A multihead weigher and a VFFS bagger can each hit their rated speed alone and still make empty bags and leaking seals once you bolt them together. The line is won or lost in the layer between them — the handshake that times the dump, the drop geometry, and the buffer that absorbs the weigher’s cycle-to-cycle variation.
The work is sequential. The control handshake has to land before any mechanical fit makes sense, and the drop geometry decides whether a matched bag rate ever becomes a clean bag.
The handshake is a 4-signal loop between the multihead weigher and the VFFS bagger, carried over Ethernet/IP. The weigher signals a weighment is ready, the bagger confirms an open bag is under the discharge, the weigher releases the portion, and the bagger seals and indexes to the next bag.
Get the exchange wrong and you make double-dumps or empty bags no matter how well the chute is aligned.
Both machines are PLC-controlled, and the timing lives on a touch screen. The filler trigger ties to the jaw-position sensors, so the dump fires against the real jaw cycle, not a fixed timer.
The choice that shapes everything downstream is discharge mode. In make-bag-on-demand mode, the weigher holds its weighment and dumps only when the bagger requests that bag — the weigher follows the bagger.
In free-running mode, the weigher dumps on its own cycle into a buffer and the bagger pulls from there. Make-bag-on-demand is the safer default for fragile or costly product; free-running earns its keep at top speed with a timing hopper to catch the surplus.
A single-source weigher-and-bagger pairing ships with the handshake and discharge mode pre-matched, which removes the most common surprise — two vendors each assuming the other owns the signal map.
When you mate an existing weigher to a new bagger, confirm the I/O map and discharge-mode support before anything is bolted in place.
Mechanical mating aligns the weigher’s discharge to the forming tube through a transition chute, governed by drop height and funnel angle. For brittle items like keto cookies, practitioners hold every drop to roughly three inches so product lands compact, not shattered.
The angled chute has to run parallel to the forming set, or catch points form where product hangs up. Size the funnel discharge only slightly larger than the upper funnel it feeds; oversizing lets the charge restructure on the way down.
Funnel angle is where fragile and sticky product demand opposite strategies in one chute. For breakable goods, a gentle slope near 45 degrees protects the charge, soft enough that everything slides in.
That same slope is wrong for sticky or long product. A shallow angle lets the stream spread and bridge, so sticky goods need a steeper wall and minimum contact with the forming tube to avoid stripping sugar. Continuous motion lowers impact velocity; swirl and bounce slow the fill.
Elongated product is its own case. For green beans, the charge releases in small staggered delays, forming a controlled string that clears the forming tube without clogging, and a pre-bag bulge adds volume ahead of the product to stop internal bridging.
The VFFS forming tube and collar are the bagger-side reference, and the chute is matched to them. The critical specification to verify is that the chute exit, forming tube mouth, and drop axis share one centerline under actual production conditions.
Combined throughput is capped by the slowest cycle in the pair. A bagger rated at 120 bpm fed by a weigher rated for 120 fills does not give 120 bpm; if the weigher delivers 40 complete weighments per minute, the bagger cannot exceed 40.
Typical VFFS machines run 30 to 120 bpm, and one rated at 120 may deliver 85 to 95 bpm after changeovers and short stops. The realistic figure sits below the spec sheet.
Head count is the weigher’s lever on that rate. A 10-head weigher cycles in 0.5 to 0.8 seconds, supporting 75 to 120 fills per minute, while a 14-head config balances speed, accuracy, and cost for snack product and holds ±0.5 to ±2 g.
The bagger’s jaw motion sets its own ceiling. Intermittent-motion jaws cap near 60 to 80 bpm because the film stops for each seal; continuous-motion jaws reach 180 to 300 bpm because they travel with the film. The same rate-matching governs the horizontal flow-wrapping line.
Bag size moves the realized rate more than any spec. At Frites Street in Arizona, a 14-head Maxpack MHW weigher on a Maxpack MFT 7 bagger runs about 15 bpm on five-pound bags of frozen french fries. That is a heavy bag and a slow target by design.
The same head count on a small snack bag runs several times faster. Plan around the slower cycle plus the buffer’s settling time; that figure, not the peak, is the rate the line holds.
A timing hopper holds the weighed charge until the bagger is ready. It is the one component that lets the pair run at a steady rate instead of stalling on every slow weighment.
The hopper enables multiple dispenses in flight — one charge descending while the next is weighed. Without it, raw dumps hit a bag not yet positioned and product flies everywhere.
Weigh cycles are not uniform. The combination calculation runs a fraction of a second longer on one cycle than the next, and the hopper smooths that jitter so the forming tube sees a regular feed.
The hopper is also a responsibility boundary — the gray area between one vendor and the next, where the weigher’s job ends and the bagger’s begins. On a two-vendor build, confirming who owns the chute and hopper matters as much as the hardware.
Sizing comes down to dump time: the gravity travel from weigh hopper to timing hopper. Practitioners clock it with a high-speed camera because it varies with density — candies race through, chips drift slowly.
The hopper must hold the charge until the slowest product settles. Under actual production conditions, measure dump time for your product rather than trusting a generic figure.
Integration-specific faults are the failures neither machine shows in isolation; they live in the handoff. Timing mismatch makes empty, short, or double bags when the dump fires against the wrong jaw position.
Excessive drop or slow product reaches the seal area as the jaws close, producing leakers and contaminated seals. Weigher surge floods the former faster than the bagger can index.
String-out ties drop geometry back to the seal — an extended stream of product that spreads instead of staying compact, carrying into the seal, throwing off the weight, and cutting output.
The causes are mechanical and traceable: excessive stagger delay, a chute misaligned to the forming set, or a too-shallow funnel. The fixes mirror them — minimize the stagger, match the chute angle to the forming set, and steepen the funnel to 65 degrees or more. Dump timing should drop product onto the jaws as they close, not before.
One deliberate exception: for narrow bags, a controlled string is sometimes desirable, because it stops product bridging across the bag mouth. A steep angle correct for a wide bag can be wrong for a narrow one.
Settling, not peak cycle, is what quietly starves the former. When product jumps against the sides of the timing hopper, it takes longer to reach the bottom of the pack, and the realized rate falls below the weigh cycle’s prediction.
Routine VFFS issues like film tracking or seal-bar temperature belong with the common VFFS problems and solutions, not the mating layer.
Start commissioning at the handshake and finish at the seal, because every downstream fault traces back to a signal or geometry upstream. Confirm the discharge mode and I/O map before mechanical work, set drop and chute angle to the product’s fragility, and size the timing hopper to measured dump time.
Then verify the realized rate against the slower cycle, not the spec sheet.
The mistake that wrecks a commissioning is treating the two machines as black boxes that just need wiring. The pairing only behaves when dump timing, drop geometry, and the buffer are tuned together — and that handoff is where a clean five-pound bag of fries and a leaker are decided.
