FREE 3D WORLD

1. Basic knowledge of machining

Common machining methods include turning, milling, planing, grinding, drilling, boring, punching, sawing, insertion, etc.

The contents related to machining include processes, machine tools, tools, fixtures, chip breaking, tool setting, in-machine measurement, tool repair, cleaning, etc.

Figure 1 Engine housing

2. Machining process

Process design is the difficulty of machining, involving machine parameters, tool selection, processing methods, materials, etc., one clamping as much as possible to complete more processing content, reduce the number of equipment.

Automated production lines require that the beats of each process be as equal as possible.

Process flow: pre-order incoming - workpiece cleaning - OP10 - workpiece cleaning - OP20 - workpiece blanking

3. Composition and layout of engine casing machining production line

The automatic production of engine block machining consists of 4 horizontal machining centers (OP10 2 sets, OP20 2 sets), 2 FANUC M-710iC/45M robots (including truss, maintenance table and claw), 1 set of visual positioning device, 3 washing machines, 1 feeding conveyor line, 1 unloading conveyor line, 2 buffer tables, 1 sampling sliding table, 1 set of ground sink, safety fence, safety door and system control cabinet and other equipment.

The 7th axis of the robot adopts a truss side hanging structure, and each robot is responsible for the loading and unloading of 2 machine tools on one side, and the 2 robots run in coordination without interfering with each other.

Figure 2 layout of machining automation production line

4. Machining cycle timing

OP10 and OP20 machining time is 120s, the total opening and closing doors of machine tools are 8s, and the cleaning time of machine tool fixtures is 10s.

The Mazak horizontal machining center machine is a rotary table double table, and the loading and unloading of the machine does not affect the machining.

The robot completes OP10 loading and unloading time 56s, OP20 and OP10 are similar, 1 robot completes OP10 and OP20 time in total 112s (56+56), less than the machining time (120s), can meet the machine tool cycle requirements.

Table 1 The robot completes the OP10 loading and unloading cycle time table

No.	Robot action	Time(s)
1	The robot walks from the waiting position to the waiting position of the machine	1
2	The robot walks from the waiting position to the pickup position	2
3	Robot pickup	4
4	The robot exits to wait position	2
5	The robot walks to the washing machine staging position	3
6	Robot hand-held workpiece cleaning	10
7	The robot walks to the unloading conveyor line	3
8	Robot unloading	3
9	The robot returns initial position	2
10	The robot walks to the load conveyor line	2
11	Robot pickup	4
12	Robot walking washing machine	2
13	Robot hand-held workpiece cleaning	10
14	The robot walks to the machine load position	1
15	Robot loading	4
16	The robot exits to wait position	1
17	The robot returns initial position	2
	合计	56

5. Detailed description of machining automation supporting equipment

5.1 Machine tools

There are many types of machine tools, common lathes and machining centers.

It is best for the lathe to have the function of spindle returning to the origin.

In order to realize the closed-loop control of machining, the machine tool is best equipped with a tool setting instrument and an in-machine probe to realize automatic workpiece positioning and process measurement, realize feedback to the control system, and automatically carry out tool supplementation.

1) Tool setter

The use of automatic tool setting probes on CNC machines greatly improves production quality. If an off-machine tool setter is used, the tool cannot be measured in a valid working state, and manually entering data into the CNC can cause errors. In addition, external measuring systems cannot be used to check tool wear and the condition of the cutting edge of the tool between machining cycles.

Tool pairs probes can be used to determine: tool length, radius, tool cutting edge wear assessment, tool breakage detection, and to check whether the tool in the spindle is correct after a tool change. These functions are implemented automatically on the machine and the measured data is written to the tool parameter table.

Figure 3 tool setter and in-machine probe

2) Workpiece measuring head

The workpiece measuring head is directly installed on the machine tool turret, and after the machine tool is processed, the tool change procedure is executed, the workpiece measuring head is taken and the workpiece measurement procedure is executed. The tool setter is installed in the designated position of the machine tool, if the machine tool cannot be moved, the tool setter is moved, and if the machine tool can be moved, the machine tool is moved. The measuring head mainly includes two parts, transmitter and receiver, and wireless, infrared and cable connections can be used between the two.

Figure 4 in-machine probes

 

3) Machine tool fixture

The fixture must have the function of automatic positioning and clamping and loosening to ensure that the workpiece can be easily accessed.

The fixture must have the function of automatically cleaning iron filings to ensure that the positioning surface and clamping surface are free of iron filings and cutting fluid.

The fixture must have the function of detecting the workpiece in place, and the method of air tightness detection can be used to automatically detect whether the workpiece is installed in place.

Figure 5 Workpiece Clamp

5.2 Robotic claws

The robot claw is mainly composed of connecting flange, parallel opening and closing three-jaw cylinder, parallel opening and closing two-jaw cylinder, fingers, finger blocks, etc., and the inner hole of the three-jaw cylinder supports to realize the positioning of the workpiece.

Figure 6 Schematic diagram of 39 robot claws

5.3 Robot trusses

The robot truss is composed of frame, servo motor, reducer, linear guide rail, rack and pinion, stroke switch, etc.

Figure 7 Rrobot truss

6. Machining Lessons

The gap between the machine tool positioning tooling and the workpiece, like the gap between the lathe spindle collet and the workpiece may only be 0.02mm, this accuracy is a bit difficult for the robot, and the claw may need to consider other auxiliary feeding mechanisms.

Tool change cycle. Some tools may need to be changed in an hour or two, find ways to reduce or avoid frequent manual tool changes.

How to detect tool wear and even broken tools? Configure the tool setter in the machine, the size measurement outside the machine or the machine tool that comes with the machine to judge the tool wear by detecting the change of motor current.

Pay attention to machine tool residue cleaning. The surface of the fixture should be as flat as possible, reduce pits, avoid blind holes, make a conical support surface, and assist chip liquid, compressed air, etc. to purge it to ensure that the fixture and the foundation surface of the workpiece are clean.

Workpiece in place inspection. You can choose an air pressure precision position sensor to determine whether the workpiece is loaded in place through the change of air pressure.

Pay attention to the material of the finger block to avoid damage to the workpiece.

The chip liquid on the surface of the workpiece will affect the dimensional measurement, and the workpiece must be cleaned and blown dry before measurement.

7. Machining case display

Figure8 Machining automation unit