The force of 4524 Newtons doesn’t leave much room for friction losses. Unless it is a ‘frictionless’ cylinder, I always allow 11-20% loss due to internal seal friction. Did this force come from the manufacturer or from a generic piston size/pressure table? If you dig a little you can probably get a % loss number from the manufacturer’s catalog. Is there any potential side loading during the pressing action? This could be causing additional side load adding to friction. Are there external guides (bearings/sleeves/shafts) contributing to friction? How straight is the pin when it starts-is it possible to start ‘crooked’? Is the rod area on the pressure side subtracting from the force? If none of the above than I’d look further at the pressure generated at worst case press and the friction factor between dry steel and aluminum-I assume that is where you started.