The automatic tool change device (ATC) of vertical machining center has two common types of tool change methods. One is that the tools are exchanged directly from the tool magazine by the spindle, and the other is that the exchange between the spindle and the tools on the tool magazine is completed by the mechanical arm. The first tool change mode is applicable to small vertical machining centers. The tool magazine is small with few tools, and the tool change action is simple, so it is easy to find and eliminate faults of tool drop in time; The second tool change mode is a relatively complex one in terms of structure and action.

The tool drop fault of the vertical machining center occurs with a long time. At the beginning, it occasionally occurs once, once a month, or even once two or three months. It is thought to be caused by accidental factors and has not attracted enough attention. It slowly occurs once or even twice a week, accompanied by the inadequate tool installation on the spindle; Later, it gradually evolved into a shift, and there were many failures, which seriously affected the production progress; Causing waste products; After careful observation, there are two kinds of tool drop faults: one is that the tool drops after the processing of this step is completed, and the other is that the tool falls on the workbench without processing at all; During the machining process of the vertical machining center, the tool change action is executed and the action sequence is normal, so there is no alarm when the tool falls out or the tool loading (installed on the spindle) is not in place. The fault will occur only when the operator checks the workpiece or hears the abnormal sound of tool drop. Therefore, batch scrap will sometimes occur due to tool drop on the automatic processing production line.

Check that the mechanical arm performs ATC tool change troubleshooting steps and stops the mechanical arm at the vertical limit position; Check the two claws on the mechanical arm and the spring supporting the claw; No problem is found, indicating that the mechanical arm holds the tool tightly and will not drop the tool when the mechanical arm rotates; Check the clamping condition of the tool. According to the analysis of the phenomenon that the tool is not installed on the spindle, it may be that the disc spring in the inner hole of the spindle cannot clamp and fasten the tool, resulting in the phenomenon that the tool is not installed in place, or even the tool falls out because it cannot be installed; After disassembling the inside of the spindle, it was found that several pairs of disc springs had been broken; Therefore, all disc springs were replaced; There are no problems during commissioning; The tool drops again after one shift; Check the tool change program. This fault only occurs during the tool change action and has nothing to do with other actions. Edit an automatic tool change repeated execution program and run this program in order to find the real cause of tool drop.

During the program running of the vertical machining center, the following conditions are found: when the spindle tool is not clamped in place or even clamped, the mechanical arm rotates and the tool falls; According to the sequence of tool change action mentioned above, analyze the tool drop fault caused by the error of spindle tool clamping in place travel switch; Open the PLC ladder diagram, monitor the travel switch, press the travel switch repeatedly, and it is found that there are 3 times of x2.5 in more than 20 times of pressing The phenomenon that 5 is in "0" state occurs twice, and X2 after pressing at the same time 5 if the phenomenon that the "1" state cannot be changed to "0" state occurs twice, it is judged that the travel switch is damaged according to the above; This switch is omronzc-q2255, replaced by cxw5-11q1, and the test run is normal; One week later, the operator still reported that there was a tool drop phenomenon. certainly, the frequency was lower, which indicates that the tool drop fault has not been completely eliminated.

Repeat fault handling operation for two hours, automatic tool change for hundreds of times; Finally, a fault was found: when the mechanical arm was not in place, the tool on the spindle was released, and the mechanical arm did not grasp the tool, resulting in tool drop, which indicates that the magnetic in place induction switch of the mechanical arm has wrong action; Replace the switch e2e-cr8c1, and the fault still exists; Check the PLC ladder diagram. The input point of this switch is X4.7； X4.7 in ladder diagram is the normally open point. When this switch is sensed, the state is "0", and when it is not sensed, the state is "1"; Its logic state is opposite to that of common induction switch; When X4.7 when the line is disconnect, X4.7 will also cause status in "1" , so check X4.7, found X4.7 at the wiring terminal behind the electromagnetic induction switch. When the tool is changed automatically, the slight vibration caused by a series of actions of the mechanical arm cam makes X4.7 wire is in the disconnected state, so when the mechanical arm is not in place, release the induction switch of the tool. Although it is still inductive, X4.7 is in the disconnected state and is in "1" status, so when the machine is not in place, the tool is released and the tool falls out; In this case, the tool drop fault refers to the tool that falls after the tool has been used for processing. In the above mentioned case, the tool falls was without any processing step.