6 Simple Rules for Rebuilding your Cold Forming Equipment

By: Mike Burkes
VP of Aftermarket ________________________________________________________

Rebuilding can mean a wide variety of things from repair of a specific machine component (transfer, feed, etc), to a complete machine renewal.  It’s all about options, so the first job should be to get a clear picture of what your machine really needs.  Don’t underestimate the importance of this first step: too often quotes are done, orders are issued, and a teardown begins following general directions like “tighten up the machine” or “give it a complete overhaul”.   

To ensure you get the most value, start with discussion between a knowledgeable rebuild technician and your operators and maintenance staff. It’s important for your rebuilder to know what shortcomings you might be seeing in your finished parts, what observations your operator may have, and the maintenance and reliability history of the machine.  Couple that with a machine inspection, and it will soon become clear whether your machine needs a complete rebuild, or if targeted repairs to certain machine components will suffice.

Once the scope of work is clear, there are six specific areas you should pay close attention to throughout the course of the project:

1.  The critical inspection phase
Inspection is the most important phase of your rebuild.  If things are missed during inspection, the best case scenario will be an unplanned delay during reassembly.  The worst case will be unplanned downtime and expense in your future.  For complete machine rebuilds, the machine should be completely disassembled and components inspected against the original prints.  Deviations in form, fit, and function should be documented for repair or replacement of parts.

Specifically for the critical power train components (crank, pitman, heading slide, etc), three specific types of inspection are needed to ensure the longevity of the machine:

All inspection data should be stored and available for your review upon request.
Multi Wave Ultra Sonic TestHardness Test
Multi-Wave Ultra Sonic Test (left) Hardness Measurement (right)

Die Penetrant Crack Detection
Die Penetrant for Crack Detection

  • Die-penetrant crack detection is the most common and basic method.  It will identify most surface cracks, but should not be the sole method used.
  • A multi-wave ultrasonic examination will identify micro-cracks or substructure flaws that are not found through die-penetrant testing.  If any components are weld repaired as a part of the rebuild, it is important that they are inspected again afterwards to ensure the repair has been completed successfully without leaving voids which could later become areas of stress concentration leading to failure.
  • Hardness measurements should be cross-checked against original design specifications to verify proper material and heat treat.

2.  The advantage of working to print
Simply put, tolerances and materials are important.  Rules of thumb about clearances in key mechanisms are often applied by rebuilders, but the problem with this is that clearances are specific to the design of the machine and mechanism in question.  Wherever possible, make sure your rebuilder has access to the original drawings, and uses them during the rebuild.  While conventional wisdom is that OEM rebuilders are more expensive, knowing is more efficient than guessing.  Technicians working to print and using original fixtures not only produce a better result, but can also usually get the job done more efficiently.

Prints
OEM Drawing (left) Veryifing Part to Print (right)

3.  Relevant experience
The long service life of cold forming equipment as well as the huge range of applications has resulted in a very wide variety of machine models over the years.  National Machinery alone has produced thousands of machines, including many different models and equipped specials.

It is important that the technicians performing repair and rebuild work have knowledge of the specific machine model being serviced.  A broad experience in cold forming machine repair and rebuild is not enough to ensure a quality result – the experience needs to match the specific machine and job at hand. 

4.  Engineering guidance
To optimize the cost of the work, you’ll want to repair and re-use components in many cases.  Doing so can be risky without the right technical guidance.  Typical examples of repair questions which might arise during a rebuild are:

  • “The shaft diameter is worn .05” below original – can it be polished and re-used with an oversized bushing?” 
  • “What pre-heating and welding procedure should be used to weld repair this crack?”

Regardless of the experience level of technician involved, these questions need to be answered by a qualified engineer who is applying design guidelines to the specific components in question.  Here again, rules of thumb can be costly.

5.  Design Upgrades
The last 25 years have witnessed a huge advance in cold forming technology.  Using a brake hose fitting as a basis for analysis, comparison of production on 1970’s vintage equipment vs. today’s FORMAX® machines shows the following:

  • Production speeds increased by 127%
  • Part TIR reduced by 53%
  • Changeover time reduced by 75%

While this magnitude of gain isn’t possible through a rebuild or modernization, it may well be possible to add some of the design improvements that have contributed to this advancement to your machine during the rebuild.

Below is a list of common design upgrades available specifically for National traditional machines.

              Traditional machines
Universal Transfer Upgrade                             
5 Degree Wing Liners                                     
Rapid Kick out Adjustment                              
Hard Plates in the Wedge Pockets                 
Controls Upgrade Packages                            
Grease to Oil Lubrication Upgrade                 
Spring Set Brake                                             
Change-over assist package                              

Transfer upgrades are a very common upgrade for traditional machine models.  Adding a Universal transfer can enable forming of a broader range of parts on the machine, which can allow you to add new business, or free up capacity on other machines.

If you own a National FORMAX machine, the modular design concept of FORMAX lends itself to easy “bolt on” upgrading.  A very wide range of upgrades have been captured and packaged for retrofit; kick-out, transfer, and controls upgrades are most commonly implemented. 

6.  Validation
Before shipment, each rebuild should be tested and validated.  For complete machine rebuilds, at a minimum the blank length variation should be measured.  If possible, send your production proven tools to the rebuilder to produce parts, and check the TIR of the part to ensure consistency of the machine.

At National Machinery, we’ve also invested in thermographic scanning equipment which is used during the machine “run in” to easily identify any lubrication or clearance issues.  These images are then stored and can be used as a benchmark for any field troubleshooting down the road.

Keeping these six points in mind should help you to get the most from your next rebuild project, and allow you to reap the benefits for many years to follow.

National Machinery is the capable and experienced partner to help you through all 6 phases of your rebuild project.  Please contact us via www.nationalmachinery.com or contact your local Sales Manager for more information.

 Thermal Image Scans
Thermographic scan of TKO         Thermographic scan of transfer
Fastener Technology International Issue: Dec. 2011

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