What Information Is Required for Custom Non-Standard Dispensing Machine Seals?

When ordering custom seals for dispensing machines, the biggest problem is often not the price, but incomplete technical information that results in seals that cannot be installed or do not perform properly.

Standard seals can be selected according to catalog specifications, but non-standard seals require more than basic dimensions. The more complete the information provided before production, the greater the chance of getting the design right the first time.

Six Essential Parameters for Custom Seals

1. Fluid and Chemical Compatibility

Simply stating that the seal is used in a dispensing machine is not enough. You need to specify the type of adhesive, whether it contains solvents, the curing agent components, and the cleaning agents used.

Different adhesives can affect sealing materials in significantly different ways. For example, acrylate components in UV-curing and anaerobic adhesives are relatively polar and may cause conventional nitrile rubber (NBR) to swell within days.

Epoxy systems containing amine-based curing agents may also attack fluoroelastomers (FKM).

The more complete the list of fluids and chemicals, the more accurately the manufacturer can recommend a compatible sealing material.

2. Operating Temperature

It is important to distinguish between continuous operating temperature and short-term peak temperature.

Continuous temperature determines whether the material can withstand normal operating conditions, while peak temperature indicates the potential risk of temporary softening, hardening, or embrittlement.

Hot-melt adhesive dispensing systems often operate at temperatures between 80°C and 120°C. In this range, FKM is commonly considered a baseline material option.

If peak temperatures exceed 200°C, the original material recommendation calls for perfluoroelastomer (FFKM) because of its high-temperature resistance.

3. Operating Pressure

Provide both the normal operating pressure and the expected pressure fluctuations.

Pressure affects the required seal hardness and whether an anti-extrusion design is necessary.

For low-pressure applications, a hardness of approximately 70 Shore A may be sufficient.

Medium- to high-pressure reciprocating applications may require a hardness of 75–80 Shore A, while high-pressure static sealing applications may call for hardness values above 85 Shore A.

These values are general reference points. Actual requirements depend on seal geometry, material, extrusion clearance, and operating conditions.

4. Motion Frequency

Motion frequency is one of the key parameters that distinguish dispensing valve seals from conventional sealing applications.

For reciprocating valve stem seals, both reciprocating frequency and linear speed should be specified.

As operating frequency increases, frictional heat can accumulate more rapidly at the sealing lip. This places greater demands on wear resistance and the self-lubricating properties of the sealing material.

In jet dispensing valves, the valve stem may cycle dozens of times per second. Conventional elastomers may not provide sufficient durability under such demanding conditions.

Engineering polymers such as polyimide (PI) or ultra-high-molecular-weight polyethylene (UHMW-PE) may be considered for suitable high-frequency applications.

5. Dimensions or Physical Samples

Providing an existing seal sample is often one of the most effective ways to begin custom seal development. The manufacturer can directly measure the component and evaluate its geometry for reproduction.

If CAD drawings are available, they should clearly specify:

• Inner diameter (ID)

• Outer diameter (OD)

• Cross-sectional profile

• Critical dimensions

• Dimensional tolerances

Dispensing machine seals are often extremely small. Some designs may have an inner diameter of only 1.5 mm, with critical dimensional tolerances of ±0.05 mm or tighter.

Accurate dimensions and clearly defined tolerances are essential for proper installation and sealing performance.

6. Valve Structure and Seal Location

Specify whether the seal is used for reciprocating valve stem sealing, static valve body sealing, or rotary shaft sealing.

Each application requires a different cross-sectional design and must accommodate different mechanical loads.

• Reciprocating valve stem seals: Require low friction and good wear resistance.

• Static valve body seals: Require effective compression sealing and low compression set.

• Rotary shaft seals: Require consideration of surface speed and the operating limits of the selected material.

If valve groove drawings are available, provide them together with the seal specifications.

The manufacturer can then verify whether the proposed seal geometry is compatible with the available installation space.

Starting with a Physical Sample vs. a Technical Drawing

There are two common starting points for custom seal development: technical drawings and existing physical samples.

When Technical Drawings Are Available

The manufacturer can produce components according to the specified dimensions and tolerances.

However, the accuracy of the final product depends on whether the original measurements and drawings are correct.

Developing a mold or manufacturing process from a drawing provides greater dimensional control and establishes a clear reference for future design modifications.

When Only a Physical Sample Is Available

The manufacturer must use precision measuring equipment to inspect and reproduce the existing component.

This approach requires greater measurement capability and manufacturing experience.

One advantage of sample-based development is that the manufacturer can directly examine the physical geometry.

However, an old seal may already be worn, deformed, swollen, or shrunken. Its measured dimensions may no longer represent the original design specifications.

If the sample has undergone dimensional changes, directly reproducing it may also reproduce those errors.

The Recommended Approach

In practice, the most reliable combination is a physical sample together with clearly identified critical dimensions.

The sample helps the manufacturer understand the seal structure, while the dimensional specifications identify which measurements must be maintained within defined tolerances.

Prototype Testing and Validation Process

For custom non-standard seals, prototype testing should be completed before proceeding to mass production.

Step 1: Prototype Manufacturing

The manufacturer produces prototype seals according to the supplied technical parameters, drawings, or physical samples.

A dimensional inspection report should accompany the samples.

Key inspection points include:

• Inner diameter and outer diameter

• Cross-sectional dimensions

• Compliance with specified tolerances

• Surface finish

• Presence of burrs, flash, or other manufacturing defects

Step 2: Installation and Operational Testing

Install the prototype seals in the actual valve assembly and test them under real operating conditions.

The test should use:

• The actual adhesive or dispensing fluid

• The actual operating temperature

• The actual valve motion frequency

The purpose is not simply to confirm that the seal fits, but to verify that it performs reliably during operation.

After several hours of continuous operation, inspect the seals for swelling, deformation, and wear.

Also check for adhesive leakage around the valve stem and any signs of sticking, delayed movement, or abnormal valve operation.

Step 3: Design and Material Adjustments

If the prototype exhibits leakage or excessive wear, adjustments may be required.

These may include changes to:

• Material hardness

• Sealing material

• Cross-sectional geometry

The more specific the test feedback, the easier it is for the manufacturer to identify potential causes.

For example, reporting that “adhesive leakage began after three hours of operation” provides much more useful engineering information than simply stating that “the seal does not work well.”

Step 4: Prototype Approval and Mass Production

Once the prototype passes testing, the approved specifications should be finalized.

These include:

• Material grade

• Material hardness

• Critical dimensions and tolerances

• Manufacturing process parameters

The approved prototype and specifications then serve as the reference for mass production.

Any subsequent changes should be reviewed and approved before implementation.

Batch Consistency and Spare Parts Agreements

The main challenge in mass-producing custom seals is not always whether the manufacturer can produce a functional part.

It is whether every production batch can consistently meet the same specifications.

Production Batch Consistency

Batch consistency depends heavily on the manufacturer's process control capabilities.

For molded rubber seals, dimensional accuracy can be affected by shrinkage during vulcanization.

Mold design and manufacturing parameters must therefore remain consistent.

During incoming inspection, samples should be checked from each production batch to verify critical dimensions and hardness.

Inspection reports should be retained for traceability.

Where necessary, buyers may also request material certificates or third-party testing reports.

Spare Parts Supply Agreements

Three important issues should be clarified before placing repeat or production orders.

1. Tooling Ownership

Specify who pays for mold development and who retains ownership of the tooling.

2. Change Notification

If the manufacturer changes the raw material supplier or modifies the material formulation, the customer should be notified in advance.

Any significant change should undergo appropriate verification before the modified seals are supplied.

3. Replenishment Lead Time

Agree on the expected lead time from order placement to delivery, as well as the minimum order quantity (MOQ).

Dispensing machine seals are consumable components. If replacement seals are unavailable when needed, production equipment may have to stop operating.

Including batch consistency requirements and spare parts supply terms in the purchasing agreement is often more valuable than comparing prices alone.

Need Custom Dispensing Valve Seals?

Looking for replacement seals or custom sealing solutions for your dispensing equipment?

At XHH Seals, we manufacture custom dispensing valve seals based on technical drawings, existing samples, and specific operating requirements. We support prototype development, replacement parts, and small- to large-batch production.

Send us your seal dimensions, drawings, or samples, along with details of the operating fluid, temperature, pressure, and motion conditions. Our team will review your requirements and help identify a suitable sealing solution.

Request a Quote: xhh@xhh-smartech.com