Choosing a filling machine starts with one question: what is your product? Not “what machine is cheapest” or “what has the most features” — the product’s physical properties determine which filling principle will work, which will struggle, and which will fail.
Match the Filling Principle to Your Product
| Product type | Viscosity (cP) | Best filling principle | Why |
|---|---|---|---|
| Water, juice, solvents | 1–100 | Gravity or overflow | Flows freely, consistent fill level or volume |
| Milk, wine, oil | 100–500 | Gravity, overflow, or timed-flow | Still free-flowing but may foam |
| Shampoo, honey, syrup | 500–5,000 | Piston or gear pump | Needs positive displacement to move |
| Sauce, paste, gel | 5,000–100,000 | Piston with agitator hopper | Thick, may contain particles |
| Cream, ointment | 50,000–500,000 | Piston with heated hopper | Very thick, may solidify at room temp |
| Flour, protein powder | N/A | Auger (screw) | Powder flows by mechanical screw |
| Coffee grounds, tea | N/A | Auger or cup filler | Irregular granules, needs gentle handling |
| Tablets, capsules | N/A | Counting or disc filler | Solid discrete units, not bulk flow |
Gravity Fillers: Simple and Fast for Thin Liquids
Gravity fillers rely on product weight to flow from an elevated tank through nozzles into containers. They are the simplest and cheapest option for thin, free-flowing liquids — water, thin oils, solvents.
Choose gravity when:
- Product viscosity is below 500 cP
- You need high speed on a budget
- Product does not foam
- Fill-level accuracy (not volume) is acceptable
Avoid gravity when:
- Product is viscous (it will not flow fast enough)
- Product contains particles (nozzles will clog)
- You need strict volume accuracy across viscosity changes
Overflow Fillers: Consistent Shelf Appearance
Overflow fillers fill until liquid reaches a return tube level, then the excess flows back to the tank. Every bottle has an identical fill height — critical for transparent bottles where consumers judge fill by what they see.
Choose overflow when:
- You fill clear bottles (bottled water, wine, perfume, glass cleaners)
- Visual shelf consistency matters more than exact volume
- Product is thin and may foam (the return flow dissipates foam)
Trade-off: volume accuracy is ±1–3% (less strict than piston), and some product is recirculated.
Piston Fillers: The Workhorse for Thick Products
Piston fillers draw a precise volume into a cylinder (the piston chamber) and discharge it into the container. They handle products from 500 to 500,000 cP — everything gravity cannot move effectively.
Choose piston when:
- Product is viscous (sauce, paste, cream, honey)
- Product contains soft particles (fruit pieces, vegetable chunks)
- You need volume accuracy of ±0.5–1%
- Your fill volume may change between batches
Watch for: particle size vs nozzle diameter (chunks must pass through the piston valve), and product that sets or hardens (heated hoppers and quick-clean pistons are available).
Auger Fillers: For Powders and Granules
Auger fillers use a rotating screw to meter powder from a hopper into containers. An agitator above the screw keeps powder flowing. Fill weights range from 1g to 5kg.
Choose auger when:
- Product is a powder or fine granule
- You need consistent weight dosing
- Product is not free-flowing (auger forces it out)
Key variables: auger diameter and pitch (determines dose per revolution), agitator speed (prevents bridging in the hopper), and container vibration (settles powder for consistent fill weight).
Accuracy: What to Actually Expect
| Filler type | Typical accuracy | Notes |
|---|---|---|
| Gravity | ±1–5% | Varies with viscosity changes |
| Overflow | ±1–3% (volume), ±1mm (level) | Level accuracy is the selling point |
| Piston | ±0.5–1% | Most accurate for thick products |
| Auger | ±0.5–2% | Depends on powder flowability |
| Net-weigh | ±0.1–0.5% | Highest accuracy but slower |
Next Step: Get a Product Test
Before ordering any filling machine, send your product sample to the factory and request a video of your product being filled on their machine. This one step eliminates most bad matches: it reveals clogging, foaming, dripping, and accuracy problems that spec sheets hide.
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