Box Shear or Gantry: Feed Shape Decides
Force ratings get compared; feed shapes get ignored. Yet the shape of the material arriving at your yard — bundled or loose, consistent or irregular, pre-sorted or as-it-comes-down — decides the box-versus-gantry question more reliably than any tonnage number. This article is the feed-shape test: how to read your own intake, what each design does with each feed shape, and why the honest answer occasionally sends a buyer to a design we do not build.
For the design comparison itself, read the box-versus-gantry guide.
Reading Your Own Feed Shape
Most buyers describe their material by grade — “mixed ferrous,” “HMS 1 and 2” — when the decision-relevant description is shape. Four shape questions map the intake:
- Bundled or loose? Tight bundles cut as predictable sections; loose irregular material needs staging before the blade.
- Consistent or variable? Consistent material — same profile, same size band — feeds any design. Variable material punishes designs that assume consistency.
- Pre-sorted or as-it-comes-down? Demolition feed arrives as it comes down; mill intake often arrives pre-sorted. The two are different operations.
- Oversized pieces — how often? The frequency of over-class pieces, not their existence, decides the design. Weekly oversized pieces are a design requirement; monthly ones are a blade configuration note.
Write the answers down before comparing any machines. They are the specification.
What Each Design Does With Each Shape
Box chamber, bundled consistent material. The box design’s home turf. Laterally compressed, horizontally cut, predictable piece geometry, contained splashing. If your intake is consistent and your buyer pays for size, this is where the box design earns its place.
Box chamber, oversized irregular material. The struggle case. A closed chamber accepts what fits through its opening, and irregular heavy pieces either do not fit or arrive in a state the chamber cannot stage. Operations with this feed shape and a box machine spend their shifts pre-cutting at the gate — a handling cost the design quietly imposes.
Gantry tank, oversized irregular material. The gantry’s home turf. The tank stages what the excavator delivers, the feed advances it to the blade, the hold-down locks it, and the cut happens on PLC presets. Demolition feed, structural sections, heavy plate — the material that defines the category’s hardest jobs.
Gantry tank, light consistent material. Works, and works well, but at this feed shape the gantry’s advantages — force ceiling, continuous duty — are advantages the operation cannot use. The honest conversation at this profile is often about the entry class or, for lighter still, the alligator.
The Test in Practice
| Feed shape | Design that fits |
|---|---|
| Bundled, consistent, lighter; buyer pays for size | Box / container shear |
| Variable, oversized, irregular; two shifts or more | Gantry shear |
| Light, loose, workshop volumes | Alligator shear |
| Heavy plate as daily diet | Gantry, mill classes |
The test is not subtle, and it is not about tonnage. It is about what arrives at the yard and how often the awkward fraction arrives.
Why We Publish the Case Against Ourselves
We build gantry shears. We also tell buyers when the box design fits their feed shape better, and occasionally when an alligator does. The reason is not modesty — it is that a buyer sold the wrong design comes back for the right one eventually, and a buyer sold the right design comes back for the second machine. The full range exists because operations genuinely differ, and the quotation names the design your numbers support.
For the gantry cases, the class follows the feed shape: light mixed ferrous at 20 to 40 tons a day is the Q91-200; continuous HMS at 60 to 80 is the Q91-630; production lines are the 1250 and above. The mixed-yard guide covers the middle of the range in detail.
Reading a Week of Intake
The feed-shape test is runnable in an afternoon, and most buyers have never run it. Take one normal week of intake — not the heaviest week, not the lightest — and record four things per load: bundled or loose, consistent or variable, pre-sorted or as-it-comes-down, and whether any piece exceeded the class boundary you are considering. A week of that record describes your feed shape better than any grade description, and it is the document the quotation should be written against.
The record also prices the pre-cutting pass. If the material needs sizing at the gate before either design can take it, count the minutes per load and multiply by loads per day — that is a per-shift handling cost, and it appears on no specification sheet. Operations that run this test usually discover their feed shape is either more consistent or more irregular than they assumed, and both discoveries change the design.
The Handling Cost of Pre-Cutting
Pre-cutting is the hidden tax of a design mismatch, and it is worth naming precisely. When material arrives in a shape the machine cannot take — oversized for a box chamber, irregular for an inclined plane — the operation sizes it at the gate until it fits. That pass costs handling time every shift, it costs a second pass with the loading equipment, and it costs the material a handling cycle it would not otherwise need. None of it appears in the machine’s specification; all of it appears in the operating account.
The test for whether pre-cutting is a tax or a choice is frequency. Material that needs pre-cutting weekly is a design mismatch; material that needs it monthly is a blade configuration note. Count the frequency in the week-of-intake record and the design answers itself.
The Design That Survives the Record
After a week of intake records, the design usually names itself — and the honest part of the exercise is letting it. If the record shows consistent bundled material at lighter weights, the box design’s containment and feeding flexibility earn their place. If it shows irregular heavy material with weekly oversized pieces, the gantry’s feed and force answer. If it shows light loose material at workshop volumes, the alligator answers. The record does not care what the buyer prefers, and that is its value: it is the one input to the decision that cannot be argued with. Operations that buy against the record stop second-guessing the purchase in month six, which is when preference-bought machines start to be resented.
The Week Record, Formalized
The week-of-intake record deserves a format, because an informal impression is not a specification. Four columns per load: bundled or loose, consistent or variable, pre-sorted or as-it-comes-down, and over-class frequency. One week of that record — a normal week, not the heaviest or the lightest — describes the feed shape better than any grade description, and it is the document the quotation should be written against. It also prices the pre-cutting pass honestly: if the material needs sizing at the gate, the minutes per load multiplied by loads per day is a per-shift handling cost that appears on no specification sheet. The record takes an afternoon and it replaces the two most expensive inputs to equipment decisions: assumption and preference.
The Record, Read Honestly
The last step of the feed-shape test is the one buyers skip: reading the record honestly. It is tempting to run the week, find the answer uncomfortable, and re-run it with a heavier week. The record only works if it is a normal week — the median, not the argument. If the record says the material is consistent and lighter than the buyer assumed, that is the specification, and the honest machine is smaller than the one in the brochure the buyer came in with. Operations that buy against an honest record stop fighting their machines; operations that buy against a hopeful one spend a decade doing it.
Buyer FAQ
How do I describe my feed shape for a quotation?
Answer the four questions in the first section — bundled or loose, consistent or variable, pre-sorted or as-it-comes-down, and how often oversized pieces arrive. Photos of a normal week’s intake help more than any grade description.
Can a gantry handle bundled consistent material?
Yes, and it does it well — but at that feed shape its force and duty advantages go unused, and the honest conversation may be about the entry class rather than the flagship.
Is the box design ever right for heavy plate?
At the top of the range the gantry’s force ceiling and continuous-duty rating decide it. For lighter plate within the box design’s ceiling, the feed shape and containment requirement decide.
What if my feed shape changes seasonally?
Declare both shapes at quotation. The configuration is specified against the heavier one, and the presets and rotation schedule get re-checked when the mix changes — the same logic as the production-line specification review.
How quickly can I get a recommendation?
Send the feed-shape answers, the daily tonnage and the loading equipment. The written recommendation comes back within two business days, naming the design and class your numbers support. The record is the specification; everything else in the decision is commentary on it.