In loop you can't use window.location=url
to call any url and do some task. Because javascript execution will be faster than you think. Once it has replaced URL in window.location, in next loop it will replace same and it will conflict with previous call.
Better approach would be calling that URL using ajax call.
I'm giving you psudo code using jQuery to do GET request.
<script>
for(var i=2;i<(rCount);i++)
{
supplier=tbl.rows[i].cells[3].children[0].value;
del_lead_time=tbl.rows[i].cells[4].children[0].value;
min_qty=tbl.rows[i].cells[5].children[0].value;
urlToCall="/prod_master/addsupp?supplier="+supplier+"&del_lead_time="+del_lead_time+"&min_qua="+min_qty;
$.get(urlToCall, function(response){
console.log(response); //you might want to see returned response
});
}
</script>