Name Id on Custom Record

I am having problems setting the 'name' field on a  custom record when running a suitescript.

For instance in the code below I set the fields in the custom record no problems and see the results in the logExecution calls. But i get an error from the final nlapiSubmitRecord. I suspect it is the use of 'custrecord_name' but cant find the correct name to use?
I am sure it is quite a simple thing I 'm missing!
Thanks
Don

var record = nlapiCreateRecord('customrecord6');
record.setFieldValue( 'custrecord_item_owner', customer);
record.setFieldValue( 'custrecord_serial_no', serialnum);
record.setFieldValue( 'custrecord_item', caseitem);