Cement Bag Making Machine: Specifying a Valve Bag Line

A cement bag making machine is the machine that cuts woven fabric to bag length, sews the bottom and folds the filling mouth of a valve bag in one pass. Yanfeng Group Co., Ltd. builds one model for this job, the YF-HKZ-600, and it is the whole of our cement bag making machine category. The important thing about specifying it is that it is the narrowest machine in a woven bag plant: its fabric roll width of 350 to 550 mm sets the weaving width, the coating width and the printing width of everything upstream of it. This guide works the line backwards from that number, with the catalogue figures for each stage.

Key definitions

• Valve bag: a bag closed at both ends and filled through a folded mouth, the valve. It is the standard sack for cement and other building materials, and it needs mouth folding as well as cutting and sewing.
• Fabric roll width: the width of the woven tube as it comes off the loom, flattened. On a valve bag line this equals the finished bag width.
• Cutting length: the length the machine cuts each bag to, which becomes the finished bag length.
• Folding width: how far the bottom edge is turned over before it is stitched, in millimetres.
• Stitch: the distance between needle penetrations along the hem, in millimetres.
• Folding width of weaving: the loom's term for lay-flat width, the range of tube widths a given loom can weave.
• Coating: a thin molten PP or PE film pressed onto the fabric to make the sack moisture-proof.

The YF-HKZ-600 in full

Every figure below is the catalogue table for the valve bag cutting, sewing and mouth folding machine.

Parameter	YF-HKZ-600
Width of fabric roll	350-550 mm
Cutting length	500-900 mm
Folding width	15-30 mm
Stitch	7-12 mm
Production capacity	25-30 pcs/min
Gross power	10 kW
Weight	5000 kg
Installing dimensions (L x W x H)	6000 x 10000 x 1500 mm

The machine is CE certified in our catalogue. Two numbers deserve a second look before you plan a building around it. The first is the 10,000 mm dimension: this is a longer machine than any other in our bag-making range, because cutting, bottom sewing and mouth folding happen in series. The second is the 500-900 mm cutting length, which is narrower at both ends than the 600-1200 mm of an ordinary cutting and sewing machine. A valve bag line is built for one bag format, not for a general sack plant; if you also make open-mouth sacks, the comparison in our bag cutting and sewing machines round-up covers the machines that do.

What the bag fixes upstream

Work from right to left along the line. Each stage has one figure that has to accommodate a 350-550 mm tube.

Stage	Figure that must match	Model and value
Weaving	Folding width of weaving covers 350-550 mm	YF-XT-750/4X suspension, 300-750 mm
Coating or lamination	Max. coating width at least 550 mm	SJ-FMF90/1000/4, 750 mm
Inner-liner lamination	Lay-flat width range covers 350-550 mm	YF-NMF/650, 350-650 mm
Printing	Max. printing width and feed width	YF-ZNY series, 700 mm image on 800 mm feed
Tape supply	Output in kg/h above the bag line's consumption	YF-SPL-80/33/800, 220 kg/h

Weaving: which looms cover the width

The suspension four-shuttle circular loom is the obvious match, and the table below shows why the wider looms are not. Figures are catalogue values at 40 picks per 100 mm.

Loom	Shuttles	Folding width of weaving	Covers 350-550 mm?	Max. speed	Fabric output	Total power
YF-XT-750/4X suspension	4	300-750 mm	fully	250 r/min	2.0-2.4 m/min	2.7 kW
YF-XT-750/4(A) little cam	4	300-750 mm	fully	180 r/min	1.4-1.8 m/min	2.7 kW
YF-XT-850/6X1 suspension	6	400-850 mm	400-550 mm only	180 r/min	2.2-2.6 m/min	3.5 kW
YF-XT-1000/4X suspension	4	450-1000 mm	450-550 mm only	220 r/min	1.8-2.1 m/min	2.7 kW
YF-XT-1050/6X2 suspension	6	750-1050 mm	no	160 r/min	2.0-2.3 m/min	3.5 kW
YF-XT-1400/4(A) little cam	4	800-1300 mm	no	125 r/min	0.9-1.25 m/min	4.5 kW

The "covers" column is a comparison of the published ranges, not a separate catalogue figure. The practical consequence: a plant that makes only cement valve bags should buy 750 mm-class looms. A plant that also weaves fertilizer or feed sacks above 1 m needs a second loom width class, and the circular loom buyer's guide sets out that choice.

Coating, liner and printing

Cement sacks are normally coated. Our single-extruder four-roller lamination machine in the SJ-FMF90/1000/4 build coats up to 750 mm of fabric at 80 to 200 m/min with two dies and four rollers, drawing 71 kW and weighing 8,000 kg. Where the customer wants a bonded film liner rather than a coating, the PLC-controlled reverse lamination machine in the YF-NMF/650 size takes 350 to 650 mm lay-flat fabric at up to 50 m/min, with 10 kW gross power plus 36 kW of heating. The full set of widths and speeds is in our lamination machines round-up.

For printing, the intelligent roll printing machine prints both faces of the fabric roll in one pass at 70 to 100 bags per minute, with a maximum printing size of 700 x 1100 mm on a maximum feed of 800 x 1300 mm. That covers a 350-550 mm tube comfortably, and bag length is changed on the touch screen without swapping printing rollers or gears, which matters when one plant runs several cement brands on the same line.

Seven steps to specify the line

1. Fix the finished bag. Width and length in millimetres, and whether it is coated, printed or liner-bonded. Width must fall inside 350-550 mm and length inside 500-900 mm for the YF-HKZ-600 to be the right machine.
2. Set the target output in bags per hour. Multiply the rated 25-30 pcs/min by 60 and plan with the lower end. Our arithmetic from the rated range, not a catalogue figure: 1,500 bags per hour at 25 pcs/min, 1,800 at 30.
3. Decide how many bag machines you need. One YF-HKZ-600 is a 1,500-1,800 bag/hour station. A plant above that needs a second machine, and a second 6 x 10 m bay.
4. Choose the loom width class. For a 350-550 mm tube, the 750 mm-class looms in the table above. Count the looms from fabric output: our production line guide works through a 50 x 90 cm cement sack at 70 g/m², about 0.063 kg of fabric per bag, and roughly 130 bags per hour from one four-shuttle suspension loom. By that arithmetic a 1,500 bag/hour valve bag station needs about twelve looms.
5. Size the extrusion line from tape consumption. The same worked example gives about 95 kg of fabric per hour at 1,500 bags per hour, which a 280 m/min flat yarn extrusion line in the YF-SPL-80/33/800 size covers with margin at 220 kg/h, 240 kW installed and 120 kW in normal operation.
6. Add coating and printing only if the bag needs them. They are the two stages a cement sack usually does need, and each adds a machine width constraint and a power load, 71 kW for the coating line in the size above.
7. Confirm power and floor space for the whole chain. 10 kW for the bag machine, 2.7 kW per 750 mm-class loom, 71 kW for coating, and 240 kW installed for the extrusion line: the tape line dominates the connected load, and the valve bag machine dominates the bay length.

Our recommendation

For a dedicated cement bag plant: one YF-HKZ-600 per 1,500 bags per hour, twelve YF-XT-750/4X suspension looms per bag machine for a 50 x 90 cm sack, one YF-SPL-80/33/800 extrusion line, and an SJ-FMF90/1000/4 coating line if the sack is coated. Specify the bag before anything else; every width in the list follows from it.

We have built plastic weaving machinery in Pingyang, Wenzhou since 1987, on a 60,000 m² site with over 200 machine tools, hold 109 national invention and utility-model patents, and are ISO 9001:2015, ISO 14001 and CE certified. Because the extruder, looms, coating line and the valve bag machine are assembled in the same workshops, the tape width, roll diameter and fabric width are matched before the machines leave the factory. Send your bag size, grammage and target output through the enquiry form and we will return a machine list and a layout for it.