Product category:
Smaller-Sized PLCs
News Release from: Rockwell Automation | Subject: MicroLogix1500
Edited by the Engineeringtalk Editorial
Team on 08 December 2003
Soldering machine OEM slashes
development time
The ability to source a complete range of automation hardware from a single supplier has enabled a manufacturer of automated soldering machinery to dramatically reduce development time.
Rockwell Automation's tightly integrated product range and the ability to supply a complete range of automation hardware through a single source have enabled a manufacturer of automated soldering machinery to dramatically reduce development time Pillarhouse International, based in Chelmsford, Essex specialises in the manufacture of automated machinery for selective soldering processes used in the production of printed circuit boards
This article was originally published on Engineeringtalk on 8 Aug 2008 at 8.00am (UK)
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The company was looking for ways to reduce lead times on its larger machines, which are always designed to order for each customer.
By selecting Rockwell Automation as its single source supplier for all control equipment, Pillarhouse has reduced the development and build time from seven to four months on these bespoke machines.
The company had developed all its control systems in house, buying in Intel processors and building its own I/O boards and stepper motor controllers from scratch, explains Paul Young, Project Engineer at Pillarhouse.
"Whilst there is a place for bespoke development, on these larger machines we can save significant amounts of time by using off-the-shelf components", he says.
"Previously, a large proportion of the machine development time was spent designing, building and testing subassembles, which were then built into a chassis.
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These had to be tested, fitted, wired and tested again before we could start to debug the machine.
We have now identified five separate build levels that can be reduced to one and this has cut three months from our build time.
By choosing Rockwell Automation we also know our worldwide customers can source replacement parts locally should they need to".
This approach has been used successfully on a machine developed for a US automotive component supplier, which required the soldering of individual connectors along the edges of a five-sided printed circuit board.
Each side of the board needed to be fluxed before soldering and the target production rate was four completed assemblies every minute.
An eight station rotary indexer was chosen to move the circuit board from the load/unload station around a succession of three alternating flux and solder baths.
The seventh station is left blank to allow the completed circuit board to cool before being returned for removal at the manual load/unload station.
The machine is enclosed to protect the operators.
Access to load and unload circuit boards is monitored using a light curtain and the machine will not index until the operator's hands are clear of the machine.
With a new board loaded, the indexer moves it to the first flux station allowing another board to be loaded behind it.
With a five-sided board and only three flux and three solder baths, four of the stations need to perform a double action, explains Young.
At the first flux station the fixture holding the circuit board is sent down to immerse the board edge into the flux bath.
The board is then rotated and the next edge immersed.
"It sounds quite simple", he says, "but the process has 16 steps involving two positioning axes controlled by stepper motors.
Reducing the travelling speed of the board as it is immersed in the flux is also important to reduce splashes".
Splashing liquid flux within the machine is wasteful, increases maintenance costs and, if left unchecked, would result in machine downtime.
These first two stepper axes and the general logic for the machine are controlled by an Allen-Bradley MicroLogix1500.
The expanded I/O capability of the MicroLogix1500 allowed for the general machine control and the two 20KHz pulse outputs, with associated programming instructions, providing an integrated solution for the stepper motor control.
After indexing from the flux station, the circuit board needs to be accurately positioned in the solder wave.
Again, there are two stepper motors controlling vertical position and rotation of the board to solder the edges previously fluxed in a sequence similar to the flux station.
As the board descends into the solder it has to be positioned to an accuracy of 0.1mm.
Two factors are critical to the process - the repeatability of this positioning system and maintaining the wave height of the solder.
The solder wave is produced by pumping molten solder through a nozzle designed specifically for the application, and a variation of just 0.5% in the pump speed has a significant effect on the wave height.
An Allen-Bradley PowerFlex4 AC drive is used to control the pump motor, with the speed reference supplied from the MicroLogix1500.
To monitor the pump speed and generate an alarm should it vary, Routeco, the Rockwell Automation distributor that worked with Pillarhouse throughout the design of the machine, suggested a simple but effective method.
Traditionally, a magnetic pick up would sense pulses from the teeth on the pump's drive cog.
These pulses were converted to a variable voltage using a frequency to voltage converter designed by Pillarhouse and fed into an analogue input of the control system.
Routeco's alternative solution was to fit an Allen-Bradley 7000 Series diffuse sensor with a fixed focal length of 15mm.
This was positioned to count the teeth on the drive cog and hence monitor its rotational speed.
With a pulse rate of 800Hz the MicroLogix1500 high speed counter input is used to monitor speed and generate an alarm should it change.
Each of the soldering stations and the two remaining flux stations have their own MicroLogix1500 units, which act as axis controllers rather than traditional programmable controllers.
This has the advantage that their programs are consistent with the main control unit's software, providing reusable code in a cost efficient package.
All the MicroLogix units are networked together using DH-485, with the main controller distributing process parameters to the other units.
An Allen-Bradley PanelView 600 is also connected to the network and provides operator control and configuration as well as displaying information on machine status and process alarms.
"I particularly liked the way the PanelView's alarm handler prioritises the messages", says Young.
"I can configure the PanelView so that higher priority alarms take precedence over any existing lower priority ones".
Rockwell Automation's integrated architecture approach to hardware and software development ensures that its complete range of automation products, including motion control, programmable controllers, drives and operator interfaces, work together straight off the shelf.
Coupled with the ability to provide all these products through a single source, and global technical support and parts availability, this enables machine builders like Pillarhouse to reduce development time and costs while offering end users lower total cost of ownership. Request a free brochure from Rockwell Automation ...
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