CHM-SGT Double Rotary Sheeter FAQ

When selecting or using a double rotary sheeter, customers often have many questions: How is it different from a single rotary sheeter? What paper can it cut? How many rolls can be unwound? Is maintenance difficult? This article compiles the top 10 questions customers ask about the CHM-SGT double rotary sheeter (SGT-1400/1500/1700), covering working principle, selection, operation, and maintenance, to help you quickly determine whether this machine is suitable for your factory.

1. What is a double rotary sheeter? How is it different from a single rotary sheeter?

A double rotary sheeter uses a synchronized rotary shear cutting principle. The upper and lower knife cylinders rotate synchronously in opposite directions, and the helical blades form a moving shear contact point, cutting the paper progressively like scissors. A single rotary sheeter uses impact cutting, with the upper knife rotating and the lower knife fixed, breaking fibers by impact force.

Core difference: Double rotary is "shearing," producing clean cuts with minimal paper dust; single rotary is "chopping," which can cause edge chipping, burrs, and paper dust on thick paper. Double rotary is suitable for thick cardboard and high-GSM paper, while single rotary is suitable for thin paper, small batches, and multi-specification production.

2. What paper can a double rotary sheeter cut? What is the GSM range?

Standard range is 200–1000 gsm, suitable for white cardboard, grey back duplex board, kraft paper, gold and silver foil paper, aluminum foil laminated paper, and other high-GSM rigid papers. For cardboard above 250 gsm, single-roll production is recommended. For paper below 120 gsm, use with caution due to high risk of crushing.

3. Does a double rotary sheeter really produce very little paper dust? Can the sheets go directly to the printing press?

Yes. Double rotary uses pure shearing, producing clean cuts with minimal paper dust. The finished sheets can go directly to the printing press without secondary trimming. This is one of the biggest advantages of double rotary over single rotary, especially for packaging paper and gold/silver foil paper that require high printing quality.

4. How many rolls can a double rotary sheeter cut simultaneously? Is there a limit on the number of unwinding rolls?

High-GSM cardboard can only be produced as a single roll. Some medium and low GSM paper can be cut with 2 rolls simultaneously. For above 250 gsm, single roll is mandatory. The number of unwinding rolls is limited by four factors: roll weight load, centrifugal force effect, tension synchronization, and edge guiding load. The lower the GSM and the softer the material, the more rolls can be unwound. The higher the GSM and the stiffer the paper, the fewer rolls can be unwound.

5. How many layers of edge guiding does a double rotary sheeter need?

Standard configuration is 2 layers; optional 3 layers. The edge guiding system controls lateral paper position accuracy. During multi-roll cutting, it prevents each roll from drifting and ensures edge alignment. Insufficient layers can cause drifting, tower-shaped rewinding, and dimensional errors.

6. How to select knives? Can tungsten carbide knives be used?

Tungsten carbide has high hardness but high brittleness, and is prone to chipping when encountering sand or hard objects in paper. For thick paper, alloy steel rotary knives are preferred. Knife clearance is recommended at 0.01–0.03 mm, about 1/7–1/10 of a hair thickness. Knife adjustment sequence: first adjust for thick paper to ensure cut-through, then switch to thin paper and fine-tune repeatedly 2–3 times. Knife adjustment quality directly determines knife life.

7. Is the investment cost of a double rotary sheeter high? Is changeover troublesome?

The purchase cost of a double rotary sheeter is higher than a single rotary sheeter, debugging is relatively complex, and changeover time is longer. These are its main disadvantages. However, for thick materials, large batches, and high-precision high-end paper production, the efficiency and quality advantages of double rotary can quickly recover the investment. If your orders are mainly thin paper, small batches, and multiple specifications, a single rotary sheeter is recommended.

8. What daily maintenance does a double rotary sheeter require?

Daily maintenance: clean knife set, guide rollers, and delivery table; check air pressure and hydraulic pressure; apply lithium grease to exposed bearings; visually inspect knives and belts. Weekly maintenance: adjust belt tension; apply gear oil to chains; drain water from air treatment unit; clean electrical cabinet dust; test tension and brakes. Monthly maintenance: clean oil tank filter; clean and calibrate sensors; calibrate knife clearance. Quarterly maintenance (engineer on-site): disassemble and inspect aluminum roller bearing wear; test solenoid valve and proportional valve sealing; back up PLC and inverter parameters. Annual overhaul (engineer on-site): full disassembly and inspection of mechanical transmission, hydraulic, electrical, knife slitting, edge guiding and anti-curl conveying systems, and overall precision acceptance.

9. Is my factory suitable for a double rotary sheeter? How to choose?

Selection formula: For thin paper, small batches, multiple specifications, and limited budget, choose single rotary; for thick paper, large batches, high precision, and high-end paper, choose double rotary.

If your factory mainly processes white cardboard, grey back duplex board, kraft paper, gold and silver foil paper, and other paper above 200 gsm, with large order batches and high requirements for cut quality, double rotary is a more suitable choice. If you mainly process offset paper, writing paper, thin paper, and other 50–120 gsm thin paper, single rotary is more cost-effective.

For more technical details or selection advice, please contact Ms. Ada.