The processing of plastics is becoming increasingly important, and not just when it comes to lightweight construction. Some plastics have clear advantages over metal, especially when resistance and corrosion protection are required. They also do not react with water, acids or alkalis, making these materials ideal for use in medical technology or, in the case of ElringKlinger, for use in analytical instruments. For a new project, the specialist in the processing of plastics enlisted the additional expertise of deburring specialist KEMPF from Reichenbach-Fils in order to carry out the complete production of special screw caps purely by machine in future.
With the takeover of a plastics processing company in 2001, ElringKlinger not only gradually expanded the Heidenheim site, but also extended its own product and service portfolio in the area of plastics production and machining. With currently 134 employees in Heidenheim, this site is one of the smaller ones, but the importance of this division is constantly increasing. Due to certain specifications and advantages offered by this material, more and more components are being manufactured from plastic, so that ElringKlinger Kunststofftechnik GmbH has specialized primarily in the processing of PTFE high-performance plastics (polytetrafluoroethylene). The fully fluorinated polymer, also known colloquially as “Teflon”, is very inert and also has a very low coefficient of friction. Another major advantage - due to its low surface tension, virtually nothing sticks to PTFE, which is why the material is also increasingly being used outside of medical technology.
Equipped with extensive expertise in this area, ElringKlinger manufactures even the most complex components from this material for its customers and is renowned for their production quality. For this reason, nothing was left to chance in the past and even the final processing step of deburring was carried out by hand, despite the high level of effort involved, in order to adhere to every specification with the utmost precision.
New production strategy
The main plant of ElringKlinger Kunststofftechnik GmbH in Bietigheim-Bissingen has been using PCD tools from KEMPF for years due to the quality requirements and, in the course of a project optimization, recommended to the Heidenheim plant that it should also rely on the deburring specialist from Reichenbach-Fils. For the upcoming production of screw caps, deburring was also to be carried out completely by machine, as there was simply no suitable personnel available for this task. Dominik Wiesner, the technical sales representative at KEMPF, then not only laid out the appropriate tools for the deburring applications, but also put together a package with a total of eight tools (including two deburring tools) in order to carry out the entire production process, including deburring, by machine in future.
The PTFE component in the main spindle machining in the lathe: The blanks are fed into the machine by a bar feeder and produced completely burr-free in the machine. KEMPF not only uses deburring tools, but also other solid carbide and PCD forming tools for internal turning, knurling, milling and threading.
Due to the complexity of the component with various contours, radii, drill holes and overlaps, not all tool solutions from the standard range could be used. In order to guarantee the desired radius shape at the bore exits of the total of 22 bores along the outer contour, a special drill with a radius tip was developed without further ado under the leadership of Markus Götzelmann, Technical Office Manager, which also countersinks the bore entry with a step thanks to its integrated step chamfer. A series of uncoated and polished (i.e. even sharper) solid carbide form tools were used for the many turning and grooving operations. The knurling on the outside is produced with a PCD forming tool from KEMPF, which is designed for higher cutting speeds compared to solid carbide tools and guarantees a longer tool life. Finally, a new feature was the use of two deburring tools, which made manual deburring, which was no longer feasible in this project for economic and personnel reasons, obsolete. Two types of the Back-Burr Cutter & Path deburring system were selected for this purpose, which are predestined for use under these conditions
Back-Burr Cutter & Path deburring system ensures machine deburring of all holes and contours
In contrast to most deburring tools on the market, the deburring system, consisting of a ball end mill and an NC data set specially adapted for this application, does not move along the bore axis, but uses a more effective variant, namely contour-parallel deburring along the edge or contour to be machined. Thanks to the individual creation of the NC data set, the milling cutter follows the contour of the component to be deburred with high precision and thus removes burrs safely and without leaving any residue, even on the back of bores. The Back-Burr Cutter & Path deburring system is therefore the first choice, especially when cost-efficient and fully automated production of components without manual reworking is required.
The Back-Burr cutter (i.e. the ball nose cutter itself) is also available in different versions for the various fields of application, which also guarantee use in plastic. For this purpose, the uncoated type “A-N” was used, which has an extremely sharp cutting geometry without rounding and is therefore ideally suited for processing PTFE.
An overview of six of the eight KEMPF tools used: 1-3 Uncoated solid carbide form grooving and turning tool, 4 Uncoated back-burr cutter, type BXC-28-A-N in special length, 5 PCD form milling cutter for knurling, 6 Radius form drill. The overall process achieved with these coordinated tools guarantees the desired speeds and feed rates, high stability and production quality in conjunction with over 80 % savings in the use of human resources.
For the screw caps to be machined, these advantages were required for the previously drilled holes, which lead approx. 33 mm into the workpiece and whose exits merge into a radius groove. The Back-Burr Cutter & Path deburring system was also used for the outer contour of the wall, as this could not be deburred easily due to the knurling. By programming the NC data set, this contour has since been deburred without any problems and all the end customer's specifications are met. There is no secondary or flitter burr (any more). Thanks to the consistent quality, there are also no more complaints, which were a recurring issue with manual deburring in the past.
The close-ups clearly show the respective machining results with and without the use of the subsequent Back-Burr Cutter & Path deburring system. For the many bores and different contours, such as the knurling on the outer wall, just two types of the same tool are sufficient to replace manual deburring and to produce secondary burr and flitter burr-free parts of the highest quality.