Today I began working on the gantry end plates by bolting on the stepper motors. Next I attempted to install the rollers on the opposite side of the gantry plate and immediately hit a snag. The drawings call for M5 x 30 mm low profile screws for attaching the roller assemblies to the gantry plate. I searched high and low and could not find these screws. I went on line and ordered 30 of these buggers and now I have to wait on the USPS. Meanwhile I thought I might bore you with how and why I selected the spindle for my CNC router.
The Router Spindle
Like most everything else involving CNC routers, there are a variety of spindle types out there. Some made for wood, some made for metal, etc. As usual there are many factors involved when choosing a spindle for either your pre-build machine, or your homemade CNC machine.
If you are building a CNC machine, then you also need to make important decisions regarding the router spindle. Again, I realize a lot of hobbyists are bound by budget and that surely applies to me. After all, that’s part of the challenge. However, there are many choices to choose from within the same price bracket.
One of the most important decisions for the hobbyists, I believe, is the noise level. If you are anywhere near neighbors or your own house, then this is a huge consideration. You don’t want to be running an extremely loud machine for hours at a time.
When looking at trim routers that can be adapted for CNC use, I see that they are all in the 1 HP range. This is equivalent to 746 watts of power. So this gave me a good starting point. However when you look at standard routers such as the Bosch 1617es and the DeWalt DW618K, they are both rated at 2.25 HP or 1.68 kw. This is sufficient power to more than handle any woodworking jobs I will attempt. Many spindle motors are listed by their rating in kilowatts instead of horsepower, so I will be searching for a spindle motor in the 0.8 to 1.5 kw range.
A 1.5-KW motor is a good choice for mid-sized to smaller machines, as well as even some large benchtop machines. You can perform the most common operations on wood and plastic workpieces as well as cut out parts from aluminum sheet.
220 volts vs. 110 volts
While it's said that an electric motor doesn't "know" the difference between 110 and 220, your electric service will. A motor running on 220 pulls half the amperage than on 110. Thus, if you want to use a 2 HP motor, it will pull about 18-21 amps on a 110 circuit. If, however, you want a 2 HP (1.5 KW) motor on your CNC machine running on 110, you'll have to furnish a 30 amp circuit which means a new breaker and heavier wire since pulling 20+ amps on a 12ga. wire can be done, but you're asking for trouble, a possible fire, and complaints from family members when the lights blink every time you turn on the machine, not to mention numerous breaker trips. Since the wiring is already in place, I can convert to 220 by simply installing a 220 volt breaker in the panel box. It’s a no brainer!
Air Cooled vs. Water Cooled
While searching through the advantages and disadvantages of hand held routers in the 1 HP range, one of the complaints was that these machines tend to run very hot, often to the point where the operator can no longer hold the router. Looking over the many choices available, it seems to me that 1 HP is the breakeven point for air vs. water cooling. There are other factors impacting how hot the router will get. Some jobs on the CNC may run an hour or more. Another factor is how hard the machine is working, i.e. type of material, depth of cut, etc. So, all things being equal, IMHO a water-cooled spindle is preferable to air cooled once we hit the 1 HP (.746 KW) point. Closed loop cooling systems for computer MPUs are cheap and readily available. In addition, water-cooled spindles are quieter than air-cooled.
Why Choose VFD Spindles
VFD spindles are a great alternative to using hand held routers to power your CNC machine. Hand routers are designed for small jobs in your hand not for running for hours on end. Hand routers often handle this unintended workload surprisingly well however they are in almost every way the wrong tool for the job.
VFD Spindle Pros:
VFD Spindle Cons:
- Significantly quieter than handheld routers
- Better speed range and availability of collet sizes.
- Much higher duty cycle – they are designed to run all day.
- No brushes to wear out.
- Higher torque in lower speed range
- Considerably better tool runout (accuracy) which leads to higher quality output and longer tool life.
- GCode Control (automatic control from software) – Most often (depending on the CNC controller) you can start/stop and set the speed of the spindle via G-code and also override these speeds from the machine control software in real-time.
- Price – doing it right with approved products will absolutely cost more than picking up a handheld router and bolting it to a CNC machine.
- Potentially RF Noisy (electronically not audibly) – Cheap or incorrectly commissioned/programmed VFD’s can send you down a rabbit hole chasing EMF noise-causing all sorts of failures during machining. It’s hard to chase noise without an oscilloscope and training.
At the end of the day the advantages of VFD significantly outweigh the disadvantages. Today we have pre-engineered systems that are truly plug and play.
And the Winner is….
Vevor 1.5kw 220v Water Cooled Spindle Motor Kit: VFD, Clamp, Pump, Pipe, and 14pcs ER-11
The kit includes the spindle motor itself, the VFD, fourteen collet inserts, a 5-m roll of tubing, a submersible water pump, and a spindle motor mounting bracket. The collet size this motor uses is ER11, which is relatively small and only allows you to use bits with a shank less than 7 mm (.276”). You could upgrade the collet assembly, but you would have to consider the limitations of the motor before attempting to put any really large bits in it. With that having been said, it is highly unlikely that we will be using tools with a shank greater than ¼” (6 mm).
- Size: 1.5 KW
- Cooling: Water cooling with pump and hoses included
- Control style: 220-V AC VFD with computer control
- Collet size: ER11
- Rated speed: 0-24,000 RPM
- Price: ~$270
- Available from: Vevor
The only concern I have is the quality of the VFD drive at this price point. However I will go with this package to start with. If the drive begins to present a problem I will replace it with a Hitachi WJ200-015SSF. One other note – I plan to ditch the pump supplied with this package in favor of a closed loop CPU cooling system.