"Vintage" CNC

No, if you look at Stuart's second post, you will see he referred to Mylar punched tape. The reference to PET is the name polyethylene terephthalate (aka PET), which is the chemical name for what is known as "Mylar", polyester, Terylene, soft drinks bottles etc etc. Your confusion Neil, not mine.

As for the computer form, I probably know PETs better than most. Back in 1980-1981 I was using CBM (Commodore Business machines) PET (Personal Electronic Transactor) computers in experimental real time, closed loop industrial control for a 10 month placement in the Controls Development Group within ICI Petrochemicals Division - the advanced R&D function based in the Wilton headquarters. That was in my year out before I started at (sorry, "went up to" ) Cambridge to read engineering.

BASIC as an interpreted language is inherently unsuited to real time control, not least due to the fact that any error in the code or an unexpected input would cause a syntax error and crash the program. We got around this by isolating the keyboard with a machine code routine that only allowed specified characters to be accepted. This required the EEPROMs to be reconfigured (change the keyboard interrupt address etc), although I can't pretend I did any of that part of the work personally. We developed a structured, consistent method for writing the programs and did rigorous testing of the various modules. At the time is seemed quite a step forward.

This solution was a much more cost-effective solution than the alternatives (PDP11 etc) available at the time by an order of magnitude or more and worked well from a technical point of view. We had the real "top end" stuff like the dual floppy drives, high res graphics cards and IEE488 interfaces - and the 80 column display(!!). We even had one of the top of the range 32k(!!) models.

Not long after this experience, we enjoyed the "home computer" revolution, with the Commodore 64 (essentially the final iteration of the PET evolution), Dragons etc in every bedroom of the world and unstructured, poorly designed(?), hacked code at every turn. That pretty much put me off computers and software until perhaps the early 90s with the exception of my final year project which was a self-tuning 16 channel PID controller based on a CPM machine (The Comart Communicator!!).

Murray

Edited By Muzzer on 18/06/2017 15:27:18

> The reference to PET is the name polyethylene terephthalate (aka PET),

Well I never knew Mylar was a trade name for PET!

>Not long after this experience, we enjoyed the "home compter" revolution, with the Commodore 64 (essentially the final iteration of the PET evolution), Dragons etc in every bedroom of the world and unstructured, poorly designed(?), hacked code at every turn

The Dragon was a strange computer! I had the opportunity to play with one, and an Oric, which was even weirder in some weays.

Fortunately I was exposed mainly to BBC micros which encouraged structured code whether in their BASIC or in assembly language (although they lent themselves to ingenious hacking).

Edited By Neil Wyatt on 18/06/2017 21:17:10

Technically BoPET, where the material is stretched.

You may recall those plastic things that held 6 packs together. If you stretched them, the material would neck down but not fail. Clearly in the process of necking down, you have the same force but now a smaller cross section area, so the stress (force/area) has increased, yet what gives first is the unstretched material remaining. In other words, the yield stress has increased significantly.

The same process is used in the production of the fizzy drinks bottles. They start out as little test tube shaped mini bottles, then they are blown out with compressed air to full size (inside a mould!), after which point they are immensely strong.

Mylar film is similarly stretched out and becomes very tough and much stronger than the basic moulded material. My word "strong" isn't very technical but it's been a long day...

Murray

Edited By Muzzer on 18/06/2017 21:21:07

I have just read the post that started this conversation with a great deal of nostalgia. I too was an apprentice at BAe Weybridge, where I had my first experience of cnc.

I remember the cnc mill, which I am sure was a Bridgeport series 1 sat in the middle of the training school workshop floor, at the edge of the milling section. Also pet computer in the little classroom at the back of the shool.with its green screen . On the side of the terminal was the box that we produced the punched tape on.

I don't recollect the instructors name for the cnc mill but the milling section was run by mr Kell who was a very thin fellow with a bad temper, he liked to show off his expertise at milling. I remember him using one of the big cinncinati mills to demonstrate how good the new strasmill cutters were, cutting a 1" dia slot thro 1 1/2 inches of dural in one pass. I got on the bad side of him when I mistakenly mixed neat tapping oil with water as suds for the machines instead of soluble oil as he instructed , all 40 gallons of it !! created a really nice soup with red oil blobs floating in it. my name was mud.

I also remember the cnc was always covered in blue foam dust , as we had to prove the programs by cutting soft foam first, lest we G00 through the vice or something. happy days.

there were ten of us technician apprentices , we started in sept 81 , an we did the cnc machining in spring 82.

paul

Sorry Neil but I have to disagree with the comments re Dragon and BBC. While the BBC was a superb machine and I taught using them from their introduction until they were succeeded by PCs in the late 1980s (including in the end CAM using GCode), they were the non standard computers.

The BASIC interpreter used on the Dragon was a stock Microsoft one as used by MsDOS, IBM, TI,  Dragon, Tandy (Radio Shack), RM, and many more. The version used on the BBC was only ever used on Acorn machines and while the strange integration of direct hardware instruction via the *FX and VDU codes was very useful and convenient compared to PEEKs and POKEs or calling a hardware interrupt, it was a dead end as far as computing is concerned.

Hardware was not very standard either - RS423 rather than RS232 serial port, 1MHz bus, non standard Parallel port implementation and the paging of application ROMS was all different to virtually every other computer.

A great machine (I still have a BBC Master here, for old times sake) but definitely non standard.

Nick

Edited By Nick Clarke 3 on 10/02/2019 08:51:54

Do you remember the appalling graphics on the Dragon? That was because of a stupid mistake in the design of the graphics controller, which assumed that European 625 line PAL receivers wouldn't object if they were fed a video signal that was based on NTSC 525-line standards which had a slightly shorter line duration - 63.5 as opposed to 64 microseconds. Since every self respecting PAL receiver incorporated a 64 microsecond delay line to average out colour errors between successive lines, not surprisingly they did funny things. All to save a few pence on the price of a crystal.

Paul,

You would have been in the intake a year after me. If I remember correctly the instructor looking after CNC was Mr Speakman. A rather large sweaty man, who was learning at the same speed as us. No blue foam in sight, that must have been a later addition. You are right about Mr Kell running the milling section, a very unpleasant person. I got a dressing down for running a face mill in reverse. Being a complete newbie, I hadn't been told to check the direction, just assumed that all cut in the same direction. Us technican apprentices were aked if we had any feedback as to why not one of the craft apprentice intake that year wanted to take up milling. I am sure it was Mr Kell who put them off.

As with the exception of the serial port which replaced the parallel port the Dragon was a clone of the Radio Shack (Tandy) Color Computer it inherited the graphics circuitry from that US model as well. It was not a case of building a better circuit but designing a different computer - hence the compromise.

In practice the graphics were not that bad in comparison to many other computers that used 4 colour low res graphics (CGA) or text only displays at the time. However I never intended to say that the Dragon was a better (or even good) computer - but rather that the BBC was the 'odd ball' A user who was skilled in modern style structured BASIC programming on a BBC would be unlikely to be able to transfer those skills to BASIC on many other computers.

Edited By Nick Clarke 3 on 10/02/2019 09:55:07

I recently dug out my apprentice training log book. Amazing what detail is in there. Pertinent to this thread was was example CNC code sheet that confirms that it was a Bridgeport that we were using back in 1981.

Edited By Stuart Bridger on 10/02/2019 09:57:20

stuart

I have found in the workshop, my old test piece machined on the Bridgeport at Weybridge. I remember the part at the bottom where the straight profile hits the curve at a tangent was a bugger to programme. It is so easy now with toolpathing software.

I have seen a picture in your albums , of the saw and file exercise , the notorious spanner. tricky to get right. The chap who instructed marking out and bench work was realy helpful ,but I cant recollect his name.

paul

Strange how small things can steer your entire life. Aged 11 at Grammar School half the new intake were ordered into the Metalwork class, while the rest went next door to do Woodwork. The Metalwork teacher turned out to be a very bad tempered old man. Everyone was afraid of him - his rages were unpredicatble.

Next year we were allowed to choose and I and several others switched to Woodwork. It was a mistake. Turned out that the Metalwork teacher retired that year and his replacement was an excellent teacher. Meanwhile, in Woodwork, I found the teacher was almost permanently absent due to a tragic series of family bereavements and learned nothing apart from understanding I preferred working in metal to wood!

At the angry old man's farewell assembly, we were told that he'd been permanently in pain since his fighter crashed during WW1. He was a hero! So my late entry into Model Engineering after retiring was due to the Kaiser invading France via Belgium in 1914 in order to defeat the French Army before turning on his real target, the slow moving Russians, who were supporting fellow Slavs seeking independence from Germany's ally, the Austro-Hungarian empire. Actually, the real reason for Germany starting a war was internal: the ruling class wished to undermine the Socialists who were challenging their authority. As Belgium's independence was guaranteed by Britain in a Treaty signed in 1839, it triggered a chain of events such that I now own a Chinese lathe ...

Dave

It was more than a clone - I worked in the same company as the designers! It used the same graphics chip but surrounded it with extra logic to "convert it" to 625 line. For some daft reason they decided to use the same graphics clock crystal as used in the 525 line version which meant that the line time was too short by 0.5 microseconds. The PAL delay line then inserted a ghost version of the previous line 0.5 microsec too late, which gave a strange "echo" on every vertical line displayed on the screen. The designer was unaware until it was pointed out to him that every modern PAL TV set incorporated the delay line. The machine's display quality was roundly condemned in the magazine reviews and the manufacturers were extremely upset by the design error. I think in the end they fitted a SCART port to a later version so a direct video feed could be used, but it was too late by then.

S O D Dave - your what-might-be-called "life's consequences" makes interesting reading - as, probably, would many of us. Coincidence, opportunity and decisions based thereon dictate our passage through life much more strongly than any conscious 'self-design'

rgds

Bill

Ask anyone and they'll have an interesting back story, though many need a lot of prodding before they'll tell it. Most of us seem to be steered through life more by a random mix of luck, accident and coincidence than talent and force of personality!

Things like doing an apprenticeship or serving in the military seem to be a rich source of life changing experiences, but I doubt anyone got to be a Model Engineer in a straight line. I'd bet money that absolutely everyone who reads this post has a worthwhile tale to tell. Please do!

Dave

Edited By SillyOldDuffer on 10/02/2019 13:24:58

I also did a lot of CNC programming and paper tape punching in the early 1980's for several firms and before that, at school. We were using Computervision CAD at the time. I remember we had a cart to carry 20 or 30 rolls of punched tape for even a simple mould machining job from CAD room to toolroom. Hours to read it all in to the buffer computer next to the machine (64 kB max RAM in it, as I recall). It was an improvement to the no-RAM realtime General Electric optical reader on the Hillyer gantry mill we had in the school shop though!

It did not take long for the toolroom guys to get tired of us hanging around loading programs, and management decided DNC was the way to go. They installed a fibre optic link system with multiplexers at each end, and more internal RAM. This worked well for a while, but the multiplexers were not robust and would "blow" channels periodically. I recall there were 12 channels per MUX, when they were all "blown" we'd swap a new MUX in. That went on for a few years.

G00 X2 Y2 Z-10 was not a good way to start the day.

I think you chaps with CNC were spoiled, typing it all in with a teletype and running directly from the tape was doing it the hard way.

Mike

I was seconded to a team working on implementing DNC at BAe Weybridge. My resposbility was the comms link from the design office computer room to the shop floor. Thie team was established just a few months before the site closure was announced. The project was canned.

stuart

do you remember the SOLAR/CLASS system with its green screen vdu s. the main menu screen had burnt into the glass of the screens, you could read the menu even if the power was off!!.

seems so antiquated now ,when I think back

paul

Paul, I certainly remember SOLAR/CLASS, the production control system. Certainly the least interesting of all the departments in the porduction phase of the apprenticeship. I have a copy of the manual in my log book. As for green screen VDU's. Single applications were definitely their enemy. When i moved into Electronic maintenance and on inot the hardware side of the IT industry, many CRTs were replaced for screen burn in. But only when they were their last legs.

Classic!