I recently bought a CNCRouterParts Benchtop Pro. It is a 24"x24" router. The thing is, it's a kit. It comes in six boxes if you get the plug-and-play electronics package with it, and you have to put it together. But it doesn't come with everything you need.
- You need a Windows computer to drive it (with Mach3), and of course a monitor, keyboard, and mouse to run it.
- Then you need a raised surface to put the whole thing on -- you're not going to leave this on your garage floor. I got a shelving unit from McMaster (48x36 2-shelf), then I bought some wheels off of eBay -- because everything in a workshop must be on wheels. The "feet" on the shelving unit were 1/4-20 bolts, so locking wheels with 1/4-20 threads worked perfectly. Then I hacked up some cross-bracing for stability.
- Also, you need to buy a spindle and a VFD to control it. And a spindle cable to connect the VFD to the spindle. And then you need a 220V circuit for the VFD, and a power cable to connect that circuit to the VFD. The Huanyang VFD seems to be the one you find all over eBay. Everyone's got one.
- Preferably the spindle has an ER20 collect chuck. You will need a set of ER20 collets.
- Dust collection is absolutely necessary. You do not want to breathe in the fine particulates that the router generates. So, you can either get a complete dust collector, or you can do what most people do: make one out of a ShopVac with a HEPA filter (otherwise you're not getting the harmful fines), an Oneida Dust Deputy DIY cyclonic dust separator, a bucket and a Gamma Seal lid with some hoses to connect them all.
- Don't forget end mills to actually cut with.
- How about toolpathing? A G-Code file tells your router what path it should take, but you have to get from your design to G-Code. This is where V-Carve comes in. I decided to get V-Carve Pro. You get a discount from CNCRouterParts if you buy a router from them. However, you can probably get away with Fusion 360. It is free, runs on Windows and OSX, does parametric design (parametric or go home) and can output G-Code.
The kit is obviously not meant to be turn-key. It is not for the impatient or the easily frustrated. But it is cheaper than most solutions, and many of those solutions still need most of the above extra things.
The 220V circuit (in the US)
What amperage circuit is needed? Well, the most common spindle is 2.2kW, which means 10 amps (2200 divided by 220). You'll need a little extra to compensate for power loss in the cable, so figure 15 amps.
But wait! The age of gasoline is nearing an end, and wouldn't you like your house to be ready for an electric car? A car charger typically runs off 220V, and the higher amperage the better. So I opted to get a 50A circuit -- 40A for a Tesla charger, plus a bit for cable loss.
The plug gives you four wires: ground, a neutral, and two hots. While each slot in a breaker box is 110V, consecutive slots are 180 degrees out of phase with each other, which is why 220V breakers take up two slots. That's how you get 220V. The voltage between the neutral and any hot is 110V, because the neutral is the conductor between the two slots and the hots are on either side.
I'll be putting a 15A breaker in the circuit between the breaker box and the VFD, because I don't trust the VFD to have its own fuse.
The spindle cable
For some reason, this was the hardest thing to obtain. It needs to be four-conductor shielded cable. It must be shielded because without a shield, such a cable will spew RF all over the place, which is bad for nearby electronics. Like, the stuff that is controlling your motors. The shield must be connected to ground on both ends.
I went to surplus stores, and by extreme chance found some, but the wires were too thick to fit in the connector that came with the spindle. You can get some from Soigeneris, but only if they have it in stock.
For some reason, there seem to be only two makers of this kind of cable: Alpha and Lapp.
I got some from Element14: Lapp Kabel Ölflex servo cable, 4 conductor, 1.5mm wires (24M9570). They sell it by the meter. I ordered 10 units, but because I'm a stupid American, I thought it was by the foot. I ended up getting more than I needed, but better too much than too little.
I wish someone sold this cable with the connector already on it.
It turns out that setting up the VFD was the hardest part of the whole project. For one thing, the VFD is very programmable. There are lots and lots of parameters you can set for all sorts of custom circumstances.
But mainly it was difficult because the instruction manual, nominally in English, is horribly written. You can search the webs and find lots of pages on how to set up the parameters in the VFD for your particular motor, but I've found some of the information to be wrong. So here is yet another page on how to set up a VFD, for a particular spindle. I'll try to explain what the parameters really mean.
But first, some myths
Here are a few myths I've found which just make no sense, and I really need to put these first. If you ever see these on a VFD page, don't pay attention to that section.
Myth #1: You need to set up the parameters in a particular order.
No. You don't. If you set PD013 to 8, that's factory reset. So of course, you would do that first. But you can set the other parameters in any order you like.
Myth #2: The max RPM of your motor should be divided by the value of parameter PD010, and that should be entered into PD144.
No. For some settings it is just coincidence that PD010 x PD144 = Max RPM. In reality, they have absolutely nothing to do with each other.
The spindle parameters
First, gather your spindle's operating parameters. If you bought one off eBay from China, you only get this data: power (kW), voltage (V), air or water cooled, max RPM. The spindle I bought is 2.2kW, 220V, air cooled, 24000 rpm max.
You're also supposed to know the spindle's maximum operating frequency. This is often 400Hz for the ones you get off eBay.
The VFD parameters
First, reset the VFD to factory settings. You don't know where that thing's been. On the front panel, hit PROG (or PRGM), and then the up and down buttons until you reach PD013. Hit SET. Change the value to 8 using the up and down buttons. Hit SET again. Now your VFD is reset.
For the next parameters, I've renamed them to make some kind of sense. For setting multi-digit values, use up and down to increase and decrease the value, and the >> key to move one digit to the right.
PD001: Command source. Set to 0. 0 means you're controlling the spindle via the front panel controls. 1 means you're using controls that you've wired up to the screw terminals. 2 means you're going to control it using RS-485.
PD002: Speed control source. Set to 1. 0 means you're controlling the speed through the up and down front panel buttons. 1 means you're going to control the speed with either the knob on the front or an external potentiometer. 2 means RS-485.
When PD002 is set to 1, there is also a jumper next to the screw terminals that you have to set. If the jumper is on the right pair, the control is the front panel knob. If the jumper is on the left pair, the control is via an external potentiometer connected to the screw terminals. Make sure the jumper is on the right-side pair.
By the way, I found setting 0 pretty weird. You only get to see the speed as a frequency, not as RPM.
PD003: Default frequency. If PD002 was set to 0, this is the frequency the motor will start running at. The frequency is directly related to the speed. Since we set PD002 to 1, we can leave this alone. But you can set it to something like 200 Hz to start at mid-range.
PD004: Rated frequency: Apparently this is for motors with a fixed frequency. Since the spindle is variable frequency, this setting can be ignored.
PD005 through PD010 set three points on a voltage/frequency curve. As the motor ramps up to your desired speed, it follows this curve. The manual usefully shows three types of curve: constant torque, low torque, and high torque. I've set mine to the values for the constant torque graph (why not).
I think that if you get a VFD with a spindle, the particular model of VFD comes with different factory settings for these depending on the spindle. Which is nice.
PD005: High-end frequency: 400 Hz
PD006: Middle frequency: 2.5 Hz
PD007: Low-end frequency: 0.5 Hz
PD008: High-end voltage: 220 V
PD009: Middle voltage: 15 V
PD010: Low-end voltage: 8 V
PD011: Minimum allowed frequency. Set to 120 Hz. Air-cooled spindles are not meant to stay at low speeds, otherwise they overheat. I understand that water-cooled spindles can go as slow as you want.
Leave the next parameters alone, and skip to...
PD070: Speed control input: Set to 1. This means that the speed will be controlled by an input voltage between 0 and 5V. This is what the front panel knob delivers. 0 means 0-10V. 2 means the control is by an input current between 0 and 20mA. 3 means 4-20mA. 4 is a combination of voltage and current.
PD071: Speed control responsiveness: Leave at the factory setting of 20.
PD072: High-end frequency: Set to 400. This sets the frequency represented by the top end of the speed control.
PD073: Low-end frequency: Set to 120. This sets the frequency represented by the bottom end of the speed control.
Now skip straight to...
PD141: Rated motor voltage: Set to 220V.
PD142: Rated motor current: Set to 11A. Why not 10? Because there will always be some loss in the spindle cable. This compensates for that. But feel free to set it to 10A. The worst that can happen is that your motor loses power at the top end.
PD143: Number of motor poles: Set to 4. This is the number of magnetic poles in the motor. It should be either 2 or 4, and is 4 for the 2.2kW spindle.
PD144: RPM at 50Hz: Set to 3000. Since the max RPM is 24000 at 400Hz, this means that the RPM at 50Hz will be 3000.
Now twist the knob all the way counterclockwise so that you'll start at the lowest speed setting. You can now hit the RUN button and your spindle should start rotating clockwise if you're looking at it from above. If it rotates counterclockwise, press STOP, shut off the power, unplug the VFD, and swap any two of the motor wires. Then try again.
The display may now be showing a frequency rather than a rotational speed -- that is, the HZ light above the display may be lit. Hit >> until the ROTT light above the display is lit. That's RPM.
Now slowly turn the knob clockwise. You should get all the way to 24000 RPM.
Hitting >> until A is lit shows you the current being used by the motor. With no load, mine ran at 1.1A.