When manufacturing an assortment of plastics, the temperature value of the process is an important criterion. The raw material has to be heated, melted, then the right thermal value of the mold has to be maintained so that the cooling of the almost finished products takes place in the specified mode.
Methods of heating molds in extrusion processes
It is suggested to increase the thermal index of the molded mass by using the following heaters:
- steam. Condensed substance is fed through a coil placed inside the unit. Despite the fact that steam is able to transfer a significant part of the energy, there are no difficulties in its transportation through communications, does not add unnecessary impurities to the semi-finished product (when it comes to the “blind” supply of the heater, through pipes), such a process is considered quite dangerous. In the production of plastics, water vapor can not always hold the desired temperature of the molten mass.
- gas. The thermal index of the semi-finished product is maintained through the combustion of natural fuel. It is easier to ensure a constant temperature here, but the need to use an open flame creates the risk of potential fire;
- electric. Distinguished by the accuracy of measurement and temperature stabilization. They are in demand due to their long service life.
Semiconductor, induction electric heaters are of low popularity due to their high cost. Analogs, whose work takes into account electrical resistance, are ordered much more often.
Types of electric heaters for molds
In most cases, molds are used for the production of serial batches of products. Given the configuration of the heated plane, select suitable products: devices are mounted in cylindrical holes, selected for round, segmental molds, flat tooling and hard-to-reach areas.
A huge range of heaters manufactured by Intmax allows to produce products for molds, pipes, individual elements of technological lines. It differs in shape and is calculated for each order individually.
- Spiral heaters. Outwardly similar to a spring, they are used in places where it is impossible to put an evenly shaped heater. These are hot runner systems, where it is necessary to heat the molding equipment along the length, taking into account the structural bends of the devices.
- Flexible heaters. They are the only solution for three-dimensional molds, easily bendable, adjusting to the desired shape of the hole. Due to the soft braiding they are fully accommodated in the grooves. Withstands higher temperatures than cartridge and spiral counterparts.
Cartridge-type heating elements: design and purpose
The products consist of a core (made of resistive wire), a powder insulator (periclase conducts heat energy well), a metal tube and leads. In order for the product to be optimally usable and inexpensive, a certain metal is always selected: brass, oxidation-resistant steel or heat-hardened steel.
They are selected in such a way that the outer part of them touch the intended holes tightly. The straight tubular shape is designed for flat channels. Customized counterparts curved at right angles or other calculated angles are produced.
Depending on the operating conditions, cartridge heaters are developed for chemically active media, for production facilities with vibration installations. There are variants with a thermocouple, which helps to see the exact thermal values of the processes. It facilitates the tracking of heating and cooling stages, making this function an automatic control mode.
Models with two connected halves work a little differently. When the temperature rises, the halves slide apart and press against the edges of the holes. When the temperature drops, they return to their original position. They provide better and faster heating of the molds for pressing. Convenient because it is not necessary to make them in diameter exactly to the format of the seat. Can be quickly removed when replacement is required.
Cartridge-type heaters take priority among all types of similar products. They are mounted on injection molding machines, extruders, and 3D printers in the production of a range of plastics products.
Correct ordering of cartridge heater
A wide nomenclature range of heaters from Intmax is used in different industrial directions. The maximum heating reaches +800⁰C. They are inserted into molds, channels, matrices.
To make an unmistakable choice before buying, it is necessary to take into account such characteristics.
Length and diameter
It should be known what is the length of the working part of the heating element, which is subjected to heating. It must coincide with the depth of the hole. With the classical scheme of placement, the diameter is selected so that there are no air gaps between the landing place and the outer surface of the heater. “Patronnik” differs from the hole by tenths of millimeters. Only then will it function efficiently, supply the calculated portion of energy to the mold and not dissipate heat through the gaps.
Power rating
To work on heating was conducted in a given rhythm, it is necessary to choose such a performance of the heating element that it provided a dense heat flow, but did not work at the limit of its technical capabilities. Prolonged work on the boundary values will lead to overheating of the element and the need for renewal. This is why heaters with a power reserve are always selected.
Equal or approximate values of thermal conductivity
Fast heating is determined by similar values of heat transfer and heat perception, which must be between the heater and the mold. Otherwise, the process will run at a slower pace, reducing the speed of production. Or the heater will not be able to reach the required heat potential in normal operation and will burn out quickly. It is imperative to install as many heating elements as the calculated number of heating elements.
Installation of cartridge heaters and checking their operation
Let’s show the order of actions when installing heaters.
- Visual inspection: the surface is clean, without stains of technical oil, stuck pieces of debris. If there are contaminants, they are removed by pneumatic blowing or wiping with solvent. It is necessary to dry the surface before installation.
- Checking the hole. The location for the TEN must have a hole with the same diameter throughout the depth. The landing place is cleaned from pieces of metal, which are waste from drilling the mold.
- “Trying on” the heater will show how correctly it would have been fitted. The gap is given 0.03-0.05 mm. The heaters are located at a distance of more than 3-4 cm from each other. The presence of an exit hole will simplify the dismantling of the spent heater.
- Lubrication with thermal paste will improve the contact zones of heaters with channels. It is important that it does not get on the exposed wires.
- Heated segments should remain inside, cold segments should remain outside. Poor installation creates conditions for insulation breakdown and subsequent fire.
- Pay particular attention to the fixing of the heating elements to reduce the risk of injury to workers in the workshop.
- Do not place the cables to be connected near hot surfaces. They can withstand +100…+130⁰C and heating can reach +350…+800⁰C. If the heating temperature value exceeds +300⁰C, choose ceramic sheathed wires (“beads”).
- Regularly check the integrity of the dielectric coating of the cables.
- The use of a thermocouple will ensure that heating is carried out within the specified temperature range. It helps the heating elements not to overheat.
When it is necessary to change the heater, it is necessary to turn it off and wait until its temperature is equal to the air temperature. The through hole helps to remove the heater that has reached the end of its life without any problems.
Who needs to order cartridge heaters?
To understand how often we are approached to order cartridge heaters in Ukraine, let’s list the directions in which they are involved.
Food direction
Making preserves, dried fruits, pasteurization of milk on an industrial scale – a responsible process that requires maintaining temperature during the preparation of food of long storage. The level of heating allows to prepare raw materials in such a way as to ensure the preservation of useful substances and prevent the formation of an environment for the development of bacteria.
Obtaining polymers
To create the desired shape, the raw material must be melted to a state of fluidity so that it assumes the desired configuration. Overheat thermally, forgoing the thermocouple? A product with degraded characteristics will come out. Reduce the temperature to below the designed temperature? Then you won’t achieve uniformity in melt consistency. Pressure molding techniques help create a product line with a wide variety of configurations.
Medtech
Thermal processes in equipment are used in pediatric cuvées (where premature babies are nursed), tanning beds, kidney cleansing machines, and for cosmetic purposes. Therefore, controlled, uniform heat aggregation is also important here.
The field of packaging materials
Many people know what thermal film and hot cutting are. Bag sealing is used in any major market, allowing people to avoid leaving bags and small packages in storage lockers. Dense film is used to pack piece goods (e.g. bottled mineral water, yogurt) in a set of a certain number of pieces.
Heating the engine in the car
In winter time, you can not do without heating the cylinders. Heaters will bring the vehicle into working condition, raising the temperature of the engine oil, coolant.
Why the decision to customize cartridge heaters is the right and cost-effective one
When you order heaters from Intmax, you get products that are precisely matched to their intended use.
For some processes, conventional heaters are sufficient, while others operate under more demanding conditions. In high-temperature heaters with wire crimping, specific resistance up to 10 W/cm² is formed.
- Development of the drawing of the future TEN is an opportunity to create it of different length, diameter, flat, flexible or stationary bent at an angle, with a round or square cross-section.
- The braid will reduce abrasion, the fiberglass jacket will increase thermal resistance. The possibility to create unheated sections will reduce energy consumption and block the possibility of overheating of the active sectors.
- A special case is the possibility to use the heating elements at two different voltage values.
- Application of flanges, threaded bushings, different ways of connection output, use of distributed power, creation of thermocouples for two-phase and three-phase network – all this expands the range of heaters use for solving specific production tasks.
Intmax specialists will accept an order for production of cartridge heaters on any working day