Hot runner temperature control and proper hot runner system management can easily get lost in the day-to-day flurry of tool changes, process setup, equipment issues and myriad other urgent matters. Compounding this challenge is the need to onboard and train new employees on why things are done a certain way and not just how. Here is a guide for training new moldmaking and molding professionals on hot runner temperature control fundamentals.
Getting System Components Production-Ready
Before turning on a hot runner controller, make sure that what you are about to turn on is production-ready. This preparation will save a lot of time and ensure safe operation.
Five critical areas to consider during this preparation include the (1) condition of hot runner heaters, thermocouples and grounding (ensure there are no direct shorts), (2) mold box connections and grounding, (3) heater and thermocouple cable connections and grounding (ensure there are no direct shorts), (4) hot runner controller connectors, maintenance and grounding and (5) incoming power and grounding. Notice the importance of proper grounding. If any one of these links in the chain is not production-ready, the system will not perform correctly.
Hot Runner Heaters, Thermocouples, Grounding and Direct Shorts
There is no sense in putting a tool into production only to have heater failure, so routinely measure the ohms of each heater within the hot runner system and compare that measurement to its intended rating. You can easily see the resistance rise when you document ohms in a spreadsheet, providing a timeline for proactive heater replacement. Also, an open circuit will be evident when checking ohms if a heater circuit is open or miswired to the wrong hot/return zone in the mold box.
Type J grounded thermocouples (t/c) are the most commonly used. Checking ohms on t/c circuits ensures continuity and consistent readings will identify if there is a reverse. You can determine a shorted t/c by applying heat to the intended t/c location. Ohms should rise. If there is a short (the t/c is closed at a different junction location), you will not see the same reaction.
Grounded thermocouples are susceptible to ground leakage from heaters when there is no effective ground connection between the hot half and the heater connectors. Most modern, integrated controllers have an auto-slave or manual slave option that enables you to run a zone off a comparable zone’s t/c, in the event you lose one. In addition, some mold boxes and controllers provide a thermocouple protection device to address the ground leakage issue.
If a ground wire is securely and cleanly fastened to the hot half and each heater connector in the mold boxes, touch the heater connector legs to the hot half to check for direct shorts. If there is continuity, then a pinched wire or a heater sheath contacting a lead upon heating the system caused a direct short.
Do not plug this tool into a hot runner controller and turn it on. A direct short poses a severe safety hazard and damages thermocouples, connectors, cables and the controller.
Mold Box Connections and Grounding
The mold box is a transition from the hot half to the heater and thermocouple cables. Based on the wiring diagram, wire each heater and thermocouple to the correct junction in the mold box and then from that junction to the back of the heater or t/c connector point. Some controllers allow reassignment of the thermocouple to a different zone if there is a miswire.
Ensure the heater connectors have a ground wire connected to the mold box and that the mold box is mounted directly to the hot half. The last thing to check is the connector pins and latches. Bent pins and pushed-back inserts are a common issue and a game stopper. Broken or missing latches will cause intermittent connections, leading to intermittent alarms, poor t/c readings and open circuits.
Heater and Thermocouple Cable Connections and Grounding
Heater and t/c cables have the same potential issues as mold boxes, including miswires, opens, shorts, missing or bad ground, bent pins and pushed-back inserts.
Cables can also have physical wear and tear, especially around the strain areas near the connectors. Ideally, cables should have service tags indicating that they are production-ready.
Hot Runner Controller Connectors, Maintenance and Grounding
Connectors on the controller have similar issues as connectors on cables. For example, pushed-back inserts, bent or missing pins, broken or bent latches, loose or missing ground wire connections.
The controller will have specific maintenance requirements as well. For example, you must update and clean filters, cooling fans, power module fuses and board components to ensure they function as designed.
Incoming Power and Grounding
Variable frequency drives (VFDs), servomotors, poor incoming power quality and poor in-plant grounding can negatively impact hot runner temperature control, so make sure that all VFD and servomotors have shielded cables. The hot runner cables should also be shielded and not run parallel to high-voltage lines. If the facility’s earth ground is inadequate, you may have to drill a hole in the floor and drive a copper grounding spike at the machine.
Below is a list of considerations when selecting a hot runner temperature controller:
1) Does the controller supply power to zones individually or in consideration of the entire system? It should consider the entire system.
2) Does the controller read each zone many times before responding and then respond to a predicted trend? It should have predictive capability.
3) Is the controller easy for all users to learn and operate? Are all functions used or only those easily found and understood? We believe all functions should easily be learned and used with a simple start-up guide.
4) Does the controller automatically detect and alarm mold problems or must you initiate the process? We believe automatic, real time response is safer and more reliable.
5) Does the controller offer molding cell integration to prevent cold shooting, tool damage, leakage and unforeseen heater failure? Can all alarms be sent from the controller? Can the controller be remotely turned on, off, boost or idled?
6) Can the controller be stored in any position away from critical floor space?
7)If you require transformers, how compact is the matching transformer?
8)Is the controller completely modular and accessible without tools?
9) Is the controller customizable to maximize the benefit for your application?
10) Is the controller easily made available for demo applications to test its performance?
If you want to produce stable and high-quality components in injection molding, high-quality hot runner controller systems are the essential key factors. One of the most important performances for hot runner controller systems when you choose the temperature controller company is temperature uniformity. In well-performing hot runner controller systems, the temperature should remain consistent at all times without changes over time. However, no matter how carefully designed hot runner controller systems are, they cannot function properly without a temperature controller.
Properly controlling the temperature of the hot runner controller systems is a dynamic task because during the injection molding process, different amounts of shear heat are generated throughout the entire hot runner system. How the temperature controller responds to these sudden and uneven heat increments directly determines whether the various parts of the hot runner controller systems can return to their original temperatures before the next injection.
Before you are ready to buy a hot runner temperature controller, In addition to price, what other considerations do you have? The manufacturer’s delivery time, brand, origin? All of them are necessary.
However, in terms of the temperature controller itself, many suppliers, in addition to providing the above information, have not told you that you should pay more attention to the following some important parameters of the hot runner controller. Which are also important indicators reflecting whether the temperature controller is worth buying in the long term.
Measurement Resolution is the minimum temperature change that the controller can distinguish. According to the temperature change, the controller calculates and adjusts output voltage, to control hot runner heaters. hot runner temperature controller inspection.
Higher resolution is conducive to the output voltage adjustment timely according to the temperature change, so as to achieve a better controlling effect for hot runner system. Measurement Resolution reflects the sensitivity of hot runner temperature controllers.
Measurement Accuracy is the deviation between the displayed temperature value and the actual temperature value measured by the controller. Hitcontrols hot runner controller measurement accuracy is ±0.25%F.S.
Control Accuracy is the deviation between the displayed temperature value and the setpoint temperature. It is affected by many factors, including measurement resolution, measurement conversion speed, control algorithm and related parameters, control adjustment speed, the condition of the controlled equipment, etc.
resolution and accuracy is point factors impact the price. Hot runner controller price from supplier is your buying cost only, we shall focus on total cost as well. Including using cost, maintenance cost, productivity, etc. A stable temperature controller makes you customer’s hot runner system more efficient, lower the defective rate.
Display Resolution is the minimum temperature change that the controller can display. The present temperature and setpoint temperature display on the control card for reading. Display resolution ≤ the measurement resolution, and depends on the number of bits of the LED or LCD.
Hitcontrols™ hot runner control module (HC15-M) display resolution is 1℃, LCD display control card HC15-S is 1℃ or 0.1℃ (can be set by parameter, factory default is 1℃).