CNC Bridgeport with Heidenhein control

Are you saying that I should just plug in a VGA LCD monitor into a 9 pin EGA output? And it will work??? Why all the fuss then? Somehow I think that the world would not miss something this great. Am I missing anything?

Er, no. But I think building an adapter may not be very difficult. You'll have to look up the signal specs for both to see.

I can't seem to find good detailed specs at the moment, however:

EGA uses TTL signals and has separate H and V sync signals as well as two bits each for R, G and B, hence the 64 colors it had.

VGA also has separate H and V sync signals (can't find signal level specs), and has three analog R, G and B signals.

Get out your scope and check the signal levels of the VGA output of a PC. You should be able to do a simple resistor ladder D/A converter type setup to convert the two TTL color bits into a four level analog signal for the VGA monitor to take. The HV sync timings will be within the capabilities of the VGA monitor, you may or may not need to adjust their levels.

A key thing to keep in mind here is that this is a CNC control, not a gaming PC and getting those 64 EGA colors to display perfectly doesn't matter as long as they are readable.

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

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

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

It is rather unlikely the control will survive the move without some new problem coming up. The older the control, the more fragile they get, as the number of separate circuit boards and connections was much higher on the early ones. This is probably a mid-80's control at the latest, and unless you were a minicomputer hardware tech in a previous life, I don''t think you want to get involved it trying to keep it running.

I adopted a 1978-vintage Allen-Bradley CNC control in 1997 and managed to get it running, which was a HUGE ordeal, requiring disassembling the paper tapes for the executive program so i could modify it, building a "BTR" so I could dispense with paper tapes, etc. But, it had major breakdowns 3 times in 9 months, and I was getting TIRED of maintaining the DAMN thing! Your Heidenhain control is likely a bit newer, but still VERY much in the aged category now, roughly 20+ years old. So, I would strongly recommend a retrofit, too. Depending on whose servo amps are in it, they may be able to be reused, which will make the retrofit easier. Depending on the type of position encoder on the machine, these may be reused, too. With Heidenhain, there may be signal converter/interpolator boxes associated especially with linear scales that need to be kept.

There are several servo interfaces available for EMC that you can choose from (I make one kind).

Jon

Depends on the condition, how long it has been since it last ran, and whether the prints for the boards come with it. If no prints, you are in a HEAP of trouble.

My experience tells me to not bother unless all it needs is a new video monitor AFTER!!!! you get it moved to your location. If it has serious problems, it can become a total time sink.

I've had GREAT results with EMC, and would NEVER go back to the proprietary control.

Jon

You need to get into it to see what is there, and what it looks like (mouse-eaten wiring, burned parts, etc.)

First, ID the motors, and see what velocity feedback it may have there (encoder on motor, tach, etc.)

Second, ID the servo amps - just follow motor armature wires back into control cabinet, and wherever they stop should be the servo amp. Westamp and Servo Dynamics were the big players at that time, and a lot of control builders used them. Docs are still available.

See if the servo power supply needs 3-phase or can run off single.

Once you have this info, you can start looking at interface hardware to connect to it. You can also decide whether to use the servo amps, or scrap them.

Jon

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

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.

tachometers and rotary encoders, no linear. He apparently re-used the servo amps. Looks like a single-phase transformer, lucky!

Jon

I use an EZ Trak Bridgeport manually when reworking a part to scribed lines and punch marks. The Jog knob substitutes for the table cranks. After a little practice to remember the button sequences it isn't that much different from using a manual DRO machine.

The CRT died on that one too.

An example of an EGA to VGA adapter:

That's good to hear. 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.

Jon

These machines generally used SEM Servo Motors and Bosch drives.

Wayne...

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 am hoping that I could fix that system and use it as-is.

Can you explain what you mean.

Tell us about it Jon.

How hard is it to take the head off to make it stand lower? 8 ft will not fit through my garage door, fsck

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)

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.

You can also add other axes such as rotary tables for even more complex operations.

Check out

Good Luck, DoN.