Advice on Old mill retrofit? + tool type

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05 Dec 2018 17:46 #121892 by simonmn
Hey guys!

I have been lucky to pick up an old Bridgeport Interact 308 CNC milling machine. I haven't gotten it home yet, so this might be a little premature posting, but I am just so exited.

It has a Heidenhein TNC 2500 controller, but both the seller and me suspect the parameters to be lost on the dead batteries. Its not really a big deal for me, since I am planning on a linuxcnc retrofit.

I am also working on a old Mazak cnc lathe with linuxcnc, which is coming along nicely... slowly, but nicely.

For you guys with experience with retrofitting old machinery, could you give me some advice on the best approach on this project?
It would be nice to be able use the old servo motors and drives. But if I have to, or it would save "time", I am prepared to get new motors plus drives. The ATC is also a big priority for me.

The thing I am a little worried about, is the documentation. The seller had a book with him, but it was more of a maintenance book for what I could see. It had some basic information about the machine, constructional diagrams over the major components, and some electrical diagrams and so on. But compared to the documentation from my mazak, its not more than a flier.

Some question that pops up in my quick research is: Different types of BT 30 Taper toolholders?

The "Flier" says it uses MAS403 tool holders, and MAS407-1 pull studs.
Now then I search for those, it gets generalized as BT/CT/JIB/MAS tool holders.

Me being really optimistic, hopes this means I can purchase BT30 toolholders, and use them without damaging the spindle. :blush:
But is that so? And what about the pull stud? I hope it isn't like Mazak machines, which use proprietary pull studs, but I have to admit, I have no clue. :side:

I hope you guys could help me, and give me some advice.

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06 Dec 2018 17:40 #121971 by andypugh

simonmn wrote: For you guys with experience with retrofitting old machinery, could you give me some advice on the best approach on this project?
It would be nice to be able use the old servo motors and drives. But if I have to, or it would save "time", I am prepared to get new motors plus drives. The ATC is also a big priority for me.

I would keep them if I could.


The "Flier" says it uses MAS403 tool holders, and MAS407-1 pull studs.
Now then I search for those, it gets generalized as BT/CT/JIB/MAS tool holders.

Me being really optimistic, hopes this means I can purchase BT30 toolholders, and use them without damaging the spindle.


As I understand it MAS403 _means_ BT30.
407-1 is 45 degree pull stud, (2 is 60 degree, 3 is 90 degree) www.vtool.ru/sht.htm

All the 7/24 tapers are compatible. My mill was supplied as 30INT, but I fitted a BT30 drawbar for pulls studs and then used BT30 holders. Then I found a cheap job-lot of SK30 holders, and shortened one drive lug to suit.
I have a couple of ISO30 tapping chucks, I am going to re-thread one (for my horizontal axis) and cut the thread off the other and fit a pull-stud for the vertical.

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08 Dec 2018 10:36 #122047 by simonmn
Thanks for the advice!
Is there a "easy" way to find the correct settings for the servos if the parameters are missing? It will be my first time working with servo motors.

I have made an order for a BT30 tool taper, and a type 1 pull stud (45 degree) today.

As for electronics, I was planning on using a Mesa 7i76e again, as I do on my lathe. Will this be enough in terms of inputs, and motion control?

Again thanks for your help

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08 Dec 2018 11:17 #122048 by andypugh

simonmn wrote: Thanks for the advice!
Is there a "easy" way to find the correct settings for the servos if the parameters are missing? It will be my first time working with servo motors.

Not really, it always comes down to trial, error, and tuning even when you have full documentation.

As for electronics, I was planning on using a Mesa 7i76e again, as I do on my lathe. Will this be enough in terms of inputs, and motion control?

Possibly not the best choice for a servo machine if the drives require +/-10V analogue control,
I would figure out the drive control scheme and encoder types before deciding on a motion control card.
You might find that something like 7i93 + 7i33TA is a better fit, or 7i92 + 7i77 if you want to use Ethernet. But it is also worth looking at the PCI cards (6i24 + 7i33 ++). If the machine has resolvers then you definitely need to be looking at the 50-pin header cards + 7i49.

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27 Dec 2018 09:40 #122946 by simonmn
Happy Holiday!

So I got the machine home a couple weeks ago, and have played a little around with it this week. Most of the documentation was in pretty rough shape, so took the time to scan everything.
As I expected, when powering on the machine, all it did was spit out parameter errors, and when navigating to the parameter list, everything was at 0.

Any way. I am not sure I have all the electrical diagrams. The ones I have seem to refer to different pages than included (properly a complete diagram folder)


(small cut from the whole A3 page only showing Y and Z)

From what I see, there is no revolvers, but there is a tachometer on each axis (For velocity measuring?) What is its purpose? Could a axis be complete in Linuxcnc without it?

I have downloaded some technical documents from Heidenheins website, which I hope to get an idea of pinouts from. But I would still very much like your opinion on what options to take.

If you need more information, or would like all the electrical diagrams i have, please tell me.

Thank you for your help!
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27 Dec 2018 09:51 #122947 by andypugh
Tachometers are used to close the velocity loop.
Basically your command voltage has the tachometer voltage subtracted from it and the resulting voltage is amplified and sent to the drive.

High command voltage and low velocity => high motor voltage
Motor at-speed => low to zero motor voltage
Low command and high speed => negative motor voltage to slow it down.

You would leave the tachos connected to the drive to close the velocity loop and then use the encoders and LinuxCNC to close the position loop, outputting velocity commands from LinuxCNC.

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27 Dec 2018 10:36 #122948 by simonmn
Thanks, that makes more sense.

How would that be connected? I guess the 7i77 in combination would be preferred for that?

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27 Dec 2018 13:28 #122954 by Todd Zuercher
Yes a 7i77 would be an excellent choice for your machine.
Like Andy said, you leave the tachos alone (leave them connected where they are, to the drives.) You'd only need to connect the encoder feedback to Linuxcnc.
You will be connecting the analog out signals from the 7i77 to the drives, and probably the drive enable signal. The analog out from the 7i77 will be the velocity command for the drive.

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28 Dec 2018 17:14 #123022 by simonmn
Done some digging in the electrical cabinet, and believe I was able to trace most of the connections I would need to connect with the servo drives from a 7i77, using the documentation of 7i77 and the official heidenhein manual.

Next would be understanding how the encoders are connected.
From what I can see in the schematics, the spindle encoder is a "traditional" encoder as I know them, with outputs A, A-, B, B- and a +5V and 0V connections.

But the encoders on X Y Z seem different
(Cut from the heidenhein technical manual)


How does this compare to the classic A B + -?
Another thing, could you tell me if this isn't right.
7i77 Encoder terminals
QA0 = A+
/QA0 = A-
GND
QB0 = B+
/QB0 = B-
+5V

Sorry if I ask too many questions, or seem ignorant to the task. I just really like to tinker with these machines, and want to learn more about them, in the process of getting them up and running.
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28 Dec 2018 19:54 #123032 by Todd Zuercher
Are those encoders or glass scales? Looks like that chart is describing interpolated scales, and you need an EXE box to convert that to quadrature signals. You may already have them (or it could have been built into the old control.)

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