+86 17727725162 jqj014950@topstarltd.com

Home / Why Does an Injection Molding Machine Run Out of Material During Automatic Feeding?

Why Does an Injection Molding Machine Run Out of Material During Automatic Feeding?

2026/09/14 By le zhan

Why Does an Injection Molding Machine Run Out of Material During Automatic Feeding

Even when an injection molding machine is equipped with a sophisticated automatic material loader, a material shortage alarm may suddenly be triggered during the automatic feeding process. In many cases, the problem is not a shortage of resin at the factory, but rather the automatic feeder’s inability to deliver sufficient material to the injection molding machine’s hopper at the speed and in the sequence required by the molding cycle.

Once the rate of material consumption exceeds the effective replenishment rate, a material shortage occurs. Possible causes of this problem include insufficient material at the source, weak conveying airflow, excessive conveying resistance, mismatched feeder capacity, or abnormal material level detection.

Therefore, rather than simply extending the suction time or restarting the feeder, one should identify which part of the material conveying path is preventing sufficient resin from reaching the injection molding machine.

Four Common Causes of Material Shortages During Automatic Feeding

When a material shortage occurs during the automatic feeding process of an injection molding machine, the root cause can typically be attributed to one of the following four factors: the raw material source, the conveying airflow, the feeder’s actual conveying capacity, or the sensing and control logic. These factors form a complete material supply chain. If any link in this chain cannot meet the injection molding machine’s resin demand, the hopper level will gradually fall. This can eventually trigger a material shortage alarm.

During troubleshooting, inspect each stage of the material conveying path in sequence instead of checking only the feeder. The four factors below are the most common causes of unstable resin supply during continuous injection molding production.

 

Four Common Causes of Material Shortages During Automatic Feeding

Automatic Feeding Cause 1 — The Feed Source Cannot Sustain a Continuous Supply of Resin

The first cause is the simplest and should always be the primary focus of troubleshooting. The feeding machine will be unable to convey material if any of the following conditions occur:

  • The material in the hopper is nearly depleted;
  • The suction tube opening is above the resin liquid level;
  • Material bridging (clumping) occurs around the suction point;
  • The wrong suction port was selected;
  • A material changeover caused a break in the tubing connection.

Material bridging is particularly common when handling irregular recycled material, dust-laden resin, or material with poor flowability. In such cases, even though resin is visible in the container, a void may have formed around the suction tube. Consequently, the operator may see that the “hopper is full,” while the automatic feeder is actually drawing in mostly air.

A simple and effective troubleshooting step is to observe the suction point during the feeding cycle. If the material does not move immediately after suction is initiated, check the feed source first before considering changes to the controller parameters.

The Feed Source Cannot Sustain a Continuous Supply of Resin

Automatic Feeding Cause 2 — Airflow Obstructions in Filters, Hoses, or Conveying Lines

Vacuum conveying relies on airflow.

Dust buildup in a filter or a partially blocked hose can reduce airflow velocity in the conveying line. As a result, the system may fail to move enough material, even when the vacuum motor operates normally. Common causes of obstruction include the following:

  • The filter is clogged with dust;
  • Powder or fine particles accumulating inside the hose;
  • Hose collapse;
  • Material buildup at pipe elbows.

These issues are particularly common when conveying recycled or ground material, as fine particles increase the load on the filtration system.

Topstar addresses this issue in several ways. For example, the TAL series single autoloaders feature a dual-layer filtration design and are equipped with a motor reverse-rotation dust-cleaning function; the detachable autoloaders series utilizes an independent filtration system and offers an optional cyclone separator.

While these designs cannot completely eliminate the need for maintenance, they effectively reduce the problem of airflow resistance increasing over time, which leads to a decline in conveying performance.

Airflow Obstructions in Filters, Hoses, or Conveying Linesraw material source

Cause of Failure 3 — Feeder Capacity or Conveying Distance Does Not Match Production Requirements

Another common mistake is selecting a feeder based solely on the motor’s rated power, without considering the actual material conveying path.

Longer conveying distances and greater vertical heights increase resistance. In addition, every elbow, hose section, filter, hopper receiver, and pipe fitting results in pressure loss. Therefore, a feeder that performs well in short-distance, machine-side conveying scenarios may experience a significant drop in actual throughput when used to draw resin from a distant storage area.

For this reason, Topstar has differentiated its feeding machines. The TAL Series single autoloaders are primarily designed as compact units suitable for direct installation and short-distance, machine-side feeding, while the TAL Series detachable autoloaders support long-distance and high-demand conveying applications.

Consequently, recurring material shortages may indicate insufficient system capacity. This often happens after production speeds increase, larger molds are installed, or material storage is moved farther away. The same issue can occur when multiple machines share a single feeder.

Feeder Capacity or Conveying Distance Does Not Match Production Requirements

Cause of Failure 4 — Sensor or Feeding Logic Did Not Trigger at the Correct Time

The fourth cause is related to the control system.

Automatic material loaders rely on material level detection to determine when to start or stop conveying. If the sensor detects incorrectly, the feeder may start too late or mistakenly determine that the hopper is full (when it is not). Common causes include:

  • The sensing area is covered with dust;
  • Improper sensor installation;
  • Inappropriate sensitivity settings;
  • Loose wiring;
  • Material properties affecting detection;
  • Incorrect timing settings for material intake or discharge.

Therefore, when troubleshooting, operators should verify whether the actual material level matches the status displayed by the controller. If there is clearly insufficient material in the hopper but the controller still indicates sufficient material, the problem usually lies not with the conveying mechanism but with the detection process or control logic.

Sensor or Feeding Logic Did Not Trigger at the Correct Time

Troubleshooting Automatic Feeding Loaders Should Follow the Material Conveyance Path

For these four causes, troubleshooting can be conducted in the following practical sequence:

CheckWhat to InspectTypical Problem
Material sourceResin level and pickup pointEmpty source or bridging
Airflow pathFilter, hose, joints and bendsBlockage, dust or air leakage
System capacitykg/h demand and conveying distanceLoader undersized
Detection/controlSensor and suction timingLate or false loading signal

This troubleshooting sequence helps avoid unnecessary adjustments. If there is no resin at the suction point, simply changing the vacuum time will not solve the problem. Similarly, if the filter is clogged, extending the suction time will only cause the motor to run for an extended period without substantially improving material conveyance.

The Key to Reliable Automatic Feeding Lies in Matching Equipment to the Process

To avoid frequent material shortages, automatic feeding equipment must be matched to the actual molding process. Manufacturers should calculate the peak resin consumption based on the shot weight and molding cycle, and confirm that the equipment can maintain sufficient conveying capacity under actual conditions regarding conveying distance, vertical lift height, hose diameter, and piping layout.

Routine inspections are equally critical. Filters, hoses, suction tubes, seals, and sensors must be inspected regularly, especially when conveying dusty recycled material. Signs such as extended suction cycles, reduced suction volume per cycle, or abnormally high equipment operating frequency often indicate a decline in conveying performance.

When troubleshooting, it is recommended to follow this sequence:

Material source → Airflow conditions → Conveying capacity → Sensing and control systems

Compared to repeatedly restarting the equipment after a material shortage alarm, this method is generally more effective in identifying the root cause of the problem.

 

Prev: Direct Pressure vs. Toggle Clamping: Which Is Better for Large Molds?

Next: Why Does Injection Molding Cycle Time Gradually Increase During Production?

TRENDING POSTS

HOT TOPIC

Get A Quick Quote