Hi
you need to create process for permitting the employee to come late or leave early. This is the role of time office in charge. Normally, the responsiblity of running the floor rests with floor manager (production manager). HR dept's responsiblity is to put the process in common to run the business smothly and at the same time controll the whims and fancies of managers with biased decisions and which may give raise to the differences and lead unrest between employees and managers or company. Hence, You may prepare a prcess document in consultation with all managers responsible for running day today business and understand current practices , keep all suggestions and ideas together then seek approval from MD whose ultimate authority to sign policy documents and responsible for the results of the business. you can even suggest the no of times max. permissible in each case, else, give some flexi hours in a month to arrive late or leave early in each permission subject to max time allowed in a day. This will help to develop a common rule in the entire organisation.