CNC Bridgeport with Heidenhein control

Ignoramus21067 wrote:


Look at linuxcnc.org, and then you need to decide how to drive the motors.

2d vs. 3D is mostly a factor of the control, not the machine itself. Anything recent (EMC2, Mach, Centroid, etc.) will be capable of full 3D contouring.
I assume your Heidenhain control had DC brush servo motors. It may have encoders on the motor, or tachometers, as well as the linear scales somebody mentioned.
Jon
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    You certainly should be able to.
    Since the existing motors are servo motors, not stepper motors, you will need a card for the computer which may be fairly expensive (about what you likely paid for the machine and the tooling).
    And you may have to make some intermediate circuitry to feed the pulses from the Heidenhein scales into the computer. Other and later brands tend to output shaped square waves (two -- at a 90 degree phase shift) so you can count how far it moved, and in which direction. The older Heidenhein ones (such as some that I have) output a sine wave, and need special shaping circuitry before feeding it to the counting circuits.

    O.K. You will have motors to move the axes. On many inexpensive home conversion projects, it will typically be using stepper motors, and the position will simply be inferred from counting the pulses fed to the steppers -- assuming that they never miss a step. This also applies to the early Bridgeport machines like the BOSS-3 Series I which has big heavy steppers, and mag amps to control the voltage to the steppers so higher speeds get higher voltages, and slower speeds get lower voltages to avoid overheating the windings. The higher speeds need the higher voltages to overcome the inductive characteristics of the windings.
    Servo motors are a very low inertia DC motor, or special AC servos. The ones which I have experience with are the DC ones. Both have a tach generator so the speed can be monitored and controlled.
    To move at a specified speed with steppers needs a train of pulses at the right intervals as long as it is moving.
    To move at the same specified speed with servos, a command voltage from the computer via a D/A converter goes to the servo amp, which maintains the speed based on the tach feedback, and the computer can be busy doing other things, and only check every so often that the motion is correct. It does this by encoding scale which generate pulse trains with motion -- or with an encoder disc on the end of the motor. This is typically fed to a counter which can be read by the computer to verify that it is where it should be.
    

    It is either 2-1/2 axis or 3-axis -- depending purely on the controller computer.
    2-1/2 axis allows moving to a given Z axis position and then cutting normally in the other two, while 3 axis allows all three axes to be changing at the same time, resulting in very complex workpiece shapes.
    You can also add other axes such as rotary tables for even more complex operations.
    Check out http://www.linuxcnc.org/ for a download of a live CD of the most recent version, and lots of other information.
    Good Luck,         DoN.
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Guys, what do you think about these controls
http://www.machmotion.com/CNC-Controls-Milling-Machine-Controls/c37_38/index.html
specifically this
http://www.machmotion.com/CNC-Controls-Milling-Machine-Controls/c37_38/p98/CNC-Mill-Control-Ultimate/product_info.html
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http://www.machmotion.com/CNC-Controls-Milling-Machine-Controls/c37_38/index.html
http://www.machmotion.com/CNC-Controls-Milling-Machine-Controls/c37_38/p98/CNC-Mill-Control-Ultimate/product_info.html
    Well ... the one thing which worries me about that one is the term "digital servo" -- which suggests that it really needs something which accepts a pulse train like a stepper drive does, rather than an analog voltage which says "move at this speed". There are Gecko drives which do this for brush type motors, which your machine appears to have, but I would personally prefer a true analog servo driver with the voltage inputs for speed command. (And your existing drivers probably expect an input range of +10V to -10V for full speed forward and reverse, with any intermediate value for any other speed.
    I like the apparent mechanical design -- though the ones which I have seen in service did not have (or need) a keyboard.
    The X15-250-5 looks like a better match for your needs, as it is designed to work with analog servos.
    Note that they all are based on Windows to run Mach3, and *you* might prefer EMC2 (linux based) for various reasons. Also -- the prices scare me. :-)
    Good Luck,         DoN.
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Ed Huntress wrote:

Heidenhain would LOVE to offer this service, but you'd better be seated for the price. Competition has driven the price way down, but I'd take a wild guess and say it is at least $15000 for a complete refit. For reliability reasons, they won't want to reuse any of the control hardware, even if it is in fine shape. So, strip it all off and replace.
There are a number of other retrofit outfits that would be cheaper, but all the turnkey retrofits are going to run over $3K, for sure. That's the Ajax, you get a box of parts and a printed manual, and a note saying "Don't call the factory, we will NOT accept your call except for broken parts. If you wanted support, you should have bought from Centroid." The Centroid control is same as the Ajax, except you pay $10K so you can call them when you run into trouble.
There are much more affordable do-it-yourself retrofit paths.
Jon
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<THUD!>
That's good to hear. <g> Retrofits have come a long way. I hope Iggy's retrofit is a successful one. I'm looking forward to hearing how a non-specialist makes out with it.
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I am hoping that I could fix that system and use it as-is.
i
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You were close. $13,000 for a model 320 control.
Invested for 30 years, it will amount for one year of my retirement.

I thikn that I should try to get this one fixed first.
i
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" snipped-for-privacy@coinet.com" wrote:

There are cheap monochrome security monitors around. They are typically in 9" or 12", but I've seen 21 inch, as well. I have some aluminum cased composite monitors that were used as computer monitors, but I haven't used any in about 15 years.
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    If that is all that is wrong -- that should be easy to fix.
    Good Luck,         DoN.
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Heck if if the CNC is totally dead you can completely retrofit it to run with Mach 3 for 500 with new motors even and add a cheap PC.
$500 for a big mill sounds pretty cheap whether any of the CNC is good or not.
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I need to do a lot of reading about CNC in short order so that I can understand all the terminology, such as double loop, etc.
If anyone can suggest an intro book into this, I would greatly appreciate and buy it immediately.
Here's a guy who converted the same exact mill to EMC2
http://machineability.com/Bridgeport_series_II.html
i
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You remember when you made printouts of coordinates and then turned the handles to those positions to make shapes? That is what CNC control does, but it will do it on all 3 motors at around 1000 times per second depending on controls. The double loop, for example, is when the control gets a feedback from the motor and also gets feedback from the scales on the axis. The motor feedback is used to sense what the motor is doing, the linear scales sense the actual table position. These could be the same but if your ball screws get a tiny amount of backlash, the motor will try to make up for it.
The servo motor gets power to run forward or backward and has something to sense turning so it can be controlled, usually through a Proportional, Integral, Derivative (PID) control loop.
My system uses motor feedback to the motor amplifiers and uses encoder or scale feedback to the CNC control. So, if my position is off a move is required, my control will send out a signal to tell the drive to move the motor at a speed and direction. The amp will send power to the motor and sense the motors movement, as the position error is smaller, the controller sends a smaller signal until the motor stops at the correct position.
RogerN
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OK, I think that I understand that. I will look for some webpage that described architecture of a CNC system. I already have all the manuals in my possession.
i
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Ignoramus21067 wrote:

Double-loop means that there are two encoders per axis, a shaft encoder on the motor and a linear encoder on the machine table. Really, the motor encoder is used to sense velocity. I am guessing from vintage and make that your machine more likely has a tachometer on the motor, not a second encoder. The tachometer feeds velocity info back to the velocity servo amplifier, and not to the CNC control.

OK, a TNC-151, that's what I thought the control would be. He mentions tachometers and rotary encoders, no linear. He apparently re-used the servo amps. Looks like a single-phase transformer, lucky!
Jon
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Jon Elson wrote:

Jon
These machines generally used SEM Servo Motors and Bosch drives.
Wayne...
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If the controls are single phase, I could then convert the whole mill to 1 phase, right? Maybe with just one 220v relay to drive a vfd from a 220v signal? (I want to disrupt the control as little as possible)
i
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Ignoramus26960 wrote:

Well, I was going from a picture of a "similar" machine, so yours could be different. But, yes, if the control all runs off single phase, then feed it 240 single phase, and rig appropriate relays to control a VFD. Might as well leave the VFD power on continuously, and switch the control inputs to the VFD (forward and reverse).
Jon
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This is exactly what I would do wrt a VFD. Fortunately, I have a VFD handy in the shed. This is the smallest one of my problems.
I also do not need rigid tapping and will not put an encoder on the head.
i
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Bob La Londe wrote:

Probably not quite. it is almost certainly a servo-driven machine, not stepper. $500 with new motors? Do you know how big a Series-II is? It stands about 8 feet tall and weighs 5000 Lbs. It uses NEMA size 42 motors driving the leadscrews 1:1.
Jon
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