Sensor FAQ & Safety Light Curtain Knowledge Base

DAIDISIKE's DQA / DQC / DQS / DQO series target the same Type 2 and Type 4 safety classifications that Keyence GL-R, SICK deTec4 and OMRON F3SG-SR cover, with comparable beam spacing (10 / 20 / 30 / 40 mm), protected heights (160 mm – 1920 mm), response times below 20 ms and dual OSSD outputs. The mechanical envelope is interchangeable in most retrofits — bracket spacing and cable types match the Tier-1 standards.

The difference is total cost of ownership. Premium-brand units carry a brand premium of roughly 3× to 5× the price of a functionally equivalent DAIDISIKE light curtain, before shipping. Because we own the production line, we can quote 7-day lead times on standard models and 3 to 4 weeks on custom heights, beam patterns, or muting accessories — without the procurement delays of an overseas Tier-1 channel.

The Type designation comes from IEC 61496 and is selected based on the risk assessment of the guarded machine. A Type 2 light curtain is approved for applications where the risk of injury is moderate and the consequence of failure is reversible (e.g. low-energy packaging, palletizers, light assembly). A Type 4 light curtain is mandatory for applications where the consequence of failure is severe or irreversible (e.g. mechanical presses, robot cells, high-speed stampers, hydraulic press brakes).

The practical engineering difference is in the internal redundancy and self-diagnostics. Type 4 systems use dual-channel monitored OSSDs, redundant microcontrollers, and beam-by-beam test pulses every cycle — they will detect a single internal fault and force a safe state before the next demand. Type 2 systems perform periodic self-tests but are not single-fault tolerant in the same way. When in doubt, choose Type 4 — the price difference is small compared to the cost of a single guarded-hand injury.

For mechanical or hydraulic punch presses, the DQA series Type 4 safety light curtain with 14 mm finger-detection resolution is the industry standard. Combine it with a DAIDISIKE safety relay (or our integrated controller models) to interrupt the clutch/brake solenoid through monitored dual-channel OSSDs. For larger press openings, the DQO no-blind-zone series eliminates the dead zone between the curtain frame and the die area.

For automatic feeder zones that require material to pass through without tripping the curtain, add muting sensors and the DQM / DQT4 series with integrated muting logic. We also stock DLD5 safety laser scanners as an area-protection alternative when you need a horizontal protective field around the press operator station.

ISO 13855 gives the formula S = (K × T) + C:

• S — minimum distance from the hazard to the curtain plane (mm)
• K — approach speed of the body part, typically 2000 mm/s for hand approach
• T — total stop time of the machine plus the response time of the safety system (seconds)
• C — intrusion factor based on detection capability; for 14 mm resolution use C = 8 × (d − 14), where d is the detection capability in mm; never less than 0

Worked example: a press with a measured stop time of 120 ms, a DAIDISIKE DQA 14 mm curtain (response ≈ 14 ms), and finger detection gives S = 2000 × 0.134 + 0 = 268 mm — round up to the next mounting-bracket increment. Always validate with a stop-time measurement under worst-case wear; brake performance degrades over time.

The choice depends on the input card of your PLC or safety relay. PNP (sourcing) outputs switch the +24 V supply to the load and are the European / global default — most Siemens, Schneider, Allen Bradley and Mitsubishi PLCs accept PNP directly. NPN (sinking) outputs switch the 0 V return and are common in legacy Japanese control panels (older OMRON, Keyence, Panasonic).

For 3-wire sensors you get brown (+24 V), blue (0 V), black (output). 4-wire sensors add a white wire for a second output or a NO/NC complementary signal. Safety light curtains use a 5-core or 7-core cable that carries two independent OSSD outputs (dual channel), the supply, and optionally an auxiliary status / EDM line. Always wire both OSSDs to a properly rated safety relay — never combine them into a single PLC input.

Most “ghost trips” are alignment problems, not electronic failures. Step 1: confirm the two columns (emitter and receiver) are parallel by eye and that no bolts have loosened from machine vibration. Step 2: power up and check the alignment LED on the receiver — most DAIDISIKE units have a multi-LED bar that turns green only when every beam is received above threshold.

Step 3: cover one column with a piece of cardboard and slowly uncover from the top down — each beam should snap into alignment one by one. Step 4: lock the brackets with thread-locker once aligned. If trips persist after alignment, look for environmental causes: welding arc flash on a neighboring station, polished stainless steel reflecting beams back to the receiver, or coolant mist condensing on the lens. We offer anti-reflective shrouds, IP67 / IP69K housings, and arc-immune filters for those cases.

Every DAIDISIKE product page has a Resources section with direct download links for the PDF datasheet, 2D installation drawings (DWG / DXF), and 3D STEP models suitable for SolidWorks, Inventor, Creo, and Fusion 360. The same files are mirrored on our central Download Center for procurement engineers who need to evaluate the full catalog before specifying a part number.

If you can't find a specific revision or you need a custom mounting bracket drawing, email daidisi888@vip.163.com with the model code and your application notes — our technical drawings team will turn it around within 24 hours during the business week (UTC+8).