Schröder GmbH automates pin table for wood processing with electrically actuated pneumatic cylinders
Today’s order slip is no minor feat: At least 15 different positions for wood, composite, and aluminum blanks with various geometries on the same machine. No longer a problem at Schröder GmbH – the company has cut down its set-up times significantly thanks to a new and unique pin table. Electronically controlled pneumatic cylinders extend within seconds, forming an inversion to the contours to be manufactured.Integrated vacuum suction cups then fix the plate so machining can begin right away.
“We have been experiencing a shift towards smaller batch sizes for years now,” states Jörg Schröder, CEO of Schröder GmbH, describing the challenge. “Quantities in the thousands used to be the norm. Today, we often produce just between 50 and 100 units.” And it isn’t the NC-controlled processing units on the machinery, but the set-up times that cause a bottleneck – especially when it comes to the work table. Saws, drills, and cutters require extra space below the workpiece to prevent damage to the table. In the industry, it is still common to produce a base with the corresponding recesses and seals and then brace the workpieces to it. “With large batches, this is definitely efficient,” says Jörg Schröder. But the smaller the batch, the more effort it takes to produce a single part and templates, register and manage them, then store them properly so they can be used again.
Based in Beckum in Germany, Schröder GmbH produces series and variant products from wood, composites, and plastic. “As a supplier, we are constantly forced to optimize costs, and unproductive table set-up times are our greatest lever,” explains the CEO, summarizing the situation. This is where master carpenter and electromechanical engineer Jörg Schröder’s idea came into play: An automatic pin table that flexibly releases the cutting contours under the plates at a software command while fixing the plates for precise, secure processing.
Together with AVENTICS, he realized an innovative pin table for a new four-spindle portal machine from MKM International in Bad Oeynhausen. Now, all it takes is a mouse-click and the AVENTICS cylinder valve units move into position within seconds, fixing the plate to be machined with its integrated vacuum suction cups. The CNC program is loaded at the same time, and machining can begin.
This is the development of an idea he implemented with MKM some years ago, when he equipped a manual pin table for plug-in pins with an LED at each position.
A software he developed transfers the part’s vacuum configuration defined in the CAD system during CNC programming to a separate mini-control, which then actuates the corresponding LEDs. This provides the machine operator with a clear indication of exactly where pins have to be plugged in. “Even so, setting up the machine table can take longer than the production of a small batch. I simply couldn't accept that this process was not automated,” recalls Jörg Schröder.
His underlying idea: Replacing the rigid metal pins on the pin table with flexible, compact cylinder valve units. The cylinder valve unit is actuated electrically by a bus system he developed, and can automatically implement the base templates created during programming. Programming itself is mostly automated. The vacuum program is assigned to the CNC program and both are transmitted to the machine together. The integrated vacuum system then secures the workpieces.
Function test one month later
As technology partner, AVENTICS helped the medium-sized company in making its concept a reality. Schröder designed a modular system consisting of four mobile tables, each measuring 1,200 x 800 millimeters and equipped with 48 cylinder valve units with 2x4 cylinders. Two tables each can be synchronized for a larger bracing surface. “Within a single month, we developed this extraordinary cylinder valve unit to run function and endurance tests,” states Alexander Minderlen, the AVENTICS employee responsible for this assembly on the developer side. Eight directional valves and a control board from Schröder are integrated into the assembly base plate to protect them from dust and chips. “We had to meet extremely specific requirements, such as height, width/grid, integrated electronic components, and a vacuum system so that the solution could be retrofitted in already installed work tables,” emphasizes the developer. AVENTICS delivers the eight-valve units preassembled and pneumatically tested. At Schröder, the processor board developed and built by CBE was then installed. The assembly is rounded off with an aluminum cover.
Each of the 384 cylinder valve units on every table are equipped with an input and output, connected to the Schröder control software via a fieldbus. All that is needed to control and monitor an entire table is a four-wire cable. Thanks to the optimally sealed vacuum suction cups, the new pin table achieves better results with a much lower energy consumption. It is also crucial for the workpieces to be level – per table, the evenness of the cylinder end positions lies in the one-hundredth millimeter range. “This is important so that we can precisely mill even the smallest of profiles on the edges of the plates,” explains Jörg Schröder.
Schröder had the first automated pin table produced for a new portal machine from MKM international and now uses it in his own production facilities. The four tables traveling in the y direction can be reached by four independent milling spindles, no matter their location. In addition, two milling spindles are assigned a drilling unit, and the remaining two spindles a swiveling saw unit. With this equipment, tool change times are down to a minimum. “We have reduced our set-up times significantly and our production has become ultra-flexible and lightning-quick,”states the tinkerer, summarizing the result.“
Other companies have worked on similar concepts, unable to carry through due to the complexity of the task,” Schröder says, smiling. He not only wants to use the automated table himself, but also markets the solution for new and installed machines and systems for the wood and plastic processing sector and other industries.