New to me mill.

J

JimG

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Have been looking for a mill for some time and just purchased a Exacto 942b with a Trav A Dial
on the x and y axis. Anyone have any experience with the Exacto mill or the Trav a Dial setup?
Are they any good. Will need a inverter or VFD setup what should I look at and any suggestions on
what I should buy and from where. This is all new to me as this is my first mill. I have a clausing lathe
but it has a 110v motor.
 
The vfd makes a good phase inverter with the added option on being able to vary the speed. Make sure to size it large enough and it's designed to be powered off of single phase. I used a Huanyang Bt series for my surface grinder. One caution is don't place any switches or controls between the inverter and the motor. Use the inverter to control the motor. There are several members here that are quite good at inverter set ups. Trav a Dials were used before the digital readout .
 
Nutfarmer said:
The vfd makes a good phase inverter with the added option on being able to vary the speed. Make sure to size it large enough and it's designed to be powered off of single phase. I used a Huanyang Bt series for my surface grinder. One caution is don't place any switches or controls between the inverter and the motor. Use the inverter to control the motor. There are several members here that are quite good at inverter set ups. Trav a Dials were used before the digital readout .
Click to expand...
 
Nutfarmer If I go straight to the motor off the VFD do I not use the the high/low switch which reverses the motor?
 
I have a 1980 Enco 2hp J head mill. I bought the cheapest vfd on Ebay that would handle 2 hp. (less than a hundred bucks at the time) I took the plug off the mill power cord and connected it directly to the vfd. I turn the power on to the vfd and press the start button. The vfd goes thru it's "soft start" cycle up. At that point I use the switches on the mill fwd-off-rev. The only other time I use the vfd buttons is when I switch the motor to "high speed" (very seldom). That errors out the vfd when I turn the motor switch on. All I do then is hit start on the vfd and the "soft start" does it's thing starting the motor.
I use the variable speed of the vfd to change the speed about 10-15% of the speed that is set up by the pulley. The motor that I have was designed a long time ago and the design parameters were based upon a 50 -60 Hertz power source. Feeding that motor with 25 or 30 Hertz power for any length of time will have negative consequences including excessive heating, reduced torque, etc. There are motors specifically designed for variable speed operation. (I have one on my lathe)


I did the same thing for my Boyar Schultz surface grinder. Just cut off the plug and wired it directly to the vfd. No other changes were made to the grinder.

My grizzly 709 lathe came with a single phase motor. I replaced it with a 3 phase motor and vfd. On that one, I ran the motor wires to the vfd and powered the Lathe and VFD off of the same 220 circuit. All I had to do was disconnect the forward/reverse power switch from the lathe control box and connect them to the vfd's fwd and rev terminals. (Grounding either one of the terminals starts the motor) All the other switches on the lathe work fine. (jog, power on, Estop, coolant)

I keep a vfd on the shelf in case I need it but have never needed it in the 5 + years or so of running them this way.
 
Correct way to convert to VFD involves rewiring switches to the proper input on the VFD to perform the original function FWD/REV, JOG, etc.

While you may be able to use the machine with controls wired standard there are many reasons not to. If you want to just plug it in and run with original controls I suggest running a static or rotary phase converter.

John
 
matthewsx said:
Correct way to convert to VFD involves rewiring switches to the proper input on the VFD to perform the original function FWD/REV, JOG, etc.

While you may be able to use the machine with controls wired standard there are many reasons not to. If you want to just plug it in and run with original controls I suggest running a static or rotary phase converter.

John
Click to expand...
I can't think of a single reason not to do it if it is the simplest way to do it and it works. I do not want to start an argument. Please enlighten me. I am curious.
Rotary's are inefficient and static's dont do real 3 phase so have reduced power. As I said in my post, I did wire my lathe forward and reverse switchs to the vfd. The mill fwd and rev switch merely switch 2 phases to change direction. If you wired the vdf to a switch it would do the same thing. I will admit that if I rewired the mill to allow all of the switching to come thru the vfd, I would not have the err condition when the motor was set for high speed. But all I have to do it hit start on the vfd. I think I have used high speed only 2 or 3 times all year. My "hook up" time for that mill was less than 15 minutes.
 
Earl said:
I can't think of a single reason not to do it if it is the simplest way to do it and it works. I do not want to start an argument. Please enlighten me. I am curious.
Rotary's are inefficient and static's dont do real 3 phase so have reduced power. As I said in my post, I did wire my lathe forward and reverse switchs to the vfd. The mill fwd and rev switch merely switch 2 phases to change direction. If you wired the vdf to a switch it would do the same thing. I will admit that if I rewired the mill to allow all of the switching to come thru the vfd, I would not have the err condition when the motor was set for high speed. But all I have to do it hit start on the vfd. I think I have used high speed only 2 or 3 times all year. My "hook up" time for that mill was less than 15 minutes.
Click to expand...
Your gear, you can hook it up however you like....

As I've been taught VFD's need to be connected directly to motors without any switches between. This allows the VFD to be tuned for the exact motor which is connected, as well as use of features on the VFD which aren't available otherwise. Yes, you can connect to the mains supply and your machine may work as desired but the extra effort to retrofit should yield benefits beyond what the original controls give you.

If anyone on this site would like to see how VFD conversions are done professionally they can look up many threads created by @mksj on here.

John
 
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