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John Stevenson27/06/2011 23:14:27
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5068 forum posts
3 photos
After the recent threads [ and flames ] on CNC and CAD I thought I'd take interested parties thru an everyday job.
 

Pretty average brush ring out of a fork truck motor, shot from the back.
 
 

A bit unusual in that this one is broken, usually they are burnt out.
Now these pictures have literally just been taken and uploaded and the idea is to try to do this in real time. probably take a bit longer as regards taking pics, uploading etc but should give a good idea. Time at the moment is 23:13pm.


John S.

 
Chris Trice27/06/2011 23:36:28
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1376 forum posts
10 photos
You working a night shift John?
John Stevenson27/06/2011 23:40:54
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5068 forum posts
3 photos
23:38
 
Drawing now done and saved as a DXF file.
 

Now onto programming this for the router to cut out of a sheet of Tufnol.
 
John S.
John Stevenson28/06/2011 00:02:19
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5068 forum posts
3 photos
23.54
 
CAM drawing done, took a bit longer than it should as I had an update to the computer last week and on reinstall of the programs all the tool files were new so had to edit the tools.
 

Second line up from the bottom tells me that this is going to take 6 minutes 17 seconds when t gets nailed onto the router in the morning. all thats then left is to counterbore the fixing holes and transfer the brush boxes over.

A couple of years ago this job would have taken me about 3 to 4 hours. now it's down to 41 minutes to get the file but it should have been less. At no point tonight have I seen the G code nor do I need to, I have a file called 27_6_11 brushring on a memory stick and that's all I need.

Total time tomorrow should be 45 minutes tops and the truck will be back running by dinnertime easily.

John S.
Tony Jeffree28/06/2011 11:11:24
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569 forum posts
20 photos
John -
 
Makes the point very nicely.
 
Another example of a 1-off that was done using CNC, and which would have been very time consuming indeed using manual techniques, involving a steep learning curve in hand-engraving just as a starter:
 
http://www.jeffree.co.uk/pages/Chapter-ring.html
 
Again, not a single line of G-code was written during this process. As observed in the text, I could have made a more traditional-looking job of the numerals; with a larger table available to me on the mill (or maybe a small CNC router), the answer would have been to draw out the numerals "properly" in CAD rather than using a rotary axis and the in-built Roman fonts.Also, the CAD/CAM tools available to me have much improved from the rather primitive SuperCam package I was using back then, so life is even simpler now.
 
A later example is this brass plaque that I engraved using a CAD drawing for the outline/screw holes and DeskCNC's in-built stick fonts to engrave the text:
 

Again, doing the same by hand would have been impractical both in terms of time and personal ability.
 
One-off work is just as legitimate a target for CNC tools as is repetition work, and IMHO the former is much more likely to be useful in the average ME's workshop.

Regards,
Tony
EtheAv8r28/06/2011 11:20:32
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111 forum posts
3 photos
This is very interesting - how long would it take to learn to use the drawing package used to generate the dxf file, and is the CAM drawing from another program, or a result of the dxf file. And then what kit is required CNC Mill wise - and is it all very expensive?
 
I am interested in this, and the process and would like to understand a little more of just what is required to do this. I am about to buy a mill, am a complete beginner and know practically nothing! CNC for non programmers sound interesting - but I would want to be able to perform some manual milling/drilling too - is this requirement mutually exclusive on a low cost single mill setup?
Jim Nolan28/06/2011 11:26:43
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77 forum posts

John,

Keep preaching you never know!

Given I have a history of bad luck when it comes to measuring hole centres the only thing I can possibly see that would take a bit of time was measuring up the original part.

On my own hobby machine Tormach offer a CNC scanning package and software to reverse engineer parts. They also have a demo video which really explains how you can get started for a relatively cheep outlay
 
Of possible interest this week I notice on the flyer from Liddle they are selling a USB microscope for about £20. Which looks exactly like the one in the video so it might be worth a punt just to see what it can produce.

Although i work from my own drawings and don't get into the refurbish or repair world. This would still seem a handy arrow to add to the quiver.

Jim

Tony Jeffree28/06/2011 11:40:13
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569 forum posts
20 photos
Posted by EtheAv8r on 28/06/2011 11:20:32:
This is very interesting - how long would it take to learn to use the drawing package used to generate the dxf file, and is the CAM drawing from another program, or a result of the dxf file. And then what kit is required CNC Mill wise - and is it all very expensive?
 
I am interested in this, and the process and would like to understand a little more of just what is required to do this. I am about to buy a mill, am a complete beginner and know practically nothing! CNC for non programmers sound interesting - but I would want to be able to perform some manual milling/drilling too - is this requirement mutually exclusive on a low cost single mill setup?
If you are reasonably familiar with PCs and Windows, getting the hang of a drawing package is fairly quick. Once you have the drawing in CAD, you save the drafing as a DXF, import that into the CAM package, where you select how it will treat the various parts of the drawing (for example, if you had drawn a circe, you might intend that to be a simple circular toolpath, or the outer edge of an "area clear" operation). The CAM program generates the Go-code, which you load into the CNC control that interprets the G-code and translates that into coordinated moves of the various axes.
 
Kit-wise, the expensive way is to buy a purpose-built CNC mill (for example, from Tormach, Taig, or Arc Eurotrade). The cheaper way is to start with a manual mill and convert it; Taig can sell you a "CNC-ready" mill that has the necessary motor mounts, to which you would add your own motors, drivers, etc. An example Taig conversion is documented here:
 
http://www.jeffree.co.uk/pages/taigcncpt1.htm
 
and here:
 
http://www.jeffree.co.uk/pages/taigcncpt2.htm
 
although these days I would probably use Mach 3 instead of Desk CNC, so the details of the electronics would change a bit.
 
There are ways of making the end result usable both manually and under CNC control. The simplest way is to use stepper motors that have double ended shafts, and transfer the hand crank to the back end of the motor. However, with Mach 3 there are several options for adding hand controls (so-called "pendant" controls) that give you manual control of the mill via the motor drive system.
 
Regards,
Tony

blister28/06/2011 20:46:37
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28 forum posts
3 photos
Well done John, I am now seriously considering CNC. The only thing that worries me is losing the skills required for manual machining. Upon reflection this shouldn't happen as at work my workshop has machines from the late 1800's driven from overhead belting by a steam engine. During the day I demonstrate 'old style machining practices' so I could keep the skills alive that way and thoroughly enjoy CNC at home
I guess you are officially "Preaching to the converted"
Well done again.
Regards,
Phil
Richard Willcox 128/06/2011 21:00:25
11 forum posts
My first post:
I am an experienced machinist, returning to it as a hobby. This is something I'm really interested in.It stimulates me as I'll be learning a new skill. Thanks for posting the link
it's one of the best demo's I've seen in ages.
 
John Stevenson28/06/2011 21:23:07
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5068 forum posts
3 photos
I don't mind taking an example all the way though but in more detail if it will be appreciated.
 
What seems to be the area of most interest ?
 
John S.
Steve Garnett28/06/2011 21:47:11
837 forum posts
27 photos
Just FYI, the images in this thread that John has posted don't show up in Firefox. Tony's one does, though. The only difference between them that I can ascertain is that whilst Tony's is hosted by this site in Albums, John's are external links to his own site.
 
Yes that seems ludicrous. Especially as if you view the page in Google Chrome, all the images work fine. And no, I can't find any settings in Firefox at all that will alter this. Ho Hum...
Andrew Johnston28/06/2011 21:52:13
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7061 forum posts
719 photos
Oeeer, I'm using Firefox and, as far as I can tell, all the images show up. I'm using version 3.6.18. I haven't upgraded to release 4, as the upgrade process fell over. Doesn't give you much confidence, if they can't even get the upgrade software to work!
 
Regards,
 
Andrew
Steve Garnett28/06/2011 22:05:45
837 forum posts
27 photos
Oh. I'm using release 5!
Tony Jeffree28/06/2011 22:12:25
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569 forum posts
20 photos
Posted by Steve Garnett on 28/06/2011 22:05:45:
Oh. I'm using release 5!
I am also using FF #5 and all the images show up just fine...
 
Don't you just love PC's?
 
Regards,
Tony
Les Jones 128/06/2011 22:19:29
2292 forum posts
159 photos
The pictures show up OK on both my PC's. One 32 bit XP pro with Firefox 4.01 the other window 7 64 bit with Firefox 5.0
Les.
dcosta28/06/2011 22:21:25
496 forum posts
207 photos
Hello Steve.

At my machine, with Firefox upgraded to version 5.0, I also can see the John's images.

Regards,
Dias Costa
Steve Garnett28/06/2011 22:26:29
837 forum posts
27 photos
Weird. It's an absolutely default installation. I've just checked the error messages for this page, and the most interesting one (apart from all the word 2007 parsing errors) is the one that says:
 
Security Error: Content at http://googleads.g.doubleclick.net/ may not load data from http://www.model-engineer.co.uk/forums/postings.asp?th=52816.
 
But that of itself doesn't explain why remote images won't display... mystery continues.
John Stevenson28/06/2011 22:31:09
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5068 forum posts
3 photos
Steve,
I think I know the answer.
 
From my records you have paid no rent this month to view my pictures.
Cough up or the boys will be round. <bg>
 
John S.
Tony Jeffree28/06/2011 22:35:58
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569 forum posts
20 photos
Posted by John Stevenson on 28/06/2011 22:31:09:
Steve,
I think I know the answer.
 
From my records you have paid no rent this month to view my pictures.
Cough up or the boys will be round. <bg>
 
John S.
Not the boys that got "Santa's Slaves" tattooed on their chests by a dyslexic tattooist, by any chance? <bg>
 
Regards,
Tony
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