Bridgeport BTC

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15 Apr 2011 17:32 #8964 by cottonbelt
Bridgeport BTC was created by cottonbelt
I am new to the forum so i am looking forward to any help with my project . I have a Bridgeport BTC Boss 7.5 mill . I would like to have an easy way to load and edit programs to the machine. Has anyone done this retro to one of these ?
Thanks

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15 Apr 2011 18:27 #8971 by BigJohnT
Replied by BigJohnT on topic Re:Bridgeport BTC
I'm sure there have been hundreds of BP knee mills converted to EMC over the years. The place to start is a survey of your machine hardware to get a grasp of what you have and what options you have...

Steppers/Servos?
Drive input requirements, step/direction, velocity +-10vdc, etc.
Feedback Encoders, Resolvers, glass scales

John

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15 Apr 2011 19:23 #8972 by cottonbelt
Replied by cottonbelt on topic Re:Bridgeport BTC
I know these are servo drives model # 400 , I will have to find out the particulars for these drives .
Does the EMC software replace the old BP control pendent for all commands?

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15 Apr 2011 19:26 - 15 Apr 2011 19:30 #8973 by BigJohnT
Replied by BigJohnT on topic Re:Bridgeport BTC
I'm not sure what "commands" you have on your pendant but normally you have a MPG and axis selection switches and maybe others and yes EMC has inputs to cover almost anything you might find on a pendant.

So you have servos, now you need to know if your drives take +-10vdc velocity input and if you have encoder feedback from the motors.

Typical servo driven machines can use a Mesa setup like a 5i20 Controller, 7i33TA Servo Interface, and 7i37TA's for I/O and a poplar choice for a PC is a D510MO motherboard. If your using a hand-me-down PC be sure and check the latency of the PC by loading EMC and running the latency test for an extended time. Laptops are not valid candidates for CNC real time control.

John
Last edit: 15 Apr 2011 19:30 by BigJohnT.

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15 Apr 2011 19:56 #8975 by cottonbelt
Replied by cottonbelt on topic Re:Bridgeport BTC
Wow I can see I have a lot of things to learn about for this project . I understand there has to be an interface piece of hardware to link EMC to my machine but I'm not sure where to look for and purchase these items. I believe I can find out the voltage signal info for my servos.

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15 Apr 2011 21:02 #8977 by BigJohnT
Replied by BigJohnT on topic Re:Bridgeport BTC
The interface hardware is the Mesa stuff I mentioned.

measnet.com if you don't know where to look.

There are also other boards but I'm not familiar with them as much.

John

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16 Apr 2011 00:10 #8980 by andypugh
Replied by andypugh on topic Re:Bridgeport BTC
cottonbelt wrote:

Wow I can see I have a lot of things to learn about for this project .

And just when you think you have learned it all, those pesky developers add new features!

Basically you probably want to keep anything which is analogue, or using a voltage > 5V.

Everything else will be replaced by a PC and EMC2.

EMC2 takes the position feedback from the encoders, resolvers, tachometers, scales (whatever your system currently uses), calculates how much speed/current/torque (depending, again, on the system) is required to get the machine from where it is now to where it needs to be in (typically) 1mS, and sends that speed/current/torque command to the drives. In its spare time it can also handle the general purpose IO, do abslutely any manipulations on the inputs and outputs that are needed and show the results on-screen.

However, EMC2 runs in a PC, and they only really understand two numbers, 1 and 0. The hardware (and expense) requirement arises when you need to convert those 1s and 0s into voltages other than 0v or 5v (or 3.3v often, nowadays).

In theory you could probably run your mill with a parallel port, 3 capacitors and three resistors with the existing drives. The results would probably be disappointing, but that is a baseline.

Pico Systems do a pretty much plug-in set of parts for your sort of conversion:
pico-systems.com/motion.html

Mesa do a huge (and slightly baffling) range of cards which can be put together to do almost anything.
www.mesanet.com

Alternatively there are interfaces from Pluto, Motenc and others, all of which can be made to work.
wiki.linuxcnc.org/emcinfo.pl?EMC2_Supported_Hardware

Though that list is a bit out of date: People keep adding new drivers and capability all the time. in fact, I think I have just finished a driver for the Mesa 7i65 (octuple servo interface) this evening, and that would be useful for your machine, though the already-mainstream quad-card is probably a less bleeding-edge option.

Unless you find a bargain somewhere, for a Servo system like yours I would suggest going with Pico or Mesa. Both are actively developed for EMC2, and the "main men" from both companies are active in these forums and the mailing list.

Bear in mind that EMC2 prefers to work with very dumb drives. The clever stuff and hard sums are all done in the PC, which is nice, as you can watch. track and plot it. Debugging is thus a whole lot easier.

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