A shutdown is the only time many wear surfaces become visible. If the team removes, cleans and stacks the parts without a record, the machine may be ready for maintenance while the evidence needed for diagnosis or replacement is already gone.
This guide is about the record around the physical work. It does not replace the extruder manual, a site-specific risk assessment, lifting instructions, material safety controls or the authorized lockout and tagout procedure. The actual stop, purge, cooling, disassembly and restart sequence varies with the machine, polymer and reason for opening the process section.
Define the teardown job before the line stops
A planned wear survey, an abnormal-noise investigation and a formulation change do not need the same evidence. Write the job question in one sentence. That sentence decides which running data, photographs, samples and measurements must survive the shutdown.
| Reason for opening | Record before shutdown | Preserve during teardown | Decision after inspection |
|---|---|---|---|
| Planned wear inspection | Running hours, material family, stable output, screw speed, torque and pressure trend | Station identity, left and right readings, both bore lobes and prior baseline | Continue, remeasure at a defined event, repair or replace |
| Abnormal noise, torque or vibration | Alarm time, trend data, operator observation and the last stable condition | Contact marks, foreign material, spline condition, bearing or shaft evidence and deposit location | Identify the fault before selecting new metal |
| Product contamination or color carryover | Previous and current formulation, changeover method, residence event and rejected-product sample | Deposit color, location, depth in the process section and any dead-zone evidence | Separate cleaning or process causes from wear |
| Element-sequence change | Current recipe, output and complete process trend at the approved condition | Both shaft sequences, each element orientation and all spacers, seals and end hardware | Rebuild the original sequence or approve a documented revision |
| Replacement or reverse measurement | Machine, gearbox, serial number, drawing revision and current service duty | Nominal interfaces, worn surfaces, datums, paired identity and measured condition | Create an approved replacement definition |
The current EJS maintenance page separates daily work from regular shutdown maintenance and gives 2,500 to 5,000 operating hours as a general regular-maintenance range. That number is useful only as a published EJS reference. It is not a universal teardown interval. A 2025 Leistritz maintenance sheet, for example, lists a six-month screw-set pull, cleaning and outside-diameter record for the machines covered by that sheet. The difference is the point: use the schedule for the exact extruder and duty, then revise it with the line's own wear history.
Save the running condition while the machine can still show it
A disassembled screw cannot tell you the output, torque or pressure at the moment the complaint occurred. Export the trends and write down the process state before the stop. If the machine is already down after an incident, preserve the last stable record and the alarm sequence instead of recreating a run for the sake of the worksheet.
| Record | What to capture | Why it remains useful after teardown |
|---|---|---|
| Machine identity | Maker, full model, serial number, gearbox identity and installed configuration | Separates similar machines and model revisions |
| Material duty | Resin, fillers, reinforcement, additives, regrind and the unit basis of each amount | Connects wear or deposits to the actual compound |
| Stable process state | Output, screw speed, torque, zone temperatures, melt temperature, pressure and vacuum where available | Creates the before-maintenance comparison |
| Complaint | When it started, frequency, affected product, alarms, sound, vibration and visible defects | Keeps the investigation tied to the original symptom |
| Service history | Running hours, last screw pull, last sequence change, prior measurements and known repairs | Shows whether a dimensional change is new or progressive |
| Evidence files | Trend export, HMI photographs, product samples and file names linked to the work order | Prevents screenshots and samples from becoming anonymous |
EJS's operating page tells operators to check process parameters during production and complete a process record sheet. That ordinary habit is what makes the later teardown useful. A maintenance team needs the process record from immediately before the stop, not an average remembered after the parts are on the floor.
The approved stop and energy-isolation procedure controls the work
The live EJS operating page describes a general shutdown path that stops feeding, removes material, stops the drive and auxiliary equipment, then cleans the process section. It also calls out electrical, thermal, rotating and heavy-part hazards and the need for lifting equipment. Use those points as hazard prompts, not as a substitute for the extruder maker's procedure.
In U.S. workplaces, OSHA 29 CFR 1910.147 covers servicing and maintenance where unexpected startup or release of stored energy could injure employees. It requires a documented energy-control procedure, trained authorized employees, control of stored or residual energy and verification of isolation. Other countries have their own requirements. The plant procedure and applicable law control the job.
Do not turn a generic web article into a machine procedure. Polymer behavior during a stop also differs. A purge or cooldown route suitable for one resin may be wrong for a reactive, corrosive, heat-sensitive or crosslinking material. Record the approved route used, the purge material if any, and the condition in which the screws and barrel were opened.
Shutdown authorization block
Work order Machine procedure revision Material hazard review Authorized personnel Lifting plan Isolation verified
Keep the signed plant record with the maintenance file. The engineering worksheet below records the parts; it does not authorize entry into the machine.
Tag the references before a bolt is loosened
Left and right are meaningless unless the viewing direction is stated. "Section 1" is also ambiguous unless the reference end and feed direction are visible. Put the reference on the machine, repeat it on the work order, and include it in a wide photograph before removal starts.
| Mark | Required definition | Where it should appear |
|---|---|---|
| Feed direction | Arrow from feed inlet toward discharge | Machine sketch, barrel map and overall photographs |
| Viewing direction | For example, viewed from gearbox toward discharge | Every left/right drawing and screw-end photograph |
| Screw A and Screw B | Stable identity tied to the declared view, not loose labels called only left and right | Drive end, removal rack and every measurement sheet |
| Barrel section | Position number plus front, middle or tail reference where applicable | Housing exterior, connection face photographs and section map |
| Top and rotation | Clock position or approved orientation mark | Ports, cooling connections, vents, side feed and end faces |
| Part status | Installed, removed, cleaned, measured, repair candidate or replacement reference | Tag, work order and photo file name |
Photograph the complete assembly, then move closer. Capture drive couplings, screw ends, barrel faces, flange pilots, locating keys, heaters, thermocouples, pressure ports, cooling connections, vents, side-feed openings and fastener positions. Put a scale in dimensional photographs, but do not infer a tolerance from a photograph.
Keep both screw sequences and every barrel section in one map
Modular screws need more than a row of loose parts. The current EJS screw-element guide calls for the two shaft sequences to be preserved before removal and records element outside diameter, bore or spline, width, pitch or disc angle, handedness, material, treatment, orientation and neighbors. A broad name such as "kneading block" cannot rebuild the sequence.
Use one axial zero for the process section. Place Screw A and Screw B on separate rows, then assign each element a position from the same reference end. Keep spacers, seals, retaining hardware and transition parts in the map. If an element spans a barrel joint, record that relationship instead of forcing every screw position into one barrel box.
| Position | Screw A | Screw B | Barrel relationship | Evidence |
|---|---|---|---|---|
| Axial start and end | Element code, width and orientation | Element code, width and orientation | Housing number, opening or joint | Top and side photos before separation |
| Working geometry | Pitch, handedness, lobe or disc details | Pitch, handedness, lobe or disc details | Feed, closed, vent, side-feed or discharge section | Drawing, part code and measured features |
| Condition | Deposit, polish, rounding, chip, crack or fretting location | Same fields for the paired position | Bore-lobe and connection-face condition | Photo number before and after cleaning |
The same rule applies to barrel housings. The segmented versus one-piece EJS guide distinguishes the replaceable unit from the complete process section. Keep each housing tied to its axial location, bore pair, heater or cooling hardware, opening type and adjacent connection faces.
Photograph deposits first, then clean for measurement
Deposits are evidence when the job concerns contamination, burning, vent carryover or an unstable process. Photograph their color, thickness, texture and axial location before cleaning. Label any sample with machine, date, station, material and which surface it came from. A bag marked "black deposit" loses most of its value.
Measurement needs a different condition. Coperion's barrel-wear diagnostic guidance states that the barrels must be clean and cool for its inspection methods. That requirement explains why one photograph set cannot do both jobs. The first set documents the as-opened condition. The second documents the cleaned surfaces and measurement setup.
| Stage | Record | Do not lose |
|---|---|---|
| As opened | Deposits, wet or dry condition, color, foreign material, contact marks and where residue bridges two surfaces | Station, viewing direction and scale reference |
| After approved cleaning | Flight lands, roots, flanks, spline, barrel bores, ports, joint faces and tool access | Any mark exposed only after residue is removed |
| Ready for measurement | Part temperature, instrument, calibration status, datum, orientation and raw reading | The link between reading, surface and photograph |
Use the cleaning method approved for the material, surface treatment and machine. The live EJS maintenance content warns against empty running and calls for material exclusion and process cleanliness. Its service-life guide also identifies damage from steel-tool or open-flame cleaning as a separate failure mechanism. A scratch created during cleaning can later hold degraded material and can be mistaken for operating wear.
Inspection should connect a surface to a station and a cause
A useful inspection record names the part, exact position and orientation. "Screw worn" is not enough. "Screw A, station 6, flight crest, gearbox view at 3 o'clock" can be checked against the paired screw, barrel lobe, operating record and future measurement.
| Area | Visual record | Dimensional record | Related question |
|---|---|---|---|
| Screw working surfaces | Polish, rounding, scoring, chips, cracks, deposits and asymmetric contact | Outside diameter or drawing-defined feature at mapped stations | Is the change local, repeated or paired with one barrel lobe? |
| Spline and drive end | Fretting, deformation, corrosion, end-face contact and retention condition | Drawing-specified spline, engagement and locating features | Did the process section fail, or is the drive interface involved? |
| Barrel bores | Scoring, polish, pitting, deposits and lobe-to-lobe difference | Bore readings at approved depths, angles and stations | Does the barrel pattern agree with the screw pattern? |
| Barrel joints and ports | Leak path, fretting, gasket or seal condition, blocked passages and deposit edges | Drawing-defined faces, pilots and connection features | Could the complaint originate at an interface rather than the bore? |
| Paired relationship | Opposing contact marks, sequence mismatch and inconsistent orientation | Drawing-defined screw-to-screw and screw-to-barrel checks | Were the parts installed and timed as the approved design requires? |
The EJS quality-inspection page calls for screw outside diameter readings at several points and barrel-bore readings at several depths and angles, with acceptance against the drawing. Keep the actual values rather than recording only "pass" or "fail." A raw measurement may later help a supplier resolve a revised drawing, a wear pattern or a replacement boundary.
If the teardown began because of torque, spline or twin-screw wear symptoms, do not close the investigation after finding the first damaged surface. Compare the two screws, both bore lobes, drive interfaces and process trend. Better alloy does not correct misalignment, a foreign object or the wrong installed sequence.
Preserve the matched identity after inspection
Once the inspection is complete, the record has to stay attached to the parts. Do not write only on removable film or packing material. Use the plant's approved non-damaging tag method and repeat the identity on the crate list, drawing and photo record.
- Keep Screw A and Screw B identifiable as one pair, even when they require separate supports or wrapping.
- Support long parts according to the approved handling plan. Do not let the packing method create a bend or point load.
- Protect machined faces, splines, flight crests, bore openings and sensor connections from impact and contamination.
- Use the approved corrosion-prevention method for the material and intended storage period. State what was applied so the receiving team can remove it correctly.
- Separate loose elements by position while preserving their sequence. Do not fill one box with unnumbered parts.
- Put the work-order number, machine identity, part list, photograph index and measurement report in the shipping record.
If EJS will quote a repair or replacement, send the record before shipping heavy parts. Clear photographs and mapped readings can show which samples are necessary and which interfaces still need measurement. The EJS custom manufacturing guide explains why a used component is evidence rather than an automatic nominal master.
Use one teardown worksheet from running line to packed parts
Print this table or reproduce the same fields in the plant maintenance system. Keep one row per event or station. The row must point to the raw file, not a photograph pasted into a report without its original name.
| Stage or station | Part identity | Observation or reading | Reference and method | Photo or file ID | Disposition |
|---|---|---|---|---|---|
| Last stable run | Machine and work order | HMI trend period and recipe revision | Baseline saved | ||
| Shutdown authorization | Machine procedure revision | Plant energy-control record | Verified by authorized person | ||
| As-opened condition | Section and declared viewing direction | Scale, station and deposit sample | Clean after record | ||
| Screw station | Screw A or B, element position | Drawing feature and instrument | Reuse, review, repair or replace | ||
| Barrel station | Housing and left or right bore lobe | Depth, orientation and instrument | Reuse, review, repair or replace | ||
| Drive interface | Shaft, spline and retention parts | Drawing revision and engagement reference | Further drive inspection if needed | ||
| Packing handover | Crate, pair and part count | Protection method and packing list | Stored or shipped |
A person who did not attend the teardown should be able to identify every part, rebuild the original sequence on paper, locate each measurement and understand the reason for the shutdown. If that is not possible, the record is incomplete.
Prepare a teardown-based EJS inquiry
Send the machine identity, original drawing, shutdown purpose, operating snapshot, declared viewing direction, both screw sequences, barrel map, raw measurements and labeled photographs. State which parts are available as samples and whether they are worn, repaired or unused.
Frequently asked questions
What should I record before shutting down a twin screw extruder?
Record the machine and gearbox identity, formulation, stable output, screw speed, torque, temperatures, pressure, vacuum where used, running hours, current complaint, alarm history and the last approved screw and barrel configuration. Export the original trend files and tie them to the work order.
Can I use a 2,500 to 5,000 hour teardown interval for every extruder?
No. The current EJS maintenance page gives that range as general regular-maintenance guidance, but the correct interval depends on the machine builder's schedule, compound, loading, operating history and measured wear. Use the approved schedule for the exact machine and revise it with documented condition data.
Should both twin screw shafts be identified as a pair?
Yes. Assign stable Screw A and Screw B identities, declare the viewing direction and preserve the paired relationship through removal, measurement and packing. Follow the machine builder's removal procedure. Do not rely on unqualified left and right labels or assume that similar-looking shafts are interchangeable.
Should deposits be removed before taking photographs?
Not when deposits may explain the complaint. Photograph the as-opened condition first, with station, orientation and scale identified. Then use the approved cleaning method and take a second photograph set of the clean surfaces before measurement.
What is the minimum record for a modular screw sequence?
Record both shafts from one axial datum. For every position, retain the element code or drawing, width, outside geometry, bore and spline, pitch or disc angle, handedness, orientation, material or treatment when known, neighboring elements and matching barrel section.
How should removed screws and barrel parts be stored?
Keep each part identifiable, supported by the approved handling method and protected at machined faces, splines, flight crests, bores and connections. Use the approved corrosion protection for the material and storage period. Repeat every identity on the tag, packing list and photograph record.
What teardown information should I send EJS?
Send the machine, gearbox and serial details, drawings and revisions, shutdown purpose, process snapshot, declared datum and viewing direction, both screw sequences, barrel-section map, raw measurements, before-and-after-cleaning photographs, part status and the requested repair or replacement scope.
Sources checked for this guide
- EJS Industry: The Operating Skill of the Extruder (2) for current EJS site guidance on process records, general shutdown stages and electrical, thermal, rotating and heavy-part hazards.
- EJS Industry: The Maintenance of the Extruder (1) for daily versus regular maintenance, the published 2,500 to 5,000 hour general range, abnormal-noise response, empty-running warning and contamination controls.
- EJS Industry: Twin Screw Elements for the fields needed to preserve two modular shaft sequences.
- EJS Industry: Segmented vs One-piece Twin Screw Barrels for replaceable-unit and barrel-section identity.
- EJS Industry: Screw Barrel Quality Inspection for actual dimensional records, multiple screw and bore readings and drawing-based acceptance.
- EJS Industry: Custom Twin Screw Barrel Manufacturing for drawing control and the limits of a worn sample as a nominal master.
- Coperion: Preventive Wear Diagnostics for clean-and-cool barrel inspection conditions and the distinction between screw removal and full process-section dismantling.
- Coperion: Maintenance and Repair for the separation of screw-shaft removal, barrel-bore measurement and component overhaul tasks.
- Leistritz: Twin Screw Report 2025 for a machine-maker maintenance example that pairs screw-set pulling, cleaning and outside-diameter records on its own schedule.
- OSHA: 29 CFR 1910.147 for U.S. hazardous-energy control requirements during servicing and maintenance.