For coffee on the go, the lid plays a very special role. Though deposit systems for cups exist, the cap usually has to be purchased or ends up in the trash as a nonrecyclable article. Their undercut sealing lips would make them too difficult for the food service partners to get completely clean. For consumers, owning their own lid and reusing it many times is an attractive option. Compared to conventional thermoplastic materials such as polypropylene (PP), silicone demonstrates its strengths here. It is flexible, antibacterial, temperature-resistant (in the home dishwasher, for example) and durable. Together with mold maker ACH Solution and material manufacturer Wacker Chemie, KraussMaffei demonstrates—with coffee lids as an example—how easy it is to get started in silicone processing when you have expert partners.
Flexible and durable:silicone forms the ideal coffee mug lid
Two variants in a single shot
On an all-electric PX 121-180 SilcoSet, two different covers are created simultaneously in one shot. One lid is for thick-walled porcelain cups and the other is for the familiar Recup deposit system, which has caught on in many cities and regions. The article weights are between about 38 and 50 grams, and the heavier Recup lid has a special feature: an attached tab provides space for an advertisement or brief message. The individual geometries and weights of the lids demand perfect balancing of the 1+1 mold, and the needle shut-offs are operated independently of each other.
The Adaptive Process Control (APC) machine function from KraussMaffei guarantees constant process control. During ongoing production, APC plus monitors the viscosity of the material and adapts the filling volume in the cycle from shot to shot.
As precise as a Swiss watch
Overall, the low-maintenance system runs as precisely as a Swiss watch—and supplies good parts immediately, even after production interruptions. No process expert for LSR is required. After injection molding, an LRX handling system removes the parts. This is followed by camera inspections for complete take-out automation and geometric correctness, and the sprue—in this case a cold runner subdistributor—is detached. Afterwards, the lids are ready for use without the need for additional tempering thanks to the commercially available low volatile silicon recipes such as the ELASTISOL LR5040 series.
Stable processes from start to finish
The greatest challenge when processing liquid silicone is surely its low viscosity. The mold and injection unit must close with an extremely tight seal to attain a stable process. In addition, the temperature control is the reverse of that for thermoplastics. The mold is heated to start the curing process. When large molds (2 cavities) are used, injection molding machines with extra-wide platens are ideal, for example the variants of the all-electric PX series. With their highly robust mechanical systems, they guarantee reliable operation here as well.
The PX 121-180 SilcoSetthe precise machine for silicone products
Thanks to their precision metering and injection unit and the perfect seal, KraussMaffei machines offer ideal conditions for reliable manufacturing of silicone products. Existing systems can also be brought up to speed for SilocSet technology. As a general contractor, KraussMaffei provides its customers with an experienced partner network, for example manufacturers of high-quality molds and experienced material manufacturers. Silicone is a growth market where continued high rates of increase are forecast in the next several years. Producers who want to take part can do so with the right partner while taking minimal risk.
Advantages of the SilcoSet technology
- Easy, safe entry to silicone processing
- Absolute platen parallelism guarantees reliable processing of low-viscosity materials
- Uniform high component quality with APC plus
- Exact shot weight consistency even with 256 cavities
- Easy changeover from thermoplastic processing to silicone processing
Benefits of liquid silicone (LSR)
- Free of plasticizers
- Temperature-resistant and thus easy to clean and sterilize
- Long service life
- Long-lasting elasticity
- Ideal for sustainable, reusable packaging solutions