When Leadwin received the 2D and 3D model from customer, customer had already finished design and prototype tests. Customer said this part was part of medical device and the resin was ABS. ABS resin was a general term and it would be better to select the resin which was bio compatible and approved by FDA. Therefore the resin was defined as MG47MD made by SABIC.
Leadwin started DFM analysis (Design For Manufacturability) and found that threads were undercut. We suggested customer to change the thread angle in order to avoid undercut. But customer said he did it on purpose. Therefore, the features of threads had to be formed by A side and B side and two action slides. Therefore, there were 4 parting lines with potential steps and flash. Customer understood the technical limitation and could live with it.
Another challenge was the 22 cm length of piston. It was so easy to get warp and deform for a 22 cm long piston. The injection pressure, speed and temperature had to maintain as uniform as possible. We selected the gate at heavy wall area and installed two water-cooling channels. We also run mold flow analysis to verify our tool design. We designed a two cavities mold so the mold could run under balance situation. The mold size was about 650 x 350 x 345 mm. It required a 100 tons – 140 tons injection machine which had enough tie bar space and platen space to accommodate this mold.