Spring-Fast M22529 – Significant Advantages over Glued-in Nylon Grommets

4 min read

Grommet edging protects aerospace wiring/the EWIS from chafe.  Since the 1950s, to provide this protection most companies have used nylon or Teflon grommets (MS21266 or BACG20Z) with adhesive.

However, there is a far better way to protect wiring which yields both significant cost savings and greater efficiency.

To give you an idea of the scope of these benefits, let's take Airbus.

The model below estimates that switching from MS21266 to the Spring-Fast NASM22529/2 grommet, could save Airbus an estimated $1.06 million per year and improve productivity by a factor of 9.5X.   The estimates are based on a trade study format with 3 production assumptions:

  • 300 aircraft per year (25 a month)
  • 100 penetrations per aircraft
  • A fully burdened wrap rate of $130

Estimated Savings Summary

The $1.6m of savings are generated by a far simpler and faster install which generates the lower cost per grommet illustrated below.  The full breakdown is in Appendix 1 below.

Aircraft per yearPenetrations per aircraftGrommets NeededDirect Cost per grommetAnnual Costs
Spring-Fast M22529/230010030,000$19.03$570,900
Total Savings

Estimated Efficiency Gains

M22529 is significantly simpler & faster to install.  This yields a 9.5X productivity gain.  See full detail in Appendix 1.

  • Installation Time per grommet                     MS21266                             70 mins
  • Installation Time per grommet                     NASM22529/2                     7.4 mins    = 9.5X productivity gain

At a time when the pressure is on for OEMs to do more with less. M22529/2 helps by improving efficiency by a factor of 9.5X based on the estimated time taken to complete a grommet install.

The M22529/2 series offers best-in-class wire protection performance with no known failures in over 35 years.

M22529/2 is fully qualified as an FAA-approved replacement part and already has NAVAIR approval supporting numerous tactical airborne platforms and a range of general aviation specifications in the last 10+ years.

Why the Savings Are So Significant

By design, M22529/2 has a far lower direct labor install cost than MS21266 due to:

  • Snap-in-place installation without adhesive
  • Superior retentive strength without adhesive
  • Immediate wire/harness routing – no fixturing or cure time delays

An Operational Impact Far Greater Than Its Size

Grommets are important as they protect the EWIS /aircraft wiring from chafe and abrasion.  In serious cases chafe can cause dangerous arcing, sparking, and fires.

However, chafe creates problems even at relatively low levels.  For example, we found NAVAIR data that showed 37% of the time when aircraft were designated as AOG (Aircraft on Ground) or NORS (Non-Operational Ready Status), the problem was wiring (and equipment by default) discrepancies due to chafe.  Nylon grommets are used extensively in commercial aviation so it is reasonable to assume the same wiring issues exist.

As a result, chafe -for commercial & military- is a major drag on readiness, availability, and efficiency.  That drag raises operational costs.  Operational reliability and performance are important procurement factors.

Why Nylon Grommets Present Serious Production Issues/Costs

The glued-in nylon/PTFE MS21266 caterpillar grommet has a costly, labor-intensive, and multi-step process outlined below:

  • Multiple items for application & safety have to be gathered in the preparation phase.
  • Edge preparation is required to ensure proper adhesion for nylon grommets: this involves abrasion with Scotch-Brite and cleaning with IPA or an acetone wipe.
  • Nylon and PTFE’s hardness & rigidity result in non-flexible conformance set onto panel edges/radii so fixturing is needed to hold it in place while the adhesive cures. Curing is a minimum of one hour and in some cases 8-12 hours.
  • Any excess adhesive has to be cleaned with a MEK solvent, cloths, and elbow grease. Both contain hazardous VOCs requiring special handling and safety precautions, as well as HazMat disposal.
  • Dis-bonding happens often due to variability in temperature, humidity, and the 2-part epoxy mixing and leads to rework – affecting the cost of poor quality.
  • Also, over time, the nylon and adhesive are more prone to failure from flight stresses. The metal chassis and the adhesive have different coefficients of expansion which under temperature variations create a shearing action that leads to cracking and a loss of integrity in the adhesive bond.

The glued nylon grommet was state-of-the-art in the 50s but now it’s as anachronistic as a home telephone.

Spring-Fast M22529/2 – Why it is Far Better

  • M22529/2 is a high-performance grommet with a polymer coating on an ultra-thin CRES substrate that snaps into place with finger pressure. It has proven performance across multiple aerospace platforms.
  • It is a caterpillar-style grommet with opposing finger-like castles that exert a compression force that creates static friction for retention without glue.
  • It has passed 20/20/20 G static load tests – even with 4 castles removed for wire bundle clip clearance.
  • Minimal FOD footprint- fewer shop consumables like gloves, cloths, adhesive, tape, solvent, and masks.
  • Easy to work with: can be removed/replaced without loss of edge retention. The ease of application makes it exceptionally good for tight access locations.

 Detailed Cost Breakdown (see Appendix 1 below)

Here are the top-line results for timing and costs which are broken down below:

  • Installation Time per grommet                     MS21266 / Nylon                            70 mins
  • Installation Time per grommet                     Spring-Fast M22529                       7.4 mins    = 9.5X productivity gain
  • Installation Cost per grommet                     MS21266 / Nylon                             $54.52
  • Installation Cost per grommet                     Spring-Fast M22529                        $19.03       = 65.1% Savings
MS21266 NylonSpring-Fast
Sub Operation -Set Up
Batch size for amortization & resulting time/costs5
Gather safety equipment fans, mask, gloves, glasses etc5$10.8500
Gather components: grommet, glue, abrasive, tape etc5$10.852$4.34
Total Set Up time/$10$21.712$4.34
Sub operation amortized time/costs2$4.330.4$0.87
Amortized batch set up costs (sub op above)2$4.330.4$0.87
Measure edge/penetration & cut to fit3$6.503$6.50
Pre-Fit for size and trim as necessary1$2.171$2.17
Deburr the edge with Scotch-brite/sandpaper1$2.170.5$1.08
Clean metal edge with IPA wipe/MEK1$2.170.5
Cut 8 pieces of tape for fixturing3$6.510$0.00
Apply adhesive to edge/MS212665$10.830$0.00
Apply grommet to edge2$4.331$2.17
Apply masking tape for fixturing3$6.500$0.00
Cure time - 45mins/$0 cost (see assumptions)45$0.000$0.00
Remove masking tape, clean up using MEK2$4.330$0.00
Inspect fit and finish1$2.171$2.17
Labor time/cost70$54.177.4$16.03
9.5X efficiency gain
Unit Grommet cost (12.75" strip)$0.35$3.00
Install cost per grommet$54.52$19.03
65% $ Savings
WRAP/Shop Labor rate$130

Key Model Assumptions

Time Taken per Step: The time estimates are based on DTi’s years of experience with clients. Your savings & efficiency increase will depend on your WRAP/shop labor rate & the steps taken in your manufacturing process.

Hourly Charge Rate: A $130 wrap/shop labor rate was used.  Most OEMs are significantly above that.

Set Up Time: In a non-production line setting, techs have to first gather materials & components.  The model assumes grommets are installed in batches of 5 which spreads out the time/cost over 5 grommets.
In this iteration of the model, for nylon, the set-up time is approx. 2 mins per grommet (0.4 mins for M22529).
If more grommets are installed per set up -say 10- then it will reduce nylon setup time to 1 minute per grommet.
If the grommets are installed in a production line setting -with no setup – this will reduce the set-up time to zero.

Savings Results: These core assumptions yield a remarkable 65% savings.   DTi are confident that OEMs will achieve at least 49% savings.  If your process is similar to the steps outlined above you will achieve the 49% if your WRAP/shop labor rate is $32.

Efficiency/Productivity Gain:  Based on DTi’s decades of experience, the model shows that a nylon grommet takes 70 mins to install vs 7.4 minutes for Spring-Fast: a 9.5X efficiency gain.

Tech Down Time During Curing: The 70 minutes includes 45 minutes of “labor process time” because the nylon adhesive requires cure time so techs have to leave and come back to complete the installation.
Clients tell us this break in production adds ~45 minutes of “labor process time” as techs have to stop, reference new work orders, move to the new job, and then do the same in reverse to go back to the grommet install job.  However, the 45 mins is assumed to be a zero-labor cost because clients tell us their techs go to other jobs.  Worst case – if you exclude the 45 minutes- OEMs will achieve at least a 3.4X productivity gain (25mins vs 7.4mins)

Additional Savings Not Included in the Estimate 

  • Lower Scrap:
    The model compares 12.75” strips but MS21266 only comes as precut strips which for a 3″ penetration/9.4″ circumference have to be cut to fit.  This yields 3.35″ of scrap (26%). M22529/2 is supplied on reels & cut to length with minimal scrap for a far higher yield.
  • Nylon vs. Teflon:
    The model assumes the use of 100% nylon grommets. However, if PTFE (Teflon) grommets are used the savings will increase as Teflon costs 10x to 28x ($3.50/$9.95) more than nylon ($0.35 per strip).
  • Fewer Consumables:
    MS21266 needs consumables: adhesive, IPA wipes, solvents, fixturing tape, gloves, masks & clean-up cloths. M22529/2 needs only IPA wipes.  This yields fewer general consumables which also attract some purchasing and inventory management overhead.  Less risk of FOD is also important.
  • Efficiency/Productivity Improvements:
    M22529/2 frees up techs to be reallocated. In the example above each NASM22529/2 grommet will save 62.6 mins (70 vs. 7.4mins).  However, if each M22529/2 grommet saves OEMs just 15 minutes, the time saved adds up quickly:
    Time saved per grommet                = 15 minutes
    @ 100 grommets per aircraft         = 1500 mins         25 hours
    @ 300 aircraft/month                       = 450,000 mins   7,500 hours
    @ 12 months production                 = 90,000 hours    A staggering 43.3 man-years.
    This small change can be a strong contributor to efficiency and backlog reduction. There is also no cost factored in for the all-too-frequent rework required when the adhesive bonding fails.
  • Sustainability:
    With fewer materials and consumables, no VOCs or PPE requirements, Spring-Fast is a greener more sustainable way to protect the EWIS in aircraft or wiring in OEM equipment.

Read more about Spring-Fast Mil Spec grommets here

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Read a related article on product benefits on ThomasNet