How can I process xml file on upload?

I solved my problem with lots and lots of testing things out.
Apparently my FormData Object was not correct.
Doing these changes to my code worked:

$('#xml').on('submit', function(e) {
        e.preventDefault();

        var form_data = new FormData(this);
        form_data.append('action', 'calculate_xml');

        $.ajax({
            url : ajaxurl,
            type: "POST",
            data : form_data,
            processData: false,
            cache: false,
            contentType: false,
            success:function(response){
                $('#response').html(response);
            },
            error: function(response){
                $('#response').text('error');
            }
        });
    });