what is different between module & card system

There's no fundamental difference - it's just a different way of packaging the electronics.

The comments below are general; there are always exceptions, so please, dear readers, don't shoot me down:

Cards needs a separate panel for controls & indicators - modules can have them on the front panel.

Modules are more robust - easier to replace in the field.

Cards plug into a backplane which can easily have over 100 inter-card connections; modules generally have fewer connections between them. Also, the backplane can carry active electronics.

In a lab environment, modules are usually preferred, as it's easier to reconfigure the mixture of module types & connections when setting up a system (not applicable to your injection moulding machines).

As I said, there are always exceptions. For instance, the Eurocard/Euromodule systems are essentially the same; take the card & wrap it up in a metal enclosure with the connector sticking out the back and a small panel on the front, and it becomes a module.

Hope this helps.