The “Pertugiatrice”, an Italian slang name, is an Automatic Drilling Machine with PLC capable of high precision designed and realized on specific based needs. An Italian industrial company produces filters for a special application like water filtering and/or treatment for industrial liquids. The active element of filters is the filter inner body that is, essentially, a pipe with a lot of calibrated holes on the surface. Those holes initially (and for a long time) were realized manually on the pipe by the manual drill. The fact is that there were various disadvantages:
- To produce a single filter body was required about from one to two weeks, a very long time if compared to industrial standards;
- Very low precision if considered that a person had to found a point in which to perform a hole very accurately;
- There was impossible to went down a specific hole diameter (less than 1mm) – this doesn’t permit the company to produce very high-level filter unit and doesn’t permit to increase revenue;
- During manual drilling often the drill machine broke down
The boss of the company asked me if there was a technical solution to optimize the production process and to increase the final product quality.
The preliminary phase started with all needs analysis including the keys following:
- The ability of the drilling machine to manage holes around 0,5mm
- Body Filter with really different physical characteristics: length from less than 100mm up to 2000mm and diameter from a minimum of 25mm up to 300mm with a very different thickness of the body
- Possibility to parametrize the step in term or distance between holes in the two axis
- The possibility of a different disposition of the holes between subsequential circumferences: aligned or crossed
- A completely autonomous system capable of complete the job without human assistance
After the analysis and studying phase was the time of the components selecting, costs estimating and designing. The designed machine was a 3-Axis positioning tool with a drill with speed controller. The components selected, divided into mechanical and electrical, were:
- Central Processing Unit: PLC (Programmable Logic Controller)
SIEMENS Simatic Step7 CPU313C-2DP – a CPU capable of manages 2 separate Profibus channels acting as a bus Master with enough memory and storage to maintain live the application software and all the data required for computation
- 2x Linear Positioning Servo-Driver: FESTO SEC-AC-305-PB – servo driver for high precision positioning controlled by Profibus
- 1x Linear Positioning Servo-Driver for Sled-Tool-Mechanical application: FESTO SEC-DC-A-PB – servo driver for very high precision positioning controlled by Profibus
- 1x Variable Asynchronous Tri-phase Speed Controller: a Toshiba Inverter Speed Controller VF-511 driving the drill motor according to a speed reference set-point calculated by a specific algorithm of the system
- 1x operator touch panel: HAKKO 7” colour touch panel with Profibus communication interface (RS-485) – this device is responsible for the human-machine interface part of the machine
- 1x main power supply unit: a Siemens SITOP Power unit that generates the right power supply for all the devices in the system
- Central Processing Unit: PLC (Programmable Logic Controller)
- Linear Axis FESTO LS-5, 2290mm total length with servo-motor MT-054, 500Watt with high precision resolver on board
- Round Axis FESTO RF-1, 390mm total external diameter with servo-motor MT-054, 500Watt with high precision resolver on board, coupled with belt transmission mechanism
- Linear Axis FESTO VP-2, 390mm total length with servo-motor 200Watt with high precision resolver on board
All the mechanical parts were assembled locally to permit the right movements of the tool. The machinery appeared like an old CNC with 2-axis servo driver.
SOFTWARE DEVELOPMENT PHASE
The software development phase started setting-up the drivers through the FESTO configuration software and connecting all the elements physically and logically, testing the reaction of the servo-drivers at the PLC commands.
The application software of the PLC was developed in Simatic Step 7 v5.3 environment organizing the whole program in different blocks grouped by their own specific designation, for example general and servo initialization, general logic, the movement logic, the global axis orientation, the communication between operator touch panel and the main commands and so on.
During the implementation phase, a lot of mechanical aspects and new needs were to be taken into account. For example, during the rotation and the positioning was necessary a constant control of the relative position of the drill tool because some mechanical part of the machine could collide. Another aspect was a not really linear surface of the pipe under production the holes could be different from previous compromising the total quality of the final product. Some manual steps were necessary because operator needed to measure some quotation directly on the pipe under production while the machine was preparing to start the cycle. A manual repositioning service was necessary in case of special or exceptional filter production.
A critical aspect of the application software computed the right speed of drill rotation during the penetration into the pipe. If the rotation speed wasn’t proportionally regulated with the penetration speed the drill tool broken down or partially destroyed compromising the total integrity of the product or could cause damage to the machinery. So was necessary to develop a calculation algorithm that was able to calculate the right rotating speed accordingly with penetration forwarding speed: the computation and algorithm were called the “perforation brain” because it was responsible for continuously adjusting the relative speed of the two drivers (penetration and rotation).
After a long period of fine adjusting, the algorithm was definitively tested and it was perfectly reliable.
The software has been developed like a multi-jump logic sequencer that is able to assume different states and to drive the right servos depending on which step is running.
The final phase started just after the first month of filter production tests. The Human Machine Interface, powered by a Hakko 7” touchscreen full-colour panel, has been developed under V Series Editor software environment. The panel inherited all the needs in terms of controls and management, giving to the operator all the information in one single point and the ability to change all the working parameters, functions, manual and automatic operations that the drilling machine can do. A huge quantity of new functionality was added and the operation panel becomes a really user-friendly interface.
The drilling machine is capable of complete autonomous job execution and with a very wide work parameters variations in term of
- pipe dimensions (length, diameter, thickness)
- horizontal space between holes
- number of holes per circumferences
- start point and end point position on the pipe
- penetration and rotation speed
- a lot of manual variation during the job
- many manual commands to obtain the exact desired result
- self-diagnostic and alarm for operator
Finally, the machine was equipped with a webcam that transmits the video during the working phase when humans are at home for launch or during the rest periods.
Actually, the “pertugiatrice” has turned off 12 candles, one per year, and is constantly under production.
The boss, in the beginning, was enthusiast, but now he is very happy and really enthusiast because that strange creature, never existed before, is even under production without any trouble and with a long story behind.
Industrial – Plastic Manipulation
Industrial machinery for body filtration part production of industrial filtering system
Finalized, actually under activity and production
- Siemens Simatic STEP7 PLC – CPU 300 Profibus Master
- HMI Operator Panel Hakko 7” Touch-Screen Color
- FESTO Axis Servo Controller model SEC-AC-305 Profibus Device
- FESTO Axis Servo Controller model SEC-DC Profibus Device
- Inverter Toshiba Compact Drive
- Siemens Simatic STEP7
- FESTO GSD and Configuration Software
- V Series Editor Panel Pro
Some interesting fact about this project are:
- To permit to the system to goes on and operates, there are two pieces of software that need to run together. The first one was into the main controller developed in AWL (instruction list in Simatic Step 7 environment) and the second one, developed in a graphical language runs in the TOUCH PANEL.
- The connection between two applications/devices is established via Profibus RS-485 cable
- Electrical Hardware
- All the electrical hardware part of the system is contained in an electrical cabinet installed under the machine.
- All cables are pre-assembled in the factory and connected to the place after mechanical installation of the components.
- Interesting Facts
- The main cabinet was arranged in one day and the mechanical structure in one week
- The test phase began during a raining weekend and on Monday, next week, the first filter pipe was produced!
- The drilling machine is actually under regular production without any interruptions
- The average amount of holes in one production is about 250-300.000
- Actually, the machine totalized a so high number of holes that is not possible to be contained in the PLC memory at all, so nobody knows really how many holes the drill makes
- The total cost of machine building (included software and design) was paid in a month