NTEP Multihead Weighers in Sticky Product: How to Stop Drift, Smear, and False Rejects

If you run an automated packaging line for oily, dusty, or tacky SKUs, you already know the pattern: the first hour looks great, then the multihead weigher starts “hunting,” the checkweigher begins firing rejects, and your team’s response turns into an unplanned cleaning marathon.

The root issue usually isn’t that the scale “can’t weigh accurately.” It’s that sticky product changeover isn’t being treated as a controlled mechanical and metrology event. When residue builds up on pans, chutes, and discharge surfaces, the system can experience weight drift, smear/carryover, and false rejects—all of which can quietly destroy throughput, giveaway, and compliance confidence.

This post focuses on the real-world headache: oily flower and concentrates, tacky inclusions (sugars/pectins), and infused powders that foul contact surfaces and destabilize dosing. We’ll connect the mechanical “why” to the compliance “why” (weights & measures expectations) and lay out practical fixes you can implement with your maintenance, ops, and QA teams.

Why sticky products break multihead weigher stability

A multihead weigher is essentially an optimization engine: it distributes product across multiple weigh hoppers, measures each hopper, and computes the best combination to hit the target weight.

Sticky product creates three failure modes that look like “scale problems,” but are mostly mechanical:

1) Adhesion and buildup change the effective mass over time

When product smears and accumulates on:

• dispersion cones
• radial/linear vibratory feeders
• weigh pans and weigh hoppers
• discharge chutes

…you create a slow, non-linear change in what the system believes is “empty.” This shows up as zero drift, unstable readings, and increasing adjustment corrections.

Even small buildup matters because the system is trying to hit very tight tolerances (especially on small formats). Your “tare world” becomes inconsistent across heads.

2) Inconsistent flow causes “starved” heads and combination inefficiency

Sticky powders and tacky inclusions often:

• bridge at the hopper
• clump and roll unpredictably
• stick and then release in bursts

That creates poor distribution across heads. The algorithm has fewer good combinations, so it may run longer cycles, throw more rework, or compensate by “overfilling” to avoid underweight risk.

3) External vibration and feeder coupling makes the system chase noise

Multihead weighers are extremely sensitive to vibration. Feed equipment that touches the frame, a poorly isolated platform, or a vibrating conveyor can inject noise into weigh cells.

Manufacturers commonly advise isolating feeding equipment from the multihead weigher to minimize external vibration and protect stability (see example guidance from Yamato Americas: https://www.yamatoamericas.com/pro-tip-how-to-properly-feed-your-multihead-weigher/).

In sticky products, operators often crank vibration amplitude to “make it move,” which can worsen oscillation, create more dusting, and amplify weighing noise.

The hidden cost: “false rejects” that silently crush throughput

Most teams feel false rejects as irritation, but the real impact is measurable:

• Throughput loss when the reject mechanism triggers and line speed is reduced to keep up
• Labor creep (one operator becomes a full-time “reject babysitter”)
• Giveaway when the system is biased toward overfill to avoid underweights
• Rework quality risk when rejected packages are reopened/handled repeatedly
• Compliance exposure if you stop trusting your own weight control and fly blind

False rejects are often caused by:

• product sticking to the package rim/threads before sealing
• powder on the outside of the container (adds weight at checkweigh, then falls off later)
• vibration/airflow at the checkweigher
• unstable tare due to inconsistent packaging components

The key takeaway: you can’t “calibrate your way out” of bad mechanics.

Compliance reality: why weights & measures cares about drift and documentation

In the U.S., weights & measures programs typically adopt or reference NIST Handbook 44 for device requirements and NIST Handbook 133 for net contents inspection procedures.

• NIST Handbook 44 (current edition hub): https://www.nist.gov/pml/owm/nist-handbook-44-current-edition
• NIST Handbook 133 (net contents inspection): https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936072

A practical way to think about it:

• HB 44 is about whether the weighing devices and systems meet technical requirements and tolerances.
• HB 133 is about whether your packaged goods in the market meet labeled net contents when sampled and tested.

Sticky products complicate net contents programs because:

• product can adhere to containers (net weight uncertainty)
• moisture loss/volatiles can shift mass post-pack (HB 133 discusses moisture loss considerations)
• “wet tare” and residue handling become operationally tricky

This is where defensible documentation matters.

EMFR-based verification + event logs: powerful, but only if the line is controlled

High-precision checkweighers can use electromagnetic force restoration (EMFR) weigh cell principles for rapid, exact mass measurement in dynamic environments (overview: https://en.wikipedia.org/wiki/Check_weigher; and an industry guide mention: https://www.storcan.com/uploads/ck/Checkweighing_Guide_EN.pdf).

In plain terms, EMFR-based systems can be excellent at detecting small deviations—especially when combined with:

• event logs (who changed settings, when, and why)
• defined tolerances and alarms
• calibration and verification records
• lot-based reporting

But there’s a catch: the mechanical system has to be stable. If sticky product buildup causes drift, your logs become a record of chaos, not control.

To make EMFR verification and event logging “defensible,” treat your packaging line like a closed-loop control system:

1) stable feeding and distribution into the multihead2) stable discharge and container presentation3) stable checkweigher environment4) documented interventions and changeovers

Practical fixes: stop drift, smear, and false rejects at the source

Below are the highest-leverage interventions we see during packaging line audits.

1) Build a sticky-product changeover SOP that is actually measurable

Most “cleaning SOPs” are vague: “wipe down,” “sanitize,” “reassemble.” For tacky and oily SKUs, you need changeover steps with acceptance criteria.

Include these elements:

• Defined disassembly scope (which parts come off every time vs weekly)
• Approved cleaning chemistry compatible with your product and materials (avoid damaging plastics/elastomers)
• Drying verification (residual moisture can create powder paste and sticking)
• Reassembly torque/fit checks (misalignment causes rubbing, vibration, inconsistent discharge)
• Post-clean “empty & zero” routine before running product (many manufacturer manuals emphasize emptying and zeroing; example operator reminders appear in multihead weigher manuals)
• First-article verification at startup (see below)

Sticky products demand “clean-to-constant,” not “clean-to-look-good.”

2) Control adhesion with surfaces, liners, and temperature discipline

If product is smearing, you’re fighting surface energy and viscosity.

Common tactics:

• Use the manufacturer’s recommended non-stick/low-friction contact parts where available.
• Keep contact surfaces cool and consistent where feasible. Warm stainless + oily product often equals smear.
• Reduce dwell time on surfaces: shorten chutes, smooth transitions, eliminate dead pockets.

If your product is heat-sensitive or becomes tackier with heat, verify that nearby motors, enclosures, or ambient conditions aren’t pushing you into the “sticky zone.”

3) Tune vibration for consistency, not brute force

Operators often increase amplitude to overcome sticking. That can:

• increase dusting/fines generation
• cause product bounce and inconsistent pan fill
• inject vibration noise into weigh measurements

Instead:

• Start with mechanical isolation (feed conveyor not touching the scale frame; stable platform)
• Use frequency and amplitude adjustments to achieve steady flow
• Adjust feed gate openings and timing so heads are neither starved nor flooded

Think of vibration as a metering tool, not a hammer.

4) Set feeder strategy for sticky inclusions: prevent bridging and clumping

For sticky mixes (e.g., tacky inclusions in a base powder), aim to:

• minimize drop height (reduces bounce and separation)
• avoid narrow choke points
• maintain consistent head replenishment

If you’re seeing clumps, you may need to:

• lower feeder speed
• change the distribution pattern
• use agitation (as allowed) upstream rather than “shaking” the scale harder

5) Stabilize the checkweigher environment to reduce false rejects

False rejects aren’t always multihead-caused. Common checkweigher destabilizers:

• airflow from HVAC or fans hitting the weigh conveyor
• inconsistent container spacing and side contact
• vibration transfer from upstream conveyors

Operational fixes:

• isolate checkweigher from upstream vibration
• verify belt tracking and level
• confirm reject timing and sensor placement
• lock in container orientation and spacing

If packages are being weighed while still “settling,” you’ll see noisy readings and unnecessary rejects.

A defensible net contents program: what “good” looks like in practice

A strong net contents program for sticky products combines device capability, process control, and documentation.

Start-up validation (first 30 minutes)

• Run a controlled startup lot
• Confirm the multihead is stable (no trending drift)
• Verify checkweigher repeatability with test weights or known references
• Document initial settings and environmental conditions

In-run verification (hourly or per lot)

• Spot-check net contents with a calibrated static scale
• Review checkweigher reject rates (false reject threshold)
• Record any interventions (cleaning, adjustments)

Changeover discipline

• Treat sticky SKU changeovers as a quality event
• Require sign-off for “clean and zero” and “first-article passed”
• Maintain event logs and calibration records

NIST Handbook 133 emphasizes uniform inspection lots and proper procedure for verifying labeled net contents (HB 133 PDF: https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936072). Your internal program should mirror that discipline: consistent lotting, consistent tare components, consistent methods.

Implementation timeline: what you can fix in 2 days vs 2–6 weeks

In 48 hours

• audit vibration and mechanical coupling
• set a sticky-product changeover checklist with acceptance criteria
• reduce false rejects by stabilizing checkweigher airflow and container spacing

In 2–6 weeks

• develop/validate cleaning methods per SKU family (oily vs dusty vs tacky)
• refine feeder/vibration tuning recipes and lock them with permissions
• build lot-based reporting and a net contents verification cadence

Recommended integrated system (Product Plug)

If you’re trying to solve drift and false rejects with a patchwork of devices, consider stepping up to an integrated approach: weigh + fill + verification designed for tight tolerances and compliance documentation.

Recommended gear: https://www.urthandfyre.com/equipment-listings/precision-weighing-system

The Canapa Precision NTEP Weighing System + Filler + Weight Analyzer + Feeder combines a multihead weigh filler with an analyzer/checkweigher designed for high accuracy and defensible control. It’s built around a compliance-minded architecture (including certification context and logging capabilities), which is exactly what you want when sticky products make your process “drift-prone.”

A field checklist: diagnose sticky-product drift in one walkthrough

Use this during a live run:

• Does the feed system physically touch the weigher frame?
• Are there visible smear points on cones, pans, or discharge chutes?
• Is residue accumulating unevenly across heads?
• Are reject rates trending upward as runtime increases?
• Are packages contaminated externally with powder/oil before checkweigh?
• Is there airflow hitting the checkweigher?
• Are operators changing settings without documenting why?

If you can’t answer these quickly, you don’t have a control system—you have tribal knowledge.

Where Urth & Fyre can help

Urth & Fyre supports teams that need more than “a machine”—you need a repeatable program:

• Line audits to identify the true source of drift (mechanical vs metrology vs environment)
• SOP development for sticky product changeovers, cleaning validation, and first-article release
• Equipment selection for integrated weigh–fill–checkweigh systems sized to your throughput and risk
• Compliance alignment support with HB 44/HB 133 expectations and documentation hygiene

Explore equipment listings and consulting support at https://www.urthandfyre.com.