Spring-Fast M22529 – Significant Advantages over Glued-in Nylon Grommets (MS21266)
3 pages / 4 min read
Grommet edging protects wiring (in aerospace the EWIS) from chafe. Since the 1950s, most companies have used nylon or Teflon grommets (MS21266) with adhesive. However, there is a far better way for both cost and efficiency.
To give you an idea of the scope of savings, let's take Airbus. DTi estimates that switching from MS21266 to the Spring-Fast M22529/2 grommet – could save them an estimated $1.06 million per year. The estimate is based on a trade study format with 3 conservative assumptions:
- 300 aircraft per year
- 100 penetrations per aircraft
- A fully burdened wrap rate of $130
The savings summary is below – for the full detail see Appendix 1.
Manufacturers/OEMs are struggling to do more with less. M22529/2 helps by improving efficiency by a factor of 9.5X based on the estimated time taken to fully complete each task.
The adhesive used on nylon grommets requires up to 12 hours of cure time so techs leave and come back. Clients tell us this causes about 45 minutes of “labor process time” which lowers efficiency. However, the model assumes a zero cost for that 45 mins and the 8-12 hour cure time as the techs go to other jobs. Your efficiency gain depends on your process.
| Aircraft per year | Penetrations per aircraft | Grommets Needed | Direct Cost incl Labor per grommet | Annual Cost/SAVINGS | |
|---|---|---|---|---|---|
| Nylon-MS21266 | 300 | 100 | 30,000 | $54.52 | $1,635,600 |
| Spring-Fast M22529/2 | 300 | 100 | 30,000 | $19.03 | $570,900 |
| Total Savings | $35.49 | $1,064,700 |
In addition, the M22529 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 also raises operational costs. Operational reliability and performance are important procurement factors.
Legacy Grommet Issues
The legacy glued nylon/PTFE MS21266 caterpillar grommet is a costly, labor-intensive, and multi-step process. Here are the main steps:
- 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 often requires at minimum 8 hours or overnight.
- 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, overtime, 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 that has a polymer coating on an ultra-thin CRES substrate that snaps into place with finger pressure. It has proven performance across multiple aero 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. Ease of application, exceptionally good for tight access locations.
Cost Breakdown (see Appendix 1 below)
- The savings model offers a comparison of the time & cost impact of installing MS21266 and M22529/2
- Installation Cost per grommet nylon MS21266 $54.52
- Installation Cost per grommet M22529/2 $19.03
Each step/operation in the installation was estimated and costed using a $130/hr WRAP rate.
Additional Savings Not Included in the Estimate
- 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.
- Consumables: MS21266 needs consumables: adhesive, IPA wipes, solvents, fixturing tape, gloves, masks & clean-up cloths. M22529/2 needs only IPA wipes for less general consumable purchasing and inventory management overhead.
- Efficiency/Productivity Improvements: M22529/2 frees up techs to be reallocated. For Airbus, 2 saved minutes per grommet: per 100 grommet plane = 28.7 hours: @300 planes/month = 8610 hours. A strong contributor to efficiency/backlog reduction.
- Sustainability: With fewer materials, and consumables and no VOCs, no PPE required using Spring-Fast is a greener more sustainable way to protect the EWIS.
Appendix 1 The Full Costing Breakdown
| MS21266- Nylon | M22529/2 - Spring-Fast | |||||
|---|---|---|---|---|---|---|
| Operation | Minutes | Costs | Minutes | Costs | ||
| Sub Operation -Set Up | ||||||
| Batch size for amortization & resulting time/costs | 5 | |||||
| Gather safety equipment fans, mask, gloves, glasses etc | 5 | $10.85 | 0 | 0 |
||
| Gather components: grommet, glue, abrasive, tape etc | 5 | $10.85 | 2 | $4.34 | ||
| Total Set Up time/$ | 10 | $21.71 | 2 | $4.34 | ||
| Sub operation amortized time/costs | 2 | $4.33 | 0.4 | $0.87 | ||
| OPERATIONAL STEPS | ||||||
| Amortized batch set up costs (sub op above) | 2 | $4.33 | 0.4 | $0.87 | ||
| Measure edge/penetration & cut to fit | 3 | $6.50 | 3 | $6.50 | ||
| Pre-Fit for size and trim as necessary | 1 | $2.17 | 1 | $2.17 | ||
| Deburr the edge with Scotch-brite/sandpaper | 1 | $2.17 | 0.5 | $1.08 | ||
| Clean metal edge with IPA wipe/MEK | 1 | $2.17 | 0.5 | $1.08 | ||
| Cut 8 pieces of tape for fixturing | 3 | $6.51 | 0 | $0.00 | ||
| Apply adhesive to edge/MS21266 | 5 | $10.83 | 0 | $0.00 | ||
| Apply grommet to edge | 2 | $4.33 | 1 | $2.17 | ||
| Apply masking tape for fixturing | 3 | $6.50 | 0 | $0.00 | ||
| Curing time 8-12 hrs - 45 mins Labor Process Time ($0 cost) | 45 | $0.00 | 0 | $0.00 | ||
| Remove masking tape, clean up using MEK | 2 | $4.33 | 0 | $0.00 | ||
| Inspect fit and finish | 1 | $2.17 | 1 | $2.17 | ||
| Labor time/cost | 70 | $54.17 | 7.4 | $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 |
These time estimates are based on years of experience with clients. Your savings will depend on your WRAP/shop labor rate and your process. The model uses a $130 wrap rate. This yields 65% savings. Conservatively we declare at least 49% savings which you will achieve if your shop rate is $32.
Read more about Spring-Fast Mil Spec grommets here
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Read a related article on product benefits on ThomasNet
