Here’s a detailed guide—drawn from what people who deal in post-press / folder-gluer machines (especially older Jagenberg / Diana 90 machines) recommend—on what to inspect, ask, test, and beware before purchasing a pre-owned / second-hand Jagenberg Diana 90 (folder-gluer / specialty folder-gluer) machine.

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What the Jagenberg Diana 90 Is / Typical Specs & What to Know Up Front

First, it helps to know what a “healthy” or “as-new” Diana 90 typically could (or should) do, so you can compare against the used machine.

From various listings, brochures, and users:

Spec	Typical / Published Values for Diana 90-/90-1/90-2 / “Specialty Folder Gluer”
Max blank (sheet) width	~ 900-915 mm
Min blank width	~ 45 mm
Max blank length	~ 750 mm
Material types handled	Corrugated (B and E flute), solid board, standard carton / cardboard grammages (often ~200-800 g/m²)
Max running speed / belt speed	Up to ~ 450 m/min for many models, depending on material and load.
Power / kVA / electrical requirements	25-30 kVA in some older versions; 27 kW listed for some used units.
Size / footprint / weight	Length often ~ 12-13 metres for a full line with packer, width ~ 1.5-2 m, weight ~ 5-7 tonnes depending on model / accessories.

Knowing these helps you judge whether what the seller claims is realistic given the condition / wear.

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What to Inspect / Evaluate (Mechanical, Operational)

Because the Diana 90 is a folder-gluer (folder + glue + feed + delivery + possibly packer / stacker), there are many subsystems. Here’s what experts say you need to check carefully, plus what tests to do.

1. Frame, Structural Condition & Alignment
   • Examine the main frame and folding sections for any visible cracks, welds, repairs, signs of fatigue. Over years of vibration, load, and mis-alignment, structural distortions can set in.
   • Check that the machine is level and firmly mounted. Misalignment can affect glue accuracy, fold timing, box integrity.
   • Inspect the folding rails / side guides, belt guides for wear, damage, corrosion. If belts run off-track or guides are worn, you’ll need adjustments / part replacements.
2. Feed / Feeder Section
   • The feeder (blank feeder) guides: are they straight, adjustable, not bent or worn? Blanks must feed smoothly without skew.
   • Feed registration: check blank orientation, blank start alignment. If feed timing is off, gluing and fold lines will be off.
   • Check for any slippage in belts, motors, drives; check whether drive motors are strong and consistent.
3. Glue System
   • Which glue unit is installed (e.g. HHS series, number of guns, type of glue: cold or hot, strip or wheel, etc.)? Is the glue system original or has it been replaced / serviced?
   • Inspect glue guns / nozzles: are they clean, worn, properly aligned? Leaks or mis-sprays are a common occurrence.
   • Glue pump(s): check condition, pressure consistency, maintenance. If pressure fluctuates, glue application will be uneven.
   • Cleanliness of glue delivery lines: old glue buildup, dried glue, blockages reduce performance.
4. Folding / Creasing / Gluing Synchronization & Mechanics
   • The folding / creasing knives, creasers, belts or chain drives: check for wear, correct spacing, alignment. Creasing tools may wear or be misaligned.
   • Folding arms or rollers: check for wobble, play, smoothness. Any vibration or slop in folding motion will degrade quality.
   • Timing and synchronization between feed, glue, folding / glue units, delivery: test running at operational speed, see if boxes / cartons are aligned properly, with correct dimensions, fold accuracy and glue registration.
5. Drive Motors, Gearboxes, Belts / Chains / Bearings
   • Motors: inspect for overheating, insulation condition, correct power. Are they rated for required speeds & loads?
   • Gearboxes and reductions: any noise, backlash, wear. Bearings in rollers / shafts: play, noise, heat under operation.
   • Belts / chains & sprockets / pulleys: are they worn, properly tensioned? Replacement of large belts or chains may be costly or require downtime.
6. Conveyor / Transfer / Delivery / Packer Section
   • The delivery belts (or carriers) that move the folded / glued product: condition of belts (wear, fraying), alignment of carriers.
   • Packer / stacker (if included): check that count / stack accuracy works, that mechanical parts / pneumatic or hydraulic actuators are functioning.
   • Box kicker, stack turner, etc. if present: working condition, speed, safety.
7. Control / Electronics / Sensors
   • Control panels / human-machine interface (HMI): are switches/buttons, readouts, encoders in good condition? Sensors for blank detection, fold registration, glue triggers etc. Check alignment and functioning.
   • Safety interlocks: are guards present? Are emergency stops functioning and placed conveniently and fully?
   • Electrical panels: wiring condition, any signs of overheating, burned insulation, corrosion, grounding.
8. Wear Parts & Maintenance History
   • What parts have been replaced recently: belts, glue unit parts, folding knives, creasers, bearings, motors. Request maintenance logs.
   • How often cleaning and lubrication have been done. A folder-gluer that’s been badly maintained will have many small issues that add up.
   • Check for spare parts availability (for your region / country) for key wear items (belts, glue heads, knives, creasers, motors).
9. Operational Testing
   • Run at various speeds, from slow to near max: see if vibrating or any misalignments / flutter in fold or glue.
   • Run production blanks (or similar stock to your material type / grammage). Look for glue consistency, fold accuracy, box quality, sheet waste.
   • Look for properties like fold scoring/creasing quality (no cracks, clean folds), glue seams properly sealed, no glue leaks or smearing.
10. Capacity & Suitability for Your Needs
    • Size ranges: Will the min / max blank widths and lengths cover your product range? If your boxes are near the min blank size, check how stable & accurate the machine is at that end. Machines tend to do better in the middle of their range.
    • Material thickness / weight (grammage) compatibility: heavier board, thicker corrugated, etc. If operating near capacity, more wear, slower speeds, more maintenance will result.
    • Speed vs expected throughput: If you need production at or near the upper speed limit (say ~450 m/min), verify that the specific unit is capable of stable operation at that speed with your material / applications.
11. Safety, Environment, Condition of Ancillaries
    • Check safety guards, interlocks, access to moving parts. Operator safety is critical.
    • Condition of the working environment: moisture, dust, temperature fluctuations—all affect mechanical condition (corrosion, rust on belts, guides).
    • Ancillary systems: glue storage, glue mixing / heating (if applicable), ventilation (especially for fumes), waste disposal, cleaning.

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What to Ask the Seller / What Documentation to Get

To reduce risk and to understand what “you’re buying,” these are things you should demand / check:

• Machine serial number, year built, version / model variant (e.g. Diana 90-1, 90-2, specialty version, etc.). This lets you find original spec sheets or parts info. Many listings (Intermak, AGM) give these.
• Production & usage history: How many hours or metres of run-length, how many boxes produced, how many operational hours per week. What shifts? Was machine heavily used or lightly?
• Maintenance and repair history: What parts replaced, when; any breakdowns; evidence of regular servicing of glue units, belts, motors, folds, etc.
• List of wear items / spare parts replaced recently: glue guns, belts, creasing tools, folding knives, rollers, etc.
• Operational test / sample run: Ask to run the machine under load, with your type of material, to produce sample boxes, set them up in the formats you will use.
• Accuracy & quality of output: Sample cartons / boxes: are glue seams clean? Are folds proper? Are dimensions consistent? Are there defects (tearing, cracking, glue bleed, misfold)?
• Photos & inspection of less visible parts: underside, internal components, motors & gearboxes, belt routing, glue pump lines, condition inside covers and guards.
• Spare parts lists, manuals, drawings (mechanical, electrical), if available. Especially for older machines, having the technical documentation is invaluable.
• Control / electrical schematic, parts availability locally. Being able to get replacement motors, belts, glue pump parts, sensors etc. locally or with reasonable shipping time / cost is very important.
• Demonstration of safety features & compliance: interlocks, guarding, emergency stop, operator safety.
• Condition of installation & alignment: is the machine portable or fixed? Will moving it cost much? How much installation and alignment would be required at your facility?

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Red Flags / Common Problem Areas in Used Diana 90s

These are the things that often turn up in machines of this age / use class, which can lead to high cost of repair or substandard performance. If you see one or more of these, investigate carefully / insist on a discount or repair before purchase.

• Significant wear or damage to glue unit: clogging, leaks, worn nozzles, misaligned guns. This can result in erratic glue application.
• Belts & folding guides badly worn: belts frayed or misaligned; guides with scoring / damage.
• Folding / creasing tools (knives, creasers) dull or damaged, leading to bad fold, cracking, inconsistent crease.
• Motor or gearbox noise / vibration, especially under load, indicating bearing wear or gearbox wear.
• Poor registration of feed → misaligned glue lines or fold lines. Blank skew, poor blank feeding.
• Output quality under high speed deteriorates: e.g. collapse in boxes, glue failure, misfolds. If machine can only run slow without problems, its “capacity” is impaired.
• Lack of parts / service in your area: difficult or very expensive to obtain replacements.
• Corrosion or rust, particularly on metallic rollers, frames, under glue units, or in guard interiors—difficult to clean or repair.
• Control system / sensors degraded: inaccurate sensors, worn encoders, poor feedback for glue timing / fold registration.

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What to Budget For / Extra Costs

Even a machine in good used condition is likely to need investment to make it reliably productive. Be prepared for:

• Replacement of wear items: belts, folding knives, creases, rollers, glue nozzles etc.
• Tuning / alignment / calibration work: making sure the folding, feed, glue, delivery are all correct.
• Potential refurbishing of drive motors, gearboxes, bearings.
• Cost of moving and installing the machine: setting level, alignment, perhaps a new foundation, proper installation of glue units.
• Local adaptation: if glue types in your use differ (e.g., you need cold glue, specialty adhesives), you may need different glue guns or pump.
• Training of operators / maintenance personnel. Older machines often require knowledge of quirks.
• Shipping / dismantling / packing costs, especially for a large folder-gluer.