Research on Machine Data Protection Method Based on Siemens 802 Series CNC System
The machine data refers to all the essential numerical values that configure a CNC (Computer Numerical Control) system to match specific machine tools. These data are pre-set by the manufacturer when the machine is shipped and are later fine-tuned during installation and commissioning based on the actual conditions at the site. Once properly adjusted, protecting this critical data becomes crucial to ensure the machine operates correctly and reliably.
At the maintenance site, several issues often arise due to a lack of understanding about the importance of machine data. For instance, some technicians may alter the data without proper knowledge, leading to malfunctions or even accidents. Others may not know how to safeguard the data, resulting in data loss and subsequent machine failure. A notable example is a VTC-20B three-axis machining center where the tool magazine's zero parameter was lost, causing incorrect indexing and a collision during automatic operation.
Since different CNC systems have varying methods for protecting machine data, this paper uses the SINUMERIK 802D system as a case study to explain its machine data functions and protection mechanisms.
The protection of machine data involves several key aspects: the memory type and storage location, the system startup method, and the backup strategy.
First, the SINUMERIK 802D system uses two types of memory: SRAM (Static Random Access Memory) and FLASHROM (Flash Read-Only Memory). SRAM stores working data that can be modified, while FLASHROM holds fixed data such as factory settings, PLC programs, and system software. The working data area includes machine data, tool data, offset values, setting parameters, R parameters, part programs, and canned cycles—essential elements for the system to function properly. The backup data area duplicates the contents of the working data area for safety. The factory data area contains default settings that cannot operate the machine alone, and the PLC sequence and user texts are stored separately.
Second, the system has two main startup methods: cold start and hot start. Cold start occurs when power is first applied, while hot start happens when the system restarts after running. Both methods offer three startup modes: Mode 0 (normal power-on), Mode 1 (default power-on), and Mode 3 (power-on from stored data). Mode selection is done via a switch for cold starts and through soft keys for hot starts.
Mode 0 loads data from the static memory, while Mode 1 reverts to factory defaults, and Mode 3 restores data from the backup area. Each mode ensures different levels of data integrity depending on the situation.
Third, data protection in the SINUMERIK 802D system relies on both internal and external storage. Internal backup is performed using the system’s soft keys, which quickly saves data to the flash memory. However, if the system fails, this data may not be accessible. External backups, on the other hand, transfer data via RS232 to a computer, offering more flexibility. There are two external backup methods: series backup, which saves all data in one file but may include version-specific commands, and partition backup, which separates data into categories for universal use but requires multiple files.
Machine data acts as the bridge between the CNC system and the machine tool, directly affecting its performance. Understanding and properly protecting these data is essential for ensuring the reliable and efficient operation of CNC machines. Without proper safeguards, even minor errors can lead to costly downtime or damage. Therefore, maintaining accurate and secure machine data is a fundamental step in any CNC system maintenance and operation process.
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