Paper folding machines and mini-offset presses both feed sheets with vacuum suckers and separate them with blow air — so they want the same thing a full offset press wants: a combined vacuum-and-pressure pump, just in a smaller size. For most folders and mini-offset machines the belt-driven YELVD / YELV pumps at the 0.5–2 HP end of the range are the right fit, delivering 600 mmHg vacuum and 10 psi blow from one compact unit.
Same air functions, smaller scale
A folding machine or mini-offset press uses air exactly as the sheet-fed press in our printing industry guide does:
- Blow air fans the top of the pile so sheets separate cleanly and only one lifts.
- Vacuum at the sucker head lifts and forwards that single sheet into the folding rollers or the printing nip.
- Vacuum hold-down (on many feed tables) keeps the sheet flat and registered.
The functions are identical; the demand is lower because the sheets and speeds are smaller. That's why these machines don't need the 3–5 HP pumps a large press uses — an oversized pump here just wastes energy and money.
The three variables that set the size
1. Sheet weight (GSM)
Heavier stock needs more grip to lift, and separates less easily, so it leans on both vacuum and blow harder. A folder running light 60–80 GSM text needs less than one folding 150 GSM cover. Size for the heaviest stock the machine will regularly run.
2. Fold count / machine complexity
A simple single-fold machine has one feed and one grip. A multi-fold or cross-fold machine cycles more air functions and handles the sheet more times, raising demand. More folds → more pump.
3. Feed speed
Faster sheet-per-hour rates cycle the suckers and blow more often, turning intermittent demand into a higher continuous flow. Size for the top speed the machine will run, not its average.
| Variable | Effect on pump size |
|---|---|
| Heavier GSM | ↑ vacuum grip and blow separation |
| More folds | ↑ air functions per sheet |
| Higher feed speed | ↑ continuous flow demand |
The right pumps: YELVD / YELV small frames
| Model | Power | Displacement | Vacuum | Pressure | Weight |
|---|---|---|---|---|---|
| YELVD-134 | 0.5 HP | 8 m³/hr (134 LPM) | 600 mmHg | 10 psi | 13 kg |
| YELVD-300 | 1.0 HP | 18 m³/hr (300 LPM) | 600 mmHg | 10 psi | 20 kg |
| YELV-300 | 1.0 HP | 18 m³/hr (300 LPM) | 600 mmHg | 10 psi | 43 kg |
| YELV-500 | 2.0 HP | 30 m³/hr (500 LPM) | 600 mmHg | 10 psi | 75 kg |
The compact YELVD-134 and YELVD-300 — light at 13 and 20 kg — suit desk-scale folders and small mini-offset units where floor space and portability matter. Step up to the heavier-built YELV-300 or YELV-500 for continuous three-shift folding or heavier stock, where the sturdier frame earns its weight in service life.
The 600 mmHg vacuum (about 213 mbar absolute) and 10 psi blow are deliberately moderate — a folder needs reliable grip and separation at speed, not deep vacuum. If those units are unfamiliar, the rotary vane basics and unit explanations there will help.
Quick match
| Machine | Suggested pump |
|---|---|
| Desk / tabletop folder | YELVD-134 (0.5 HP) |
| Standard folder / small mini-offset | YELVD-300 (1 HP) |
| Heavy-duty / continuous folder | YELV-300 or YELV-500 |
Sizing method
- Start from the machine's air spec if the builder gives one — always the best baseline.
- Size for heaviest stock and top speed, not typical running — the pump must cope with the worst case without stalling the feed.
- Leave headroom. A folder pump loafing at 70–80% is quieter and lasts longer than one at its limit. Under-sizing shows up as misfeeds and doubles at speed — the classic symptom of a starved feeder.
- Match the pressure need. The blow side is often the binding constraint; confirm the pump delivers the separation air the machine wants.
The full flow-and-vacuum sizing logic, including why you don't size on the free-air number, is in choosing a vacuum pump by CFM and vacuum level.
Where a plain pump fits instead
If the job is a sealed vacuum hold-down table — plate-making, small die-cutting, a screen-print bed — rather than a sheet feeder, you want steady deep vacuum, not vacuum-plus-blow. There a straight ACME high-vacuum pump holds the bed firmer. And for a clean-room or food-carton folder where oil must stay out of the air, the oil-free YBDVP dry pumps are the alternative. Match the pump to the job: feeder → YELV; sealed table → ACME; clean air → YBDVP.
Diagnosing feed faults from the pump side
When a folder or mini-offset misfeeds, the fault is often at the pump or its plumbing, and the symptom points to the cause.
| Symptom | Likely pump-side cause |
|---|---|
| Doubles / sheets sticking together | Weak blow (separation) air — pressure side short or leaking |
| Missed sheets / weak grip | Weak vacuum — sucker leak, clogged filter, or undersized pump |
| Misfeeds only at top speed | Pump at its limit — no headroom for the fast cycle |
| Gradual worsening over weeks | Loading inlet filter, tired oil, or worn vanes |
Notice the split: blow faults cause doubles, vacuum faults cause misses. Before blaming the machine's suckers, check the pump's reserves — a folder that fed cleanly for years and now doubles at speed usually has a fading blow side or a starved pump, not a mechanical fault in the feeder.
Sizing for stock changes
Folders rarely run one stock forever. A shop that switches between light text and heavy cover should size the pump for the heaviest, most stubborn stock it handles, so the same machine feeds card as reliably as it feeds bond. Under-sizing to the average stock guarantees misfeeds the day a heavy job arrives — and a print shop's heavy jobs are usually its most profitable, so the pump should never be the reason you turn one down. The small step up from a YELVD-300 to a YELV-500 is cheap insurance against exactly that.
Keeping a folder pump healthy
- Filter the inlet — paper lint and anti-set-off powder score vanes fast in a print shop.
- Keep it ventilated and level — belt-driven pumps like an easy, cool life.
- Hold the service intervals — oil changes on oil-sealed units and vane checks keep grip and separation crisp.
Folding sits in the same pull-print-pack workflow as the rest of the print shop — see the printing and packaging applications page.
Summary
Paper folders and mini-offset presses need the same vacuum-and-blow a big press does, in a smaller size, so the compact belt-driven YELVD / YELV pumps at 0.5–2 HP are the natural fit. Size on the heaviest stock and top feed speed with headroom — under-sizing shows up as misfeeds and doubles. Reach for an ACME high-vacuum pump instead when the job is a sealed hold-down table, or oil-free YBDVP when the air must stay clean.
Tell us your folder or mini-offset make, stock weight and speed and we'll size the pump. WhatsApp +91 9311693322 or email sales@yashblowers.org.