[zerodegreec]

Recently converted my BF20 to a 3axis CNC. Have a C6 board and currently have it setup for speed control only (via Mach3). My motor control is a Chinese knock off of the KB speed controller. But so far is appears my control is identical to the KB controller.

Noticed in the manuals Here and Here "Inhibit" that is defined as "Dynamic Brake Circuit". Is this really an electric brake?

Additional question, any resources on direction switching via Mach 3? Really want to set this up for rigid tapping without going to a Servo spindle. With an electronic brake and direction control via the C6, I am hoping its a possibility. :idea:

[Al_The_Man]

The method used by the simpler KB is known as 2 quadrant control, they just use 2 SCR's and 2 diodes in the power bridge, this means that you do not have dynamic braking and the only way to reverse is to reverse the motor leads, either by switch or relay.
If you read through the manual, it show that at the same time you have to Inhibit and reset the drive.
This is done by incorporating the I1 & I2 connections on the reversing device.
This ensures that the drive is reset so it goes through an acceleration process, as otherwise you could damage the drive by going from high rpm fwd direct to rev.
There are high end KB models that are 4 quadrant, these have a few more features including dynamic braking and Tach input and such options such as setting the command for fwd/rev through the speed pot, IOW, centre would be zero, and either end of the pot would be fwd and rev.
If you want tighter spindle control, it may pay to look at the 4 quadrant type and use a motor with a tach.
But rigid tapping usually entails a feed back device on the spindle, higher end controls use and encoder.
Al.

[DICKEYBIRD]

Hey Al, since we're on the subject, I have a C11 BOB/speed control working nicely with a KBIC-120/Baldor 3/4 hp motor on my lathe. It's hooked up with forward direction only now but I do want to add reverse capability later.

The C11 has the same speed control function the C6 does along with 2 relays, 1 with NC contacts and 1 NO. I know how to wire up a manual DPDT switch for DC motor reversing but the 2 relay deal zings clean over my head.

Do you have any suggestions where to look for a diagram or a link?

[Al_The_Man]

Here is a good electronics site that would give you an idea, if you want CNC control then the P.B. would be a M3 & M4 relay, you can ignore the O/L contact, but you would need a N.C. contact on both M1 & M2 for the I1 & I2 terminals.
M5 would be the Off relay.
M1 & M2 would be a power relay with contacts heavy enough for DC switching.
You could pick up a reverser off ebay, these also have mechanical interlocks and the DIN style usually have the option to add auxiliary contacts on the front.
Motor control circuits : Ladder Logic
Al.

[DICKEYBIRD]

That's an awesome website Al, thanks! Got that one in my favorites now for sure. It'll definitely help my electro-challenged self a lot!:cheers:

[samco]

linuxcnc can do rigid tapping even with just the printer port. (you do not need a servo on the spindle) You do need a spindle encoder so linuxcnc can slave the axis to the spindle. The encoder needs to be a conventional 3 channel (quadature with index). If you are going to use the printer port - you will be limited by the speed at which the computer can count the encoder. People have used 100ppr/400 quad encoders.

here is a video with just printer port hardware (there is though inexpensive interface hw for linuxcnc)

https://www.youtube.com/watch?v=C740zS9R9kk

sam