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Member postings for DrDave

Here is a list of all the postings DrDave has made in our forums. Click on a thread name to jump to the thread.

Thread: Emco F1 Mill Upgrade
19/06/2018 21:11:17

Some more progress to report. All three axes work under their own steam and I have run some of Centroid’s sample g-code files. All seems OK: I just need to work up the confidence to start cutting metal now. The only significant mod left is to install the home switches. These are a nice-to-have, rather than a must-have, so it is my own inertia stopping me!

This is the new controller, a modified Apple mac G5 with the guts stripped out. The 5, 12 & 24 v PSUs are in the base, the old Apple PSU used to be, with a 36 v PSU on top. From left to right a re the spindle driver (KBIC), drivers for axes X, Y and Z (with room to add A if required). The Acorn controller card is under the top plate. A much neater job than the old PC case would ever have been.

7f927d22-5fc9-4dc2-a18d-3f0c644c005b.jpeg

The cables to the mill come out the top of the case:

f6e5bef9-67b7-49fd-a1c2-ba262647edea.jpeg

And it fits in the same space that the old Dell PC sat:

13ff9ae6-3660-44d2-b887-0874bd4bdc07.jpeg

The blue wire is the Ethernet cable to the Windows 10 PC that controls it via Centroid’s software. I have moved the ammeter for the spindle and the e-stop from the old controller to new homes on top of the mill:

22bc9fdb-f111-4d0e-8ff3-8a52b06fe3d1.jpeg

Thread: Lost and Found
19/06/2018 11:55:10

I knew that I had a nearly full bag of cable tie bases but, after a few days looking, I had given up on finding them. Since I was passing Toolstation this morning (other shops are available), I dropped in to get a new bag. When I got home, I found the old bag on the table next to the cupboard that my jacket lives in... sad

‘Tis true: if you want to find something, buy a new one.

Thread: PID Controller - MEW 269 - wrong connector
18/06/2018 22:39:15

There is nothing magic about the cold junction or where it is physically located: it is at the transition from “thermocouple material” to copper. So long as you measure the temperature of the cold junction, all is well. The cold junction is inside something like a handheld instrument so that cold junction temperature measurement can be integrated in the instrument. I suspect for Model Engineering projects, changing to copper in a Molex connector and feeding into the instrumentation via XLR plug will give acceptable results, even using ambient temperature as the cold junction temperature. The Wikipedia entry on thermocouples (or that referenced byMichael Gillian on p1) gives a good overview.

Ducks and awaits incoming criticism!

18/06/2018 19:07:25
Posted by Michael Gilligan on 18/06/2018 18:55:31:

Good to have your input, Dr Dave ... But I like to think I made that reasonably clear in my reply to XD 351, on p1.

MichaelG.

True, but I didn’t recall anyone pointing out the importance of measuring the cold junction temperature. Too many post to remember the details?

18/06/2018 18:48:38

It has been too many decades since I last used a thermocouple for me to remember how we wired them up. So I had to go back to basics (Wikipedia) to find out. What seems to have been missed in much of the above is that a thermocouple gives the temperature difference between its hot and cold junctions, not the hot temperature. The cold junction is typically within the instrumentation: the instrument measures the cold junction temperature by a different means (cold junction compensation) and uses this, with the thermocouple voltage, to calculate temperature. Hence the need to use “thermocouple material” all the way to the cold junction. After this, copper is fine.

Room for one more angel on this thermocouple?

Thread: Aircraft General Discussion
15/06/2018 15:24:31
Posted by Neil Wyatt on 15/06/2018 15:22:45:

House shook yesterday evening, peeped out and saw a Chinook heading south east at about 100 feet.

It is a little-known fact that helicopters do not fly: they make so much noise that the earth rejects them.

Thread: Service in 2018
15/06/2018 15:10:23

Following the collapse of Maplins, I have taken to using RS Components instead. I have placed internet orders in the evening & had Parcelforce at the front door by half ten the next day each time. Last night, I placed an order at 8:45 pm and received my parcel at 10:15 this morning. Remarkable. And their items are all “post free”.

Not so nice for the people shipping the order from RS at midnight, though.

Thread: Aircraft General Discussion
14/06/2018 16:42:13

I have just heard that John Farley (former Harrier Chief Test Pilot) died last night. He leaves a large hole in the aviation world. I only met him a couple of times, when I was working over in Farnborough, but I remember him as a real gentleman. Full of anecdotes and a complete disrespect of pomposity.

RIP John.

Thread: What did you do Today 2018
11/06/2018 11:19:57
Posted by Sam Longley 1 on 10/06/2018 19:33:33

One would assume that it is quite a while since our warships had sails instead of engines

Some years ago, whilst working in Germany, I I had to travel to Toulon to catch a ride on the Charles de Gaulles aircraft carrier. Talking to a (German) colleague, I said that I had to leave to get the flight because we were due to sail the following day. He gave me a strange look, then said “Sail? But she is nuclear powered!” We forget where some of our language originates from.

Thread: Emco F1 Mill Upgrade
01/06/2018 13:08:59

Major milestone reached: I can control spindle speed from the PC now. Firstly, I tried using an old Dell computer case to put all of the control gear in. It might have worked, but was very much a pig’s ear. But I finally managed to get an old Apple G5 tower computer last Saturday. It is far larger and, more importantly for me, has lots of flat areas to mount bits on.

I had one scare whilst trying to get a pair of the old cooling fans to work. There are 4 wires per fan: ground, 12v, temperature and control. I had no idea which wire was which (they are all black) so I started to try every combination to find one that works. Part way through this process, the fan glowed orange and emitted the magic smoke. “Oh dear, that’s fried it”, I said. It must have been the temperature sensor that I fried with 12v because I finally found a combination the works.

Now to get the steppers installed, wired up & working. Then some microswitches to define “home”, a major omission on the original machine.

16/05/2018 21:23:19

First stepper installed. Originally, I wanted motors with a single-ended shaft but I have ended up with double-ended shafts. With hindsight, this has an advantage that I had not expected. After fitting, I turned the motor with a spanner (there is a flat machined on the shaft) the ensure that the bed moves, which it did. However, it felt a bit stiffer than I expected, so I took the motor out again. Turning the motor was a lot easier. Motor re-installed and it is now a lot easier to turn. I suspect that the drive belt was not correctly fitted to the pulley for the first installation. Without the ability to manually check the installation, I would have continued and probably damaged the belt.

I am now trying to squeeze all of the electrical gubbins into an old PC case, so fitting the other two motors will have to wait.

Thread: Congreave Clock
16/05/2018 11:18:01

Our local (Bedford) auction house had a Congreave clock in a recent auction. I have fancied one of these ever since I was a lad, but I suspected that it might be worth more than my pension could stretch to. So I made a concious decision to miss the auction, which was just as well because the hammer price was £1,600 (or about £1,500 more than I can afford).

Thread: Emco F1 Mill Upgrade
16/05/2018 10:59:05

I’ve stripped out the old steppers and the new ones are a very similar size.

Motor-comparison.jpeg

The drive shaft is shorter (21.2 vs. 25.4 mm) so I cannot re-use the roll pins to retain the drive pulleys. A drop of Loctite 641 and fingers crossed: I don’t think that they will come off again if they are not right. To get the location right, I set up the motors on the surface plate and touched the height gauge on their mounting face. The height gauge was lifted 25.4 mm and used as a reference for locating the pulley. The pulley fit is slightly loose, so I used a screwdriver to hold the pulley against the gauge until the Loctite had cured. The first motor was tried on the mill & appears to fit, so the rest have been done, too.

Pulley-height-setting.jpeg

14/05/2018 18:24:09

Thanks for the feedback on Linux. It is a couple of year since I tried to investigate LinuxCNC, so I cannot remember where I failed. I think that it was at the “mount the drive” stage. I will drag out my old Linux laptop & try again, just to have a play. But I must get the mill working first!

14/05/2018 12:00:55

The Danish supplier is at **LINK**.

The steppers are NEMA 23 with ¼” shafts, as you say. The shaft is slightly shorter than the Emco ones. The pulley on the stepper has a roll pin at the outer end: this will be in fresh air on the new steppers, so I am thinking of Loctite (or similar) to hold them together. Otherwise, the attachment bolts should be in the same place as the originals and the change should be simple. Or that is the theory.

Dave

14/05/2018 11:24:28

The new power supply arrived this morning. All wired up and all three steppers wiring away happily on the bench. More importantly, Mrs Dave was out, so another parcel was smuggled into the workshop without the Domestic Authority knowing. Result!

Next, the hard part of physically fitting the steppers to the mill.

14/05/2018 09:55:08

After the recent demise of the controller for my cnc mill, I decided that the time had come for an upgrade.  I hope to explain here the steps (forward and backward) that I take to get my machine working again.

Last week, the controller jammed in the fast jog mode, making it impractical to use.  I had been thinking of upgrading for some time, but this has twisted my arm.  In addition to a new controller and software, the stepper motors will be changed.  The original motors are of a 5-phase design and are not compatible with moden drivers, so they have to go, too.

<>What controller should I go for?  Linux?  I have built Linux computers before so that should be easy, shouldn’t it?  No.  After spending a couple of hours trying to “mount” a USB stick, and failing, I rejected the world of Linux.  Which leaves Mach 3 or 4.  Not quite what I want, but it seems to be popular.  Fortunately, Muzzer recently mentioned Centroid’s Acorn controller on another forum thread.  A quick check on their website and it looks like just the job.  I ordered one from Denmark & it arrived a couple of days later.

<>Another box has arrived from Cnc4you (I have no affiliation to any of these companies, I am just say what I have done in case anybody wishes to follow in my footsteps) full of stepper motors and their drivers.  It is all spread out on a table, ready for wiring up & bench testing.

<>Centroid’s website has a series of videos showing how to wire the bits, how to set up the computer & software.  Excellent.  So it is all wired up and - it is not working...  The problem, I hope, is that the stepper drivers need a 5 volt supply, which is not available from the supplied PSUs.  I am awaiting delivery of a 5/24 volt supply from RS and will continue when it has arrived.

Edited By DrDave on 14/05/2018 10:05:45

Edited By JasonB on 14/05/2018 10:40:59

Thread: What did you do Today 2018
04/05/2018 21:18:32

I have had my milling machine for some years now and it has given good service. Whilst it is a CNC machine (Emco F1), it gets most use as a manual machine using the jog controls to drive the axes. Until today. The rapid traverse button has stuck down, giving me a choice of top speed or nothing on all three axes. I have been putting off an upgrade for as long as possible, but it looks like I will have no choice now.

On the up-side, I now have room in the workshop for my drilling machine (the old Emco control box is LARGE!). It will require some work to make it useable. I don’t even know if it works. The table has been abused more than most. But at least it was cheap: when I collected a surface plate “won” on ebay some years ago, the vendor threw the drill in for free. Perhaps he knew something that I am about to find out...

Original drill.jpeg

Thread: Aircraft General Discussion
29/03/2018 16:50:41

What looked (and sounded) like the BBMF Dakota flew past a few minutes ago. It always makes me feel years older than I am when I see it: the very first aircraft that I flew in was a Dakota, back in the 70’s.

Thread: What did you do Today 2018
16/01/2018 22:53:15
Posted by David Standing 1 on 16/01/2018 22:06:17:
Posted by DrDave on 16/01/2018 21:54:07:

I take it that is a 'small block' V8 wink

If I have done my maths right, it should come in at under 50cc. So yes, a very small block V8!

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