The piston pump has a charging stroke in which material moves into the pump illustration 2) and a dosing stroke in which material is metered out (illustration 4). Between charging and dosing, the piston rotates to open and close the corresponding ports (illustrations 1 and 3). The dose stroke is numerically controlled making the volume and flow rate extremely accurate and repeatable. After leaving the piston pump, the material can proceed directly to a dispensing needle or a mixing chamber. Read below for more information on the dynamic mixing chamber.
The metering pumps are made of low-wear ceramic material. Several bore sizes are available to provide a range of volumes. The smallest version can dispense volumes as low as 0.1mm³ with high precision and repeatability.
Dispensing heads that use reciprocating pumps include the mono-component numerical volumetric dispenser (NVD), the two-component numerical volumetric dispenser (NBD), the mini mono-component numerical volumetric dispenser (mini-NVD) and the mini two-component numerical volumetric dispenser (mini-NBD). The primary limitation of reciprocating pumps is they cannot continuously dose shots larger than the volume of the pump cavity. This is one reason we also offer continuous flow progressive cavity pumps.
Two-component material mixing
When applications require two-component materials, mta uses separate pumps for the resin and hardener components before mixing. This applies to the piston and continuous pumping technologies. Since we use individual pumps for each material, we can precisely control the mixing ratio with high repeatability.
After the pumps meter the materials, the resin and hardener move separately into a dynamic mixing chamber. A rotating mixing blade mixes the materials inside the chamber. As with the pumps, the blade’s speed and number of rotations are also numerically controlled. This provides the correct number of folds without damaging the material.
Dynamically mixing the material provides two significant advantages over static mixing tubes. First, we can 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, very little residual material reacts between doses and the pot life is maximized. This means mta’s dynamic mixing systems can dose much smaller volumes of material than are possible with static mixing tubes.