I want to open the powershot A510, to remove IR filter

I’m only familiar with the Canon SX series but it’s highly likely that the lens construction will follow the same principles.

From the limited number of A series disassembly guides on this site it looks like you’ll have to remove the main logic board to gain access to the back of the lens. You should then find the image sensor and IR filter are secured by 3 screws. You will need to scrape away the locking compound in order to undo them. If the image sensor doesn’t then lift off it can only be stray traces of locking compound holding it.

My SX200IS lens disassembly guide should help you.