Hi guys,
I have a CNC converted LMS 3990. I built the control system myself, changed over to 300in-oz holding torque steppers and ball screws, running GRBL, using Fusion 360 for CAM, have been happy with the results thus far.
This weekend, I was running a .375" square EM 2 flute HSS at 2500 RPM, about 12-14ipm, about .030"-.040" depth of cut in a 1.5"x2.5"x7.5" billet of 6061-T6.
The 2D adaptive clearing would take a variety of cuts, many were light, there was only one pass per level that was even somewhat 'heavy' but I'd say there were 10 minuts or so between this pass. I was blowing chips out manually, and using WD40 intermittently during machining. Work piece was not getting hot during machining. Overall the part looks great thus far, and I'm happy with the results.
I noticed the 500W brushless spindle motor was too hot to touch, the head near the spindle was hot to the touch (I could still hold me hand on it), and the column was even getting warm.
My question is for other 3990 users, preferably those with CNC conversions, is this kind of heat normal? I was a bit worried to be honest, and fired off an email to LMS customer service to make sure there isn't something to be worried about. I don't feel I was pushing the machine too hard. The Chinese HSS end mill still looks great, literally brand new looking after the 2.5 hour operation so I don't think the speeds and feeds are a problem. I also don't think the depth of cut was too aggressive, so not sure why it's getting so darn hot.
Any help is appreciated. I found some other threads on this forum about the belts possibly rubbing in the head, or too much preload. It sounds like the poster was mainly discussing this with the 'high speed' IE: 5000 RPM belt conversion kit. I am using the standard setup with 0-2500 RPM spindle.