Comparison
| Torsion bar (WC67K) | Electro-hydraulic servo (WE67K) | |
|---|---|---|
| Axes | 2 | 4+1 |
| Repeatability | about ±0.1 mm | about ±0.05 mm |
| Crowning | none | motorised crowning |
| Bending speed | about 100 mm/s | about 160 mm/s |
| Typical controller | TP10 | ET15 / / DA53T |
| Suits | simple bending, budget first | multi-step, multi-batch, frequent changeover |
How to read this table: these are the usual ranges for the two classes, not acceptance values for a specific machine. The actual configuration is written into the contract.
The three differences that actually matter on the floor
1. Crowning. This is the biggest one and the one fewest buyers ask about.
During bending, the force pushes the ram down and the bed up; both deflect in the middle. The result is an angle at mid-sheet that is more open than at the ends. A machine with motorised crowning lifts the middle of the bed to cancel that, and the crowning value changes per program — because deflection depends on thickness, bend length, V opening and material.
A machine without crowning still bends. But on long sheets you either accept the middle-to-ends deviation, or compensate by hand and accept the time it costs.
Practical rule: the longer, thinner and tighter-toleranced the part, the more crowning is worth. On short parts it does almost nothing.
2. Axes. 2-axis means the machine controls ram stroke and back gauge. 4+1 means the back gauge also moves in more directions, plus a supporting axis.
What it means in practice: on a part with several bend steps at different positions, a multi-axis machine runs the whole program without an operator stepping in. A 2-axis machine makes the same part, but the operator repositions and re-sets between steps.
3. The controller. TP10 does the basics. ET15, and DA53T give multi-step programming, simulation, and on some units angle measurement with automatic compensation.
The controller is what the operator touches every day. It is the part of the configuration most worth thinking about — and the easiest place to save money in the wrong spot.
The one question that actually decides it
How many different part types do you run in a day?
- One or two, large batches → torsion bar is enough. Set up once in the morning and run all day. The extra money spent on servo will sit idle.
- Five or more, small batches → electro-hydraulic servo. The saving is in every changeover: call up the program, crowning sets itself, the back gauge drives to position. Multiply by changeovers per day, then by days per year.
This is a changeover-count problem, not an accuracy problem. Many buyers choose wrong because they ask "which is more accurate" instead of counting how often they switch.
The most commonly misjudged point
"CNC" is not a quality grade. It only says the machine is program-controlled.
A machine badged "CNC" with 2 axes and no crowning behaves more like a torsion-bar machine than like a 4+1 axis servo machine. When comparing two quotations, do not compare the word "CNC" — compare three lines: axis count, repeatability, and whether crowning is included.
Those three lines say more than any description.
Before you decide, do this
Bring one of your own real parts and bend it on both machine types.
Not the easiest part — the hardest: the longest, the thinnest, or the one with the most steps. Measure the angle mid-sheet and at both ends, and count how many times the operator has to intervene.
Those 10 minutes will tell you more reliably than any comparison table — including the one above. We keep both lines in stock in Vietnam. Bring a drawing or bring the part.