Consider an illustrative retrofit: a Type 4 curtain is installed neatly, but the press's actual stopping time and clutch type were never checked. The appearance cannot demonstrate protection. This is a design warning, not a reported customer installation or test result.
Press access can expose operators and other workers to crushing, shearing and ejected material. Older machines also need a review of their control system, braking, valves, stored energy and maintenance condition. Use the punch-press photoelectric protection selection overview only after the machine's suitability and required safety functions are established.
Step 1 — Risk assessment, before you buy anything
Identify the press type, clutch/brake or hydraulic system, controls and jurisdiction. Under OSHA's presence-sensing press guidance, a full-revolution-clutch press cannot use this point-of-operation protection. A part-revolution label alone also does not prove suitable stopping or control reliability. Assess all operators and access paths, ejection and stored-energy hazards. Read the older-press retrofit checklist before choosing hardware.
Step 2 — Choose resolution from the hazard, not the catalogue
Light curtain resolution is the smallest object the curtain is guaranteed to detect. For press work the practical bands are:
| Resolution | Detects | Typical press use |
|---|---|---|
| Documented 14 mm detection | Specified finger-size test object | Candidate for evaluated finger-access geometry; not universal approval |
| Documented 20–30 mm detection | Specified larger test object | Only where the risk and positioning method support it |
| Coarser / multi-beam access devices | Model-specific access detection | Separate reach-through, field-height and restart assessment; muting not assumed |
Select the manufacturer's specified detection capability, not beam pitch or a hand-guard product name. DQA/DQC data pair 10 mm pitch with 18 mm detection, so that pitch does not establish finger detection. Check the complete field, side access and space behind the curtain. A higher optical safety Type does not compensate for incorrect geometry.
Step 3 — Measure the real stopping time
The calculation needs the worst-case stopping performance of the actual machine and its complete protective chain. Record the measurement trigger and endpoint so the sensor, logic and final-element delays are neither omitted nor counted twice. Do not use an unexplained historical datasheet value as the present machine stop time.
Have competent personnel measure stopping performance with an appropriate instrument under controlled conditions specified for the press, including relevant load, speed, temperature and stroke position. Keep people out of the danger zone and use approved test procedures. Include the required deterioration and measurement allowances; an inadequate or unreliable stop must be corrected before optical safeguarding is accepted.
Step 4 — Calculate the safety distance (ISO 13855)
For an applicable approach configuration, S = K × T + C illustrates separation based on approach speed, total time and intrusion allowance. T includes sensor response, safety logic, output/final elements and machine stopping, with required allowances. Apply ISO 13855:2024 and the relevant machine-specific requirements, including reach-over, under, around and any required minimum distances; this single equation is not the complete assessment.
Use the ISO 13855 safety-distance guide alongside the machine standard. Document the actual stopping measurement and every additional delay in T. Recalculate if the sensor, controller, stop elements, settings or machine performance change.
Step 5 — Monitor the stopping performance over time
A commissioning measurement is not a lifetime guarantee. Changes in brake, clutch, valve and mechanical condition can affect the stop. Preserve the allowable stopping limit and the required inspection and monitoring plan in the machine documentation.
A stopping-performance monitor checks the specified performance limit and prevents further operation when it is exceeded; it cannot repair a brake or guarantee prevention of every degraded stop. OSHA 1910.217(c)(5) requires the specified control system and brake monitor for its covered manual point-of-operation feeding/removal applications. Determine the corresponding measures for other press types from their requirements, and investigate any excessive stop before returning the machine to service.
Step 6 — Handle the material feed without opening a hole
Material crossing an optical field does not automatically justify muting. Evaluate guarded feed tunnels, the position of the field and an approved machine-cycle safety function. Muting and blanking may be used only where the machine requirements and selected equipment support the specific validated application.
A muting function needs documented safe logic, sensor arrangement, sequence, timing and measures preventing a person from accompanying or following the load into danger. Blanking is different and can change effective detection and required distance. An ordinary PLC cycle signal or timer must not bypass the protective stop. Compare muting and blanking and the press and feed-system safeguarding guide against the exact press and controller manuals.
A word on PSDI — and why we advise against it
PSDI uses an evaluated presence-sensing sequence to initiate a press stroke. It is not the same as clearing a field, resetting a fault or issuing an ordinary start command. Do not wire automatic reset or PLC logic to imitate it.
This retrofit guide does not authorize PSDI. For covered US part-revolution mechanical presses, 1910.217(h) and its mandatory certification/validation requirements apply, including an OSHA-recognized independent validation organization. An engineer's signature alone does not meet that process. Establish the applicable legal route and all required validation before considering PSDI in any jurisdiction; no throughput gain is asserted here.
The standards, briefly
Identify the actual machine scope. ISO 16092-1:2017 is used with the applicable press-specific part and excludes press brakes; its stated scope is not retroactive to presses manufactured before publication. A competent assessor must determine its role in an older-machine modification alongside applicable law. ISO 13855 addresses positioning, IEC 61496 the device, and ISO 13849-1 or IEC 62061 the complete safety function. Do not transfer a mechanical-press rule unchanged to hydraulic presses or press brakes.
Throughput — the part everyone actually worries about
Evaluate throughput with the actual loading sequence after the safeguarding concept is valid. Better layout and reliable alignment may reduce unnecessary handling or trips, but a curtain does not guarantee faster cycles than a guard. Never shorten separation, suppress diagnostics or weaken reset behavior to meet a production target. Record any measured production result separately from the safety validation.
Where DAIDISIKE fits
The DQS press photoelectric guard is a product to assess against the actual press requirements. Its documented dry-contact interface must not be described as a dual safety OSSD pair. DQE and DQA do not have an established Type 4 classification in the available documentation. For DA31, exact input compatibility needs evidence and current material does not establish EDM or cross-fault monitoring. Neither a product name nor a relay can replace site stopping measurements and validation. Request the specific documents before proposing the combination.
The bottom line
A defensible retrofit records machine eligibility, risk reduction, documented detection and interfaces, measured total stopping performance, safe geometry and controlled restart. Validate the full installation with the manufacturer's prescribed test piece and approved stop/fault checks under safe conditions, then maintain it at the required intervals. No single device makes an unsuitable press acceptable, and no faster production outcome is guaranteed.