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  1. #41
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    Perry,

    As I said I know nothing about what you are doing but it seems to me in basic talk that you are braking down the function of the control board by board....? If I'm correct how do you approach this task ? Is it a matter of looking at the components on the board and the schematic then just knowing how it operates or are you digging into the actual software code and figuring out what the board does ? or is it a combination of both ?

    This seems like rocket science to me, as a shop owner I get to use my controls and software menu by menu and would not even know how to look at anything beyond that, (under the hood) Don't worry I'm not planning to try I'm just very interested at your approach to getting this machine running. Most of us would be happy with a clean functioning machine and a fresh coat of paint if even that. If it runs the program get it making chips is how it's done here.

    Ron

  2. #42
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    Don, your editor sucks the big wombat! I was writing a novel and hit Ctrl-A to select all, then Ctrl-C to copy, but your dang editor cancels the post when you do that!

  3. #43
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    Just to be clear, the control and electronics work fine on my Fadal at present, it was the iron that needed major help.

    The process of reverse engineering the control started with researching the history of the Fadal control. On the VMC Electric website they give a few pieces of information about the process of creating the control.

    They said they used an Imsai 8080 to develop the NC executive. If you read closely you'll see they used the NC software to process G-code into NC tapes for their other machines. This specifically includes applying cutter radius compensation and other stuff that old NC systems couldn't do.

    Well, the Imsai 8080 was a clone computer of the MITS Altair 8800. The Altair used a bus comprised of 100 connections on a card edge, derived from a bunch of surplus mil-spec connectors they were able to obtain.

    The S100 bus name came from the clone market being tired of referring to the Altair bus because Altair was a competitor. Later the S100 bus became standard IEEE-696, which was only retired a short while back.

    Looking at the card cage in the Fadal control, it's obvious they based their design on the S100 bus, which was popular back before the IBM PC came out. Prior to the PC many computers that hobbyists and enthusaists used were based on the S100 bus design. This allowed you to separate the functionality of each subsystem into a separate card.

    Fadal didn't adhere to the S100 bus specification much, they mapped signals roughly into the same locations, but they went significantly off book. The power distribution is simplified and many of the S100 signals are not implemented.

    The process of reverse engineering the cards done thus far (video and CPU) starts with Eagle CAD and the background investigation I did above. I used information from S100computers.com to make a custom part in Eagle which represents the S100 card edge and pinout. I also created several parts for the special Intel chips used for interfacing to the S100 bus and Intel CPU. All of the datasheets for the components are available online, you just have to search and follow the rabbit hole.

    Once I had the components defined, I placed them in an empty schematic sheet roughly in the same location as they appear on the boards. Generally speaking, chips that are close to eachother on boards are functionally grouped, due to the routing requirements.

    The Fadal boards are comprised of 2 layers, a top and bottom, this makes them easier to reverse engineer because I can follow the path through the boards. The top layer (component side) is generally devoted to traces (wires) that run horizontally between components. The bottom layer (solder side) is devoted to traces that run vertically.

    The logic behind how the boards are layed out is based on standards for generating printed circuit boards. You find the east-west, north-south routing commonly on 80's vintage stuff because they didn't have sophisticated auto routers. It's similar to the difference between a zig-zag toolpath and the tool paths generated by the new fancy HSM CAM tools.

    The process of tracing each connection involves using a mechanical pencil as a pointer, a flashlight to see traces that go under chips, and a Fluke DMM in beep continuity mode. From that point it's a matter of picking an interesting looking portion of the board and tracing the connections to the bigger chips. Then I work on bus interface chips and finally all the little logic chips spread around the board.

    The boards are comprised of logic chips that implement one of the following types of operations: count, de-multiplex, boolean logic, and flip-flop. There are specialist chips that do very one dimensional tasks, like combine separate read/write lines into a single read and write bus.

    Once you map out some of the signals, you can make inferences about what other signals are and avoid actually tracing those. For example, if you have a latch that has AD0 on one pin and A0 on the corresponding latched pin, then it's safe to assume that AD1 is A1 and so forth. There are several chips like this, though you have to be careful because Fadal swapped some pin assignments to make board routing easier. This is a dead giveaway that a human spent considerable time looking over the layout and hand routing some, or many, of the signals.

    Reading the datasheet and understanding what each pin does on a chip and how the chip functions, that allows you to perform a sanity check on the schematic and detect errors. There were several errors I made due to reading the wrong pin number (looking at the mirror image of a chip can cause these errors), etc. If you spend some time trying to understand what the designer was doing, you can use that understanding to validate the schematic and check it against the real board with a DMM.

    Once I had the boards mapped out I could then go back to the software, which is straight machine code. Looking through the machine code I can search for addresses derived from the board logic, such as video display writes.

    I discovered that Fadal put a secret diagnostic routine into the system ROM that causes the machine to self-test the keyboard, ROMs, and RAM. The diagnostic mode is triggered by inserting a jumper block into J2 of the video card, this is read at startup and if inserted it will go into diagnostic mode.

    It displays this menu:

    T1 = KEYBOARD TEST VER 1.6
    T2 = VERIFY EPROMS
    T3 = RAM TEST
    T4 = RAM EXPANSION TEST
    T5 = EPROM CHECKSUM
    TX = JUMP TO CNC

    I've also learned that there is some peripheral in the 0x1000 segment that the control talks to a lot, and since I know RAM is at 0x6800, I know it's not memory.

    Looking at pictures on Ebay of memory cards, I see that the external memory cards can live at the following addresses:

    6XXXX
    7XXXX
    8XXXX
    9XXXX
    AXXXX

    But since 6XXXX is taken by the on-board memory, only segments 7-A can be used, limiting the control to 256KB of additional memory (two of the 128K cards). The 128K cards have 2 jumper wires on J5 that select the segments they belong in.

    Now that I've learned this information, I can go back and search the code more. But based on my research yesterday, it may not be possible to run the original ROMs on a faster processor because there are delay loops that seem to depend on the speed of the processor. For example, fetching a key from the keyboard seems to involve some hard coded delays.

    Anyway, this was all more for my understanding than any sort of commercial endeavor. The machine works as is, but I may use this information to increase the amount of memory in the system or make my own video card.

    I can go to Digikey right now and pick up a 512KB ram chip for $6.44, that's a heck of a lot easier to interface than 16 separate chips.

  4. #44
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    Went to install gibs, the taper doesn't match the table, tomorrow I will figure out where things went wrong. The small end is too big by 0.030, over 9 inches. That's about 0.0035 per inch error.

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    The gib mystery has been solved, to a degree that I can fix the problem.

    My machine is #8503166, so it was made in March 1985. My table has a nominal 1/4" per foot gib taper. The drawing that the supplier has says Fadal uses a 0.95 degree taper, which just so happens to be about 5mm per 300mm (0.9549).

    It looks like Fadal went metric on the gib angle at some point, and their drawings don't indicate this revision.

    The big problem is going to be for anyone trying to get gibs and having old taper and new taper mixed together.

    The 5 inch gibs are still 1/4" per foot, or 1.2 degree nominal.

    My table has a 1.203 (EDIT) degree gib angle. I measured this by clamping a 4 inch gage block to the gib surface, then using a .501 gage pin to zero a digital caliper on the big end, then measuring the difference on the small end.

    The distance between centers of the gage pin was 4.501 and the measured difference was .0945.

    The drawing calls out a tolerance of +/-0.1 degrees on the gib taper for the 5" gibs, this is wide open and way too lax. The difference of .1 degrees over 9 inches is 0.015"!

    BTW, measured with a caliper, even accounting for +/-0.002 tolerances, the angle is still within 0.02 degrees. I'll double check everything before I commit cutter to steel.

    My plan is to setup the gibs on a sine bar in the Kurt vise on my BP, then recut the back side of the gib so it has the proper taper.

    I should have a YouTube video of this in a few days.
    Last edited by Perry Harrington; 11-12-2015 at 01:34 AM.

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    M&J technologies might have all the answers your looking for. It was started by a factory guy. They have access to some serious parts.

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    You know that chain lube line upgrade was intended to be under the saddle not in the side of the table IIRC. BUT I love the idea I was thinking along the same line.

  9. #48
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    I have the answers, at some point fadal changed the taper. I'm gonna recut them on the BP with a sine bar. I realize the lube kit went under the table on later models, on this one all the lube is in the saddle, so I just appropriated a bunch of useful parts from a later design. I suspect when fadal went from the narrow 12" X to the wider 14" X, they changed the taper to 5/300mm instead of ¼"/foot.

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    Ha Ha! I just finished remachining the gibs in the Bridgeport. The first operation was to square up the gibs so I could gang clamp them, this involved clamping them as a pair and skimming 0.017" off one side and 0.005" off the other side so they were square and parallel.

    To re-cut the taper I used a Sine bar set at 1.2 degrees in a Kurt 3600V vise.

    I faced the gibs off using one of those Sandvik RA245 high shear 5 insert shell mill cutters, then I used an 8 flute 1/2" EM to machine the 0.010" step into the gibs.

    When I was done, final inspection revealed that I achieved a 1.206 degree taper on the gibs! The table is 1.203, so the difference is 0.003 degrees, which is 50 millionths per inch. I think I got lucky with the bridgeport.

    I reinstalled the gibs and adjusted them for the 0.0005" deflection requirement, then a little snugger (just the feel on the gib screw). I can still push the table back and forth, but it achieves the 0.0005" max deflection requirement.

    While I was trying to indicate the table I notice the saddle was deflecting 0.005" when I was prying on the gib straps (that's the recommended approach to apply force while adjusting the gibs). Now I gotta take the gibs out of the saddle and see what I'm up against, probably more fubar gibs...

    Luckily they have the right gibs in stock and they are the correct taper.
    Last edited by Perry Harrington; 11-13-2015 at 01:18 PM.

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  12. #50
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    Kick ass. How did you go about holding the gibs in the vise? I had to make new ones for my Tree, and being long, skinny, and thin definitely took some pondering on how to hold them, especially with the sine bar.

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    Quote Originally Posted by KC130Loadie View Post
    Kick ass. How did you go about holding the gibs in the vise? I had to make new ones for my Tree, and being long, skinny, and thin definitely took some pondering on how to hold them, especially with the sine bar.
    I had to square them up, then I clamped them side by side with a parallel, against the fixed jaw. I used a deadblow hammer to smack them down on the sine bar periodically. The thin end of the gib was not as snug as I'd want. The gibs were 9" in a 6" vise. I could have clamped them straddled across 2 vises, but I was worried about the table being out that far and the knee twisting under the load. I have 2 vises on one end of the table and a rotary on the other end, when milling in the center it's more or less balanced.

  14. #52
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    The saga continues. I got the X all sorted, then the X motor starts vibrating like a shaker when running at full jog.

    I ran it slow and saw the sheetmetal motor mount moving back and forth, so I took the motor off and inspected the lovejoy couplers. They looked newish and the key on the motor was sticking out about 1/4"...WARNING WILL ROBINSON!!!

    Someone had been in there and replaced the lovejoy coupler, gee I wonder what else they messed up?

    I stuck an indicator on the motor mount and found 0.0045" movement of the motor mount, the high spot being almost exactly across from the keyway of the coupler.

    One would think a lovejoy coupler would provide some misalignment protection, well not enough as it turns out.

    I pulled the coupler off the end of the screw again and measured the runout on the shaft end of the screw, 0.003" runout, so there's at least half of my problem

    I'm proceeding to remove the thrust bearing retainer and check those to see if they are borked. I'm hoping I can just replace the thrust bearings and fix the problem.

    I'm worried that some dog-face bent the end of the ballscrew when they replaced the lovejoy coupler, that'll be fun to fix!

  15. #53
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    Ok, so I pulled the X ballscrew and set it up on v-blocks to indicate any runout. The drive end of the screw only has about 0.0005" runout, the middle of the screw is in the same boat, so the screw seems to be in okay shape with that regard.

    I pulled the thrust bearings and the grease looked pretty gross. The lovejoy coupler indicated on the bench shows 0.0045" runout on the od of the coupler. Now these are sintered material and are not precision turned ODs, but then again the drive lugs are also sintered at the same time. I'm thinking this coupler is crap and I should get a new one.

    My concern is that these couplers are keyed, but the new ones I see are not keyed, so there is no positive drive registration between the screw and the motor, allowing the screw or motor to slip.

    Now, there is nothing to prevent me from running a keyway broach down the bore and giving is a keyway.

    Does anyone have experience with this type of coupler for a ballscrew: MTR-0154A

    Are they secure enough?

    I'm gonna get new thrust bearings and seals and a new (precision) coupler, with the hopes that will silence the noise and eliminate the vibration. Worse comes to worse, I'll just turn up a solid coupler myself, the Shizuoka had that and it worked fine.

    I pulled the front saddle gib and it was in much better shape than the table gibs were. The table gibs didn't have oil retainer groove in them, the saddle gibs have the retainer and distribution grooves, with big holes through the center. Mine measure out at .537, so I'd guess they were .545 or .550 new.

    I think I can get away with those gibs on the saddle for now, but I want to put turcited gibs in because they offer better lubricity and tighter tolerance.

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    Huzzah! I got the X axis back together with new bearings and a new coupler (the old was was loose and genuinely never would be as tight as the new one).

    I'm happy to report that the X-axis works fine now with minimal vibration and is able to full rapid without vibrating the machine.

    I even ran the servo calibration program and got all 3 drives tuned the same so they all have the same control signal for the same speed.

    It took a minute to realize I had to run the test program because 150ipm in a single axis move is actually faster on any single axis than a move on a hypotenuse (which the speed is measured across the hypotenuse and not the individual axes).

    So, the spindle works (though accel and decel are dreadfully slow) and does ~5500rpm in mid-range, I ran it for an hour tonight and it doesn't get hot or noisy. The bearings have a little rattle, but the spindle is a ways away from replacement.

    The Y axis is showing signs that it needs new thrust bearings. I decided that all the vibration is caused by the thrust bearings being knackered, because the Y does the same thing the X did. I'll order some new thrusts for the Y and see how it goes, before I decide to buy a coupler for it.

    Well, the machine is fully functional as-is and could make chips. I think I want to replace the bearings on the Y before I move the machine, because getting to the back of it will be hell after it's moved.

    I'll post a video I took of the machine after it's uploaded. EDIT: FYI, to make it display inline on the page you have to use 'http://www.youtube...' just like it says in the dialog. Youtube gives you https:// URLS by default and the PM forum software doesn't grok those correctly.

    Last edited by Perry Harrington; 11-21-2015 at 03:09 PM.

  17. #55
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    Its hard to say if its the thrust or the ball nut. When they sound like that usually the ballnut could use a fresh set of balls.

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    There is no doubt in my mind that the screws need some attention.

    I don't see any external ball returns on the nuts, how do you load and unload the balls?

    Did Fadal use the small-big-small-big order in the screws? How much size difference between the balls?

    I built a screw for my Shizuoka a long time ago. I bought rolled stock from McMaster and used the original nut, but purchased oversized balls from a ball supplier.

    I still have a bunch of balls leftover, .125, .1255 and .1258 I think, if memory serves correctly.

    When I did the Shizuoka I was able to re-ball it to zero backlash, and I re-did the spindle too. I sold it and the guy that bought it 2 years after I sold it, called me and said "it's got 0.020" backlash in the Z, help!" I told him that it was fine when I sold it and to check for broken hardware.

    Methinks the machine was crashed pretty hard a couple times after I sold it. I *never* crashed it that hard.

    Worst crash(es) I've had were 1) due to my error, rammed tool into chuck jaws and ripped station off turret plate 2) Machine went haywire and did same thing.

    Fortunately Hardinge turret plates aren't that expensive and they replace with 4 bolts, I've got a perfect one sitting on the shelf. I've always fancied brazing the broken stations back on as an experiment.

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    Perry I don't know but I believe they used a simple set screw or insert. To the best of my knowledge they used the same size balls and that being an inch screw might have the same dimensions of a later inch ballscrew like the NSK ones. I am not a ballscrew expert I don't want to pretend but it seems to me that one would have to play the ball size game a few times to get some proper preload.

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    Well, another couple of hours went somewhere...

    I decided to do a quick test to see just how bad the backlash is on this machine, I was expecting dreadful.

    I know the Z has backlash, since when I pulled the motor I could rotate the screw back and forth, I didn't measure it today.

    I started with X, threw a 0.00005" indicator in the spindle and zeroed the BL comp, jog approached the fixture on the table and zeroed the indicator. When it was done I had maxed out the BL comp at 0.0063 in the middle of the table, that seems to be enough, but the screw needs service.

    The Y axis was a very pleasant surprise. I zeroed the comp, jogged to 0.005 preload on the indicator, then did an incremental move 1" off and back. I was dumbfounded!

    0.0001" backlash on the Y screw in the middle of table travel (which isn't to say it's the same at the ends, but it's a starting point).

    So the Y screw looks like a champ and the Z and X screws will need some work. Now besides the spindle, it seems someone also replaced the Y screw at some point in this machine's life. The grease that was in the X thrusts was black, the new NSK replacements had what looked like Kluber Isoflex 15 (or a generic white lithium base).

    ...

    I bought a bunch of pull studs for holders I already had on hand. I had a mix of Lyndex, Command Tool, and Maritool. Can you guess which ones are closest to the CAT40 spec?

    I bought a handful of pull studs from the same vendor I've gotten everything else for the Fadal.

    The shoulder on the pull studs was ground on a OD grinder, the lot of 15 measured .6405, .6390, and .6410. Guess what the CAT40 spec is for the pull stud shoulder?

    Guess how they got it wrong?

    The spec is .6360.

    When you read a micrometer .6405 is half way between 15 and 16, wanna bet the grinder was reading 5-6 and thinking .635-636?

    I chucked them up in an emergency collet and recut the shoulders on the Hardinge HC, damn fine finish too.

    And the winner is: Maritool, his holders were .639 across 4 I had, the 5th was .650!

    Attached Thumbnails Attached Thumbnails 20151121_180722cs.jpg  

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    Yes that centering shoulder should be dead on. I have had mixed luck with some Maritool items but for the most part they sell very very good products. That shoulder being out so far is rediculous. I can just picture a FEA on a drawbar grabbing more on one side.

    On a side not I am just starting to drink my morning coffee. But I think if I read it right you comped backlash by jogging?

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    No, I used JOG to perform a unidirectional approach of the fixture so I could then perform moves away and towards the fixture.

    I remember the old Bandit docs talking about unidirectional approach as a way of generating toolpaths that wouldn't be subject to backlash error.

    In application, let's say you have a knife profile you want to cut out, you start at the tip of the knife and make an X move toward the handle end, only the Y axis moves back and forth to cut the features.

    UDA does have its flaws in that there is accumulated error if you have backlash compensation enabled, but the value is insufficient.

    If you have an old Bandit control without BL comp, then the table always has the same amount of error because the screw always ends up in the same place with the table lagging the move.

    So, in theory it's actually better to disable BL comp for an axis if you cannot comp it enough, then the error will be constant instead of accumulated.

    I'm going to find out what it costs to get a rebuilt screw, have a screw rebuilt, and what's involved in re-balling the X screw. Since I've done re-balling before it doesn't bother me, I just need to know the details of ball arrangement, count, and ball track access.


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