There is nothing like PMS for unskilled labours. Generally they are used for loading or unloading or other menial work like gardening, cleaning etc. Please confirm what type of work blue collar workers do in your company. Then we will be able to tell you whether the work can be measured or not.
By the way, getting the blue collar workers is not that easy. If they leave the job, getting their replacement is not that easy. Therefore, be little slack with them. After all, they are not paid more than minimum wages. Therefore, why bother about small fries or those who just draw minimum wages? There are big sharks at the top level. Please measure their performance accurately!
In regard to blue- collar workers generally speaking, no formal performance appraisal system exists in majority of organisations at least in India.
The main reason is , time bound wage scales and grades are applied to them largely through wage settlements with the Union or also unilaterally. The wage differentials are determined by skill level and seniority and Annual increments are fixed in steps of of five years span extending up to 20 years or more as applicable to given skill level i.e unskilled, semiskilled, skilled and highly skilled .
In other words , the annual increments are automatic on completion of every year except for the poor attendance, misbehavior or poor performance increments are withheld in individual cases by way of disciplinary action.