Vertical Mill - $300 Craigslist

A 30 cent IC VS how many hundred dollars for a conversion? How much time spent rewiring it? Lost income from that time spent doing the conversion?

Who gives a shit about You tube? I would be doing other work in the shop while it was running. That is why the computer in the shop isn't online. It stores schematics and parts inventory.

Yawn. I don't need that.

I'd rather be writing code for embedded applications, and have no desire to go into the junk business. A computer of that age is very cheap to fix, if it is repairable, and I would likely have the ICs or other parts in stock so I would save all the time and money of converting it. Also, there are floppy interface to USB stick units to allow you to store 100 different programs on a machine, and you don't need another computer in the shop to run the machine.

Note that a certain age of electronics has problems with electrolytic capacitors. The formula for the electrolyte was pirated, but what they stole was a wrong formula, and many capacitors made with that formula continue to fail. Most seem to be used in computers and similar devices -- which would certainly impact CNC controllers made during that period.

Considering how much progress there has been in CNC controls, and "linuxCNC" (the new name for "EMC2", which turns to to be too similar to some computer security company) has many advantages over the old ones.

For example, the old controller for the Bridgeport mills (BOSS-3 through BOSS-6 at least) used a DEC LSI-11 CPU card, which is limited to

64K of address space. This includes the firmware which implements the CNC itself, and the RAM into which G-code programs are loaded.

And memory in older controllers used to be specified in "feet" (feet of punched paper tape, with each byte taking 1/10", so a foot of tape is equivalent to only 120 bytes of program. If the whole address space of the LSI-11 were available for the program, that would only be

546.13 feet of memory. And at least half of that was really taken up by the firmware. Lots of PROMs.

The memory in the BOSS-3 through BOSS-6 machines is quite limited, so they had to be set up (for larger programs) to read in as much as the memory could hold, run that program, then read the next chuck in and continue. This is a significant limitation if you were trying to call functions (which had to be in memory the full time) or were trying to run a loop (which might be longer than the memory present in the machine). Disk drives were not even a thought. The choices for input were:

1) Punched paper tape (produced on another computer in the main office of the plant). 2) Hand entered on a teletype or computer terminal (or now, downloaded from the serial port of a PC, which might be the very machine which generated the G-code. 2a) The teletype would have a punched tape reader, and punch available, so that was sort of a third way to read things in. and to save a program once you had it doing what you want.

Newer machines had miniature cassette tape drives, including the Anilam Crusader II, and my little Emco-Maier Compact-5/CNC. (The latter has the 6502 CPU which is at least as limited as the LSI-11, and probably more so given the less efficient instruction set, so more firmware was needed to do the same amount of control.) (I do plan to build a linuxCNC controller for the spare Compact-CNC, and replace the steppers with servos eventually.)

Enjoy, DoN.

It depends on the old controller. If I have a mill, I want it to *use* it, not to have it serve as a collector's item. And given the limitations in the old BOSS-3 through BOSS-6 controllers, the linuxCNC (was EMC2) does so much more, and does it so much more efficiently, that the upgrade is hard to resist.

However, I spent quite a bit of time making a gear to repair a Tektronix 7000 series oscilloscope plugin, just to make it work again. Check out:

I think that I posted this here before, and I think that you saw it before too. FWIW, I've found a place which has replacements for all the gears in that thing *except* the one which I made. :-)

Enjoy, DoN.

It's a lot easier to resist when you are in poor health, and have very limited funds.

Yes, you did a good job. You should offer those gears on Ebay. :)

That's a strange statement.

i

Before EMC (the original one) or Mach, I bought an Allen-Bradley

7320 control from a guy in California and got it running, with great difficulty. It didn't come with the executive tape or servo amps, which were supposed to be part of the package. I had to make my own servo amps (this was before eBay, too), get an executive tape from a guy who repaired these, and then patch the executive for the encoder resolution I had. I built my own BTR also, using an old laptop for storage of G-code.

I COULD repair it, and had to do so on a regular basis. This was a 1978-vintage control, and I was trying to use it in 1996-1998. So, it was roughly 20 years old at the time. EMC came along just as I was getting seriously frustrated by unreliability of the thing. There were some problems with the original EMC, and so I went back and forth a couple of times (I had rigged some connectors so I could switch between the two pretty quickly.) Well, after the 3rd swap, EMC was good enough that I never powered the A-B control on again.

Besides the reliability issue, EMC stored G-code on a computer with a hard drive, you could edit the G-code on the EMC PC, the PC was on the local network, You could run primitive diagnostics on the machine, and the servo response was a lot "snappier". I'm probably missing a bunch of other features.

A PDP-11 based control is probably a few years newer, but many of those controls had a VERY limited user interface. Not too bad for selecting a stock program and running it, but pretty primitive for editing programs at the machine, for instance.

Oh, and finally, if you look at what the vultures charge for a board out of a 30 year old control, you could replace the entire electronics of a modern Pico Systems or Mesa interface from computer through the servo amps for what one replacement board would cost.

Jon

Jon, I have repaired electronics for over 45 years. That's how I made my living, and a lot of that work was to repair digital circuits. My computer work has ranged from the KIM and the 4004 processor, to embedded controllers aboard the space station. I have a copy of 'Linux CNC' and most of the parts on hand to build a mini mill but a machine that size would get very little use in my shop. I should still have a full set of the manuals from Heathkit for their LSI-11 based computer which basically kitted the DEC system, under license. I have repaired a lot of equipment without manuals. I have a dozen National Semiconductor memory boards for that series that were pulled from working DEC systems. I could probably design and build a replacement for any bad board for less than the vultures want. Or just buy the non working stuff for salvage from someone else guts when doing a conversion.

Most of the parts I would be making would be to repair existing tools, or to prototype a design project. I am 100% disabled and no longer have access to the machine shop where I worked, so I am trying to piece together what I want, for whatever time I have left. It's the only way I can work, given my health and my budget.

What's strange is that you feel that everyone has to do things your way. I see things as repairable items, you see things as scrap value.

I agree. It is a statement from someone who has not spent any time with modern CNC equipment and CAD/CAM systems. My little hobby projects routinely have G-code over 1,200 lines, some vastly more.

You're right, and I don't want to learn yet another programing language. Most days my close vison is nearly useless, so that I can't spend hours staring at a monitor to write software, or design complex mechanical parts.

Since the machine is over 1000 miles away, it's all rather pointless for so many of you to keep harping on how I should do things.

Sorry to hear that :(

You're the one harping on us how we should revive the antique control and live with it's tremendous limitations rather than upgrade it to a modern control.

At any rate, in April or so I will be doing another cross country trip up to the frozen northeast, and before I go I will search around to see if there is a similarly good deal along the way I can pickup to retrofit for my shop.

Exactly. Both Pete and I have machines based on modern PC controls, so we speak out of actual knowledge.

Pete, you will be VERY happy if you come across a Bridgeport Interact sized machine. But you likely will need to use a servo based control system.

I can look for one for you and let you know if I come across anything.

i

Ignoramus15658 fired this volley in news:3NWdnViZ1NtaidzSnZ2dnUVZ snipped-for-privacy@giganews.com:

Ig, when you upgraded your control, did you re-use the servo drivers in the Interact, or go to commercial 90V drivers? And power supplies?

LLoyd

Lloyd, I sold the original Bosch drives and went to $30 AMC 30A8 80 volt drives. I lost half the max speed, which is something that I could not care less about, since high speed is only used for jogging. I ended up having a 60 IPM jog speed, which is all I need.

Part of the reason was that Bosch drives needed three phase, part was that I burned one by accident, and part was that I wanted to have simple replaceable drives.

It was a huge learning experience and very time consuming, but I ended up with something that I like and I learned a lot.

i

Ignoramus15658 fired this volley in news:ENqdnSDA3IXqhdzSnZ2dnUVZ snipped-for-privacy@giganews.com:

Good reasons! My drives are DC, and still eminently repairable with off- the-shelf discrete parts, but hardly "replaceable", as the complete drivers are pretty scarce. I'll give some thought to that issue.

Lloyd

One of those AMC drives went bad on me, replacement was trivial.

i

I'm not suggesting that method is for someone else. I simply stated that I could make it work, and with what little use it would get, It wouldn't make financial sense to tie up that much cash.

Which frozen Northeast? It's 45F outside.

jsw

Yeah, I was going to say something about that. I'm going fishing tomorrow, in fact.

Saturday morning I returned from frozen Chicago. It was 49 deg. at O'Hare on Friday.