References // Automatic assembly machine for railing bars and cross connectors (domestic appliance industry)
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| Automatic assembly machine for railing bars and cross connectors (domestic appliance industry) |
Flexible assembly facility for furniture railing bars
Who doesn't know this?: When you install new furniture, you find out that drawers jam or front panels are crooked. In this case, railing bars come in very handy to solve the problem as they can be used to align furniture parts. Although it is commonly considered a cheap product, a railing bar must meet strict requirements in terms of quality and tolerances during manufacture. These requirements are comparable to the stringent criteria applied in the automotive industry.
HENKEL + ROTH GmbH accepts this challenge by presenting its newly developed assembly facility for the manufacture of railing bars. The four component parts of a railing bar, i.e., a tube, two screw-in parts and a cover shell are fed to the plant in a fully automatic process and then assembled. Every assembly subprocess is monitored using sensors. All parameters relevant in terms of quality like tube deflection, screw-in torque values, or the overall length of a railing bar are measured by sensors and checked continuously.
The plant comprises a total of eight integrated and interconnected stations.
The first station ensures component loading. Here, tubes are taken out of the belt bunker, and positioned on the conveyor belt via a feeder. A level check sensor indicates whether enough parts are available in the bunker. A roller is used to single the tubes. Tube feeding, handling and processing must be done carefully. To avoid scratches, all machine parts which enter into contact with the coated tubes are made of plastic material.
After separating them, a cycle conveyor carries the tubes to the different work stations.
The cover shell is fitted to the tube in a next step. Component feeding is done by a combination of vibratory and linear conveyors which also ensure the sorting and the correct positioning of the parts.
A testing station will then measure tube bending by using a displacement measuring system.
The first screw part is screwed on in the fourth station. An automatic servo screwdriver (spindle) is used to screw in the tube insert. Torque and thread engagement are monitored by sensors. Screws are fed via a belt bunker and a flexible tube.
After this, the second screw part (coupling) is assembled in station 5. Parts are fed by a mechanical gripper to this station. The controllers in stations 4 and 5 are equipped with LCD displays. The control processes are programmable, and the data for the screwing operations can be called at any time. Data archiving on a PC is possible through an interface on an optional basis. Specific parameters are predefined, including, e.g., the frictional resistance depending on the spindle. A self test which comprises a functional test of the spindle is carried out before starting production.
The overall length of the assembled railing bar is checked in station 6. For quality assurance, the machine setter is calibrating the measuring equipment using a length standard on a regular basis.
Another sensor monitors the straightness deviation of the railing bar by runout measurement at this station.
The last station of the assembly plant is the removal, inspection and packing station. A visual inspection of the complete railing bars is performed here, and the bars are packaged manually.
The control unit of the assembly facility is equipped with a graphic display to visualise measured data and process steps. This makes machine handling considerably easier. Among other features, this system indicates at which position parts are missing, which bunker is empty or whether the machine door is not closed.
A large number of parameters is measured and recorded during operation, and may be displayed at any time. Piece counters have been integrated to provide detailed information on the number of pieces processed in total and in every shift in addition to quantities for determined purchase orders. It is also possible to obtain information on box contents enabling the machine to stop when a desired quantity is reached.
Whenever rejected parts are identified, the error display can be analysed to allow easier troubleshooting. Faults are displayed in plain language to ensure quick fault correction.
In addition to fully automatic production, this assembly facility also allows manual manufacture. Every station in the plant and every cylinder can be selected one-by-one. This makes the setup of the machine considerably easier.
As a matter of course, particular care was taken to ensure the operator friendliness and industrial safety of the machine. The plant is enclosed completely by guard doors, and emergency switches (buttons) are installed at all accessible positions.
The plant has been designed by HENKEL + ROTH to allow the processing of railing bars with a length of between 280 and 650 mm. An operator can select the corresponding length and other parameters applicable to the railing bars to be manufactured at the control unit. Belt spacing is controlled mechanically. This allows the continuously adjustable manufacture of railing bars with different lengths. Mechanical retooling is very easy to perform. The stations including an oscillating conveyor, spindles or testing facilities are mounted to single blocks which can be adjusted to the required positions without problem.
Flexible retooling:
This assembly facility can be used for the assembly of two variants of add-on pieces, and it can be used in a highly flexible manner for railing bars with a length of between 250 mm and 700 mm. Resetting to a new length is carried out easily by turning a handwheel to change the width of the cycle conveyor while all assembly equipment is also moved to a new position.
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