Mold Temperature Controller Explanation: A mold temperature controller is an industrial device used to control temperature of molds. It precisely regulates mold temperature by heating or cooling a medium, improving product quality and production efficiency.

 

Main Functions:
Precise Temperature Control: High-precision temperature control system with an accuracy of ±1℃, ensuring stable product quality.
Efficient Energy Saving: Utilizes efficient heating/cooling technology, resulting in significant energy savings and reduced production costs.
Safe and Reliable: Multiple safety protection devices, including over-temperature, overload, and phase loss protection, ensure safe operation.
Easy Operation: Intelligent control system with a touchscreen interface; simple parameter settings make it easy to use.
Benefits of using a mold temperature controller: Improved product quality, stable temperature, and reduced defect rate; Increased production efficiency, shorter molding cycle, and increased capacity; Reduced production costs, energy saving and environmental protection, and reduced energy consumption; Extended mold life, reduced thermal stress, and mold protection.
Application areas: Injection molding industry, die casting industry, rubber industry, chemical industry, food industry, and pharmaceutical industry.

1.1 Mold temperature controllers are divided into oil-based and water-based types. Main difference is that main circulating medium in an oil-based controller is heat transfer oil, while in a water-based controller it is water.
1.2 Oil-based mold temperature controllers are further divided into ordinary oil-based and high-temperature oil-based types, water-based mold temperature controllers are also divided into ordinary water-based and high-temperature water-based types.
1.3 Temperature control range of a mold temperature controller is as follows:

 

1.4 Oil-based mold temperature controller: An oil-based mold temperature controller uses heat transfer oil as heat transfer medium. Oil-type mold temperature controllers have an oil reservoir. During operation, heat transfer oil enters system from reservoir, is pumped into mold or other equipment requiring temperature control by a circulating pump, and returns to system after exiting controlled equipment, repeating cycle. Heat transfer oil is heated by a heater; when temperature probe detects that medium temperature reaches set value, heater stops working. When temperature is below set value, heater starts working, and stops working again when temperature reaches set value. This cycle continues.
1.5 Water-type mold temperature controllers: Water-type mold temperature controllers use clean water/cooling water as heat transfer medium. A water-type mold temperature controller is a closed-loop circulation system. During operation, cooling water enters system through a water supply valve, is heated by a heater, then pumped into mold or other equipment requiring temperature control by a circulating pump. After exiting controlled equipment, it returns to system, repeating cycle. When temperature probe detects that medium temperature reaches set value, heater stops working. When temperature is below set value, heater starts working; when temperature reaches set value, it stops working. This cycle repeats continuously.

2.1 Mold temperature controllers are mainly used in injection molding, magnesium-aluminum die casting, rubber mixing, and plastic extrusion. In injection molding and die casting processes, uneven or inappropriate mold temperatures can lead to unstable product dimensions, resulting in defects such as product deformation, sticking, surface depressions, internal shrinkage cavities, and thermal bubbles. It also affects production cycle, causing instability in filling and cooling times. Lifespan of mold can also be shortened due to excessive cooling or heating, leading to thermal cracking of expensive steel.
2.2 Mold temperature controllers are essential equipment in other industries, though they may be called different things. For example, in rubber mixing mills, they are called temperature control systems or temperature controllers; in extrusion equipment, they are called temperature control devices; and in PVC sheet roller temperature control, they are called oil heaters. These devices generally involve rapid heating followed by a heat-holding process. However, in rubber equipment, after heating, a long cooling process is required.
2.3 Mold temperature controllers are widely used in plastics industry, primarily for following purposes: Reducing production of defective products; Improving product molding efficiency; Improving product appearance and suppressing defects; Accelerating production progress, reducing energy consumption, and saving energy.
2.4 Selecting a mold temperature controller based on required temperature for processing different raw materials in injection molding.

 

3.1 A mold temperature controller consists of three main parts. As shown in figure:

 

Pump Brands: Commonly used pump brands in industry include SPECK (Germany), Calpeda (Italy), Grundfos (Denmark), YUANSHIN (Taiwan), and Aulank (Kunshan).
3.2 Heater Material:
Copper Tube. Advantages of copper tubes: high thermal conductivity, relatively pressure resistant; Disadvantages: prone to scaling and difficult to clean.
Stainless Steel Tube. Advantages of stainless steel pipes: Less prone to scaling compared to copper pipes; Disadvantages: Lower heat transfer rate compared to copper pipes.

A mold temperature controller consists of a water tank/oil tank, a heating and cooling system, a power transmission system, a liquid level control system, components such as temperature sensors and injection ports. Normally, pump in power transmission system drives hot fluid from water tank/oil tank (equipped with a built-in heater and cooler) to mold, then back from mold to water tank/oil tank. Temperature sensor measures temperature of hot fluid and transmits data to controller in control section. Controller adjusts temperature of hot fluid, thereby indirectly regulating mold temperature. If mold temperature exceeds controller's set value during production, controller will open solenoid valve to connect water inlet pipe until temperature of hot fluid, i.e., mold temperature, returns to set value. If mold temperature is lower than set value, controller will turn on heater.
4.1 Working principle diagram of an oil-type mold temperature controller:

 

4.2 Working principle diagram of a water-type mold temperature controller:

 

Mold temperature controllers use either direct cooling or indirect cooling methods. Indirect cooling separates cooling circuit from main circuit, while direct cooling integrates cooling circuit directly into main circuit. Water-type mold temperature controllers typically use direct cooling. Oil-type mold temperature controllers, however, use indirect cooling because water and oil cannot mix during heating, usually employing plate heat exchangers.
High-temperature water-type mold temperature controllers typically operate above 160℃. Therefore, internal main circuit circulates high-temperature steam, resulting in high internal pressure. Direct cooling would require external water pressure exceeding internal main circuit pressure for direct cooling to enter, posing a safety hazard. Therefore, high-temperature water-type mold temperature controllers also often use indirect cooling. Advantages and disadvantages of direct cooling: Direct cooling is only suitable for lower temperatures, but it offers rapid cooling.
Advantages and disadvantages of indirect cooling: Indirect cooling is suitable for high-temperature mold temperature controllers, but its heat exchange rate is slow, and heat is lost during heat exchange. Therefore, when actual temperature of medium deviates significantly from the set value, direct cooling with its greater cooling capacity is preferred.

6.1 Special cases require calculation:
A. Calculate heater power (KW) = W * Δt * C * S / 860 * T
W = Mold weight (KG); Δt = Temperature difference between required temperature and initial temperature; C = Specific heat (oil (0.5), steel (0.11), water (1), plastic (0.45~0.55)); S = Safety factor (1.5-2), smaller value can be used for a single machine; T = Time to heat to required temperature (hours)
B. Determine pump size requires understanding customer's required pump flow rate and pressure (head)
P (Pressure Kg/cm2) = 0.1 * H (Head M) * α (Specific gravity of heat transfer medium, water = 1, oil = 0.7-0.9)
L (Required flow rate of medium L/min) = Q (Required heat of mold Kcal/H) / C (Specific heat of medium: water = 1, oil = 0.45) * Δt (Temperature difference between circulating medium entering and exiting mold) * α * 60
6.2 Precautions
When selecting a mold temperature controller, following points are main considerations; Appendix: Selection of chiller paired with injection molding machine:
A. Q (Cooling capacity Kcal/H) = Q1 + Q2
Q1 (Heat carried into mold by raw material Kcal/H) = W (Weight of raw material injected into mold per hour KG) *C * (T1-T2) * S (Safety factor 1.5~2)
T1: Temperature of raw material in feed pipe; T2: Temperature of finished product when removed from mold; Q2: Heat generated by hot runner (Kcal/H)
B. Quick Calculation (Not applicable to hot runners)
1RT = 7~8 OZ 1OZ = 28.3g (including safety factor)
1RT = 3024Kcal/H = 12000BTU/H = 3.751KW
1KW = 860 Kcal/H 1 Kcal = 3.97BTU
3. Cooling Tower Selection = A + B
A. For Injection Molding Machines
Cooling Tower RT = Injection Molding Machine Horsepower (HP) * 0.75KW * 860Kcal * 0.4 ÷ 3024
B. For Refrigeration Units
Cooling Tower RT = Refrigeration Unit Cooling Tons (HP) * 1.25