For plastics processors and extrusion lines
Our extruder gearbox repair covers single-screw and twin-screw boxes, lab-scale to large production, in our own shop in Hillsborough, New Jersey. When an extruder gearbox fails, the line stops. We strip it, find out why, make the parts that cannot be bought, and put it back together timed and measured.
Stanley Zala came out of Davis-Standard, and extrusion has run through this shop ever since. Over the years we have machined thousands upon thousands of parts for Davis-Standard, Egan, Gloucester and Sterling extruders — the same machines still running in plants across the country.
Zambello, who build extruder gearboxes in Italy, brought us to their factory for two days of training on their units, twin-screws in particular: how they are built, how they are timed, and where they fail. When one of these boxes comes apart on our bench, we are not meeting it for the first time.
Most gearbox shops diagnose the fault, order the components and bolt them back in. When a part is obsolete or the lead time runs to twenty weeks, that is where it stops.
We machine gear blanks, shafts, housings and adapters here, and our gear-cutting partner cuts the teeth. If a component no longer exists, we measure the worn one and make a new one from it — the same way we handle reverse engineering on any other part. Send the complete unit or just the one broken component. We work from either.
Single-screw gearboxes — the work centers on the thrust bearing and the axial load path. A single-screw box spends its life pushing against the melt, and that is usually where it tells you what is wrong.
Twin-screw gearboxes — shaft alignment and timing, co-rotating or counter-rotating. The gear train is re-timed on the way back together, and the checks are repeated before the case is closed.
Single-screw extruder gearbox after its overhaul, restored and repainted.
Twin-screw gearbox opened for inspection, gear train and bearings in the housing.
Gear train reassembled and re-timed before the case is closed.
Inspection, housing bore repair and a finished rebuild from our shop. More photos and videos are in our gallery.
The same five stages on every box, single-screw or twin-screw.
The case is cleaned inside and out so the inspection shows what is actually there.
Every part is removed, marked and recorded, so nothing goes back in the wrong place or the wrong way round.
Gears, bearings, shafts, seals and housing bores are measured. A rebuild that does not find out why it failed will fail again.
Worn housing bores are line bored. Obsolete gears, shafts and adapters are machined here rather than waited on.
The box goes back together to its clearances. On twin-screws the gear train is re-timed and checked before the case closes.
A blown film producer in California had a gearbox that could not be supported any longer — no parts, no replacement, and nothing left to offer. The whole line was built around it.
We machined a new large mounting plate and a gearbox-to-extruder adapter so a new Zambello heavy-duty single-screw box could take its place on the existing frame. The customer kept the line and the extruder, and changed only the one part that had become unobtainable.
Bearings and seals — 1 to 2 weeks.
A full rebuild — 6 to 10 weeks.
If gears have to be cut new, the job can run longer, and we tell you that when we quote rather than when it is late. If your line is down, say so on the call — see emergency machining.
The work that happens here, and the one step that goes to a partner.
| Gearbox types | single-screw and twin-screw, co-rotating or counter-rotating, lab-scale to large production |
| Housing line boring | in house, to 20″ diameter over roughly 50″ |
| Lifting | to 10 tons |
| Made in house | gear blanks, shafts, housings, adapters and mounting plates |
| Gear teeth | cut by our gear-cutting partner from blanks machined here |
| Checks on reassembly | runout, tooth contact and backlash, among others |
| Turnaround | bearings and seals 1 to 2 weeks; a full rebuild 6 to 10 weeks |
Yes. Single-screw work centers on the thrust bearing and the axial load path. Twin-screw work centers on shaft alignment and timing, co-rotating or counter-rotating.
Bearings and seals take 1 to 2 weeks. A full rebuild takes 6 to 10 weeks. It runs longer only if gears have to be cut new, and we say so when we quote.
No. Send the complete unit or just the component that failed. We work from either.
Yes. We measure the worn part and make a new one. Gear blanks and shafts are machined here, and our gear-cutting partner cuts the teeth.
We have machined thousands of parts for Davis-Standard, Egan, Gloucester and Sterling extruders, and trained at Zambello’s factory on their gearboxes. Other makes too — send it.
Runout, how the gears interact and their tooth contact, and backlash, among others. On twin-screws the gear train is re-timed and checked again before the case is closed.
Yes. When a box can no longer be supported, we can machine a new mounting plate and a gearbox-to-extruder adapter so a replacement box fits the existing frame and extruder.
The gearbox is one part of the drive. These are the services around it.
Email photos and the nameplate to sales@zalamachine.com or use the quote form. For the rest of our gearbox work see industrial gearbox repair, and for the parts around the drive see extruder components.
