High precision volumetric dispensing
Volumetric dispensing systems are both mechanically defined and numerically controlled to precisely control the volume and rate of material dispensed. This is different from time-pressure systems in which the dose volume can fluctuate depending on many variables: temperature, viscosity, time (pot life), air volume, system pressures, etc.
mta offers two primary technologies for volumetric dispensing, reciprocating piston pumps, and continuous-flow progressive cavity pumps. Between the two technologies, we can provide solutions for a broad range of materials. mono- or two-component materials, in a variety of dispensing processes, including adhesive bonding, sealing, potting, and conformal coating.
Volumetric dispensing based on piston-cylinder pump
The piston pump works volumetrically, meaning the stroke of this piston is driven by a numerically-controlled actuator. Unlike time-pressure systems that can fluctuate depending on temperature, viscosity, and feeding pressure; numerically-controlled systems are mechanically defined. This makes them very accurate and repeatable.
The metering pumps are based on low-wear ceramic piston-cylinder pumps. There are several bore combinations available to provide a range of volumes. The smallest version enables dispensing quantities down to 0.1mm³ while maintaining the highest precision and repeatability.
The mta volumetric dispensers use a combination of linear and rotary motion. The linear motion defines the amount of material dispensed (see 2 and 4 in on the image below). While the rotary motion (see 3 on the image) switches between charging and dosing.
After leaving the piston pump, the material can proceed directly to a dispensing needle or to a mixing chamber. Read below for more information on the dynamic mixing chamber.
Continuous volumetric dispensing based on eccentric screw pump
mta dispensers are able to continuously dispense liquids and highly-viscosity materials using a rotating low-pulsation displacement system. This allows to apply long sealing or adhesive beads in a highly precise contour.
The basic principle is based on motor that directly drives a rotor with one or more helical windings eccentrically within an elastomer stator. The eccentric movement of the rotor created a series of cavities that push the material through the pump. The stator’s complex geometry provides consistent displacement at any phase of rotation, so the flow does not pulsate. The dosing volume is determined by geometry of the stator and rotor. Likewise, the flow rate is directly proportional to drive speed.
The rotors, stators and pump housings are available in a range of materials, so we are able to find combinations suitable for a variety of applications. For example, pharmaceutical and medical industries often require inert materials in the dispensing systems.
After leaving the continuous pump, the material can either proceed directly to a dispensing needle or to a mixing chamber.
Two-component material mixing
When applications require two-component materials, mta uses separate pumps for the resin and hardener component before mixing. This applies to the piston and continuous pumping technologies. Since we use individual pumps for each material, we are able to precisely control the mixing ratio with high repeatability.
After the pumps meter the material, each the resin and hardener move separately into a dynamic mixing chamber. A rotating mixing blade mixes the material inside the chamber. A numerically controlled actuator controls the speed and rotation. This allows the mixing to provide the correct number of folds without damaging the material.
Dynamically mixing the material provides two significant advantages over static mixing tubes. First, we are able to size the mixing chamber according to the shot size – not the number of folds. Hence, the chamber can be much smaller than static mixing tubes. Second, the reaction does not begin until the material is ready to be dosed maximizing the pot life. As a result, there very little residual material reacting between doses and the pot life is maximized. This means mta’s systems are able to dose much smaller volumes of material than are possible with static mixing tubes.