Staking

[oscar280zxxx]

We have a process where we are staking a rivet into a piece of thin sheet metal with an Air-Mite pneumatic press. We have done this successfully for years, but recently we have starting seeing issues where the diameter of the pin expands and deforms the sheet metal beyond the acceptable tolerance. How can I direct the movement of the metal more into forming a head, and less into expanding the pin? I have checked the parts and they are all very close to nominal.

 

[mfgenggear]

OP
start with a fish diagram
add to this diagram causes of the failures.
for instance what changed
examples

rivet part Number change
assembler/mechanic change
improper or proper instructions
leader ship change
new hires with improper experience
defective tools
defective rivets

write up the shop for cause and corrective action.
or consult with the lead mechanic for their advice,

also there plenty of you tube videos how to properly install a rivet.

audit the planning and parts list for correct instruction and part numbers.

PS one more word of advice
grab your best mechanics do a test assemble a couple of parts.
videotape and take pictures write down how the tools where set up, pressure settings
the condition of the tools and correct tools.

 

[tygerdawg]

working for years, now not working?
Your task is to answer a simple question: what has changed?
(or in a worse case: what multiple things have changed?)

Adding to the list above:
supplier changes
process settings change (e.g., air pressure)
material spec changes or variation (e.g. bad heat treatment)
changes in personnel / changes in equipment maintenance

In a couple of my previous lives I've seen a process go boom due to something as seemingly benign as seasonal humidity changes. Once a production line failed because a part's corner radius was made sharp and square with a previous process, but rounded slightly with the "improved" process, but still met the drawing. The rounded corner feature produced bad results.

Sometimes the most subtle of variations can bring down the house. And the only way to find them is deep data driven analysis.

 

[3DDave]

The force required to form the rivet can either have gone up or gone down, but the radial deformation of the rivet seems like it is limited by the strength of the plate. The other contributor is the rivet has a larger volume due to an increase length and/or diameter.

You could look and see if anyone has increased the pressure to compensate for a larger volume rivet trying to smash it flatter than the excess material will allow over the previous pressure.

If the pressure hasn't been changed then that would point to weaker sheet metal unable to contain the radial expansion.

 

[mfgenggear]

Yes in fact , undocumented change of length of rivets was once common and is a great point.
as I noted above, run test with different lengths of rivets. Document it all. Discuss with the personal who were making it right.

 

[mfgenggear]

this is the reason I liked fixed or frozen process after a first article. and it all past.
if the current hardware, parts or what ever has not changed.
look at procedures or personal.
people love to change stuff.

 

[oscar280zxxx]

Thanks for all the great replies but these are all bridges that have already been crossed. I'm looking for information on the fluid dynamics (for lack of a better term) of the metal being pressed. What effect does changing the speed, or tool shape have on the process?

 

[EdStainless]

And if people tell that 'nothing has changed' it means that things that don't measure have been changed.

 

[mfgenggear]

Thanks for all the great replies but these are all bridges that have already been crossed. I'm looking for information on the fluid dynamics (for lack of a better term) of the metal being pressed. What effect does changing the speed, or tool shape have on the process?

not a good answer, good luck

 

[mfgenggear]

op
did cross off the list. tells what you found out. you are jumping to conclusion.

did you go to the floor and discuss it with your mechanics. if you don't talk to your guys on floor you will fail.
sometime the hardness changes slightly the tolerances are slightlydifferent. and the phenmatic air pressure has to be adjusted.
it will change slightly every different batch of rivits.
did you setup a test run. no

 

[mfgenggear]

tip
AI Overview



+1

A pneumatic rivet gun typically operates at an air pressure between 80 and 100 pounds per square inch (PSI), using compressed air to forcefully pull the mandrel of a rivet, expanding it to secure a joint between materials; this pressure can vary slightly depending on the specific rivet gun and rivet size being used.

Key points about pneumatic rivet guns and their air pressure:

• Operating range:
  Most pneumatic rivet guns function effectively within a pressure range of 75 to 100 PSI.
  
  
• Importance of correct pressure:
  Setting the right air pressure is crucial to properly set the rivet without damaging the material or the rivet gun itself.
  
  
• Higher pressure for larger rivets:
  Larger diameter rivets may require slightly higher air pressure to achieve proper clamping force.
  
  
• Air consumption:
  Besides pressure, the air consumption of a pneumatic rivet gun is also important, typically measured in cubic feet per minute (CFM).

 

[mfgenggear]

You can install solid rivets with a hammer, but power riveters make the job easier. More oversized rivets require more power, so you may need a pneumatic rivet tool for large jobs. The force of the rivet gun must be greater than the yield strength of the rivet.Nov 27, 2024

Bay Supply Blog - Rivets, Fasteners, and Tools

Bay Fastening Systems is an Authorized Master Distributor for Top Brand engineered fasteners and installation systems.

blog.baysupply.com

Rivet Tools 101: A Beginner's Guide to Efficient Fastening​

What are the three tools used to set pop rivets?



What is a riveting tool?


A rivet gun, also known as a rivet hammer or a pneumatic hammer, is a type of tool used to drive rivets. The rivet gun is used on rivet's factory head (the head present before riveting takes place), and a bucking bar is used to support the tail of the rivet.

 

[mfgenggear]

According to information available, the typical operating pressure range for an Air-Mite pneumatic press is between 25-30 psi minimum and 120 psi maximum; most models are designed to deliver their rated force at 100 psi air pressure.

Key points about Air-Mite pneumatic press pressure settings:

• Maximum pressure: 120 psi
• Operating pressure for optimal force: 100 psi
• Force calculation: The force applied by the press is directly related to the air pressure, so adjusting the pressure allows you to control the force applied.

 

[3DDave]

How did you go back and confirm that all the materials conformed and still do? Did the metallurgical lab do a full workup?

I ask because that would have been part of the problem statement and posted as an attachment to see.

It's probably simpler.

The equipment is worn out or the operator no longer cares.