Sealing of control cabinets and electrical distribution boxes made of plastic


The groove contours of electronic distribution boxes and the very narrow grooves of micro-distribution housings are seamlessly sealed with the sealing foams of the polyurethane-based FERMAPOR K31 or the silicone-based FERMASIL product families.
The prerequisite for the exact application of sealing foams, even in very small discharge quantities for very small housings with narrow grooves, is the contour-accurate FIPFG application with our fully automatic DM 502 mixing and dosing machine or, alternatively, with the 3E dosing cell.

From smaller to larger electrical distribution boxes, the CNC-controlled precision mixing head doses liquid sealant into the groove of the housing or cover with high dosing and repeat accuracy. The dosing process must be very precise, especially when dealing with very narrow grooves. After the dosing cycle, the coupling point of the room-temperature-curing foam gasket closes seamlessly and is almost invisible. 

The overall design of the component and foam gasket complies with the applicable standards and protection classes (IP and NEMA) and protects the installed electronics against moisture and dust. For outdoor use, our temperature-resistant silicone foams are very suitable for protecting the electronics from extreme weather conditions.



Animation of sealing process of distribution boxes with Sonderhoff DM 50x and shuttle table on one level


Material systems for control cabinets and electrical distribution boxes made of plastic


After more than 30 years of practical experience of the sealing of electrical distribution boxes, the foam gasket (tested according to DIN EN ISO 1856) shows very good recovery behavior (DVR) even after years of use.

The resilience of polyurethane foam is > 95 % (DVR < 5 %) and that of silicone foam > 97 % (DVR < 3 %). This allows the repeated opening and locking of the electrical distribution boxes for maintenance, whereby the sealing function remains permanently intact.


The different reaction phases of the sealing foam in the chronological sequence.


Reference material



Specific requirements
    FERMAPOR K31-A-9025-2-VP2          FERMASIL A-91-VP2

Mixing ratio

  4.5 : 1   1 : 1

Pot life time

  33 sec.   56 sec.

Tack-free time

  5 min.   5 min.

Viscosity of the A component

  44,000 mPas   15,000 mPas


  0.2 g/cm³   0.3 g/cm³

Hardness (Shore 00)

  35   52

Temperature resistance

  from -40 to + 80 °C   from -60 to +180 °C


  Plasma for e.g. PP and PE   Primer P8 or TEROSON SB450

In addition to the reference products, we develop material systems according to your individual requirements. Influencing factors include pot life until start of foaming, curing time, and the viscosity, hardness and adhesion properties.


Frequent opening and reclosing of control cabinets and electrical distribution boxes, while remaining sealing effect

The very good resilience of the foam seal allows repeated opening and reclosing of the electrical distributor for maintenance purposes without the leakage deteriorating. After closing, the housing is tight and the sensitive electronic parts are protected against splashing water and the effects of the weather.


The video shows the polyurethane foam seal FERMAPOR K31 in a cross section in a groove - first in the uncompressed state, then about 50 % compressed, so that the sealing function of the seal is given and the component is tight.

Cross-section of a polyurethane foam bead in the groove without compression


Cross-section of a polyurethane foam bead in the groove with approx. 50 % compression

DM 502 mixing and dosing system with 3-axis linear robot and a conveyor belt for the feeding of parts


Flexible and fully automatic – 
fully in line with your requirements

Through our combination of individual material systems, customer-specific mixing and dosing machines and skilled process expertise, you receive solutions from us to meet your technical and commercial requirements.

For the construction of your control cabinets, we as process experts offer you individual consulting for the optimal integration of fully automated material application processes with the Formed-In-Place Foam Gasket (FIPFG) technology into your production. You can select different configuration and equipment options for semi-automatic or fully automatic production systems.

In the illustrated reference configuration of our DM 502 mixing and dosing system, the control cabinet parts are fed to the dosing station on a transfer belt at the cycle rate specified for your production, where they pass under the 3-axis linear robot.

The components with plastic surfaces are pretreated with plasma, whereas the components with powder-coated or stainless steel surfaces are pretreated with primer.

The 3-axis linear robot takes over the CNC-controlled movement of the precision mixing head above the component with contour accuracy. The primer or plasma is applied at the same time. This results in the improved adhesion of the foam gasket. We also offer the use of a primer exhaust station depending on the primer to ensure professional air cleaning on the machine.

For the sealing of the control cabinet parts and electrical distribution boxes, the CNC-controlled MK 800 PRO precision mixing head applies sealing foam to the preprogrammed contour. This process is fully automatic with a high level of dosing and repeat accuracy. The seal closes seamlessly with an almost invisible coupling point. The applied material foams and forms an elastic soft gasket with the desired foam hardness at room temperature.

CONTROL 2 WT 1-LEVEL shuttle / sliding table MP 2 Mobile panel Mixing head 825 PRO Dosing machine cabinet Control cabinet Supply Tap Elevator


Optionally available: CONTROL touchscreen operating panel (21.5“) for operating the dosing system

More information to our operating panels

WT 1-LEVEL shuttle / sliding table

Two pick-up plates operating in pendulum mode in one plane

More information to our shuttle tables

MP 2 Mobile panel

The multifunctional MP 2 mobile panel (10.1” WXGA TFT) enables convenient operation of the dosing system.

More information to our operating panels

Mixing head 825 PRO

MK 800 PRO precision mixing head with high-pressure water rinsing or alternative component rinsing system

More information to our mixing heads

Dosing machine cabinet

The dosing machine cabinet contains the components of the dosing periphery, e.g. the dosing pumps.

More information to our dosing machine cabinets

Control cabinet

The control electronics, safety engineering and industrial PC are installed in the control cabinet.

More information to our control cabinets

Supply Tap

Optional: Automatic SUPPLY TAP drum refilling station for low-viscosity products, e.g. isocyanate (B-component)

More information to our refilling stations


Optional: Automatic ELEVATOR drum refilling station for the A-component with pneumatic lift and agitator

More information to our refilling stations


The basic solution for standard applications

Dosing cell for easy handling and high process stability


The reference configuration of the 3E dosing cell shown is a low-pressure mixing and dosing system for two components for the partially and fully-automatic application of sealing foams.

The 3E dosing cell takes up little space due to its compact design, and as a CE-compliant cell, it does not require additional safety fences or light barriers. This is a pre-programmed Plug & Work version that is delivered pre-assembled in a container. As soon as electricity, water and compressed air are connected and the material is prepared in the material pressure vessels, production can begin. The costs of installation and training courses can therefore be kept to a minimum. 

The 3E dosing cell can process liquid, medium- and high-viscosity material systems based on polyurethane or silicone. The applicte is adjustable from 0.5 to 5.0 g/s. Experience shows that this is the range that can be used to represent 90 % of control cabinet applications. 

The optional shuttle table enables the processing of components of different sizes in one plane. Continuous operation is guaranteed by the two shuttle tables that can be moved manually in pendulum mode. For larger parts such as the control cabinet panels and doors, the two shuttle tables can be connected to form one large sliding table.

The CNC-controlled MK 825 BASIC precision mixing head for two material components applies paste-like polyurethane sealing foam with repeatable accuracy to the control cabinet parts that have a powder coating or consist of stainless steel. If stainless steel control cabinet parts should receive a primer application to improve adhesion, this can be prepared manually or with auxiliary equipment outside the dispensing system. In the case of electrical distribution boxes, our dosing technology ensures a very precise dosing application into the very narrow grooves in the housing contour.

With the CE-compliant 3E dosing cell, an immediate, safe start to production is possible, as well as efficiency-enhancing space and cost savings.