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Invert-A-Bolt™ Products in Lean Manufacturing
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IVB Products are routinely used to implement lean manufacturing initiatives
in the work environment.
By eliminating dedicated fixturing and the related costs (tool design,
manufacture, maintenance & storage) and creating standardized tooling
& work practices, it is possible to become significantly more efficient
& productive. See the Cessna
Aircraft Continuous Improvement News letter describing the benefits of using an Invert-A-bolt™(IVB) Common Modular Fixture.
An Invert-A-bolt™ Universal Common Modular Fixture (UCMF) consists of a flat plate tooling fixture with Invert-A-bolt™ fasteners set on standard centers and used in conjunction with locating pins on diagonals. Additional versatility is realized by using multi-purpose holes at the pin up locations making it possible to screw other modular tooling components into the fixture as well. The manufacturer is able to realize the benefits of using both IVB fasteners (for hog-outs) and off-the-shelf modular tooling components (for castings, forgings, etc.). IVB Common Modular Fixtures are available turn-key.
Typical usage of an IVB UCMF consists of setting up a part in a picture-frame, using the fasteners at the tab locations for hold down, while simultaneously locating at the bushed hole locations in the fixture. The picture frame machining concept is ideal for many parts since hard location against datums is not required. 
Typical machining sequence for over-the-top tabbing in picture frame machining configuration using IVB fasteners:
1. Prep the stock to accept the IVB fasteners and locator pins. Prep for the fasteners consist of drilling a through hole and tapping (or thread-milling) a thread for about 1/2" deep. Prep for the locators would be a drill/ream operation for whatever size locating pin is to be used.
2. Load the stock into the fixture. Rough side 1 of the part. No clamps are used. Nothing is in the way of the machining. No clamp changes or avoidance of clamps is required. This looks like a pocketing operation. It's best to leave the excess on the flange top to keep the setup rigid as possible. At the IVB fastener locations, tap the thread about 1/2" deep.
3. Flip the part over, locating on the outer "frame" which should be at the height of most of the internal ribs. Shim as required, and rough/finish side 2. Locate as much as possible of the stock material on the base plate. This adds stability to the process versus having it up in the air while machining. Again, no provision for clamps is made. Side 2 is completed including the outside mold line.
4. Flip the part over. Finish Side 1 except the tops of the flanges.
5. Last operation - thin the tabs to aprox. .02"-.03". Part is complete.
6. Snap the tabs and perform minimal handwork to top of flange to clean up.
Invert-A-bolt™ UCMFs are used to implement Six Sigma Initiatives to eliminate variations by creating standardized workholding:
Design for Six Sigma (DFSS) - Workholding
- Define: The number of setups & the associated
setup time is hurting our ability to be competitive. Creating a mill
fixture for every part is capital intensive and adds to our non-recurring
costs. Non-recurring costs are too high, especially since we generally
don't get paid for those costs up front, rather they must be amortized
over the run of production parts.
- Measure: Moving clamps around and stopping the
machine to do it cost too much. Counter-bored bolts are always in the
way of the process and require more setups to get around them especially
in mult-axis machining. Manufacturing a fixture plate for every new
part requires design, program and fab time.
- Analyze: By using picture frame machining concepts
and tabbing schemes it was possible to eliminate the use of clamps.
By establishing a standardized mill fixture plate it was possible to
eliminate design, program and fab time. It was also possible to eliminate
producing a mill fixture for every new part.
- Improve: Implement standardized workholding techniques
and eliminate duplicate milling fixtures by incorporating modular fixturing.
Convert tooling to Invert-A-bolt™ Universal Common Modular fixtures
for horizontal machining cells. Use Invert-A-bolt™ fasteners to
replace bolts and clamps for vertical machining.
- Control: Establish standardized workholding procedures.
Train operators, CNC programmers and tool designers to "think
Lean" and maximize the benefits of using Invert-A-bolt™ fasteners
for workholding.
High-Speed Machining and Throughput
- Define: The efficiency of our high-speed machines
is reduced due to vibration and un-stable setups.
- Measure: We are running our spindles at 60% of
possible due to vibration in the setup.
- Analyze: By getting the holding power of our clamps
closer to the fixture plate we can improve the stability of the setup.
The taller the clamp setup, the more vibration we encounter.
- Improve: Replace clamps with Invert-A-bolt™
fasteners which are contained in the fixture plate and hold the part
as close to the base as possible.
- Control: Establish standardized workholding procedures.
Train operators, CNC programmers and tool designers to maximize
the benefits whereever possible of using Invert-A-bolt™ fasteners
to create stability in the setup.
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