High force density
High force in little space — decisive for a compact housing.
Drive system: turning rotation into a precise stroke
The current main approach under investigation is a brushless DC motor (BLDC) combined with a planetary roller screw. The motor's rotation is converted into a precise linear stroke of the pressure plate.
Currently favoured approach — not yet fixed in the design.
Operating principle
One stroke in five steps
- The BLDC motor produces rotation.
- The planetary roller screw converts the rotation into linear stroke.
- A linear carriage and guide keep the pressure plate from tilting.
- The pressure plate moves the membrane from the mechanical side — ejection.
- The return stroke allows the chamber to refill.
Rationale
Why this approach is being investigated
Precise position control
The stroke can be set, measured and controlled precisely.
Few intermediate stages
Fewer mechanical transmission elements, potentially high efficiency.
Working range
Force and stroke from the current concept calculation
| Quantity | Value | Status | Note |
|---|---|---|---|
| Pressure-plate force, main system | approx. 150–250 N | Design target | design range |
| Stroke | approx. 10–20 mm | Estimate | depends on effective membrane area |
Stroke at 120 ml ejection — depending on membrane area
| Effective membrane area | Required stroke |
|---|---|
| 50 cm² | approx. 24 mm |
| 70 cm² | approx. 17 mm |
| 90 cm² | approx. 13 mm |
Simple calculation volume ÷ area. Final values are not yet fixed in the design.
Redundancy
Backup drive: small, independent, limited
In addition to the main drive, a smaller independent backup drive is under investigation — with its own motor, its own screw and, as far as possible, its own load path. It does not have to reach the full stroke. The target is an emergency ejection of approximately 60 ml; the aim is bridging and emergency operation, not full everyday output.
| Rate | Calculated output at 60 ml |
|---|---|
| 60 / min | 3.6 l/min |
| 80 / min | 4.8 l/min |
| 100 / min | 6.0 l/min |
Rough calculation of target volume × rate — not a measured value.
Wear
Lubrication and wear concept
The drive is designed for low friction, controlled guidance and very high cycle counts. The aim is to minimise contact stress, backlash, lubricant ageing and particle generation by design. Under discussion:
- encapsulated long-term lubrication of the mechanical drive
- avoiding sliding friction wherever possible
- smooth acceleration and reversal profiles, no hard mechanical end stops
- particle traps or filters as an optional addition
A permanent oil-circulation pump has been discussed but is currently not a preferred baseline approach: it would add heat, lines, filters, seals and failure points.