ATM removed plastics flash automatically

Tag : blow moulded products

ATM was well acquainted with automotive industry laser cuttingapplications, which are finely toleranced operations demandingprecise programming and robot path control.
Such components have clearly defined datum points that allow alaser and robot to easily meet the dimensional and profile tolerances required.
ATM told manufacturingtalk that there were a number of distinctdifferences between laser cutting automotive projects and thePolypipe products.
The blow moulded part has a larger tolerance band and the material is very different.
* Coping with problems - there were three different sizes ofproduct to be laser cut (300mm, 750mm and 900mm).
Not only had a system to remove flash from the moulding, but italso had to cut two 360 deg paths.
ATM decided that the best approach would be for the robot to holdthe part and manipulate it under a fixed laser cutting head.
A 6-axis robot system with a horizontal reach of 2000mm and apayload capacity of 50kg, was chosen to provide the working rangeand handling capacity required for these large components.
ATM chose Rofin-Baasel UK for the laser system, based upon Rofin'sextensive application experience and the excellent reputation for reliability of Rofin CO2 lasers.
A diffusion cooled slab laser with an output power of 2,5kW, wasselected for the project.
Detailed consideration also had to be given to fume extraction and filtration for this project, as the parts being cut areproduced from 100% regrind material.
It meant that the blow mouldings can contain a number ofcontaminants which could have a detrimental impact on theperformance of any extraction and filtration system .
Following a series of trials, a multi stage dosing filter systemwas developed, with the air extracted from the cell being dosedwith calcium carbonate before reaching the filtration system.
To minimise the time associated with cleaning filters and removingdebris from the filtration system, two sets of filters wereincorporated.
This enables one set of filters to perform a self cleaning cycle,depositing any dust and debris in a bin, whilst the systemcontinues to run using the second set of filters.
* Work cell concept - the work-cell concept incorporates twocomponent fixtures at the operator load and unload station.
This enables the robot to deposit a completed part and immediatelypick up a new part ensuring minimum time is lost between the lasercutting operations.
With an internal safety door closed to protect the operator, thefinished part can be manually removed and another part loaded forprocessing by the robot.
The robot gripper system and the component location fixtures, incorporate quick change tooling features to enable the system to handle the three differentproduct sizes produced within the cell.
* Meeting tolerance specifications - the dimensional tolerances required flash to be removed from all areas around the mould tool joint line, and in places this flash can be up to 12mm thick.
In addition, to enable the flash being removed to be re-processedmore easily, the larger areas of waste material had to be cut intosmaller pieces.
This required intricate programming by the ATM engineers to achievethe balance between reducing the size of the waste material andmaintaining the target cycle time.
A major issue was the need to produce trimmed components with aminimum of excess material, on components which have potentiallylarge part to part variations in size.
The variation on each component meant that it was not possible toestablish a consistent datum position, from which program offsetscould be generated, and this led the ATM engineers to develop ahighly unusual but extremely effective solution.
In almost every laser application, the beam is focussed to a finespot, at a particular distance from the nozzle or optics , to generate a small spot size and enable precision processing ofthe part.
Even with a powerful laser such as the Rofin DC025 a spot size of1.0mm is achievable at the appropriate focal distance.
This application however did not require such degrees of accuracy,owing to the variations in part tolerance, and ATM turned this toits advantage.
By developing clever programming techniques and using the laser'Out of Focus', a larger spot size was achieved.
Using the laser outside of its focal point would require more laserpower to cut the material, and ATM's initial choice of a 2,5kWlaser proved to be a major contributing factor in developing thisfinal solution.
The larger spot size together with the higher power settings on thelaser enabled the system to not only achieve the cut profilesrequired during flash removal, but the high temperatures reachedduring the trimming operation also partially melt the cut areaproviding a smooth aesthetic finish on the part.
Polypipe has achieved its objective of turning a labour intensiveand arduous task in to a cost effective and highly reliableautomated system.
ATM has also clearly demonstrated that difficult and unusualautomation applications can become a reality using a combination offield proven hardware lateral thinking, and a determination tosatisfy the customer's requirements.