Door production

Cost-efficient production for batch size 1

The multitude of products produced by door manufacturers requires individual solutions to complex requirements in door production.IMA has specialised on this sector, the machines of the IMA SYSTEMS product class offer exactly the solution that economically fits.

Big IMA sizing and door rebating machine for the company neuform - Türenwerk

With the new IMA panel sizing and door rebating machine, a door “can” be complete in size and rebate shape after four passes. This is the short formula to which the 2012 investment project of the company neuform-Türenwerk Hans Glock GmbH & Co. KG can be reduced.

In the introduction, the word “can” has deliberately been used because the statement is only true for single rebate doors. Being one of the most potent manufacturers of building doors, the company neuform-Türenwerk produces doors with the broadest variety of rebate profiles. These include also double and triple rebate features that meet particularly high demands placed on radiation and sound insulation, security, weather exclusion and fire resistance.

In the preliminary studies, the products were classified by their sequence of production. These have resulted in currently 20 families of parts. Most of the products will be produced in four passes. But there are also specific features that will require eight passes to be complete with all of the sophisticated details. With the machine manufacturer IMA, the renowned door manufacturer found a suitable partner to implement this high-end production technology for batch size 1. The development team did the preliminary work required, the order was placed in 2011. In the summer, IMA started with the design and building of the processing plant. Commissioning of door production on the new plant is being carried out from the third quarter 2012. The modern panel processing technology will be installed in the Zeulenroda factory in the district of Plauen in Thüringen.

The production of building doors places particularly high demands on the design of the processing plant. Dimensions up to 3200 mm x 1600 mm and a thickness of up to 92 mm had to be considered. In addition to that, the weight of a large door can be up to 250 kg. Hence, an important challenge was to configure a work cell for automated complete machining. It was the company IMA, the specialist for door processing machines, that met the challenge best. In the IMA work cell, each door edge is processed in throughfeed with high reproducible quality by starting with a raw panel. This avoids the necessity to have a separate pass through a double end tenoner which would only be used to produce accurately sized reference edges. The single-side machine design is also responsible for the fact that no additional setup times are generated by the numerous order-specific sizes and design variations. Only for major changes in thickness, a short time for setting up the top conveyor cannot be avoided.

The classification of the products obtained in the planning phase specifies the orientation of the workpieces processed in the machine, the number of turning operations and turnover operations and the required positions of the workpieces in the finished parts stack. For the part programming, this definition of the production sequence can be used to exactly determine the shape of the leading and trailing edges of the workpiece. Also the preparation work performed on the edge to be processed can be identified. The customer-specific IMA ICOS programming system considers the possibility of selecting these boundary conditions.

Basically the company‘s job management system provides a separate data block for each pass of a workpiece. This contains the required subprograms and the variable data. The variable data are directly used for adjusting the over 120 CNC axes. There are, however, further parameters that need to be computed. These are for example the thickness of the edging tape and the current tool dimensions. On request of the company neuform - Türenwerk, the IMA software offers many more correction possibilities. That means, the adjustment of an axis or the function of a unit can be adapted to temporary developments without affecting the standard program.

The preliminary studies were based on the special IMA technique of integrating the door sizing operation in the edge bander. The specific infeed system on the single-side Combima machines allows for accurate external dimensions and rectangularity of the finished door leaf. In the first pass for transverse processing, two infeed dogs operating perpendicularly to the feed direction feed the raw panel at defined points into the machine. Hence, perpendicularity of the door top edge relative to these points is established. After that, the two longitudinal edges are processed. Different from otherwise common panel sizing on edge banders, the side stop required for longitudinal processing is not designed as an alignment fence. The longitudinal side stop is formed by two alignment pins against which the door leaf is placed. They are set exactly to the infeed points of the first pass. Mounted on a slide movable in feed direction, they move along with the door leaf as it is fed into the machine until it is firmly engaged and gripped between the feed chain and top conveyor belt so that it is securely transported.

With this infeed method, the accuracy and design of the core layer is of no significance – no matter if it is made of specific panel materials, chipboard with or without tubular-railed core or a solid wood framework. Due to the IMA infeed system, the overhangs of the blank door slab are split equally i.e. the overhang removed on both sides is approximately the same.

On the feeder at the infeed end as well as on the repositioning device at the outfeed end of the Combima, vacuum lifting equipment is used to handle the up to 250 kg heavy components. The feeder picks the raw panels up from the stack or from the panel return conveyor and puts them on the automatic infeed system. Infeed and alignment by the infeed system is effected automatically, as described above. The repositioning device places the panels longitudinally on the narrow return conveyor. This reduces the floor space requirements in the width dimension. The speed of the movements is controlled as a function of the weight and surface characteristics. Both the infeed and repositioning systems are equipped with turning devices so that the door entering on the feeder is oriented as required. On the return conveyor, a turnover device will rotate the parts about the high edge if the previous top side has to be placed on the feed chain so as to serve as the dimensional reference.

The equipment of the Combima has been designed to accomplish the complex task of manufacturing only angular rebate profiles. The sizing zone uses a scoring saw and a sizing hogger. Each rebate is then pre-milled by a scoring hogger and completed by a rebate hogger. For some applications, a prism-shaped cutting tool does the fine shaping of the rebate. The large hogging cross-sections require motors with a power of up to 30 kW at 6000 rev/min. Since some of the neuform doors are made with solid wood inlay banding, also chamfer cutters are used for edge fine finishing. Two motors are equipped with combination tools to either cut grooves or shape surfaces.

The edge banding zone is downstream from the sizing zone. The company neuform uses veneer as well as melamine paper edgings. Veneer is available as tape from reel in raw design or completely lacquered. For a high-quality rebate edge banding, IMA has used its proven combination of special slotting, chamfering and end trimming units. They make sure that also veneer edgings with difficult grain structures are laid flat against the rebate surfaces and around the rebate corners. This combination of units also guarantees that the rebate edgings join up properly on both upper corners of the door. No edging tape is superposed on each other, butt-joint edgings are cut at exactly right angles and are fitted tightly together. A clean chamfer is cut on each of the external edgings. No manual touch-up is necessary. The only exception is the point where a standard door leaf rebate and a counter-rebate form the corner. For these points, complete processing is not intended.

Downstream from the rebate edge banding zone, this new machine incorporates further high-performance milling units. They cut grooves for seals and profiles to be inserted in the edge-banded rebates.

Further downstream from the grooving area are units for lacquering the solid wood rebate surfaces or the raw veneers, divided into units for pre-lacquering and final lacquering. The fine finishing of the wood surfaces or of the hardened pre-lacquered layer is carried out by a rebate sander and a wide belt sander respectively. The latter sands the door stop face. The vacuum lacquering station consists of two units. One unit lacquers the door stop face, the other one coats the entire surface of the rebate. With the vacuum method, there is almost no loss of lacquer.

Doors with special demands placed on lacquering technology leave the machine non lacquered. The lacquering operation is then performed by hand on a stack. To prevent the applied lacquer from sticking to the visible face of the door, the first operation in the Combima has been to glue a protective foil onto the edging tape area. Due to the sizing and the other machining operations, this foil is accurately flush with the edge and hence allows for precise separation of the visible face from the side profile.

Since the workpieces are large and heavy, IMA has equipped the machine with two sets of parallel feed chains and top conveyors. With this double work-holding, even the heaviest components are guided precisely through the machine, despite all the forces applied by the working units. The spacing between the chains is 90 mm. Hence, components as small as 300 mm width rest on both chains. Due to their single-side design, the machines do not need any setup time for length and width adjustment. In order to minimize setup times also for changes in thickness, the top conveyor is divided into three sections each of which can be adjusted separately. As a consequence, the setup time for thickness adjustment is about one minute instead of two and a half minutes. This time is only taken into account for thickness changes which are not compensated for by the 4 mm elasticity of the top conveyor.

With the current machine length, the total length of the feed chain was greater than the length for which the chain has been designed by IMA. That’s why the feed chain and the top conveyor have been split into two sections respectively located upstream to the lacquering station. The particularly reliable design of bridging the end pulleys of the conveyor sections allows for uninterrupted transport of workpieces. This is especially important for narrow pieces such as fixed door leaves, which will be transferred from one section to the next even when placed transversely. The accurate work-holding position also remains unchanged as the doors enter the sanding and lacquering station. Angle deviations or any offset of the components passing through the machine would result in poor lacquering quality.

With this high-tech investment, the company neuform Türen has laid the foundation for centralized processing of all door leaves and their accompanying components. The compact and clear-cut structure of the work cell will allow it to be directly integrated in the production flow. With the edge banding technology of the IMA work cell, which is indeed complex but unsurpassable in quality, neuform continues to set new standards in door production.

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