What’s the value of sacrificing production time to warm-up a spindle? There are several reasons to institute a warm-up routine, but for starters, it’s the same reason athletes warm-up their muscles before competition. Spindles, just like muscles, work best when they operate at optimum temperatures.
PREVENT WEAR AND ENSURE ACCURACY
When a spindle sits idle (whether it’s a grease or oil-air spindle), gravity generally takes the lubrication to one spot where it rests until the next start-up. This means when you start your program without warming-up, the first revolutions of the spindle may be dry or unevenly lubricated, which can cause spindle wear and damage.
Having the spindle warmed up and all the bearings and raceways properly lubricated before you make the first cut will help reduce loads and prevent wear of the bearings. While bearing wear won’t damage the spindle to the point of failure, it will increase the load over time.
In the machining process, cold and warm temperatures affect accuracy. The spindle and components are cold when a machine sits idle, but as the machine warms up, their length and size increase. Thermal growth has already taken place in a warm spindle which means from the first part you run to the last, the spindle size will be the same, ensuring part accuracy.
OKUMA machines supplied by GreenBau Technology display various maintenance and proper operating instructions. For example, in our case a vertical 3-axis machining center GENOS M460-V-e, we have the following indications:
1. Do not turn the tools at speeds that exceed their maximum operating limit. Failure to do so may result in serious injury. See the tool manufacturer’s specifications for the permitted speed limits. Especially when using tools with removable pads, be careful not to exceed the allowable rotation speed to prevent the pads from coming loose.
2. Use dynamically balanced tools. If excessive vibration occurs while rotating at high speeds, stop the tool rotation immediately.
3. Do not rotate the shaft without attached tools.
CREATE A WARM-UP ROUTINE
An easy way to create a warm-up routine is to use the calendar timer option on your machine to start the function. This way, the warm-up process can be scheduled to start before you even walk through the shop door.
Before we start, let’s not forget that we need a tool fixed in the main shaft, for heating we can choose a 5 mm drill.
An example of a CNC program for warm-up a spindle of vertical center (OKUMA GENOS M460V-e):
Why we chose these values of speed and running time, because they are specified on the machine (or in the manual) and for our machine we have the recommendation at 15000 rpm a clockwise rotation at 4000 rpm for 10 minutes (we can pass the value of 600 seconds or the calculation formula 60 seconds * 10 minutes) and then another 10 minutes at 9000 rpm:
GreenBau experts can give you advice on implementing a spindle warm-up program or help craft a solution for your specific machine. They can also assist you with using the warm-up function if you already have it on your machine.
Be sure to take the time to perform this easy task. Just a few minutes of warm-up time will protect your machine tool investment and boost accuracy.