Top performance DC motors for minute quantities

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When it comes to accurately applying the correct amount of soldering paste, adhesive, lubricant or sealant, a dosing pump can provide the ideal solution. Chemical dosing pumps support numerous applications, from semiconductor and electronics manufacturing to optics and medical technology.  

But growing trends towards miniaturisation presents a challenge for dosing pump designers. How can we make these dispensers more compact, without compromising precision? The answer may lie within the drive system, driven by DC motors. 

ViscoTec Pumpen- u. Dosiertechnik GmbH manufactures a range of dosing pumps for production and assembly processes. In 2008, its preeflow^® micro-volume dosing unit set a new industry standard in precision dispensing.

To meet demand for smaller dosing systems, ViscoTec has developed the Preeflow^® eco-PEN range. These automated volumetric dispensing systems allow for precise dosing with accuracies of ± 1 per cent. Minimum dispensing quantities of 0.001 ml are possible with a wide range of chemicals. 

Dosing system operation

These dosing units operate on the principle of displacement. At the heart of the dispenser unit is a pressure-sealed, rotating displacement system. It consists of a self-sealing inner rotor and the outer stator.   

Controlled rotating movement of the rotor allows for effective transport of the liquid. Moving the liquid backwards can be done by reversing the direction of rotation. This level of fluid control allows for neat material separation, with minimal dripping and maintained accuracy. This mechanism prevents damage to the material, allowing effective dosing of a variety of chemicals. 

The system is self-sealing and can achieve dosing pressures of up to 20 bars with non-self-levelling liquids. It’s important to account for the viscosity of the dosing material, as maximum dosing pressures and self-sealing will decrease with lower viscosities.  

For dosing of more aggressive materials, other variants are available. This includes a stainless-steel version, ideal for dosing solvents or abrasives. Organic and inorganic acids with a pH lower than 4 can also be safely dosed. 

Compact drive electronics

Achieving a high feed pressure in the chemical dosing system requires a high-torque drive. Working together with FAULHABER, a compact drive system solution was developed to meet the specified requirement. 
 
The top choice for a great price-to-performance ratio was a brushed DC motor with encoder and planetary gearhead. The resultant drive block measures just 22 mm in diameter, with an overall motor length of 32 mm.

Choosing a motor with brushed commutation makes pulse-width regulation and changes in rotation direction simple. Several DC motors are available, offering continuous torques of 10 to 28 milli Newton meters.  
 
Addition of the planetary gearhead helps to maximise motor torque, providing ratios of 9:1 to 23014:1. FAULHABER designs gearheads to distribute load over numerous contact points. This allows them to offer a more robust and long-lasting performance. Suited to frequent start/stop operation and load changes, they’re an ideal choice for dosing pump applications. 
 
A push-on encoder increases the overall length by only 1.4 mm, while delivering up to 512 pulses per revolution. This allows for precise feedback on the rotor position, facilitating precise measurement with drip-free material separation. 

The gearheads and motor bearings have lifetime lubrication. This makes the dosing system long-lasting, maintenance-free, and easy to integrate and use.  
 
The full eco-PEN case study is available on the FAULHABER website. 

EMS has partnerships with several leading drive system manufacturers, including FAULHABER. To find out more and to discuss your product, get in touch with a member of the team today.