Member postings for DerryUK

<As a specifier, you have to take headache pills, and be extremely patient with these techis, because they really do think differently and they talk a totally foreign language, even though all my techis are U.K. based.>

Ketan that's the fault of the provider not yours.

Derry.

I suspect you'll get a better response if you start your own thread John.

Put 3 phase and 415v inverters and motors in the title.

Derry.

Thanks for the thoughts John.

I do have a charge pump out (enable) signal that I can feed to my stepper drivers (DRV30/S) but my motor driver (4QD Uni) doesn't have an enable input.

I am however using a PWM signal (5 volts) for speed control so it seems reasonable that I could AND that with the enable signal to give me enable control over the spindle motor.

Derry.

I am building a small CNC lathe driven by LinuxCNC and I want to mount the e-stop switch on top of the headstock. I will use it to cut the mains power to the lathe's motors and electronics.

Othe than having to tell the PC software that the lathe has lost power are there any disadvantages to this?

Derry.

My R8 can take threaded shank cutters to stop this sort of thing happening.

<Sorry can't help, you don't have a profile.>

Whats going on here? Mike needs some help not comment on how he runs his life.

Derry.

I recently wen to RAF Cosford to view the Bristol 188. I want to build a simulation of it in my X-Plane 10 flight sim. First thought as I arrived was blummin cheek, they charge for parking. Anyway I paid my 80p and breezed into the entrance. “One concession please” I said to the young lady on the desk. “It’s free for you Sir”, crickey I thought that’s a good deal and then she added, “but it’s free for everybody.”

I used to look after a DC3 and one time we were coming into land to clear customs at Manston after a trip to Germany. I was sat towards the rear and looking at the runway through a passenger window, I could just make out the edge of the runway. A red flare went off! My heart-beat went up a bit as I wondered what was wrong with our aircraft!

The pilot abandoned the landing and opened up the engines for a go-around but needless to say we landed OK. When the pilot walked down from the cockpit he told us that the airman at the end of the runway had never seen a Dakota before and when he could only see the main wheels he thought the nose wheel was still locked up so fired his flare. Of course he soon spotted the tail wheel as we flew past him!

That aircraft is now with the RAF and is the subject of the Haynes Dakota manual.

Derry.

Interesting letter from Brian Thompson on the editors bench. Brian doesn’t want to start small and the Editor asks what’s to be done.

I have every sympathy with Brian but he answers his own questions really. He doesn’t want to make a toolmakers clamp but he worries about breaking a tap in a £184 casting. I worry about breaking taps but after you have tapped dozens of holes you get a feel for what is right and what is wrong so you can then tackle that casting with a bit more confidence.

In the end I’ve come to the conclusion that perhaps Brian should build his models from kits of premanufactured parts, at least to start with. He won’t have to worry about breaking that tap and he will see the results of his efforts sooner which is just what he wants.

Derry.

PS phew and I never said that you can’t run without learning to walk first.

I bought this one for £13

Ebay

Edited By David Clark 1 on 09/03/2012 11:41:32

I like your disc John S. Can I ask how you made your slots?

By extending one slot and using several sensors you have a neat way of syncing your A and Z outputs. What's the max speed you run your disc at and any issues with the sensors rubbing on the disc?

Interesting what John H said about being able to change the encoder scaling in LinuxCNC (EMC2), it just so happens that the supplier I had been considering offers a 200PPR at the cheaper price so I think I’ll give one of those a go.

Thank you all for your input.

Derry.

Following on from Tony Jeffree's article in MEW 186 I am looking for a rotary encoder to measure spindle speed. My lathe top speed is 3000 RPM.

I am intending to use LinuxCNC software which by default requires an encoder with A=100 PPR and Z=1 PPR.

The best new shaft driven encoder I can find on ebay (or anywhere else) is £65. A possible option would be to use a cheaper (£35) A=1000 Z=1 encoder with an external divide by 10 on the A output.

Anyone know of another source of suitable encoders?

Thanks,

Derry.

Edited By DerryUK on 07/03/2012 16:01:55

<It is approximately 850 miles from Land's End to John O'Groats, and actually, that puts Harrogate about as central to the UK as you can get from a geographical point of view.>

Yes but when the Scots vote themselves out of the UK you can change that to Lands End to Newcastle. So middle then will be Nottingham.

Hang on, didn't there used to be a lathe manufacturer there once?

Derry.

PS when the Scots go we can all enjoy a tax-cut.

http://www.linuxcnc.org/

Seemingly someone beat them to it with the previous name.

I have sent you an email John.

There are several utube videos, I noted the following address on one of them:

Cadet Plus

Conect Numerical Control Limited

Hawthorn Road

Castle Donnington

Leicestershire

DB74 2QR

01332 853332

John and Bazyle thank you for your replies.

You are right, it is based on the Hobbymat, in fact now I have it apart there is still some bright yellow paint remaining of the original.

The Eurotherm controller is U/S and before I buy a replacement I thought I would review my options. I have not run the motor

The current motor spec is:

GEC DC Machine

Size = MD7175

Ins Cl = F

No = MG26625601/08

Wdg = Shunt

RPM = 3000

Kw = 0.37

V = 180

A = 2.5

Size = 130mm x 210mm

Controller = RS237-3170

Eurotherm 506

If I keep the current set-up the I have been considering http://www.diycnc.co.uk/html/spindle_boards.html as an interface between the Eurotherm and PC.

Derry.

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet002-1.jpg

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet003.jpg

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet005.jpg

I don't post here very often...

Thanks for the input, the 4QD site looks interetsing. Here are some images

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet002-1.jpg

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet003.jpg

http://i692.photobucket.com/albums/vv286/Derryuk/Conect%20Cadet%20CNC%20lathe/ConectCadet005.jpg

The current motor is 130mm x 210mm.

I am currently stripping a Conect Cadet cnc lathe for cleaning and refurbishment. Looking at the spindle motor I have been thinking about what might be a suitable replacement. The current motor is a GEC DC 370W driven by a Eurotherm 506 supply. The motor drives the spindle via a 3:1 speed reduction toothed belt direct drive, no gearbox.

One problem I have discovered with this setup is that the motor is full of swarf. Conect have fitted a blanking plate over the motor main ventilation holes and subsequent owners have seemingly fitted bits of insulation tape over the rest!

The first question. Is this setup (no motor ventilation) safe? Is the motor likely to burst into flames?

I have been reading a bit on the web looking for a possible replacement. The current setup only allows for manual speed control and I would like software controlled (probably via EMC2). The obvious solution is to go for a 3-phase motor with an inverter. Are there any other options? I couldn’t seem to find any DC motor solutions.

With my current setup I would loosely seem to have a 1000rpm 1.5HP drive so was thinking in terms of a 1.1kW 2800rpm 1:1 drive motor as a replacement. But on reading http://www.lathes.co.uk/page27.html thoughts on the matter especially regarding having some form of drive ‘slippage’ as a safety feature (when the tool is driven into the chuck in error) perhaps I would be better with a with a non-toothed 1:1 belt with a no more than 370W motor?

Derry.