Skeleton can be 30–50% of sheet mass on a cup web. If that scrap leaves in bags, you pay twice. An online crusher at the former plus a blender on the extruder is the default AMT layout.
| Online crusher | Offline crusher | |
|---|---|---|
| Duty | Live skeleton, minutes back to the hopper | Start-up lumps, reject cups, purge |
| Best for | Continuous PP/PS webs | Mixed chunks that would jam a high-speed unit |
| AMT | LS-Online-Crusher | LS-Offline-Crusher |
PP cups often run 20–40% closed-loop regrind. PET is stricter: dry again and watch IV. PLA likes low regrind until the process is stable. Dust from dull knives becomes gels in thin PET.
Layout that actually closes the loop
Pipe diameter, filter, and blender sit on the same drawing as the crusher. A 20 m hose across a forklift aisle is how plants “have a crusher” and still buy virgin. Keep the return short, label PP versus PET hoppers, and weigh the blend once per shift so gram weight does not drift.
Worked mass balance
500 kg/h sheet, 40% skeleton → 200 kg/h returns if the loop is closed. That is the extruder margin you already sized at 10–15% — do not sell it and buy virgin to replace it. Include crusher, LS-850 mixer, and loader in the same quotation so pipe diameters match.
Fault map — what the line is telling you
| Symptom | Likely cause | First check |
|---|---|---|
| You “have a crusher” and still buy virgin | 20 m hose across a forklift aisle | Short return, filter, blender on the same drawing |
| Gram weight drifts every shift | Regrind % not weighed | Weigh the blend once per shift; lock 20–40% PP |
| Gels in thin PET | Dull knives, dust, or PET/PP mixed hoppers | Sharpen; separate hoppers; dry PET again |
| Online unit jams on start-up lumps | Wrong crusher for chunks | Offline crusher for purge; online for live skeleton |
| Cup color shifts after a PET trial on the PP line | One hopper, two resins | Full clean — not a “quick flush” |
RFQ checklist — send this in one email
Fill what you know; blank is better than a guess. Attach it on Get a Quote with photos of resin or flake.
- Sheet kg/h and expected skeleton % (often 30–50%)
- Resins on the line (PP / PS / PET / PLA) — one hopper or two
- Distance from skeleton exit to extruder hopper
- Online vs offline already owned; mixer size (LS-600 vs LS-850)
- Target closed-loop % and whether food-contact rules apply
Frequently asked questions
Can I use one crusher for PP and PET?
Not in the same hopper without a full clean. Color and IV contamination are expensive.
Will regrind change cup weight?
It can. Keep the blend ratio in the recipe and check gram weight each shift.
Where does the crusher sit?
At the skeleton exit, not across the hall in a dusty yard.
Do I still need a manipulator?
For pick-and-place of finished parts, yes — that is a different machine from the scrap loop.