An automatic capsule filling machine works by indexing hard capsules through eight sequential stations on an intermittent-motion turntable: (1) capsule feeding & orientation, (2) vacuum separation of cap and body, (3) powder dosing via tamping pins, (4) pellet/granule filling, (5) defective capsule rejection, (6) capsule closing, (7) finished capsule ejection, and (8) bore cleaning. On a machine like the HIJ NJP-1200C, this complete cycle repeats fast enough to produce 54,000–72,000 finished capsules per hour with a dosage difference of ≤±3%.
Key Takeaways
- The entire fill cycle happens in one turntable revolution — every bore visits all eight stations in identical sequence, which is why fill weight stays consistent.
- Dosing accuracy is created at Station 3: five tamping stages progressively compress powder into a uniform slug inside the hole plate before it enters the capsule.
- Vacuum separation at −0.02 to −0.06 MPa is the most common failure point in daily operation — capsule quality and humidity control matter as much as the machine.
- Unseparated capsules are rejected before dosing, so no API is wasted on scrap capsules.
- A downstream sorting polisher removes dust and automatically ejects low-weight, empty, and damaged capsules to complete the quality loop.
If you already know what an automatic capsule filling machine is, this guide goes one level deeper: exactly what happens inside the machine, station by station, and which parameters at each station decide whether your batches pass uniformity testing. All numbers below are the verified factory parameters of the HIJ NJP-1200C automatic capsule filling machine, an intermittent-motion, hole-plate (tamping-pin) filler in the 1,200-capsules-per-minute class.
The Machine Layout: One Turntable, Eight Stations
Picture a circular turntable carrying segment bores — paired upper (cap) and lower (body) segments machined to your capsule size. A precision intermittent graduator rotates the table in fixed steps: index, stop, work, index again. During every stop, all eight stations act simultaneously on whichever bores sit in front of them. One full revolution equals one complete capsule life cycle, and because the graduator indexes each bore to exactly the same position every time, every capsule experiences identical mechanics.
The 8-Station Cycle, Step by Step
1Capsule Feeding & Orientation
Empty capsules drop from the hopper (or an optional vacuum capsule feeder on high-volume lines) into a magazine that rectifies them body-down, cap-up using the diameter difference between the two halves. Correctly oriented capsules slide into the segment bores. Poorly stored capsules — too dry, too humid, or deformed — start failing here, which is why the machine’s specified working environment is 21 °C ± 3 °C at 40–55% relative humidity.
2Vacuum Separation
A vacuum manifold beneath the lower segment pulls at −0.02 to −0.06 MPa, drawing the capsule body down into the lower segment while the cap is retained above by its larger diameter. The two halves are now physically separated, exposing the open body for dosing. This is the most sensitive station in daily production: worn segment bores, weak vacuum, or low-quality capsules with inconsistent lock rings all show up here first.
3Powder Dosing — The Tamping-Pin Station
The accuracy-critical heart of the machine. A rotating dosing disc (hole plate) sits inside the powder hopper; as it turns, its bores pass under five successive tamping pins, each compressing a little more powder into the bore until a uniform slug is formed. At the transfer position, a pushrod ejects the finished slug directly into the waiting capsule body. Slug density — controlled by tamping pressure, powder bed height, and disc thickness — is what holds the NJP-1200C at ≤±3% dosage difference for fills above 300 mg with 40–80 mesh granulation.
4Pellet / Granule Filling (Auxiliary)
Machines configured for combination products carry a second dosing unit here, volumetrically dispensing enteric-coated pellets or sustained-release granules on top of (or instead of) the powder slug. The NJP-1200C supports granule + powder mixed filling in the same capsule — the standard architecture for two-phase release formulations.
5Defective Capsule Rejection
Any capsule that failed to separate at Station 2 still has its cap seated — so its bore never received powder. A mechanical ejector removes these unopened capsules into a reject container before closing. Because rejection happens ahead of dosing transfer, no API is lost on scrap capsules, protecting yield on expensive formulations.
6Capsule Closing
The upper segment aligns the cap over the filled body, and closing pins press the two halves together to the capsule’s specified closed (locked) length, engaging the lock rings. Too little pressure and capsules pop open in the polisher or blister feeder; too much and they dent or telescope. Closing pressure is set per capsule brand and size during changeover.
7Finished Capsule Ejection
Ejection pins push the closed capsules out of the segments onto the discharge chute. On integrated lines, the chute feeds straight into a capsule sorting polisher rather than a collection bin.
8Bore Cleaning
Compressed air blasts residual powder out of the empty segment bores while the 2.2 kW dust collector (210 m³/h) captures it at the source. Clean bores prevent cross-cycle weight drift and capsule jamming — a key reason the machine sustains a ≥99.5% capsule qualification rate over long runs.
Watch the Full Cycle Run
After Filling: Polishing & Automatic Sorting
Filled capsules leave the machine carrying a fine dust layer that would smear blister film and fail visual inspection. A capsule sorting polisher (such as the JFP-110A that pairs with the NJP-1200C) solves this in one pass: capsules travel through a rotating sieve-net cylinder where a spiral brush polishes and de-dusts the surface, a vacuum recovers the removed powder, and a clean compressed-air gate automatically ejects low-weight, empty, damaged, and loose-piece capsules before the good product exits. With 300,000 capsules/hour polishing capacity, one polisher never bottlenecks the filler.
The Five Parameters That Control Fill Weight
| Parameter | What it controls | Typical adjustment |
|---|---|---|
| Powder bed height | How much powder is available above the dosing disc | Hopper level sensor + auger feed rate |
| Tamping pin pressure (×5) | Slug density and final weight | Spring pre-load per tamping stage |
| Dosing disc thickness | Maximum slug volume | Selected at changeover for target fill weight |
| Machine speed | Dwell time at each tamping stage | Frequency conversion / PLC recipe |
| Powder properties | Flow into bores and slug cohesion | Granulation (40–80 mesh ideal), moisture, lubricant level |
Notice that only four of the five are machine settings — the fifth is your formulation. This is why an honest manufacturer always asks about your powder before promising an accuracy number, and why choosing the correct capsule size for your dose matters; the capsule filling machine size selection guide walks through that calculation.
Forester Xiang
Founder & Chief Engineer, HIJ Machinery · 20+ years · 100+ facility audits across 30+ countries
“When a line suddenly starts producing weight variation, operators instinctively blame Station 3 and start turning tamping screws. In my experience the real culprit is upstream more than half the time: separation, not dosing. A capsule that separates late or crooked receives a partial slug, and the weight scatter looks exactly like a dosing problem. My rule on any audit: before touching the tamping pins, check vacuum degree, inspect segment bore wear, and run a hundred capsules from a fresh box. If the scatter disappears with new capsules, your machine was never the problem.”
Frequently Asked Questions
How does an automatic capsule filling machine separate the cap from the body?
A vacuum manifold under the lower segment pulls at −0.02 to −0.06 MPa, drawing the capsule body down into the lower segment bore while the cap is held back by its larger diameter. The two halves separate cleanly, leaving the open body exposed for dosing. Capsules that fail to separate are detected and mechanically rejected before any powder is dosed.
How do tamping pins control capsule fill weight?
A rotating dosing disc passes its bores under five successive tamping pins, each compressing additional powder into the bore until a uniform slug forms. Slug density — set by tamping pressure, powder bed height, and disc thickness — determines the final fill weight, which is how machines like the NJP-1200C hold a dosage difference of ≤±3% on fills above 300 mg with 40–80 mesh granulation.
What happens to capsules that fail to open in the machine?
Unopened capsules keep their caps seated, so their bores never receive powder. A dedicated rejection station ejects them into a scrap container before the closing station, which means defective capsules waste no API — only the empty capsule itself is lost.
Why do filled capsules need polishing after the filling machine?
Filling leaves a fine powder dust on the capsule surface that would smear blister film, interfere with printing, and fail visual inspection. A sorting polisher brushes and de-dusts each capsule inside a rotating sieve cylinder, recovers the removed powder by vacuum, and automatically ejects low-weight, empty, damaged, and loose-piece capsules before the good product moves to packaging.
How fast does one filling cycle run?
On an intermittent-motion machine in the 1,200-capsules-per-minute class, the turntable indexes many bores through all eight stations simultaneously, producing 54,000 to 72,000 finished capsules per hour. Each individual capsule spends only a few seconds traveling from orientation to ejection.
About HIJ Machinery
HIJ Machinery (legal name: Wenzhou Trustar Machinery Technology Co., Ltd) is a pharmaceutical and packaging machinery manufacturer founded in 2004, headquartered in Rui’an, Wenzhou, Zhejiang, China. HIJ designs and builds capsule filling machines, blister packing machines, and complete turnkey packaging lines exported to 30+ countries. This article was reviewed by Forester Xiang, Founder & Chief Engineer, drawing on 20+ years of packaging machinery engineering and 100+ pharmaceutical facility audits across 30+ countries. HIJ equipment is CE-marked, manufactured to ISO 9001 standard, and follows a cGMP-ready design philosophy.
See the 8-Station Cycle Run On Your Product
Send us your formulation details — we’ll run a filling test on the NJP-1200C, film it, and send you the weight-variation data along with a complete FOB quotation.
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