Precision Static Mixer

Product Overview

The precision static mixer is a small-bore inline mixing device built specifically for the metered dispensing of two-part reactive chemistries — epoxies, polyurethanes, methacrylates, silicones, polysulfides, and the family of structural adhesives used in automotive, electronics, aerospace, and medical-device assembly. It is a direct evolution of our industrial static-mixer line, redesigned around the unique demands of low-flow, high-precision dispense: short mix length, clean disassembly, low dead volume, and a housing that can be specified either as a reusable stainless assembly or as a disposable cartridge that is discarded at end-of-life.

Inside the housing, 12 to 32 right-hand/left-hand helical elements (SS316L for the reusable line, PP or PA66 for the disposable cartridge) are stacked in alternating rotation. Each element forces the stream to split, rotate 180°, and recombine with its neighbor; the cumulative effect over 24 elements is approximately 4 million theoretical sub-streams, which is what allows the mixer to deliver a coefficient of variation of 1% or better on the discharge — well inside the cure-window of even the most ratio-sensitive two-part systems.

Compared to dynamic (impeller) mixers used in the same service, the precision static mixer has no moving parts, no seals to wear, no electrical power, and an order-of-magnitude lower purge volume. The trade-off is that it cannot compensate for ratio error upstream — if the metering pumps drift off-ratio, the discharge will follow. For that reason, the mixer is designed to be paired with positive-displacement or gear metering pumps whose accuracy is independently verified, and the system-level design assumes a 0.5-1% pump accuracy as the floor for the achievable end-of-arm mixing precision.

Three product variants cover the bulk of the application space. The standard reusable stainless mixer is the workhorse for high-volume production cells where the dispense volume per shift is large and the cost-per-shot of a disposable cartridge is uneconomic. The disposable cartridge is the choice for low-volume or multi-chemistry cells, for pre-mixed-and-frozen applications, and for any process where cross-contamination between batches is unacceptable. The medical-grade variant adds a Class VI / USP <87> biocompatibility certification, gamma-stable construction, and a 100% lot-traceable element set.

Design Features & Working Principle

The mixing elements are pressed from 0.4-0.6 mm SS316L sheet (or injection-molded PP/PA66 for the cartridge variant) into a four-vane helical form. Each element has an outer diameter of 4.7-9.8 mm depending on the housing size, with a vane twist of 180° over the element length of 3.0-5.5 mm. Elements are stacked alternating R-H and L-H so that each joint is a 90° turn, and the cumulative twist over a 24-element stack is 12 full 180° rotations.

As the two metered streams enter the housing, they are immediately subdivided by the first element into four quadrants. The 90° turn at each element joint forces the quadrants to cross over into the adjacent channel; the next element then splits each quadrant again, producing 16 sub-streams. By element 12, the cross-section contains approximately 4,000 sub-streams; by element 24, the count exceeds 4 million. The residence time through a 24-element housing is on the order of 0.2-0.5 s at typical dispense rates, which is short enough to prevent premature reaction in most two-part systems (typical pot life > 30 s at dispense temperature).

The housing itself is a precision tube with an internal surface finish of Ra ≤ 0.8 μm. End connections are machined from bar stock and welded to the tube by orbital TIG; the welds are passivated and dye-penetration-tested before assembly. For the disposable cartridge, the housing is a single injection-molded PP or PA66 part with integral male/female luer or UNF thread, and the elements are ultrasonically welded in place — the entire cartridge is then bagged in a nitrogen-purged foil pouch for shelf life of 18-24 months at room temperature.

Three options that frequently matter in dispense applications: bayonet-mount cartridges for quick-changeover in production cells (change time < 5 s); integral static mixers with a purge port for color-change or chemistry-changeover with zero disassembly; and low-residence ("dead-volume") tips that reduce the wetted volume between mix point and dispense tip to as little as 0.05 mL — important for shot sizes in the 0.1-1 mL range where every microliter of internal volume is material wasted at the end of a run.

Technical Specifications

Parameter	Value
Mixing Element Count	12 / 18 / 24 / 32 elements (standard); custom up to 48
Element Material (Reusable)	SS316L, 0.4-0.6 mm sheet, mirror finish
Element Material (Disposable)	Polypropylene (PP) or Polyamide 6.6 (PA66), natural or white
Housing Material (Reusable)	SS316L tube, SS316L end fittings, orbital TIG welded
Housing Material (Disposable)	Single-piece PP or PA66, ultrasonic-welded elements
Housing Bore	5.0 / 6.3 / 8.0 / 9.8 / 12.0 mm (standard sizes)
Working Pressure (Continuous)	16 bar (standard SS316L) / 70 bar (heavy-wall variant)
Proof Pressure	24 bar (standard) / 105 bar (heavy-wall)
Burst Pressure (Min.)	48 bar (standard) / 175 bar (heavy-wall)
Viscosity Range	50 to 250,000 cP (metered streams individually)
Mix Ratio Range	1:1 to 100:1 (by volume)
Discharge Coefficient of Variation	CoV ≤ 1% (24-element, 1:1 to 10:1 ratio, 1-500 cP)
Residence Volume (24-element, 6.3 mm bore)	2.1 mL nominal; "low-volume tip" 0.05 mL post-mix
Temperature Range (SS316L)	-40°C to +200°C (EPDM o-rings standard)
Temperature Range (PP Cartridge)	0°C to +80°C
Temperature Range (PA66 Cartridge)	-20°C to +150°C (dry); +80°C in water/glycol
End Connections (Reusable)	1/4-28 UNF, 1/2-20 UNF, 1/8 NPT, 1/4 NPT, compression fittings
End Connections (Disposable)	Bayonet (Nordson-style), luer-lock, integral Luer taper
Surface Finish (SS316L Wetted)	Ra ≤ 0.8 μm (electropolished optional to Ra ≤ 0.4 μm)
Pressure Drop (24-element, 1:1, 50 cP, 20 mL/s)	0.4-0.8 bar
Biocompatibility (Medical Variant)	USP <87> Class VI, ISO 10993-5, gamma-stable to 50 kGy

Selection & Sizing Guidance

Three parameters drive the precision-mixer selection: the metered flow rate per dispense cycle, the viscosity of each component at dispense temperature, and the ratio of the two streams. The general procedure is to (1) compute the total volumetric flow rate Q from the dispense cycle (shot volume × shots/min ÷ 60), (2) select a housing bore from the Q-vs-pressure-drop curve (target ΔP ≤ 1.5 bar at the worst-case viscosity), and (3) select the element count from the ratio and CoV target — for ratios above 20:1 or CoV targets below 1%, add 6-12 elements to the standard 24-element stack.

For abrasive or filled systems, derate the housing bore by one size to keep the flow velocity below 1.5 m/s and limit erosive wear on the element leading edge. For shear-sensitive chemistries (e.g. shear-thinning waterborne adhesives), keep the same bore but specify the longer 32-element housing so the average shear rate stays below 5,000 s^-1 across the full stack. For high-ratio systems (50:1 and above), specify the asymmetric housing with an off-center injection port so the minor component enters the major stream as a thin annular sheet — this raises the local mixing intensity by a factor of 3-4 at the same element count and is the only practical way to hit CoV < 3% at ratios that would otherwise require 48+ elements.

Typical Applications

Automotive structural adhesive bonding. Body-in-white adhesive dispense cells typically meter a 1-component polyurethane or 2-component epoxy at 4-8 mL/s, with a mix ratio of 1:1 to 4:1. The precision mixer is mounted on a robot end-effector directly upstream of the dispense nozzle; the 24-element SS316L version delivers CoV ≤ 0.8% at the bead, which keeps the lap-shear strength variation of the cured bond within ±5% of the design value.

Electronics underfill and encapsulant. Single-component capillary underfills and 2-component glob-top epoxies are dispensed at 0.05-0.5 mL/s onto BGAs, QFNs, and power modules. The disposable PP cartridge is the standard here, with a luer-lock outlet and a 0.3-0.5 mL post-mix tip to keep waste at end-of-shift to a minimum. Cartridge life is 12-72 hours of active dispense, after which the wetted volume is replaced.

Medical device assembly. Two-part silicone potting for catheters, sensors, and implantables uses the medical-grade precision mixer with Class VI certification. The 18-element housing in SS316L with electropolished internals handles viscosities of 5,000-80,000 cP at 0.5-2 mL/s, with documented lot traceability from raw element to packaged cartridge.

Aerospace composite repair. Two-part methacrylate and epoxy paste adhesives used for in-field composite repair are mixed in 10:1 to 50:1 ratio via the asymmetric 32-element housing. The mixer's 200°C rating and SS316L construction allow the same cartridge to be used on hot-bond repairs at cure temperatures up to 175°C, and the high-ratio asymmetric geometry holds CoV ≤ 3% even at 50:1.

Cartridge-based field dispensing. For applications where the metering pump is replaced by a manually-operated dual-cartridge gun (typical in construction-chemicals anchor bolt systems), the disposable PA66 mixer is sold pre-attached to a 1:1 or 10:1 ratio cartridge. The user attaches the mixer, primes the gun, and dispenses — the mixer is replaced at the start of every shift or when the cure time of the mixed bead exceeds the design pot life.

Installation, Cleaning & Maintenance

The reusable SS316L version is designed for periodic disassembly. End caps are removed with a 12-mm hex; the element stack is then slid out as a single assembly and either solvent-flushed (MEK, acetone, or chemistry-specific solvent) or ultrasonic-cleaned at 40 kHz for 10-15 min. Reassembly is torque-controlled to 8-12 N·m on the end-cap threads; a new set of EPDM or FKM o-rings is fitted at each reassembly. A typical cleaning cycle is 30-45 min including disassembly, cleaning, reassembly, and leak test.

The disposable cartridge is replaced as a unit. Production cells that run a single chemistry for 8+ hours typically change the cartridge once per shift; cells with frequent chemistry changeovers change with every changeover. Always prime the new cartridge with a 2-3 mL dispense before resuming production, to displace the air pocket at the inlet manifold.

Flushing protocol. For cured or crystallized residue inside the reusable housing, soak for 2-4 hours in chemistry-appropriate solvent at 40-60°C, then follow with high-pressure solvent flush at 4-6 bar. Never use a wire brush or metal scraper on the element surface — the vane edges are sharp by design and any deformation will destroy the mixing geometry.

Storage. Disposable cartridges are shipped in nitrogen-purged foil pouches with desiccant. Shelf life is 18-24 months at 5-25°C for PP and 12-18 months for PA66. Once removed from the pouch, the cartridge should be used within 30 days; longer exposure to ambient humidity degrades the PA66 dimensional stability.

Comparison with Disposable Plastic Cartridges

Parameter	SS316L Reusable	PP Disposable	PA66 Disposable
Pressure Rating	16 bar std / 70 bar HW	4 bar	8 bar
Max Temperature	200°C (EPDM)	80°C	150°C dry
Viscosity Range	50-250,000 cP	50-15,000 cP	50-50,000 cP
Abrasive Filler Tolerance	High (carbide edge option)	Low (softens at sharp edges)	Medium
Reuse Cycles	500-1,000 cycles	Single use	Single use
Cost per Shot (relative)	0.3× (amortized over 500 cycles)	1.0× (baseline)	1.2×
Biocompatibility	Optional Class VI	Not rated	Class VI on request
Cleaning Method	Solvent flush / ultrasonic	Replace	Replace

Frequently Asked Questions

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