Router question - how important is speed control?

[maxcnc]

I'm looking to buy my first CNC Machine.  I have a Bosch Colt router, but it's the single speed unit, not the variable speed unit. When trimming laminate or routing edges I've never missed the ability to lower the spin speed, I'm not even sure why I would need to.  Experienced Millright users: are you running your spindle/router at full speed all the time anyway, or do you need the ability to lower the speed at times?

[aforww]

Mar 24, 2017 12:08:10 GMT maxcnc said:

I'm looking to buy my first CNC Machine.  I have a Bosch Colt router, but it's the single speed unit, not the variable speed unit. When trimming laminate or routing edges I've never missed the ability to lower the spin speed, I'm not even sure why I would need to.  Experienced Millright users: are you running your spindle/router at full speed all the time anyway, or do you need the ability to lower the speed at times?

See my post on the Beginner information. Spindle speed is important for milling for numerous reasons. Spindle speed varies for cut type, mill type, material, and work time. Now, it's not so important in the lower speeds as seen in older vertical milling machines where many run at 10k RPM all the time but with a router ripping along at 30k RPM, it's a good idea to have a lower end. 

[maxcnc]

Thanks for the info. Is there a document somewhere about how to connect the 400W spindle to the arduino so you can control the speed in the programming?

[aforww]

That I can't offer any input on as I have never used the 400w spindle kit.
I imagine though that if you do a Google search for UGS or GRBL spindle Speed control, you'll get on the right track.

[Derek the Admin]

Not really. Frankly, I decided not to do it because it was more prone to configuration error. Essentially you unplug the potentiometer from the speed controller and wire in the PWM pin to Z Limit (Yes, I said "Z Limit") on the CNC shield. Then tie the ground terminal next to the "PWM" terminal to ground on the CNC shield.

Now, you'll need to use X loader to reflash the grbl firmware onto the Uno board using the one called "Grbl Laser/Spindle Hex" at www.millrightcnc.com/resources. This will turn on hardware pulse width modulation which emits the PWM signal from the pin labeled "Z limit" and will move Z homing switch functionality to "Sp En" on the shield. It sounds crazy, but the pin reassignment is necessary.

From there, the code M3 enables pulse width modulation, the intensity of which is set by S commands. That firmware goes from all the way to 0 with S0 to all the way to 12000 rpm with S12000.

All that said, Aforww is right about how speed control is helpful. It's not an absolute necessity though, depending on what you're intending to mill. The first machine I ever built (different than the M3) used a fixed speed DW660 (30k RPM) and I cut hundreds of pieces on it.

[aforww]

Mar 25, 2017 3:54:50 GMT Derek the Admin said:

Not really. Frankly, I decided not to do it because it was more prone to configuration error. Essentially you unplug the potentiometer from the speed controller and wire in the PWM pin to Z Limit (Yes, I said "Z Limit") on the CNC shield. Then tie the ground terminal next to the "PWM" terminal to ground on the CNC shield.

Now, you'll need to use X loader to reflash the grbl firmware onto the Uno board using the one called "Grbl Laser/Spindle Hex" at www.millrightcnc.com/resources. This will turn on hardware pulse width modulation which emits the PWM signal from the pin labeled "Z limit" and will move Z homing switch functionality to "Sp En" on the shield. It sounds crazy, but the pin reassignment is necessary.

From there, the code M3 enables pulse width modulation, the intensity of which is set by S commands. That firmware goes from all the way to 0 with S0 to all the way to 12000 rpm with S12000.

All that said, Aforww is right about how speed control is helpful. It's not an absolute necessity though, depending on what you're intending to mill. The first machine I ever built (different than the M3) used a fixed speed DW660 (30k RPM) and I cut hundreds of pieces on it.

What's the deal with the unnatural pin assignment? Not owning one I can't experiment with all the new GRBL and UGS updates. Is it a function of the software versions or of the hardware? 

[Derek the Admin]

The CNC shields we use are just not designed with that in mind. The author of Grbl had to move some pins around to take care of onboard hardware PWM functionality that didn't exist where the spindle enable pin was originally mapped.

Derek

[aforww]

Ahhh gotcha. We should fix that lol.