Roll grinders are considered to be an intricate part of the overall rolling process. The rollers are the tool to a smooth clean surface finish. They will create a mirror image on the work performed, i.e. if the roller is scratched then also, so will be the rolled sheet.
Cleaning the coolant is as important as dressing or changing the wheel on the roll grinders. The appearance of burning or staining can show that dirty coolant runs hotter, because of a reduction in its heat transfer capability. Staining can also show an increase in undesirable soaps or scum. The appearance of scratches or dullness is another subjective technique that relates to coolant clarity.
Clean coolant will also increase the number of pieces worked before wheel dressing is needed. Dirty coolant will glaze the wheel prematurely.
Clean coolant creates cost reductions in two main operating areas: Product quality and tool life.
Clean coolant ensures product quality. “Constant” clean coolant allows the manufacturing process to maintain its performance close to original design parameters.
Regardless of the process used, the tools of the operation are protected from excessive wear, abrasion and heat. Dirty coolant can glaze the grinding wheel prematurely.
Consequently, tool life and effective performance are increased. Clean Coolant also has a positive effect on productivity and has direct correlations for reducing cost in:
Although related to the first two inputs, scrap reduction is a direct correlation to the use of clean coolant. Contaminated coolant is like a worn cutting tool. Both will produce rejects.
Machine downtime, due to maintenance, is reduced. Production speed and/ or operating hours can be increased when a process works with clean coolant.
A properly designed closed-loop filtration system with temperature control, where necessary, will reduce coolant losses due to evaporation and spillage. This reduces the need for fresh coolant makeup.
Once a coolant is dirty and must be discarded, additional costs are created by the frequency of dumping. Coolant filtration extends coolant life, which reduces this frequency. This reduction offers the following cost savings:
Every dump demands a fresh batch. With the escalation of raw material prices, this cost continually climbs. When the coolant is oil, the replacement cost factor is probably the highest input in the economic evaluation.
Disposal of Spent Coolant
Although this is listed as a second cost factor, many water soluble coolants exhibit a higher cost for disposal than the cost of fresh replacement. Disposal may consist of trucking to remote dump sites or breaking the emulsion for safe discarding.
Labor for Cleaning
During shutdown, manpower dollars are spent to remove the liquid and “shovel” the accumulation of sludge. Since this is performed during non-production hours, it usually involves premium time pay.
If shutdown occurs during the normal work day, there is a loss of productivity. Machine time is a valuable factor to lose.
Machine Tool Life
The constant exposure to dirt and abrasive debris shortens the performance life of critical machine parts. Clean coolant will extend the intervals between major machine overhauling, and is an important factor in any routine preventative maintenance program. This affects not only machine tools, but pumps and heat exchangers as well.
Housekeeping, safety and operator morale are all enhanced when the coolant and the equipment affected by the coolant are clean.
There is sufficient evidence to believe that clean coolant helps reduce the probability of dermatitis. One theory states that the metal fines, in solution, break the protective barrier on the skin, leaving it vulnerable to the hazards.