Automatic Bottle Capping Machine with Torque Control

Small workshops and college labs that fill bottles in small batches still cap most bottles by hand. Hand capping is slow, tiring and inconsistent: one operator grips a cap harder than the next, so some bottles leak while others are so tight that threads strip or thin caps crack when opened. The Automatic Bottle Capping Machine with Torque Control answers that inconsistency with a bench-scale machine that moves each bottle into position, places a cap, and tightens it only to a set torque limit before releasing it. A conveyor carries bottles to the capping station, a sensor confirms a bottle is present, a feeder chute presents a cap, and a current-sensing drive stops the capping head as soon as motor current reaches the torque threshold. The result is a repeatable cap on every bottle in the batch, without the guesswork of hand tightening, at a scale and cost a small shop or a student team can actually build and maintain.

A bottle enters on the conveyor, a cap is placed on its mouth, the torque-limited head tightens the cap to the set limit, and the finished bottle leaves on the belt. The conveyor indexes the bottle into the capping station and the presence sensor confirms it is in position before anything moves. The feeder presents a cap over the bottle mouth, the head lowers, grips the cap and spins it down the thread while the controller watches motor current. When current reaches the torque threshold, the head stops and lifts, the conveyor indexes the bottle out, and the missing-cap check confirms a cap is present before the next bottle arrives. If no cap is detected, the machine flags the bottle and pauses so the operator can correct it. The whole cycle then repeats for each bottle without the operator touching a cap.

1. The operator loads empty bottles on the infeed end of the conveyor and fills the cap feeder with matching caps.
2. The conveyor indexes one bottle into the capping station and the optical sensor confirms a bottle is present.
3. The feeder presents a single cap above the bottle mouth and the head lowers to grip the cap.
4. The geared DC motor spins the chuck while the controller monitors motor current continuously.
5. When motor current reaches the set torque threshold, the controller stops the head and lifts it clear of the cap.
6. The conveyor indexes the finished bottle out and the missing-cap check confirms a cap is present.
7. If a bottle leaves without a cap, the fault light shows and the machine pauses for the operator to correct it.
8. The operator sets head height and torque limit again only when the bottle or cap size changes.

Tech stack:

• Aluminium extrusion frame with belt conveyor
• Geared DC motor with capping chuck
• Current sensor for torque-limit detection
• Microcontroller-based control board
• Optical bottle-presence sensor
• Gravity cap feeder chute
• 24 V DC power supply with control box
• Indicator lights and torque-setting knob

The strongest capabilities of this build are its torque-limited capping head, its indexed conveyor with bottle-presence sensing, its adjustable head height for different bottle sizes, and its missing-cap handling. The torque-limited head is the heart of the machine: instead of spinning a cap for a fixed time, the drive watches motor current and stops at the set limit, so soft and stiff caps alike finish at the same tightness. The conveyor indexes one bottle at a time into the capping station and waits for the sensor before the head moves, which keeps spacing steady and prevents dry runs. Height adjustment lets the same machine serve short and tall bottles, and the missing-cap check catches the one failure a busy operator is most likely to miss. Together these give a small-batch line that an operator can run, adjust and fault-find without specialist tooling.

• [Torque-limited capping head — implemented] A geared DC motor drives the chuck through a current sensor; the controller stops the head when motor current reaches the torque threshold set by a knob, so tightening ends at a repeatable limit rather than after a fixed time.
• [Indexed conveyor with bottle-presence sensing — implemented] The belt moves one bottle at a time into the capping station and only starts a capping cycle when the optical sensor confirms a bottle is present, which prevents empty cycles and keeps bottle spacing steady.
• [Cap feeder and placement — implemented] A gravity chute feeds caps one at a time to the placement position above the bottle mouth, so the operator only refills the feeder instead of handling every cap by hand.
• [Adjustable head height — implemented] The capping head rides on a height-adjustable mount, so the machine can be set up for short and tall bottles within its size range without rebuilding the frame.
• [Missing-cap detection and flagging — implemented] A check after the capping station flags a bottle that leaves without a cap, using an indicator light and a pause, so an uncapped bottle is caught on the line rather than in a packed box.
• [Torque setting and status indicators — implemented] A front-panel knob sets the torque limit and indicator lights show running, capping and fault states, giving the operator a clear view of what the machine is doing at a glance.
• [Reject pusher for uncapped bottles — optional] An optional side pusher can divert a flagged uncapped bottle off the line automatically, offered as an add-on for buyers who want hands-off rejection.
• [Vision-based cap inspection — future scope] A camera check for tilted or cross-threaded caps is future scope only; it is not part of the delivered build and would need its own lighting, mounting and testing work.

• Bench-scale bottle capping machine with conveyor, cap feeder and torque-limited capping head
• Control box with torque-setting knob, indicator lights and fault pause
• Calibration guide for setting torque limit and head height for a new bottle or cap size
• Operator checklist for daily start-up, feeder refill and cleaning
• Project report PDF (background, mechanism design, torque control logic, testing procedure)
• PPT presentation for final review
• Viva Q&A preparation document (torque, current sensing, indexing, cap handling)

Requirements

• A bench or table that can hold the machine footprint, plus a nearby mains power outlet for the power supply.
• Sample bottles and caps in the sizes the buyer wants to run, supplied before final calibration so torque and head height can be set on real parts.
• A clean, dry indoor workspace for assembly, calibration and demonstration runs.