What does a 12-station rotary machine buy you?
Motionwell Automation designed and built a 12-station rotary indexing assembly machine for a global medical device manufacturer. The machine assembles safety syringes and blood collection tubes at a cycle time of 15 seconds per part.
The project required integration of multiple automation technologies: servo-driven rotary indexing, vibratory bowl feeding, SCARA robotic pick-and-place, and medical-grade vision inspection. All components were designed for ISO Class 7/8 cleanroom operation.
A rotary table trades flexibility for station density. Twelve operations sit inside a footprint that a linear line would need three times the floor space to hold, and the part never changes carrier between the first station and the last, so orientation is established once. That single-carrier property is what makes per-part traceability tractable: the nest position is the part identity for the whole build. Similar constraints shape most custom special purpose machine builds in regulated manufacturing.
How is the machine built?
12-Station Rotary Indexing Table
The core of the machine is a precision rotary indexing table with 12 work stations. Each station performs a specific assembly or inspection operation:
- Component loading via vibratory bowl feeders
- Servo-driven assembly with controlled force profiles
- Multi-point vision inspection (dimensional, presence, orientation)
- OK/NG sorting with automated reject handling
- SCARA robot for final pick-and-place
Vision Inspection System
The vision inspection system meets stringent medical device quality standards with:
- Keyence vision cameras at multiple stations
- Contour recognition for dimensional verification
- Presence and orientation detection
- Automated OK/NG sorting with reject bins
- Full traceability of inspection results
The inspection routines, lighting and reject logic follow the same practice set out on our machine vision inspection capability page.
SCARA Robot Integration
A SCARA robot handles high-speed pick-and-place operations at the output station, sorting assembled products by inspection result and loading into packaging trays. The four-axis SCARA arrangement suits flat-plane pick-and-place for the reasons set out in our note on SCARA robots in electronics and device assembly.
What are the headline machine specifications?
| Parameter | Specification |
|---|---|
| Stations | 12-station rotary index |
| Cycle Time | 15 seconds/part |
| Robot | 4-axis SCARA pick-and-place |
| Vision | Keyence cameras, medical-grade |
| Cleanroom | ISO Class 7/8 compatible |
| Construction | Stainless steel, poka-yoke |
How is assembly quality proven on every part?
Servo-Driven Indexing Mechanism
The rotary indexing table uses a servo-driven cam indexer rather than a pneumatic or Geneva mechanism. The servo motor provides programmable motion profiles with controlled acceleration and deceleration, eliminating the mechanical shock of fixed-dwell indexing. Indexing repeatability is +/-0.05mm at each station position, verified during commissioning with a laser tracker measurement over 1,000 consecutive index cycles.
The servo drive enables variable dwell time at each station, allowing longer-duration operations (such as press-fit or vision inspection) without penalizing the cycle time of faster stations. Motion profiles are stored as recipes in the PLC and can be adjusted without mechanical modification.
Jig and Fixture Materials
All workholding jigs on the rotary table are machined from nylon (PA66) or POM (polyoxymethylene/acetal) engineering plastics. These materials were selected for two reasons:
- Electrical insulation: Nylon and POM prevent static discharge that could damage sensitive medical device sub-components during assembly. Surface resistivity exceeds 10^12 ohm, meeting ESD-safe handling requirements for the cleanroom environment.
- Wear resistance: POM provides excellent dimensional stability and low friction coefficient (0.2-0.35 against steel), ensuring consistent part location over hundreds of thousands of cycles without generating particulate contamination that would compromise cleanroom air quality.
Jig contact surfaces are precision-machined to +/-0.02mm tolerance with polished finishes to prevent marking or scratching product surfaces.
Pneumatic Press-Fit with Force Monitoring
The assembly stations that perform component insertion use pneumatic press-fit actuators with integrated force monitoring. Each press cylinder is equipped with a strain-gauge load cell that measures insertion force in real-time throughout the press stroke. The PLC records the complete force-displacement curve for every assembly cycle.
The system implements closed-loop feedback control: if the measured insertion force exceeds or falls below the programmed tolerance window at any point during the stroke, the press immediately halts and the part is flagged for rejection. This catches conditions such as misaligned components (force too high), missing components (force too low), or damaged parts (irregular force profile). Force data is logged per serial number for full traceability.
Vision System Lighting
The Keyence vision inspection stations use dome lighting (diffuse hemispherical illumination) rather than ring lights or bar lights. Dome lighting creates uniform, shadow-free illumination across the entire inspection field of view. This is critical for medical device inspection where:
- Component edges must be measured without shadow-induced dimensional errors
- Surface defects (scratches, contamination, flash) must be detected uniformly regardless of their angular orientation on the part
- Translucent or reflective medical-grade materials (polycarbonate, stainless steel) would create specular highlights under directional lighting that interfere with contour recognition algorithms
The dome lights use white LED arrays with diffuser panels, providing consistent color temperature (6500K) for repeatable color-based inspection criteria.
Validation Documentation
Motionwell delivers the machine with a complete IQ/OQ/PQ (Installation Qualification, Operational Qualification, Performance Qualification) validation documentation package. The IQ verifies that the machine is installed per the design specification, including utility connections, safety system wiring, and software version control. The OQ confirms that each station operates within specified parameters under worst-case conditions. The PQ demonstrates sustained production capability over a minimum of three consecutive production runs.
All validation protocols are prepared in compliance with GAMP 5 guidelines for automated systems in regulated manufacturing. The documentation package includes test protocols, executed test records, deviation reports, and a final validation summary report suitable for regulatory audit. The protocol structure and the split between supplier and customer responsibilities are described on our computer system validation capability page.
Where the customer needs the force curves and inspection results to land in a controlled record rather than a CSV folder, the machine data can be routed into an electronic device history record system.
Constraints and trade-offs
A servo cam indexer rather than a Geneva or pneumatic index. Mechanical indexing is cheaper, needs no tuning and cannot lose position. It was rejected because a fixed-dwell mechanism forces every station to live inside the same dwell window, which means the press-fit and vision stations set the pace for all twelve. The servo drive lets each station keep the dwell it actually needs. The cost is a motion-profile recipe layer that has to be version-controlled and re-qualified when it changes, which is not free in a validated environment.
Rejecting on the force-displacement curve rather than on downstream vision alone. A camera at the end of the table would catch most of the same defects with one sensor instead of a load cell at every press station. The force window was chosen because it localises the fault: force too high means misalignment, too low means a missing component, an irregular profile means a damaged part – and all three are attributed to the station that caused them. What you pay for is a load cell per press station and a full curve stored per cycle per serial number, which is a meaningful data volume over a production year.
POM and nylon nests rather than aluminium. Metal locates better and machines to tighter tolerance. Engineering plastics were chosen because a nest in a Class 7/8 room must not shed conductive particles, and static discharge from a metal nest can damage sub-components during handling. The trade-off is creep under sustained clamping load, so nests are treated as wear parts with a planned replacement interval rather than as permanent tooling.
Dome lighting rather than ring or bar lights. Dome heads are bulky and occupy vertical space directly above the inspection station, which constrains how a gripper can approach that station. They were still chosen because translucent polycarbonate and polished stainless both throw specular highlights under directional light, and a highlight sitting on a contour edge is indistinguishable from a real dimensional deviation to the measurement algorithm.
The machine is built around one product family. Twelve stations tuned to a syringe geometry are not re-taskable to an unrelated device by recipe alone; that would mean new nests, new feeders and re-qualification.
Related work
This project demonstrates Motionwell’s custom machine design and inspection work for the medical device industry, and the same disciplines carry into pharmaceutical packaging lines. Cleanroom construction detail is covered in our cleanroom automation guide, and broader direction of travel in medical device automation trends.
If you are specifying an assembly machine and need the validation package scoped alongside the mechanics, send us the device drawing and the target cycle time.