6-Axis Robotic Insert Molding Automation for Precision Gears: Ming-Li’s Latest Case Study

At Ming-Li Precision, automation is more than moving parts from one station to another. Our latest precision gear insert molding automation project combines a six-axis industrial robot, an automatic insert feeding system, custom-engineered precision fixtures, and positioning verification to support consistent, repeatable insert placement during plastic injection molding.

Developed around the specific requirements of a precision gear application, the integrated system demonstrates how robotic handling, mold engineering, and process control can work together to reduce manual intervention and improve manufacturing consistency. Behind the robot is what Ming-Li has done since 1983: in-house precision mold engineering and precision injection molding, with more than 5,000 precision molds built, including over 1,000 insert molding molds.

Project at a Glance

Application	Precision plastic gears with molded-in inserts
Process	Insert injection molding
Robot	Six-axis industrial robot with purpose-designed gripper
Insert Feeding	Automatic vibratory feeding system
Fixturing	Custom-engineered precision fixtures
Quality Control	Automated positioning and placement verification
Insert Mold	Precision insert mold designed and built in-house by Ming-Li
Quality System	IATF 16949 certified

Watch the Automated Precision Gear Insert Molding Process

See the automatic feeding, robotic pick-and-place movements, fixture alignment, and mold-loading sequence in our latest factory video.

▶ Watch the video on YouTube

How Our Six-Axis Robotic Insert Molding System Works

1. Automatic Insert Feeding

A vibratory feeding system organizes and delivers individual inserts to the pick-up position. Controlled feeding establishes a repeatable starting point for the robotic loading sequence and reduces the need for manual insert handling.

2. Six-Axis Robot Pick-Up and Transfer

A six-axis robot uses a purpose-designed end-of-arm gripper to pick up inserts and transfer them between stations. Its multi-axis motion provides flexibility when approaching components, navigating the work envelope, and accessing the injection mold.

3. Precision Fixtures and Insert Alignment

Custom precision fixtures support consistent insert orientation and placement. Fixture geometry and gripper design are developed together to help maintain alignment before the insert reaches the mold cavity.

4. Precision Positioning and Placement Verification

Positioning checks are incorporated into the automated sequence to verify that inserts are correctly presented or located at the relevant station. These checks help reduce the risk of incorrect placement before the molding cycle proceeds. The inspection method is selected according to each part’s geometry and quality requirements.

5. Robotic Mold Loading and Insert Injection Molding

With the mold open, the robot transfers the insert into the designated mold position. The robotic sequence, tooling, and injection molding equipment are coordinated so that the insert can be held in place for the molding operation. Molten engineering plastic is then formed around the insert according to the approved mold and part design.

6. Repeatable Automated Production Cycle

After the molding sequence, the robot and feeding system prepare for the next cycle. By combining feeding, handling, fixture positioning, and molding into a coordinated process, the system is designed to support repeatable production with less manual handling.

The Foundation: Precision Insert Molds Built In-House

Robotic automation can only be as consistent as the mold it loads. For this project, the insert mold, the molding process, and the automation cell were engineered together by one team, so insert locating features, cavity accuracy, and robot motion all work to the same tolerance targets.

Since 1983Precision mold making

5,000+Precision molds built

1,000+Insert molding molds

±1 μmUltra-precision machining

Insert Mold Design for Robotic Loading

Our mold engineers design insert locating pockets, retention features, shut-off surfaces, and gripper clearance specifically for robotic loading. Getting these details right in the tool is what allows a robot to place an insert the same way every cycle, without flash, insert movement, or damage during mold closing and injection.

Ultra-Precision Tooling Manufacturing

Gear cavities and insert seats are machined in-house on YASDA ultra-precision machining centers with ±1 μm capability, together with GF AgieCharmilles EDM and wire-cut equipment. Keeping 100% of tooling in-house gives us direct control over cavity accuracy, faster mold trials, and quicker tooling adjustments.

Gear Molding Process Engineering

Engineering plastics such as POM, PA66, PPS, and PEEK shrink unevenly across tooth thickness, root, and hub. Ming-Li applies DFM review, Moldflow analysis, and tooth profile shrinkage compensation in the mold to achieve accurate molded involute geometry and stable backlash, with typical gear tolerances of ±0.01 mm and down to ±0.005 mm for micro gears.

Gear Metrology and Validation

Molded gears are validated with double-flank gear rolling tests and dimensional inspection supported by our metrology and CT capabilities. Process capability is monitored to a CPK target of ≥1.33 for high-volume production under our IATF 16949 quality system.

Learn more about our insert molding mold and overmolding tooling and precision gear mold engineering.

Why Automation Matters in Precision Gear Insert Molding

Precision gear components can be sensitive to insert position, molded geometry, and assembly consistency. Even small variations in insert alignment may affect the finished component’s fit or performance. For this reason, automated insert molding for precision gears requires more than a robot: it requires precise tooling, reliable part presentation, stable gripping, and a verified loading process.

• Consistent insert orientation: automatic feeding and dedicated fixtures reduce variation during handling.
• Repeatable robotic mold loading: programmed six-axis motion supports precise and consistent insert transfer.
• Reduced manual intervention: integrated automation helps limit operator-dependent handling steps.
• Process reliability: positioning verification helps identify incorrect insert presentation or placement before proceeding.
• Scalable manufacturing approach: customized automation can be developed around production volume, part geometry, and quality requirements.

One Engineering Team: Precision Tooling, Gear Molding, and Custom Automation

Ming-Li Precision brings together in-house precision mold engineering, plastic injection molding, insert molding, and custom automation. This integrated approach enables our teams to consider mold access, insert retention, gripper clearance, fixture tolerances, and inspection requirements early in the project.

We work with customers on applications where precision plastic gears, metal inserts, and other engineered components must be manufactured consistently. As an IATF 16949-certified manufacturer in Taiwan, Ming-Li also supports automotive-oriented quality systems and structured process development.

Learn more about our custom automation solutions and precision plastic gear molding capabilities.

Frequently Asked Questions

What is robotic insert molding?

Robotic insert molding uses an industrial robot to place metal or plastic inserts into an injection mold before plastic is injected around them. Automating this step replaces manual insert loading and supports more consistent insert positioning from cycle to cycle.

Why does mold design matter in automated insert molding?

The mold determines whether an insert can be located, held, and overmolded the same way every cycle. Precise insert pockets, retention features, and shut-off design prevent flash and insert movement, while accurate cavities and shrinkage compensation keep gear geometry within tolerance. That is why Ming-Li designs and builds the insert mold in-house alongside the automation.

Why use a six-axis robot instead of manual insert loading?

A six-axis robot can approach the mold and fixtures from multiple angles and repeat the same programmed motion every cycle. This helps reduce operator-dependent variation, limits manual handling near the mold, and supports stable, repeatable production.

Which parts are suitable for automated insert molding?

Automated insert molding is commonly considered for precision plastic gears and other components with molded-in metal inserts, such as shafts, bushings, or threaded inserts, especially where insert orientation and repeatability are critical.

What information do you need to evaluate an automation project?

Please share your 2D/3D drawings, insert specifications, material requirements, expected annual volume, and automation objectives. Our engineering team will review the part, mold, and process together to recommend a suitable approach.