We're responsible for building-----we're responsible for manufacturing-----we're responsible for training
Door leaves up to 2800 mm formed straight enough to close on the first hang — and an honest note up front: the frames are roll-formed, and we do not make those.
A steel door splits cleanly into two manufacturing problems that require different machines. The leaf is a large flat panel — typically 0.8 to 1.2 mm galvanised or cold-rolled sheet, 2000 to 2400 mm tall, folded on all four sides with a hemmed or returned edge. That is panel bender work, and a D (2500) or D+ (2800) model covers the full leaf height without splitting it.
The frame is a constant-section profile, and it is roll-formed. No panel bender, press brake or turret punch produces a roll-formed frame section, and STON CNC does not supply roll-forming lines. Door manufacturers either run a separate frame line from a specialist supplier or buy frames in. We state this at the start because it is the single most common mismatch in steel door enquiries, and discovering it after an order is expensive for everyone.
STON CNC (Qingdao Ston Mechanical Technology Co., Ltd.) is a Chinese original manufacturer of CNC panel benders and turret punch presses, founded in 2006 in Qingdao, China. All equipment described here is built inside STON CNC's own 20,000㎡ factory, from casting and heat treatment through machining, assembly and inspection. Machines carry ISO 9001 quality certification and CE marking under Machinery Directive 2006/42/EC, and are exported to more than 80 countries. View certifications and patents →
The leaf, its skins and its internal reinforcement are all folded sheet. That is where the labour, the straightness problems and the surface scrap in a door factory actually sit.
A door that is not straight will not close, and the fault appears on site rather than in your shop. Straightness of roughly 0.2 mm per metre and angle accuracy of roughly ±0.5° per metre across the full leaf height are what keep hanging a first-time operation instead of a shimming exercise.
Door factories routinely try to buy one machine for both. A roll-formed frame section and a folded leaf have almost nothing in common as manufacturing problems. Treating them as one purchase is how projects end up with a machine that makes half the product.
One door range becomes dozens of leaf variants once glazing, louvres and hardware positions are combined. Turret punching produces louvre blades, vision cut-outs, hinge and lock preparations from a program, so a new variant is a drawing rather than a tooling order.
Machine length is chosen by your tallest leaf. Splitting a 2400 mm leaf into two bends to fit a shorter machine creates a joint that has to be hidden, which defeats the purpose.
The frame row is the important one on this page. Everything else about door leaves sits comfortably inside the forming window.
| Parameter | Panel bender | Flexible edge folding machine | Notes |
|---|---|---|---|
| Typical leaf gauge | 0.8–1.2 mm | 0.8–1.2 mm | Well inside capacity |
| Cold-rolled / galvanised max | ≤2.0 mm cast / ≤1.5 mm welded | — | At full bending length |
| Stainless steel max | ≤1.2 mm cast / ≤1.0 mm welded | — | For stainless door ranges |
| Max forming length | 2800 mm (D+) | 2000 mm | Choose by your tallest leaf |
| Bending height | 5 mm min / 170, 300, 400 mm max | 4 mm min / 100 mm max | By configuration |
| Edge finishes | Positive and negative, 0–180° | Arc, dead edge, offset | Hemmed leaf edges use dead edge |
| Straightness | approx. 0.2 mm/m | approx. 0.2 mm/m | Decides whether the door closes |
| Angle accuracy | approx. ±0.5°/m | approx. ±0.5°/m | Across the full leaf height |
| Door frames and profiles | Not possible — roll-formed product, not supplied | Separate process and supplier | |
| Utilities | Three-phase 380 V, 0.6 MPa air | Configured to destination voltage | |
Door leaves, skins, louvre panels and kick plates in 0.8–1.2 mm, up to 2800 mm, folded on all four sides with hemmed or returned edges. This is core panel bender work.
Door frames, jambs, stiles and any constant-section profile. These are roll-formed products from a separate process and supplier, and no machine on this page produces them.
Hinge reinforcement plates, lock boxes, threshold parts, and heavy gauge hardware mounts. One press brake alongside the leaf cell covers all of it.
Risk assessment follows EN ISO 12100; safety-related control functions such as light-curtain interruption and emergency stop are specified to EN ISO 13849-1. Hydraulic press brakes supplied into the EU are built against EN 12622. Machines placed on the EU market carry CE marking under Machinery Directive 2006/42/EC with the accompanying technical file. Quality management is certified to ISO 9001, and machined structural tolerances follow ISO 2768. For the finished doorset, EN 1634-1 covers fire resistance testing and EN 16034 covers fire resisting and smoke control characteristics of pedestrian doorsets. These apply to your tested assembly, not to the forming machine — what the equipment contributes is the dimensional consistency the tested configuration depends on being reproduced in production.
On the machines this means fully enclosed rear fencing, protective covers on all protruding moving parts, laser guarding that halts motion when the protected zone is broken, over-tonnage protection on turret punch presses, and grating-ruler offset-load detection on panel benders.
A door factory needs all three processes. What matters is knowing which one each part belongs to before buying anything.
| CNC panel bender | CNC press brake | Roll forming | |
|---|---|---|---|
| Part geometry | Flat panels folded on all four sides | Any bend line, heavier gauge | Constant cross-section profiles |
| Typical door parts | Leaves, skins, louvre panels, kick plates | Hinge plates, lock boxes, thresholds | Frames, jambs, stiles, glazing beads |
| Maximum length | 2800 mm | 4100 mm | Effectively unlimited |
| Straightness over 2.4 m | approx. 0.2 mm/m | Crowning and operator dependent | Excellent, fixed section |
| Operators | 1, or 0 with automatic loading | 1–2 on tall leaves | 1 per line |
| Response to a new door variant | Program change, minutes | Tool change and gauge reset | New roll set, weeks |
| Does STON supply it? | Yes | Yes | No — different process |
If your business is primarily frames rather than leaves, this page is not the right solution and we will tell you so on the first call. Frame lines come from roll-forming specialists; what we equip is the leaf side of the factory.
Figures below describe the direction and mechanism of the change. Actual results depend on your part mix, batch size and shift pattern — we model them against your own drawings before quoting.
| Item | Press brakes only | Panel bender leaf cell |
|---|---|---|
| Operators per 2.4 m leaf | 2, plus a third for turning | 1, or unattended with truss loading |
| Handling of the coated face | Dragged across the back gauge each bend | Vacuum pick-up, no contact |
| Leaf straightness | Crowning and operator dependent | approx. 0.2 mm/m |
| Doors that need shimming on site | Common when angles drift | Reduced by closed-loop angle control |
| New leaf variant | Tool change and first-article proving | Program recall |
| Louvre and vision preparation | Separate operations | One clamping on the turret punch |
| Night shift | Requires a full crew | Runs unattended with loading and stacking |
Payback logic we use with customers: (annual labour released + reduction in rework and scrap + additional saleable output) ÷ installed equipment cost. We build this with your real numbers rather than publishing a headline figure that would not match your plant.
Cast-iron frame models to 2500 and 2800 mm forming length — full leaf height in one clamping. Full-electric servo closed-loop control, ground lead screws, grating-ruler offset-load detection.
View press arm type →
Dead edge, arc and offset bending for hemmed leaf edges and returns. Up to 25 concurrent servo axes, 42CrMo forged blank holder, patented 360° rotating suction feeding.
View folding machine →
Louvre blades, vision panel cut-outs, hinge and lock preparation and stiffening ribs in one clamping. ±0.1 mm accuracy, X-axis to 2500 mm with secondary positioning to 5000 mm for tall leaves.
View SF series →
Exchange-table fiber laser for leaf blanks, vision apertures and variant work that does not justify tooling. Burr-free edges on galvanised and coated sheet.
View laser unit →
On a 2.4 m leaf, automated loading removes the two-person lift that causes most coated-surface damage. Native interface, compatible with most robotic arm and gantry brands.
View truss system →
Hinge reinforcement plates, lock boxes and threshold parts in heavier gauge. Direct-drive servo, mechanical crowning compensation, multi-axis CNC back gauge.
View PBE series →Founded in 2006 and headquartered in Qingdao, one hour from major export ports and the airport. Casting, heat treatment, machining, welding, assembly and inspection all happen inside our own 20,000㎡ factory. That is why a configuration change for a 2800 mm leaf line does not become a six-month subcontracting problem.
Door production runs to building completion dates. A leaf that does not close is rejected on site, at the most expensive possible point, so machine accuracy and support response are part of the same conversation.
Specifications on this page verified against STON engineering documentation on 4 August 2026. Forming limits are confirmed against your own drawings before quotation. Published on 4 August 2026 · Last updated 4 August 2026 · Reviewed by Vicky Xu, Head of Overseas Sales.
Leaf height decides the machine. Send your tallest leaf and your most complex variant and we come back within 24 hours with a model recommendation and a clear scope — including what we will not be supplying.
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Whether you're upgrading an existing line or starting a new project, STON will customize a CNC solution for your production.
