Three-Tec's twin-screw feeders excel especially at efficiently feeding poor-flowing powders. Thanks to the sophisticated design, all product-contact components can be disassembled and cleaned in just a few steps and a short time; all contact surfaces are stainless steel grade 1.4404 (AISI 316L). Automatic cleaning systems such as wash-in-place (WIP), clean-in-place (CIP) or sterilize-in-place (SIP) are available as options.
Two basic housing types are available: FB (flat-bottom) models guarantee precise feeding of free-flowing to poor-flowing, moist or bridging products across the ffc 1–5 flowability range; B (standard fluted) models are a more economical solution for free-flowing powders and micro-granules. Either housing type can be converted to gravimetric operation at any time by adding a weighing and control unit.
- Precise feeding even for complex product behavior; a wide flow-rate range from 5 g/h to several tons/h
- Can be converted to gravimetric operation at any time by adding a weighing and control unit
- Easily interchangeable feeding tools — auger, concave or spiral screws
- Tool-free, fast changeover of feed screws with bayonet fittings
- Wide open screw channel, low residual material
- Custom design to customer requirements; GMP, FDA and/or ATEX-compliant options
Gravimetric or Volumetric?
Every ZD model can be operated on either of two principles, depending on whether a weighing unit is added to the same housing. The choice depends on process precision needs and budget priorities:
| Criterion | Volumetric | Gravimetric (Loss-in-Weight) |
|---|---|---|
| Operating principle | Constant-volume feeding via screw speed | Continuous weight measurement via load cells with automatic speed correction |
| Precision | Can drift as material density changes | High accuracy independent of material variability |
| Setup/cost | More economical, simple setup | Higher investment due to weighing and control electronics |
| Typical use | Small-scale, non-critical process steps | Continuous production, frequent recipe changes, lines requiring traceability |
| Long-term cost | Higher risk of material waste | Lower raw material waste thanks to precise feeding |
All ZD models can be ordered in either mode; the gravimetric version can also be obtained later by adding a weighing unit.
Choosing a Housing Type — FB or B?
| Feature | FB (Flat-Bottom) | B (Standard Fluted) |
|---|---|---|
| Flowability | ffc 1–5 (poor-flowing to free-flowing) | Free-flowing |
| Material behavior | Moist, bridging, caking products | Free-flowing powders and micro-granules |
| Bottom scraper | Standard — high bottom cleanliness | None, simpler construction |
| Residual material | Very low (high yield) | Standard |
| Typical industry | Pharmaceutical, food (high cleanliness requirements) | General plastics/chemical applications |
Model Range
| Model | Housing | Screw Diameter / Flow Rate | Typical Use |
|---|---|---|---|
| ZD 5 FB | Flat-bottom | 5 mm · 0.003–0.8 dm³/h | The world's smallest flat-bottom twin-screw feeder; flow rates below 100 grams/hour, expensive/small-quantity active ingredients |
| ZD 9 FB | Flat-bottom | 9 mm | Small-scale laboratory feeding, integration with ZE 9/12 extruders |
| ZD 12 FB | Flat-bottom | 12 mm | Medium-scale laboratory/pilot feeding |
| ZD 22 B / ZD 22 FB | Fluted / Flat-bottom | 22 mm | Poor-flowing and free-flowing powders |
| ZD 32 B / ZD 32 FB | Fluted / Flat-bottom | 32 mm | Poor-flowing powders and micro-granules |
| ZD 55 FB | Flat-bottom | 55 mm · 17–5,565 l/h | With differential weighing, ~265 kg (including control unit and housing) |
| ZD 80 FB | Flat-bottom | 80 mm · 0.02–1 mm particle | Large-scale feeding of fine powders and micro-granules |
Flow rate values vary with material properties; a trial is recommended for exact project data.
Control Options
| Volumetric control | LOGO! · Potentiometer (analog/digital) · Frequency inverter |
|---|---|
| Gravimetric control | Siemens FTC/FTA weighing electronics, S7/HMI |
| Screw speed | 1–500 rpm (AC motor standard on 12 mm and larger housings, servo motor optional) |
| Screw/agitator control | Can be controlled together or independently |
Application Areas
| Industry | Applications |
|---|---|
| Plastics | Granules · Masterbatch · Side feeding on extruders |
| Food & Feed | Grains · Pet/fish feed · Food supplements · Flavorings · Textured vegetable protein · Powdered beverages · Flour, starch, bakery ingredients |
| Pharmaceutical | Active ingredients · Excipients · Feeding tablet presses · Multi-feed systems · Batch filling or continuous feeding |
| Chemical | Detergent · Minerals · Fertilizer · Toner · Metal powders · Ceramics · Dry ice · Cosmetic products |