrap, downtime, and a completely disrupted production line.
Understanding frequent mistakes, how to avoid them, and the associated causes can help maintain efficiency, quality, and profit standpoints.
Here is a list of 10 mistakes when conducting metal forming that could ruin an entire production line:
1. Improper Material Selection
The key to scalable metal forming operations either is having the right material in the first place. Using a grade of material or condition of material that has incorrect properties (wrong temper, thickness, or alloy) will ouch your processes.
If you use material that is too hard, it may crack when formed, or if it is too soft, it may wrinkle or tear during manufacturing.
- Impact on Production line: Using incorrect material may cause excess material waste, excess die wear, excessive tool breakage, and excessive non-conforming parts which will stop the line dead in its tracks while operators spend considerable time trying to solve the processes.
- How to Avoid Issue: Read copies of engineering specifications and material certifications carefully. Material testing on the material properties (e.g., tensile strength, yield strength, elongation properties, etc.) to confirm that the properties of the material will work should be done prior to starting production, and should be part of any every production start-up process. Work closely with material suppliers to determine that the correct grade and condition is provided.
2. Incorrect Die Design or Fabrication
The die is important in a lot of metal forming processes. If the die is poorly designed or manufactured, there can be problems related to improper clearance, incorrect radiuses, no venting or incorrect die geometry.
- Impact on Production Line: Scrapped parts, burring, wrinkles, tears and galling can emerge from a bad die which can result in high scrap rates, more die maintenance, long downtimes for die changes or die rebuilds.
- How to Avoid: Hire experienced die designers and precision die fabrication. Use simulation programs (FEA) to validate die designs ahead of die fabrication. Use great inspection processes during die fabrication, including dimension inspection and material hardness testing of the die parts.
3. Insufficient Lubrication
Lubrication is key for reducing friction between the workpiece and the die, avoiding galling, increasing tool life, and promoting material flow. This is a typical mistake that is common and sometimes surprisingly hard to catch.
- Impact on Production Line: Without adequate lubrication we expect galling (material transfer from the workpiece to the die) of parts, leading to defects on the surface, increased forming forces, and premature die wear, which causes more frequent cleaning and polishing of dies and additional time lost on production.
- How to Avoid: Choose the right lubricant for the material and forming operation. Apply the lubricant consistently and in sufficient amounts. Regularly check lubrication systems (spray nozzles, roller coaters, etc.), and maintain them.
4. Incorrect Press Tonnage or Speed
Using too little or too much tonnage or using a press too slowly or too fast can be harmful to the forming process. If there is not enough tonnage, the part may be poorly formed.
If there is too much tonnage, the press and the material may become overstressed. Also, if the press speed is not correct this can create forming problems such as cracking or springback.
- Impact on Production Line: Parts may be incomplete, components may crack, and springback may be excessive, or even cause damage to the press machine. This affects part quality and may cause expensive press repairs for the company when downtime comes into play.
- How to Avoid: Estimate the forming tonnage. Check the press capacity for the job. Maximize the press rate using property, die design, and material specifications – typically determined by trial and error, but safely in the operating window.
5. Inadequate Material Handling
Handling of material before, during, and after the forming process can greatly influence the resulting product, to include that improper handling of coils (coil handling is critical), wrong feeding of blanks, not ejecting a part well is costly in time lost and damage incurred.
- Impact on Production Line: Scratched or dented material will yield defective parts. Jamming while feeding or ejecting can halt the press, driving up down-time and potentially damaging tooling or parts.
- How to Avoid: Establish material handling procedures, use appropriate lifting equipment (where appropriate), maintain cleanliness in the workspace and train operators in best practices. Ensure feed and eject stations are set-up correctly and being maintained.
6. Poor Tooling Maintenance
Tools and dies wear and are subject to breakdown. Failing to maintain tools or dies regularly such as checking for cracks, sharpening, and polishing, can lead to detrimental effects on production.
- Impact on Production Line: Damaged or worn tooling leads to bad part quality (such as burrs and inconsistent dimensions), increased forming forces or load on forming equipment, and ultimately tool failure. Tool failure will stop production for replacement or repairs.
- How to Avoid: Ensure all tooling has a proper preventative maintenance schedule. Inspect tooling for damage and warning signs. Sharpen or polish tooling when you see signs of wear. Track tooling life and performance variables to identify trends.
7. Lack of Process Control and Monitoring
Problems can be missed until it’s too late if a process isn’t properly monitored. This doesn’t just happen because tonnage is not monitored, but can also happen with a lack of monitoring for lubrication flow, dimensions of parts, and temperatures, among others.
- Impact on Production Line: Defects can happen lower in the process, and not be discovered until later processes. The larger problem is that scrap can build up over time. When things are happening in real-time, it becomes a guessing game, which can lead to more downtime.
- How to Avoid: Use in-process monitoring systems (e.g. tonnage monitors, vision systems, sensors, etc.) and continuously take and monitor operating statistics. Understand operating statistics so that deviations from standard conditions can be detected early on. Use statistical process control (SPC) to observe trends or follow risks to sustain the future.
8. Ignoring Springback
Springback, the recovery that material makes after forming, happens all the time when forming metal. If you either ignore or miscalculate springback, the end product could be a part that doesn’t meet dimensional tolerances.
- Impact on Production Line: The parts will go out of tolerance which will require re-working or have high scrap rates. The production line will slow, increasing manufacturing costs.
- How to Avoid: Design dies with consideration of springback (i.e., overbending). Use simulation software to preempt springback. Utilize trial runs and update tooling as necessary based on measured springback. Use coining or restrike operations to minimize springback.
9. Inadequate Training of Operators
Operators are the last line of defense against production issues. The lack of training in turnarounds, materials handling, quality checks, or troubleshooting could mean more expense because of those errors.
- Impact on Production Line: Operators may simply not see the warnings, or may not read the warnings correctly, and the adjustments may not be accurate, and the materials may be mis-handled, which could mean damaged parts, tooling or machinery, and costs are related to standing time and scrap.
- How to Avoid: Training programs need to be formalized and used for each operator, which include the operation of machine, safety precautions, along with quality spec’s and some basic trouble-shooting. A mentoring program, with new operators by a more senior operator, should also be utilized so they can engage in new operations fundamentally with basic experience
10. Neglecting Quality Control Checks
Not doing enough quality control on the parts of the production line can lead to defective parts to move on in the process and waste many hours, resources, and potentially lots of customer complaints.
- Impact on Production Line: The defective parts usually go unnoticed and defects are discovered in the assembly process and in some cases could be discovered after shipment occurs. This could cause expensive rework and to potentially recall the product and massive damage to the company’s reputation if the defects were severe enough. It could require re-manufacturing of an entire lot, which completely derails the cycle of the production process.
- How to Avoid: Set up in-process quality control (best-in-class) inspection and final quality inspection. Use all measuring tools to check for conformance (calipers, micrometers, CMM’s, etc). Use intuitive acceptance criteria. Train quality control personnel well, and establish feedback loops to control for known variables.
If manufacturers identify and address these 10 common metal forming mistakes systematically, they can improve their production lines in efficiency, quality, and profitability, therefore avoiding costly downtime and continue to produce on a high-yield operation.