CNC Mill - Page 1
Forum section: electronics / general

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 24, 2014, 08:02:52 am
content: A couple mounts ago I purchase a CNC mill. A 1985 Bridgeport Series 2 R2E4 with a Boss 9 controller. It is weights about 3000lb's (1400Kg), 2 HP spindle, and 600W servos I think. The controller is died, not sure why. Does not matter however as I had intended to replace it with a PC based controller. All and all a nice machine for under $2000. And in eevblog style I had to take it apart before I could turn if on. Truth be told I don't really have 3 phase power at the time of getting it.I thought that some other people would like to see the 1980's design and construction of the electronics.Here is a link to the manual, has all the schematics in it and descriptions of how it works.http://igor.chudov.com/manuals/Bridgeport/R2E4-Boss-Manual-Lloyd.pdfThis is the view of the operators right side cabinet. This cabinet contains all the brains of the machine as well as the servo drives on the sheet metal carriers in the middle.Here is the main processor board of the machine, this is a 2 CPU machine, one for user interface and higher level functions, second is for lower level control of the motion of the machine.This is the second half of the main brain of the machine. This mostly stuff like logic and interface type stuff.This is the second brain of the machine. This is what handles carrying out all the motions of the machine. This takes input form the encoders and limit switches and outputs analog signal for each of the servo drives, I have 3 but there was a option for a 4th.Both of the processors used I believe are Motorola 68000's. I am not sure about any other specs on the processors. I do love the use of 7400 logic every where in this machine.All the boards are what seem to me to be 4oz Cu boards. Kind of heavy for just doing 5V logic.If any one is interested in seeing more or better pictures of the electronics let me know and I will do so.

author: mc
author_rank: Regular Contributor
timestamp: November 24, 2014, 11:38:18 pm
content: 74 series logic was the only viable option back then!Now, a single FPGA can do everything all those 74 series chips and processor done, in a fraction of the space, and with lots of processing power left. I like seeing this old tech, and I often wonder how long it took to develop and how, as I'm guessing simulators were not that great back in the 80s.What controller/software are you planning on retrofitting?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 25, 2014, 05:12:33 am
content: Wow, didn't one of these kill a Terminator back in '84?

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 25, 2014, 07:08:00 am
content: Quote74 logic is kind of personal for me, My first EE class about 4 years ago was digital design. It was nothing but 74 logic. Thought I would never directly see much of anything with large scale use of it. Then VHDL happened. I am sure it could be done in a very small FPGA or even a CPLD. If you do not count the processors. Also kind of cool to thing there where products in the 80's with dual cores.QuoteI am using Linux CNC. I already have a couple of mesa cards. I am also making some custom little boards to make the conversion easier.The question becomes is there anything cool that I can do with these old boards?QuoteHaha, it was send back one year to kill the Terminator that send back in time to kill John Conner.I love it!

author: rob77
author_rank: Super Contributor
timestamp: November 25, 2014, 07:33:54 am
content: Quote from: thewyliestcoyote on November 25, 2014, 07:08:00 ami would hang them on a wall like paintingsit's a piece of art !

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 25, 2014, 07:37:20 am
content: QuoteI agree, I have seen them for sale on ebay for kind of crazy amounts. I dont want to do that. Maybe frame them.I would be interested to see whats on the ROM's. Does anyone have any ideas on how to get that information off easily?

author: Kjelt
author_rank: Super Contributor
timestamp: November 25, 2014, 08:04:27 am
content: Beautifull and instead of modern FPGA designs fully hobbieist servicable and repairable(ep)Roms you can read out with an eprom programmer, you can get cheap ones for $50 on ebay.But unless you are a 68000 assembly veteran it probably is of little use, you might see some plaintext strings in the code like dates, names, functions menu items, but thats probably it.

author: sca
author_rank: Regular Contributor
timestamp: November 25, 2014, 08:43:06 am
content: Quote from: thewyliestcoyote on November 25, 2014, 07:37:20 amNah, flog 'em and buy tooling. You can never have enough tooling...sca

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 26, 2014, 03:02:18 am
content: QuoteTrue that!

author: KG7AMV
author_rank: Frequent Contributor
timestamp: November 26, 2014, 06:56:32 am
content: 3 phase use a VFD, Suggest you dump the bridge port electronics, Go with a PMDX-126, Ethernet Smoothstepper, Some good Drivers and Mach 3! Get it making chips!

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 26, 2014, 07:52:31 am
content: QuoteI am told the VFD will be in the mail on Monday or Tuesday. I am not using about 60% of the electronics. The servo drives are the big exception to this. I plan on using the in the time being because they are easily serviceable by me and already have them. Cost is a very big factor in this conversion. I am working on a update to the servo drives that are on the machine that is a big improvement over them. But this is not my plan to use right away. I am already committed to Linux CNC for this. There are a couple of reason but it mostly comes down to a am a "Linux guy" for the most part. I also like the flexibility of the LinuxCNC. The faster this machine gets running, the faster I don't have to put up with why did you buy that.

author: KG7AMV
author_rank: Frequent Contributor
timestamp: November 26, 2014, 07:55:14 am
content: Keep the servos just get a servo drivers will work with the PMDX-126 and ESS...

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 26, 2014, 08:03:53 am
content: The drives I have work fine. in fact is only 9 wires to connect then to the controller I have now. I am laying out some boards to make the process cleaner. So that is kind of a hold up.

author: mc
author_rank: Regular Contributor
timestamp: November 26, 2014, 11:44:20 pm
content: I love the entertainment provided by people who think that everybody should use what they've used, despite the fact the OP has already stated what they're going to use and that they already have the required interface cards.LinuxCNC does the job. I personally won't use it, mainly due to support and documentation being 'challenging' to find. I did consider it a couple years ago, however I struggled to find the required documentation for the MESA cards I would of needed, and most questions regarding them were unanswered.In the end, I personally opted for a Dynomotion KFlop+Kanalog combo, which combined with Mach3 (KMotionCNC support for lathes was very minimal at the time) ticked all the boxes. It allowed me to do everything I needed (analog servos, 24V logic), and I now have a digitizing machine running a KFlop+KStep (KMotionCNC doesn't support writing data to files), with another KFlop+Kanalog lying waiting to go into my big mill.And there's nothing wrong with using the original drives. I'm guessing they'll be +/-10V input, with the controller closing the loop. Biggest issue on older servos, is they mostly used tachs/resolvers, which can cause issues interfacing to new controllers, as most modern controllers only accept a quadrature input i.e. rotary encoder.Are there Mesa cards that can handle resolvers?

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 27, 2014, 01:28:08 am
content: Yeah LinuxCNC is not the easiest to get setup and running. It is vary flexible and configurable. As a user experience I don't think it is to bad and if you don't like it, FIX IT. lolThey are +/-10V input and the PID is done in the host PC. The encoders are dual encoder/tach. The mesa card just takes the index and the encoder outputs. From everything that I have read has indicated has said this will not be a problem.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 27, 2014, 07:39:05 am
content: I helped out replacing the control on a Fadal mill with a KFLOP & KAnalog. Part of the conversion was remove the old encoders & tachometers and go off the newly fitted encoders directly. If I remember right, the drives themselves got analog feedback from the tachometers. That feedback had to be disabled. That is to say, the control commanded a speed via a +10-(-10)v signal to the drive, and the drive drove the motors based on feedback from the tachometer. The more signal from the tach, the less it pushed the motor. The less signal from the tach, the harder it pushed.Disabling the feedback took some tracing out on the drives to figure out the circuit. We used a light bulb for a dummy load while figuring it out, which took a lot of stress out of the situation and gave nice feedback. In the end the conversion was quite successful: the machine was quite a bit faster and more accurate. Back then there was a bit of an issue with the USB buffer on the KFlop that made feed holds not asynchronous to the commands that were being fed to the control. That is a real bad thing as you can imagine you want to feed hold you want to have it happen right away. But last time I heard they had fixed this. (It may have only been for external devices connected via the KAnalog, but you really want a physical switch and not be messing around with a mouse when you want a feed hold.)

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 27, 2014, 09:16:33 pm
content: I really like the fadal machines, I would have one if it wasn't for them being so big and there cost.Hmm, That is interesting about the tach feedback was a problem. When I get to that point I will be sure and let you know what I end up having to do. I am trying to minimize the changes I have to make to the machine to save time and money.USB always amazes me for CNC controllers. I have done some stuff for work and personal projects trying to do real time software defined radio for 802.11N and AC wifi and some radar stuff. These have timing requirements on the order of 250uS to 5mS. This was basically impossible for our applications. There is good data rate but there is so much jitter and latency on the bus. I am guessing that all the lower level functions on done on the USB device and the PC only does the higher level decision making like sending the next G-Code to the controller. This is a great way of doing it, but it is not what I want to do. All the same applies to Ethernet based controllers.As for the real button, I am wiring the front panel directly into the PC using ether parallel port or an additional mesa card. So I should be able to run the machine from what was the original controls. I may mount a LCD in where the CRT is currently. I also have a hardwired remote pendant with Estop, MPG, and some other controls.

author: mc
author_rank: Regular Contributor
timestamp: November 27, 2014, 11:59:37 pm
content: The thing with LinuxCNC, is I don't want to fix it, I want to use it, which I think is it's biggest failing.I'll admit I'm a windows guy, and it makes life in CNC alot easier. My machines make me money, so my priorities are a bit different from a typical hobbyist, as I want to fit something, and have it running with minimal hassle, rather than spend hours coding something that already exists in other software.Have you found any manuals for your servo drives?If you can find one, it should make your life a lot easier with configuring the drives for a different controller.For USB/Ethernet, the PC is usually just sending trajectory data with he motion controller handling all the critical timing stuff.It does mean there is a delay from changing something on the PC, to the motion controller carrying it out, but for most things it's not noticeable, although it does vary depending on motion controller and software. Some combinations can have very noticeable lag.However when done correctly, it works just aswell as any other motion controller, and quite a lot of the high end controllers now use ethernet. USB is generally not used in industrial enviroments as it can be succeptable to noise problems, and is the only negative thing about the KFlop I can think of, but in several years I've only seen one person have a problem with it.A major advantage is that if the PC does die, which is usually the most unreliable electronic part, you can simply plug in a different computer, load the required software/config for that machine, and away you go again.Personally, I have a computer dedicated to each machine, with configs backed up to a memory stick, all the software required installed on my laptop, so if a computer does die, I can connect my laptop, load the latest backup, and be running again within a few minutes.But anyway, keep the progress posts going. It's always nice to see how other people carry out retrofits, and how they solve any issues they have along the way.

author: thewyliestcoyote
author_rank: Regular Contributor
timestamp: November 28, 2014, 04:47:03 am
content: QuoteThey are in the machine manual. They include all the schematics, all the hookup, and troubleshooting information. Chapter 6 and 7 cover just about everything needed.http://igor.chudov.com/manuals/Bridgeport/R2E4-Boss-Manual-Lloyd.pdfI have plans to make backup images of the controller and post all the configuration files. So same kind of thing. I cant think of a much worse mitigatable problem then having the controller crap out.