Just thought I would give you all the heads up here. My lower spindle bearing has just cooked itself… Twice.
On the underside of the CNC spindle motor there is a black cap, within this is a labyrinth seal, sort of an obscured seal which is designed to restrict the flowpath of air getting to the bearings underneath said cap.
The first motor died after almost a year of operation. The bearing was found to be completely caked in what appeared to be Jarrah dust from a piece of timber that I had been cutting at the time. Somehow, it had made its way through the labyrinth seal and into the toolhead itself.
Contacted Snapmaker, because the printer was out of warranty, was asked to spend US$75 on a new toolhead motor. Replaced the toolhead at my own cost.
Anyways, back to cutting again. Less than two or so (off the top of my head) hours into operation, and lo and behold, the Labyrinth seal was beaten again by timber dust. Another seized bearing. I have since sent them an email regarding this.
Just wanted to know if other users had experienced seized lower bearings in their toolheads before. If this is a common issue, it is something that i think needs to be addressed with a revision or update to the design of the head, or perhaps redesigning this part so that it is more compatible either with standard brushless toolheads available on the open market, or alternatively redesigning this motor so that the bearings are replaceable.
Upon dismantling my dead motor to see the cause of death, i found a few interesting things:
1: the manufacturer of the motor’s website is completely broken. Spinpowertech is the manufacturer, and no information is accessible or available.
2: The top bearing is a regular 608ZZ bearing
3: the lower bearing is a 6903Z bearing. This bearing was the cause of death. The bearings themselves sounded extremely worn and loose.
4: Both bearings are steel cased and not rubber shielded.
5: These spindles are practically unservicable by end-users. To take the first old motor apart to autopsy it, it quite literally required me to smack the back of the motor shaft with a hammer to get the spindle out of the motor housing. The lower bearing and the labyrinth seal collar are press-fit to the motor housing and spindle shaft. This alone makes the spindles practically throw-away items if they break.
6: The motor appears to be a similar design to a conventional RC Car style motor. It has a 4-pole shaft magnet and a 2-pole stator design with three power wires and six sensor wires with identical wiring to an RC Car sensored motor, albeit the sensor wires use 3.3v logic whilst a conventional RC Car motor uses 5V logic.
7: The motor size is about 46mm by 87mm, a size used in 1/6th scale RC motors.
8: Doing some napkin math, the motor is either a 750KV or 1500KV motor (KV = Revs per Volt)