A Technical Guide to the Hartek Conical Twin-Screw Extruder

For researchers and compounders working with high-viscosity materials—rubbers, engineering resins, and bio-based polymers—the difference between a successful formulation and a failed experiment often comes down to three critical parameters: temperature profile, screw speed, and draw ratio. These are not merely settings to be dialed in arbitrarily; they are interdependent variables that determine melt quality, dispersion efficiency, and final product properties.

The HTPS conical counter-rotating двухшнековый экструдер from Hartek Technology provides the precision and flexibility needed to master these three pillars of extrusion. Below is a technical guide to understanding and optimizing each parameter for your specific materials.

1. Temperature Profile: The Thermal Foundation of Melt Quality

Why Temperature Profile Matters:

Different polymers require distinct thermal histories. Setting the correct temperature profile ensures:

Complete melting without thermal degradation
Optimal melt viscosity for consistent flow
Proper additive dispersion
Reduced pressure fluctuations at the die

2. Screw Speed: Balancing Shear, Throughput, and Residence Time

The HTPS-40 is equipped with a 1.3 kW servo motor with a rated speed of 1500 RPM and a maximum screw speed of 500 RPM. The servo drive offers precise speed control, allowing researchers to dial in the exact shear input required for each formulation.

Why Screw Speed Matters:

Screw speed directly influences:

Shear rate: Higher speeds generate more mechanical energy, improving dispersive mixing but also increasing melt temperature
Throughput: Speed determines output rate
Residence time: Faster speeds reduce the time material spends in the barrel, which is critical for heat-sensitive polymers
Filling ratio: Higher speeds help reduce the filling ratio of screw channels, which positively affects torque requirements

Speed Selection Guidelines:

Heat-sensitive materials (PLA, TPU, PVC): Operate at lower speeds (50–150 RPM) to minimize frictional heating and shorten residence time
High-viscosity rubber or heavily filled compounds: Higher speeds (300–500 RPM) boost shear for better dispersion
General rule: Start at approximately 100 RPM and increase incrementally while observing melt temperature and motor current

3. Draw Ratio: The Bridge Between Extrudate and Final Product

The draw ratio—the relationship between the cross-sectional area of the extrudate exiting the die and the final product—is often overlooked but critically important for achieving desired mechanical and dimensional properties.

Why Draw Ratio Matters:
Draw ratio influences:
Molecular orientation: Higher draw ratios align polymer chains, improving tensile strength
Final dimensions: Determines the cross-sectional area of the finished product
Surface quality: Affects smoothness and defect formation
Mechanical properties: Impacts modulus, elongation, and toughness

Key Considerations for Draw Ratio Optimization:

Material type: Amorphous polymers (PS, PC) can tolerate higher draw ratios than semi-crystalline polymers (PE, PP) which may undergo strain-induced crystallization
Melt strength: Materials with higher melt strength (e.g., rubbers, elastomers) can withstand greater draw ratios without breaking
Cooling conditions: The rate and uniformity of cooling after extrusion significantly affect how well the drawn dimensions are maintained
Die design: The relationship between die exit area and take-up speed determines the actual draw ratio achieved

Practical Approach:

When developing new formulations on the HTPS-40, systematically vary the take-up speed while keeping extrusion parameters constant. Observe the relationship between draw ratio and:

Filament/film diameter uniformity
Surface defects (melt fracture, sharkskin)
Mechanical properties of collected samples

Start-Up Procedure for Optimal Parameter Development

Set temperature profile based on your material’s thermal properties (refer to the inverted-V guideline)
Allow 30-minute heat soak for thermal equilibrium
Start screw at low speed (5–20 RPM) and gradually increase to target
Begin feeding slowly while monitoring the main motor current
Adjust cooling as needed to maintain stable melt temperature
Collect samples at various draw ratios to identify optimal conditions
Document all parameters—the HTPS-40’s touchscreen HMI allows easy storage and recall of successful recipes

From Lab to Production: Scale-Up Confidence

The conical screw geometry of the HTPS-40 closely mirrors that of industrial-scale conical twin-screw extruders. This means the temperature profiles, screw speeds, and draw ratios you optimize on this 40 mL unit can be transferred directly to production lines as startup parameters—not approximations, but directly applicable data.

Specification of Conical Twin-Screw Extruder

No.	Параметр	Conical Twin-Screw Extruder Specification / HTPS-5
1	Вместимость	40 mL
2	Servo Motor Power	1.3 kW, rated speed 1500 RPM
3	Max Screw Speed	500 RPM
4	Диаметр винта	Conical Φ5.4 / Φ25 mm, length 240 mm
5	Screw Structure	One‑piece integral screw design
6	Screw Material	38CrMoALA (nitrided steel)
7	Направление вращения	Counter‑rotating / Co‑rotating (switchable)
8	Бочка	Split‑type (clamshell) barrel structure, material 440C stainless steel
9	Heating Zones	6 zones, 200 W per zone
10	Max Operating Temperature	350 °C
11	Cooling System	Combined air and water cooling
12	Mixing Modes	Dual‑mode design with diverter valve – freely switchable between circulation mixing and extrusion modes
13	Control Interface	Touchscreen HMI control
14	Overall Dimensions (L×W×H)	550 × 650 × 1000 mm