Greg Koenig@gak_pdx
Never use fully synthetic coolant. For the love of the machining gods, I’ve seen 4 month old machines that look like a decade of hard service because: synthetic coolant. Don’t know why anyone even bothers selling it.
Synthetic has two big drawbacks:
1- It strips lubricant off of everything in the machine. Every seal goes dry, every greased area gets washed out, every mechanism goes crusty. Your tool setter gets rickety, your way wipers crack.
2- it deposits this tacky talc on everything. This eats paint, and generally makes everything in the machine suck to work on. Your workholding needs constant cleaning, your ball screws and linear guides need extra PMs.
On those 4 month old machines, we had a complete spindle failure… what happened? They used through spindle coolant, and that tacky film built up in the Deublin rotary union’s carbide:carbide seal. This seal actually seals under pressure, and opens a bit when under no pressure (the fluid acts to keep it cool, so when the spindle runs without coolant, this design keeps it from burning up at 20k RPM). Remaining synthetic coolant dried across these faces, and prevented them from closing fully- every time the TSC was turned on, a tiny dribble of coolant leaked from the union. This worked down the shaft, infiltrated the spindle when the machine was powered down (Brother uses positive pressure on the spindle casting to prevent contamination). Well under 2 oz of this synthetic coolant washed all the Kluber grease from the upper spindle bearing, leading to spindle death with <100 hours of production. Sad!
Synthetic coolant is the devil!
(And I had to personally deny the warranty claim, and that sucked. We warned them about the evils of synthetic coolant at install, they fully understood the issues and the warranty does not cover damage caused by full synthetic coolant. Even warned them *this* can happen… but their FDA facility documentation and cleaning process was based on this coolant, selected 12+ years ago. They had no choice.)
