Most torch collisions and unexplained stops on a large welding cell trace back to one thing: a part placed outside the robot’s working range. This article explains which limits to check before you buy a welding robot, how to place parts so the robot can reach every seam, and what to record if a collision does happen.
What should you check about a welding robot's working range?
Check three numbers against your largest parts: welding height, single-position welding width and rail length. On the JTCLASER 9-axis cantilever workstation the welding height is 0–1.8 m and the welding width 3.5 m. Taller parts should be laid down, nothing should sit past the rail's limit point, and the Z lift must clear overhead cranes.
1Which welding robot working range numbers matter?
A welding robot cell has a working envelope, not just a robot reach. On a cantilever welding robot the envelope comes from the rail (X), the cantilever (Y), the lift (Z) and the robot arm together. Compare these numbers with your largest and most awkward parts before you compare anything else:
| Number | 9-axis cantilever (reference) | What it decides |
|---|---|---|
| Welding height | 0–1.8 m | The tallest seam the torch can reach with the part standing |
| Welding width | 3.5 m per position | How wide a panel can be welded without repositioning |
| Rail length (X) | Configured per order, e.g. 22 m | The longest part, or how many parts can be laid out in a row |
| Y / Z strokes | 2.5 m / 1.5 m | Cross reach and lift |
| External-axis accuracy | ±0.5 mm static, ±0.8 mm moving | How repeatably the torch returns to a scanned point |
Figures are from the published reference configuration; your quotation states the values for your cell. If your parts are taller than 1.8 m standing or wider than one cantilever position, compare with a 9-axis gantry workstation and read cantilever vs gantry welding robot.
2How should tall parts be placed?
- Lay tall parts down or place them on the floor
A part that stands taller than the welding height can often be welded lying on its side. In one structural steel project a part about 2.1 m tall stood just 1.55 m high once laid down, with the seam at 0.85 m.
- Mark the rail limit point
The X axis stops at a limit switch. A part placed past that point leaves seams the robot cannot reach, and the robot stops at the limit. Paint the limit line on the floor so every shift sees it.
- Adjust the scan position for unusual parts
For tall or offset parts, the scan reference point, camera angle and transition-point offsets can be adjusted so the camera and torch approach from a safe direction.
3How do you prevent torch collisions?
Welding robot collision avoidance is mostly discipline at the part, not software. These habits prevent most collisions on a cantilever or gantry welding robot:
- Check the path preview before every new part type
The preview shows the torch path generated from the scan. A path that cuts through a stiffener or swings wide at a corner is visible before anything moves.
- Watch overhead when raising the Z lift
Overhead cranes and hooks are the most common obstacle above a cantilever cell. Keep the emergency stop in hand when lifting.
- Do not move a part after scanning
If a part is knocked or shifted, rescan it. The path belongs to the position that was scanned.
- Keep tack welds and clamps clear of seams
Clamps placed on the seam line are obstacles the template does not expect.
4What should you record after a collision?
A good record makes the cause clear on the first call to technical support. Capture all of this before resetting:
| Record | Why |
|---|---|
| Scanning or welding? | Separates a scan-path problem from a weld-path problem |
| Alarm screen and program line | Shows exactly where the motion stopped |
| Full robot pose | Shows which axis or the torch made contact |
| Photo of the part placement | Including the rail limit mark and any clamps |
| What changed before | Part position, scan settings or template |
After any collision, inspect the torch neck and the camera bracket before resuming. A bent torch or a shifted camera changes where the robot thinks the seam is; ask technical support whether a calibration check is needed.
5Pre-purchase checklist
Before you request a quotation, gather these facts about your parts and compare them with the welding robot working range. They let the supplier size the rail, choose between cantilever and gantry and confirm reach. A fuller list is in the robotic welding feasibility study, and site readiness is covered in is your factory ready for a 9-axis cantilever workstation.
- Largest part: length, width, height
Standing and laid down.
- Highest seam above the floor
Compare with the welding height.
- Narrowest access
Stiffener spacing and plate height decide whether the torch and camera fit between plates.
- Overhead clearance
Crane hook height above the planned cell.
- Daily volume and part mix
Decides rail length and whether alternating work zones make sense.
Frequently asked questions
What is the welding height of a cantilever welding robot?
It depends on the model. On the JTCLASER 9-axis cantilever workstation the welding height is 0–1.8 m. Parts taller than that should be laid down or welded on a gantry cell.
Why does a welding robot stop at the end of the rail without welding?
The part is probably placed past the X-axis limit point. Mark the limit on the floor and keep the whole part inside it.
What should I check after a welding torch collision?
Record the alarm, program line, robot pose and part placement, then inspect the torch neck and camera bracket and ask technical support whether a calibration check is needed.
Check your parts against the working range
Send us the dimensions of your largest part and your highest seam. We will tell you whether a 9-axis cantilever fits or a gantry layout is the better choice.
- JTCLASER field commissioning and after-sales records, 2026
- JTCLASER 9-axis cantilever welding robot workstation, published reference configuration