To add ink to an Epson ET-3600, start by ensuring the printer is on and open the ink tank unit cover. Then, open the cap of the ink tank you want to refill. Take your new Epson ink bottle, and carefully open it. Hold the bottle upright and slowly insert the bottle tip into the tank's filling port. Gently squeeze the bottle to add ink; avoid overfilling by stopping at the upper line on the tank. After refilling, securely close the tank's cap and the ink tank unit cover. It's recommended to use gloves during this process to avoid any potential mess. Remember, using genuine Epson inks ensures the best quality and longevity for your printer.

Titanium grades are classified based on their composition and mechanical properties, affecting their application in various industries. Grade 1-4 are commercially pure (CP) Titanium, with Grade 1 being the most ductile and Grade 4 the strongest but least ductile. CP Titanium is widely used in chemical processing and marine environments due to its corrosion resistance. Grade 5, also known as Ti-6Al-4V, is an alpha-beta alloy, and the most commonly used titanium alloy, offering a high strength-to-weight ratio, making it ideal for aerospace, medical devices, and sports equipment. Grades 9, 12, 23 are other notable alloys, each with specific properties like enhanced corrosion resistance or higher strength, tailored for specific applications like industrial, aerospace, and medical use. Choosing the right titanium grade requires considering the mechanical demands of the application and environmental conditions it will face.

Polypropylene (PP) is regarded as a semi-rigid and highly flexible polymer. Its flexibility can be adjusted through copolymerization and the addition of plasticizers. Typically, polypropylene exhibits excellent resistance to fatigue, making it ideal for hinges and flexible parts in design. However, its rigidity and flexibility are highly dependent on the molecular weight and the proportion of comonomers (like ethylene) in copolymers. PP's versatility is showcased in its wide range of applications, from rigid containers to flexible packaging films and automotive parts. Though not as flexible as some elastomers or specific plastics like PVC, its balance between stiffness, toughness, and moldability makes it a popular choice in various industries. Adjustments in its polymer structure can further enhance or reduce its flexibility, demonstrating polypropylene's adaptability to specific requirements.