Taking the CNC Plunge

I can turn the power to the stepper off and manually mill with my G0704 no problem. However, it is much easier for me to use the MDI (Manual Data Input) to use the mill like a programmable power feed. Say you need to mill a slot. Align the cutter as you would manually just use the arrow keys or pendant to jog the cutter and set your zeros. switch to the MDI screen (Mach3) type g00z-.03 (enter) <enter> z rapids to -.03" doc. Type g01x2.5f.5 (enter)<enter> the mill will move the table 2.5 inches at .5 ipm. You can do a lot of one off work by just typing one line at a time. If you need to repeat a command, at the MDI line hit the up arrow to scroll up to the code you want to reuse and (enter) <enter>.

I would also suggest reading Jumps4 thread, he converts a 45 class mill. http://www.hobby-machinist.com/showthread.php?t=8187 its a few pages back.</enter></enter></enter>
 
maker of things said:
I can turn the power to the stepper off and manually mill with my G0704 no problem. However, it is much easier for me to use the MDI (Manual Data Input) to use the mill like a programmable power feed. Say you need to mill a slot. Align the cutter as you would manually just use the arrow keys or pendant to jog the cutter and set your zeros. switch to the MDI screen (Mach3) type g00z-.03 (enter) <enter> z rapids to -.03" doc. Type g01x2.5f.5 (enter)<enter> the mill will move the table 2.5 inches at .5 ipm. You can do a lot of one off work by just typing one line at a time. If you need to repeat a command, at the MDI line hit the up arrow to scroll up to the code you want to reuse and (enter) <enter>.

I would also suggest reading Jumps4 thread, he converts a 45 class mill. http://www.hobby-machinist.com/showthread.php?t=8187 its a few pages back.</enter></enter></enter>
Click to expand...

I've read Jumps4 thread several times. Lot's of valuable information there. His thread also has a link to an X2 conversion that walks through the wiring details. Jbolt has a thread on his PM-932 conversion that is also very helpful. For those of us that don't have a strong background in CNC these are an excellent source of information. Steve (Jumps4) and Jay (Jbolt) have offered to help me through my conversion. A couple of stand-up guys.

Tom S
 
Just curios...

Has anyone done a CNC to a knee mill?

Both Jump and Jbolt's threads are good reads... need to go through them again.

Being new to hobby machining (have some shop experience from decades ago), I probably will use the machines manually for a while... then do the CNC conversion on the mill.

Does anyone have the link to Jump's lathe CNC conversion? THX
 
GA said:
Just curios...

Has anyone done a CNC to a knee mill?

Both Jump and Jbolt's threads are good reads... need to go through them again.

Being new to hobby machining (have some shop experience from decades ago), I probably will use the machines manually for a while... then do the CNC conversion on the mill.

Does anyone have the link to Jump's lathe CNC conversion? THX
Click to expand...

Here's the link - file:///C:/Users/Tom/Documents/Machining%20Related/CNC%20Conversion%20Info/RF-45%20ZX-45%20CNC%20Converstion%20by%20jumps4.htm

Tom S

Edit - My bad! I posted the link to my file location. Here's the correct link - http://www.hobby-machinist.com/showthread.php?t=8187&highlight=cnc+conversion
 
Read through Jump's MILL conversion thread....

Would like to read Jump's LATHE conversion thread... Does anyone have the link to the LATHE thread... THX!

(Sorry for the repeat question... I have posted the wrong link many a time myself... :) )
 
Those motors' torque ratings are crazy. They will be very slow. You would most likely get much better performance by using smaller motors with belt drives.

Also, what are the other specs on the motors? Voltage, current and inductance?

What about the drives, what is their max voltage?

I wouldn't be surprised of the kit components are not well matched to each other.
 
awander said:
Those motors' torque ratings are crazy. They will be very slow. You would most likely get much better performance by using smaller motors with belt drives.

Also, what are the other specs on the motors? Voltage, current and inductance?

What about the drives, what is their max voltage?

I wouldn't be surprised of the kit components are not well matched to each other.
Click to expand...

1600 oz-in motor specs - 5.7V/3.5A, 22mH/phase

4200 oz-in motor specs - 5.36VDC/8.0A, 12mH/phase

The DQ880MA driver is rated at 80VDC. The DQ2722M is a combined driver/power supply. The driver output voltage is not listed in the eBay ad so I'll have to do some digging. Steve used the same motors and drivers for his conversion and made a reference to being able to machine at up to 200 in/min. The intent of the conversion is for me to learn about CNC. I'm certain it will have adequate speed butiIf it runs slower than a production based machine I'm not concerned.

Tom S.
 
Just to put things in perspective. I did a controls upgrade on a commercial 4x8 foot CNC router, with a 12HP spindle motor, and retro-fitted it with NEMA 34, 1200 oz/in stepper motors. The original motors were 400 oz/in DC servo motors. It is common practice to oversize the steppers to try to prevent de-coupling under load.

The reason for the upgrade was the old computer died and a replacement was not available. The customer also wanted to run Mach3 on the machine, and it is difficult to use Mach3 to drive an analog (the DC motor controllers) control system. So we went with stepper motors and a parallel breakout board from ebay. The stepper motors and drivers for this project were purchased from Automation Direct at about double the cost of the system from Wantai, but they are a known quantity. I built my own 80V, 500 watt power supply to run the system.

The 5 pitch lead screws are driven by timing belts that are geared down by a ratio of 1.3:1 on the X and Y axis and 3:1 on the Z. Normal cutting speeds are in the range of 150 IPM, with rapids at 300 IPM. It will rapid at about 600 IPM, but that is frightening and starts getting a bit squirrely, so it is limited. Z moves are limited to about 60 IPM rapid, and normal plunging speed is in the 20 IPM range. It is set up to run 20,000 micro steps/revolution so things operate very smooth.

Mach3 will not run the router at these speeds due to the limitations of the pulse train generator in the software, so we changed the motion controller and software to a much higher speed, and considerably more expensive system. Mach3 will work OK for slower speed systems like milling machines, plasma cutters, and table top routers.

The point of this is that in metal machining you will never run speeds anywhere close to the maximum stepper motor speeds so that is not really a factor in determining what stepper motors to use, but more torque = good. The torque curve of stepper motors is almost flat until you hit the motor's mid speed range, then it starts dropping off. Most of my metal machining is done in the <20 IPM range, with maximum rapids at 100 IPM.

In general, maximum stepper motor speed is a function of available voltage. The motor current is limited by the drive, but the voltage really controls the pulse rise time and therefore the motor speed. The highest voltage rated stepper driver I have seen is 80V.

This is not an endorsement, but assuming that the Wantai motors and controllers perform as advertised, I would say that they will have plenty of power and speed for a milling machine or lathe CNC conversion.
 
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