Excessive Shim Use in Roll Forming Machines – Causes, Inspection, Troubleshooting & Alignment Fix Guide
Excessive Shim Use
Roll Forming Machine Tooling & Pass Design Failure Guide
Excessive shim use is a tooling setup issue in roll forming machines where technicians rely heavily on shims to correct roll alignment, tooling position, or roll gaps instead of addressing the underlying mechanical or tooling problem. Shims are thin metal spacers used to make small adjustments in machine setup, allowing precise alignment of rolls, shafts, and tooling components.
In properly maintained roll forming machines, shims are sometimes necessary to fine-tune alignment or compensate for small manufacturing tolerances. However, when large numbers of shims are used or when thick shim stacks are installed, the machine setup can become unstable and difficult to maintain.
Excessive shim stacking may indicate deeper problems such as roll stand misalignment, incorrect tooling dimensions, worn machine components, or improper pass design.
Because roll forming relies on extremely precise alignment of roll stations, shim stacks that are too large or poorly controlled can introduce additional mechanical instability into the forming process.
Excessive shim use commonly affects roll forming machines producing:
- metal roofing panels
- standing seam roofing systems
- metal wall cladding panels
- structural roof deck profiles
- steel framing sections
- purlins and structural components
Typical production problems associated with excessive shim use include:
- roll misalignment between stations
- inconsistent roll gaps
- profile dimension variation
- strip tracking instability
- uneven forming pressure across the strip
Operators may also notice that machine setups become increasingly difficult to repeat or maintain when shim stacks grow too large.
Maintaining correct machine alignment and tooling dimensions is essential for minimizing shim usage and maintaining stable roll forming operation.
Causes of Wear or Failure
Excessive shim use usually develops gradually when technicians repeatedly adjust machine alignment without correcting the root cause of the problem.
Several factors may lead to this condition.
Roll Stand Misalignment
If roll stands are not properly aligned with each other, technicians may add shims to compensate for the misalignment.
Over time, shim stacks may become excessive.
Incorrect Tooling Dimensions
If roll tooling is manufactured with slight dimensional errors, technicians may attempt to correct the setup by adding shims.
Worn Machine Components
Wear in bearings, shafts, or roll stand housings may create alignment issues.
Instead of repairing the worn components, shims may be added to compensate.
Frame Distortion
Older roll forming machines may experience slight frame distortion due to long-term forming loads.
Shims may be used to adjust roll positions when the machine frame is no longer perfectly aligned.
Improper Maintenance Practices
If machine maintenance procedures do not address root causes of alignment problems, shim usage may gradually increase over time.
Improper Setup Procedures
Technicians unfamiliar with proper roll forming setup may rely on shims instead of adjusting roll stands or tooling correctly.
Why It Happened and What Caused It
From a mechanical engineering standpoint, excessive shim use typically indicates that the roll forming machine or tooling system is no longer aligned according to its original design geometry.
Roll forming machines are designed with specific structural alignments that allow the upper and lower rolls to remain parallel and centered along the forming line. When these alignments are correct, only minimal adjustments are required during machine setup.
Shims are intended to provide small corrections when needed, but they should not be used to compensate for large mechanical deviations.
When shim stacks become large, several mechanical problems may develop.
For example, thick shim stacks may introduce flexibility into the roll mounting system. Under forming loads, these stacks may compress slightly or shift position.
This movement can alter roll alignment during production.
In addition, excessive shims may complicate the setup process because technicians must manage multiple thin components that may shift or become misaligned during installation.
Over time, the reliance on shim adjustments may mask deeper mechanical issues such as worn bearings, bent shafts, or misaligned roll stands.
Correcting the root cause of alignment problems is essential for restoring stable machine operation.
How to Inspect the Problem
Inspection Procedure
Diagnosing excessive shim use requires evaluating the shim stacks and the overall machine alignment.
Step 1 – Inspect Shim Stacks
Examine the number and thickness of shims installed in roll stands or tooling assemblies.
Large stacks may indicate alignment problems.
Step 2 – Inspect Roll Alignment
Use precision alignment tools to verify that the rolls remain parallel and centered.
Step 3 – Inspect Machine Frame
Check whether the machine frame shows signs of distortion or structural misalignment.
Step 4 – Inspect Tooling Dimensions
Measure roll tooling components to verify that they match the design specifications.
Step 5 – Review Maintenance Records
Check whether shim stacks have increased over time.
Gradual growth may indicate unresolved mechanical issues.
Step-by-Step Technician Guide – How to Fix
Correcting excessive shim use requires identifying and addressing the underlying cause of the alignment problem.
Method 1 – Reduce Shim Stacks
Remove unnecessary shims and re-establish proper roll alignment using machine adjustment systems.
Method 2 – Realign Roll Stands
Adjust roll stand positions to restore correct machine geometry.
Method 3 – Replace Worn Components
Repair or replace worn bearings, shafts, or housings that may be causing alignment problems.
Method 4 – Verify Tooling Dimensions
Ensure that roll tooling components match the intended specifications.
Method 5 – Perform Full Machine Alignment
In severe cases, a full machine alignment procedure may be required to restore correct geometry.
Preventative Maintenance Tips
Preventing excessive shim use requires maintaining proper machine alignment and addressing mechanical problems early.
Limit Shim Stack Thickness
Use shims only for minor adjustments rather than large corrections.
Perform Regular Machine Alignment Checks
Routine alignment inspections help detect developing problems.
Maintain Accurate Tooling Specifications
Ensure that tooling dimensions are correct before installation.
Repair Worn Components Promptly
Addressing wear early prevents alignment problems.
Document Machine Setup
Keeping accurate records helps identify changes in shim usage over time.
FAQ Section
What are shims in roll forming machines?
Shims are thin metal spacers used to make small alignment adjustments in machine setup.
Why is excessive shim use a problem?
Large shim stacks may introduce instability and indicate deeper alignment issues.
What causes excessive shim use?
Roll stand misalignment, worn machine components, or incorrect tooling dimensions may lead to excessive shimming.
How can excessive shim use be detected?
Inspection of shim stacks and machine alignment can reveal the issue.
Can excessive shimming affect panel quality?
Yes. Misaligned rolls may cause profile defects and inconsistent forming pressure.
How can excessive shim use be prevented?
Regular machine alignment checks and proper maintenance help minimize shim adjustments.