Extrusion dies for plastic pipes are among the key products of the Dutch supplier company Romit. By optimizing production with a Heckert HEC 800 Athletic HV MT milling / turning center, they were able to reduce the total processing time of such tools by up to 65%.
For Auke Sjoerd Tolsma, CEO of Romit BV in Dedemsvaart, the situation is clear: "We need to optimize our production continuously in order to survive in an increasingly competitive global environment." His company was formed in 2001 from the machining department of Rollepaal BV, one of the leading global manufacturers of extrusion lines for PVC and PO pipes. In the same year it was founded, Romit already acquired the neighboring tool- and mold-manufacturing company Ramix, thus extending its range. As a result, the company, which employs approximately 70 staff, quickly became an established service provider for machining and assembly tasks serving the plastics industry, oil and gas drive engineering, and the maritime sector.
The manufacture of extrusion dies has remained one of Romit's core tasks. Auke Sjoerd Tolsma applied his optimization initiative to the demanding precision machining of these components: "Extrusion dies are manufactured mostly as single parts or mini-series of up to three pieces. Because of their rotational symmetry, they mainly require turning, but also drilling and milling. Until recently we used vertical lathes and bed-type milling machines for the purpose. But the time spent on machine changes and weaknesses in process reliability gave us the idea of switching to complete processing and automation."
In early 2013, CEO Tolsma and his machining specialists began their search for a turning / milling center that is able to machine the components, which measure up to 850 mm in diameter and weigh up to two tons, in a maximum of two setups. In addition, the sought after machine should reliably meet the required tolerances in order to also permit unmanned operation and handle maximum spindle hours.
Of five multi-functional machines tested with a reference component, two provided the level of performance required. In the end, a number of essential details, such as the load capacity of the table and the simple use of strongly cantilevered tools, determined the final decision: In mid-2014, Romit invested in an HEC 800 Athletic HV MT milling / turning center made by the Chemnitz Heckert GmbH, which is part of the Starrag Group, a global technology leader in precision machine tools. Auke Sjoerd Tolsma explains: "I've long been aware of Heckert as a renowned supplier of machining centers for serial production. The test operations finally convinced me that Heckert can also provide high-performance solutions for the complete machining of individual parts." And adds, satisfied: "In our case, the best solution even."
Productive single-item production
Milling / turning center realizes savings of up to 65 percent
The HV-head has two working positions, horizontal and vertical, in which it can pivot even when the spindle is running. If the respective final position is reached, the head is locked in a Hirth coupling. The positive fit this creates contributes to a high stability, which is especially important in turning. The turning tools, for which HSK-100T holders are used, are disengaged when the spindle is inserted and fixed with a second Hirth coupling, secured against turning with the positive connection. Thanks to the overall stability, it is even possible to use 450-mm long standard turning tools, which would require damped boring bars in other machines.
Other important criteria in the decision-making process were the inclusive pallet changer and the option to integrate the machine into an automation solution with pallet storage. Auke Sjoerd Tolsma explains: "At the time, a dual changer system was important for us so we could already reclamp parallel to machining." In addition to the standard 800 x 1000 mm pallet with T-slots, he ordered two round pallets 1000 mm in diameter, also equipped with T-slots and a claw system. In order to be able to precisely align rotationally symmetrical workpieces on the setup station already, he had it equipped as a highly precise swivel load/unload station with a bearing that has a rotational accuracy of under 1/100 mm.
Promising prospects
After its successes with the complete machining of extrusion dies, Romit is extending the scope of application of the milling / turning center. In the meantime, contour parts for mold making have been milled, and the HEC 800 HV MT is also earmarked for single parts from the area of compressors. After all, those in charge have set the initial target of 100 hours’ operation per week.
To make production even more cost-effective, Romit invested in a new CAM system, which masters milling and turning equally and is able to map and optimize complete processes. Next in line is the planned automation system and other machines, probably beginning with a slightly smaller five-axis center. The plans have already been drawn up.
