At the beginning of 2020, a sudden epidemic disrupted everyone's rhythm and changed everyone's lifestyle. For example, even today, wearing masks is still one of the most important means of epidemic prevention.
At the beginning of the pandemic, the demand for masks surged, leading to a supply shortage, and companies across the country rushed into the mask industry. Now, although the supply and demand relationship for masks has stabilized, mask-making machines remain a hot commodity in light industrial manufacturing machinery.
In reality, many mask-making machines are still in a "naked" state, meaning all moving parts are exposed without any protection. Personnel operating, cleaning, and maintaining these machines are at risk of injury at any time. While such machines might be acceptable during a crisis, in the current situation of supply and demand balance, with many companies making mask production a routine project, and even more machinery manufacturers exporting their mask-making machines to Europe and the United States, such bare machines are unacceptable from a safety perspective.
So what kind of security measures should be chosen for such a machine? We can get some answers from the two comparison images below.
First, there is mechanical protection. By adding fixed protection to enclose the main moving parts inside, operators cannot directly access these potentially harmful structures, such as servo-driven printing rollers, when the machine is running normally.
Secondly, for parts that require material threading, including meltblown fabric inlets, ear loop holes, and finished product outlets, holes / grooves can be made in existing fixed protection to allow the raw materials to pass through smoothly. In accordance with the requirements of EN ISO 13857 for opening size and safety distance, personnel can be prevented from reaching / touching dangerous movable parts inside.
Subsequently, considering that manual intervention is required when threading raw materials and that some necessary adjustments require personnel to directly interact with the moving parts, a portion of the fixed protective structure was modified into a movable protective structure (safety door). When the safety door is opened, the related mechanical actions are stopped through a safety circuit and remain stationary until the safety door is closed and reset.
Next, based on the risk assessment results and in accordance with the method defined in EN ISO 13849-1 as PLr (Required Performance Level), an appropriate performance level is selected to design the safety functions:
Input section: Select a safety interlock switch that meets the PLr level requirements, such as the PSENmag series or PSENcode series;
Logic section: Similarly, select safety relays that meet PLr level requirements, such as the PNOZ sigma series or the more customized MyPNOZ product .
Output Section: The most important moving parts in a mask machine are usually controlled by servo drives. Opening the safety door and cutting off the power to the servo drive via a safety circuit to stop the movement is a feasible approach. Alternatively, using a drive product with STO (Safe Stop) function to stop the motor rotation via an STO circuit is also preferable. However, both methods require a long restart time, significantly impacting production efficiency, especially in situations where the safety door is used frequently. Therefore, servo drives with Safety Stop ( SS ) function, such as the PMC series, become the best choice to avoid efficiency losses caused by restart time. Other moving parts, such as direct-drive motors and cylinders, can also achieve power and air supply interruption safety protection by directly cutting off the power supply to the relevant components via a safety circuit.
Furthermore, while opening the safety door can prevent moving parts from operating, there are indeed tasks that require human-machine coordination, which is what is known as "operating the machine with the door open." Therefore, operating control devices like PITjog become an ideal choice when both safety and usability are guaranteed.
Pilz can provide users with more relevant standards and product information, and is committed to providing users' machinery and employees with high-quality safety advice in the second half of the pandemic and into the post-pandemic era.
