Dimensional Tolerances for Rubber Products

Dimensional tolerances for rubber products are allowable variations in part or material size. They’re expressed as plus or minus values, or as a range of measurements. During the seal design process, engineers record tolerances on part drawings so that vendors can source materials and fabricate products that meet or approximate the required dimensions.

If parts or materials are out-of-tolerance, seal failure can occur. For example, if a door seal is too large, the door may not shut. If the seal is too small, water or weather could enter. Coils and cut lengths also need to have the proper dimensions. That’s why your part drawing represents a contract that your distributor or fabricator needs to keep.

Yet engineers have an important responsibility, too. If the tolerances you specify are impossible to achieve, you won’t be able to get the sealing solutions that you need. It’s not because you selected the wrong vendor or manufacturing process. It’s because rubber isn’t like metal.

Rubber vs. Metal

Sometimes, designers specify tolerances that are too tight for rubber products. This leads to confusion and frustration during the seal design process. Typically, these engineers are used to working with metal – a material with different properties. Because metal parts support tight tolerances, it’s assumed (incorrectly) that rubber also supports a high degree of precision.

Rubber has many useful properties, but it can’t match metal’s tolerances. That’s because rubber is more sensitive to environmental conditions such as heat, cold, and humidity. The kind of tooling and equipment that’s used with rubber affects tolerances, too. If you’re used to working with sheet metal or metal profiles, you may find there’s a learning curve with rubber materials.

Fortunately, there’s a resource that explains what you can expect.

The RMA Handbook

The RMA Handbook is a technical publication that contains dimensional tolerances for molded and extruded rubber products. The U.S. Tire Manufacturers Association (USTMA), an organization formerly known as the Rubber Manufacturers Association (RMA), publishes the RMA Handbook and shares this information with distributors and fabricators of industrial rubber products.

If you’re wondering whether this resource is authoritative, consider the organization’s membership:

  • Bridgestone Americas
  • Continental Tires, The Americas LLC
  • Cooper Tire & Rubber Company
  • Giti Tire (USA) Ltd
  • Goodyear Tire & Rubber Company
  • Hankook Tire America Corp.
  • Kumho Tire U.S.A., Inc.
  • Michelin North America, Inc.
  • Pirelli Tire North America
  • Sumitomo Rubber Industries
  • Toyo Tire Holdings of the Americas
  • Yokohama Tire Corporation

Across the supply chain, the RMA Handbook provides a common language that’s easy to understand. Dimensional tolerances are organized into tables and assigned classes. By adding an RMA class to your part drawing, you can clearly explain what a distributor or fabricator needs to know.

RMA Drawing Designations for Molded and Extruded Parts

It also helps to have a basic understanding of how the RMA Handbook is structured. Molding and extrusion are both rubber manufacturing processes, but they subject elastomers to physical changes in different ways. Consequently, molded parts and extruded parts are covered in different chapters. Moreover, there are different RMA classes for molded parts and extruded parts.

Chapter 1 of the RMA Handbook describes four levels of dimensional tolerances for molded rubber products. There’s a separate table for each class along with information about dimensional terminology.

A1 High Precision
A2 Precision
A3 Commercial
A4 Basic

Chapter 2 of the RMA Handbook describes three levels of tolerances for extruded rubber products.

1 Precision
2 Commercial
3 Non-Critical

There are also separate tolerance tables for spliced extrusions (cut and spliced lengths) and for unspliced extrusions (cut lengths). Spliced extrusions use drawing designations S1, S2, and S3. Unspliced extrusions use drawing designations L1, L2, and L3 instead. Complete this form to see these tolerance tables.

Get Help with Dimensional Tolerances for Rubber Products

Elasto Proxy is a distributor and fabricator that can help you specify dimensional tolerances for rubber products. To get started, contact us.

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Seal Design Starts With This Formula

Seal Design

Finished gaskets follow a formula. Seal design begins with compound, hardness, and profile selection. Custom seals and gaskets that account for these factors can fill the gap, withstand the environment, and meet business and technical requirements.

Let’s take a closer look at what you need to know. Continue reading Seal Design Starts With This Formula

Enclosure Sealing and Insulation: Performance Properties and Applications

enclosure sealing

What’s the right enclosure sealing and insulation for your application? There’s a lot to consider.

Elasto Proxy custom-fabricates seals, gaskets, and insulation for enclosures that house machinery and equipment. These industrial rubber products can provide environmental sealing, acoustic insulation, flame resistance, EMI shielding, chemical resistance, and other performance properties. As the following examples show, enclosure sealing and insulation varies by application.

Environmental Sealing and Acoustic Insulation 

Gensets or generating sets supply off-grid electricity. They consist of a diesel or gasoline-powered engine and an electrical generator (such as an alternator) that converts mechanical power into electricity. To support repairs and maintenance, this equipment is housed in an enclosure with a door. The genset’s door gaskets provide environmental sealing, but the enclosure also needs acoustic insulation.

Sealing a genset door isn’t a job for just any rubber product. Static seals are fine when there’s no relative motion between mating surfaces, but dynamic seals are recommended when there’s motion or movement between sealing interfaces such as a door and door frame. Rubber gaskets also need to resist compression set – the permanent deformation of a material – when the enclosure door is closed.

Rubber gaskets provide some acoustic insulation, but an engine in an enclosed space is loud. Sound absorbers made of acoustic foams can be “tuned” to address these frequencies. Sound barriers and vibration dampers also support noise control. That’s important for complying with workplace limits on noise exposure and avoiding “noise pollution” in areas such as neighborhoods.

Flame and Fire Resistance 

Manufacturers of electrical and electronic systems may need enclosure gaskets that are made of fireproof rubber. The UL 94 standard from Underwriters Laboratories (UL) defines 12 different flame ratings, so it’s important to determine which rating applies to your design. Engineers also need to consider whether the rubber gasket or the entire enclosure needs to meet this demanding standard.

Compounds that are described as “capable of passing UL 94” or “compliant with UL 94” probably don’t have a UL yellow card – proof that Underwriters Laboratories (UL) has tested and recognized the material. However, these less-expensive materials may still meet your requirements. Before selecting a compound then, engineers need a complete understanding of the application.

EMI Shielding 

Electronic devices and equipment that are housed in an enclosure may require protection against electromagnetic interference (EMI) that can disrupt or damage circuits. The causes of EMI are numerous and can include both manmade and naturally-occurring sources. In industrial and commercial settings, the causes of EMI typically include brush motors, computer circuits, and lighting.

Gaskets made of particle-filled silicones provide both EMI shielding and environmental sealing. These metal-filled elastomers also provide electrical conductivity and resist a wide range of service temperatures. For applications that require resistance to fuels and industrial fluids, EMI gaskets made of particle-filled fluorosilicones are used.

Chemical Resistance

Enclosure gaskets are also needed by the pharmaceutical industry, which uses solid dosage processing equipment to manufacture finished doses of medication in tablet or capsule form. Often, these solid doses are coated to mask the medicine’s taste or odor, protect the drug in the stomach, and to control its release profile. In turn, these coatings may contain chemicals that can attack rubber.

Fluorosilicone enclosure gaskets can withstand these chemicals. These rubber gaskets also provide other performance properties such as excellent stability over a wide temperature range. Fluorosilicones gaskets resist compression set, too. Fluoroelastomers are more expensive than some other compounds but are cost-efficient to produce with the right cutting and bonding techniques.

Choose Enclosure Sealing and Insulation from Elasto Proxy

Elasto Proxy custom-fabricates enclosure seals, gaskets, and insulation with the right performance properties for your application. We use water jet cutting, offer a variety of bonding methods, and can help you with seal design and compound selection. If you need enclosure sealing and insulation solutions, please contact us.

Value-Added Manufacturing: Parts Marking, Kitting, and Custom Packaging

Value-Added Manufacturing

Value-added manufacturing transforms engineered products into goods that save you time and money. It’s different than fabrication, the process of manufacturing a product like a gasket from a semi-finished material like an extrusion. By outsourcing fabrication and leveraging a vendor’s value-added services, you can reduce costs and improve efficiency.

Consider the following example. Instead of paying your employee to cut and bond gaskets, you outsource the gasket fabrication. If you’re using a relatively expensive employee to cut-and-bond, you’ll save money on labor costs. You’ll also reduce material waste from mis-cuts and improve material yields. Yet outsourced fabrication can do even more.

Value-added manufacturing like parts marking, kitting, and custom packaging make your products faster, easier, and less expensive to order, receive, stock, pick, and install. That’s true for gaskets as well as for thermal and acoustic insulation. Even rubber floor mats provide an opportunity for added value.

Let’s take a closer look. Continue reading Value-Added Manufacturing: Parts Marking, Kitting, and Custom Packaging

Better Bonded Gaskets for Sealing and Insulation

Better bonded gaskets improve quality and perceptions of quality. They reduce labor costs and support sales, too.

Bonded Gaskets

Finished gaskets need strong bonds to provide reliable sealing and insulation. In applications where rubber gaskets are visible, bonds that look better also suggest higher product quality. Buyers of specialty vehicles, commercial ovens, and electrical enclosures (just to name a few) don’t want to see bonded gaskets that look like they’re ready to pull apart in the corners or that need touch-ups.

Even in applications (such as HVAC systems) where finished gaskets are hidden, failure is expensive. Replacing the rubber seal in an air conditioning unit may cost more than you realize. In addition to paying for a replacement part, there are direct labor costs. Indirect costs including traveling to and from the job site, scaling ladders, pulling and replacing panels, and completing paperwork. Over time, it all adds up.

Gasket bonding may seem simple, but it’s skilled labor. You can buy your bonded gasket equipment, but machines don’t come with expertise. Even in an age of digital manufacturing, some activities still require craftsmanship. Plus, some bonding methods require cuts that you don’t have the equipment to make. You can try using guillotine saws or hand tools, but you can’t match water jet cutting. Continue reading Better Bonded Gaskets for Sealing and Insulation

Vendor Consolidation is Right for Rubber Products

Vendor ConsolidationVendor consolidation is a procurement strategy where you reduce the number of vendors that your company buys from. Businesses don’t want to become overly dependent on a single vendor or a handful of vendors, but there are costs – and risks – from having too many suppliers. There are also benefits to lowering the number of vendors that you do business with. Let’s take a closer look. Continue reading Vendor Consolidation is Right for Rubber Products

Service Truck Bodies: Five Rubber Parts You Need to Know

Service truck bodies need five types of rubber parts: fender flames, bulb trim, rubber mats, anti-slip grip tapes, and rubber bumpers.

Service Truck Bodies

Service trucks bring tools to the repair site so that you don’t have to send vehicles or equipment back to the shop. These utility trucks are equipped with compartments that provide easy access to repair tools like drills, wrenches, and socket sets. Service trucks made by companies such as Ford, Freightliner, GMC, and International also carry diagnostic tools like engine fault-code readers.

Service truck bodies are usually made of lightweight, rust-proof aluminum or durable, power-coated steel. Wherever metal parts meet (such as the edges of a door and a tool compartment), surface irregularities can create small gaps that require sealing and insulation. Rubber parts are also needed to protect the fenders, tool shelves, and vehicle back-end. To provide secure footing, anti-slip grip tapes are used.

As the image that accompanies this article shows, Elasto Proxy custom-fabricates five parts for service truck bodies:

  • fender flares
  • bulb trim
  • rubber mats
  • anti-slip grip tapes
  • rubber bumpers

Let’s take a closer look at each.

Fender Flares (ES18-017-E70)

Fender FlaresFender flares fit over the wheel well and provide protection against mud, water, and road debris. Whether you’re on-road or off-road, your tires can kick-up small rocks that damage your service truck body. You can also kick-up stones that damage nearby vehicles or equipment. The fender flares that Elasto Proxy supplies are easy-to-install and last a long time under real-world road conditions.

Bulb Trim (EC28-515-EM)

Bulb TrimBulb trim provides sealing and insulation for the rounded corners on compartment doors. These rubber parts have separate bulb and retainer sections, each of which can use a different material and have a different durometer. The bulb section compresses to form a seal when the door is closed. Elasto Proxy doesn’t just fabricate bulb trim. We help you to select trim seals that won’t over-compress, kink, or leak.

Rubber Mats (FMD-250-60-Z)


Rubber mats with a diamond pattern prevent tools from sliding while the service truck is moving. They also protect tool shelf surfaces from dents and scratches. Rubber mats are often used in flooring, but their cushioning and non-slip surface makes them a good choice for tool storage. Elasto Proxy can cut rubber sheets to precise dimensions and source these materials in colors such as black, gray, and brown.

Anti-Slip Grip Tapes (ST-032-21-GT)


Anti-Slip Grip Tapes

Anti-slip grip tapes provide personnel with secure footing when they step on the back-end of the service truck body to gain an elevated position. These anti-slip tapes have a textured, high-friction surface and are made of a durable rubber such as vinyl. The anti-skid safety tapes that Elasto Proxy fabricates can also withstand outdoor environmental conditions.

Rubber Bumpers (MB-070-C80)

Rubber Bumpers

Rubber bumpers protect service truck bodies from low-force impacts. These rubber parts cost less than truck body repairs and are easy-to-install with standard metal fasteners such as screws, bolts, and washers. The 75-durometer (Shore A) rubber bumpers that Elasto Proxy supplies come with pre-drilled holes and are available in various shapes and sizes.

Find Rubber Parts for Service Truck Bodies

Elasto Proxy provides mobile equipment manufacturers with custom sealing and insulation solutions. As the image that accompanies this article shows, we supply fender flares, bulb trim, rubber mats, anti-slip grip tapes, and rubber bumpers for service truck bodies. We also supply rubber parts to maintenance and repair organizations (MROs) that help keep fleets of trucks moving.

Unlike other suppliers to the heavy truck industry, Elasto Proxy combines digital manufacturing with value-added solutions. Our water jet cutting equipment works directly from your CAD files for speed and accuracy. We also offer a variety of gasket bonding methods and provide parts kitting services. Elasto Proxy even store your rubber parts and ship them to you from our warehouses.

Contact us to find parts for service truck bodies.

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Three Ways to Solve Your Skilled Labor Shortage

Skilled Labor ShortageDoes your manufacturing company have a skilled labor shortage? You’re not alone if you do. Demand for manufactured products is high, but the unemployment rate is low. Time isn’t on your side either. Today, 30% of the skilled workers in manufacturing are older than age 55. These Baby Boomers aren’t ready to retire yet, but they won’t stay on your factory floor forever.

Meanwhile, many of today’s students are choosing college or university instead of the skilled trades. Maybe it’s because they think that manufacturing jobs are dangerous, dirty, or boring. Maybe it’s because they’d rather sit at a computer in an air-conditioned office than stand on a concrete floor next to a machine. Some may remember how family members lost jobs to plants closings or down-sizing.

What’s the solution to your skilled labor shortage then? Do you need to wait for new programs to provide workers? Will automation eventually solve your problems instead? These solutions may sound promising, but you can’t keep waiting if you want to keep your customers happy today. You need a solution now. The good news is that you can get it from your supply chain if you know where to look.

Let’s consider your options. Continue reading Three Ways to Solve Your Skilled Labor Shortage

Seal Rounded Corners by Starting with These Three Measurements

Seal Rounded Corners with Bulb Trim Seals Do you need to seal rounded corners against wind, water, dust, or dirt? Bulb trim seals are industrial rubber products that provide sealing and insulation for machine doors, vehicle hatches, and equipment enclosures. They’re designed to seal rounded corners and have separate bulb and retainer sections. Each of these sections can use a different material and have a different durometer or hardness.

With bulb trim, the bulb section compresses to form a seal when the door, hatch, or enclosure is closed. The trim or retainer section attaches to a flange or substrate. To choose bulb trim for your application, you need to specify the bulb size, bend radius, and flange thickness. By choosing the right bulb size, you can avoid over-compression. The right bend radius and flange thickness help to avoid kinking and leakage. Continue reading Seal Rounded Corners by Starting with These Three Measurements

What’s in the Elasto Bag? Sealing and Insulation Samples for Mobile Equipment

elasto bagDo you need thermal, acoustic, or thermal-acoustic insulation for forestry, mining, construction, or other types of mobile equipment? Maybe you need cabin flooring or floormats instead. The Elasto Bag, a sack full of samples from Elasto Proxy, contains sealing and insulation that you can see for yourself and hold in your hands. It’s easy to request an Elasto Bag, but what’s inside when you get it?

The Elasto Bag contains at least nine samples of sealing and insulation. (We can also include samples of  edge trim, bulb trim, or D-shaped profiles with adhesives if you need them). Let’s take a look at what’s inside the Elasto Bag so that you’ll understand what you have or can get. Along the way, you’ll see links where you can download product specifications. Continue reading What’s in the Elasto Bag? Sealing and Insulation Samples for Mobile Equipment