How to get started with CAD/CAM for machining and engraving?

[richardandtracyParticipant @richardandtracy]

I am curious.

Do any of these packages cope with engraving on a curved cylindrical surface ?

Regards,

Richard

[John Stevenson 1Participant @johnstevenson1]

Quite a few do as all they do is break arc up into samll lines and substitute the Y axis moves for A [ rotary ]

but there are programs out there that will tak any G Code and convert it to rotary no matter what program has done the code in the first place.

Wrapper is one that comes to mind.

**LINK**

[richardandtracyParticipant @richardandtracy]

Thanks John, Looks good.

Regards,

Richard

[blowlampParticipant @blowlamp]

For CNCWrapper to work, you need to ensure that the G-code you feed it doesn't contain any arcs (G02 & G03), but only straight line moves such as G00 & G01.

The upshot is that you might need to alter a setting in your CAM program to make it output only lines, or alternatively, use a 'lines only' post-processor.

Martin.

[richardandtracyParticipant @richardandtracy]

I think I should be able to write a little program to convert any arcs to straight lines and substitute into the relevant lines.

One of my 'hobby' programs was to convert HPGL to DXF, so a little G Code routine wouldn't be too much of a problem.

Regards,

Richard

[Sub MandrelParticipant @submandrel]

I have an old A3 pen plotter made for use with a BBCcomputer (using VDU commands), but it also takes HPGL and Sweet Pea commands.

I might try fitting a small engraver head to it and try some CNC engraving.

Neil

[John Stevenson 1Participant @johnstevenson1]

Neil,

Because a pen plotter is usually limited bythe fact it has a simple up / down for a Z axis you might be better going the diamond drag engraving route which is idea for a plotter as you only need up / down and the spring loading does the rest. no spindle motor.

 

This is an example of diamond drag engraving done on stainless, as a guide the OD is about 2"

 

 

That text in the centre is TTF and has an inner and outer and is 0.5mm high

 

Edited By John Stevenson on 01/06/2013 10:52:31

[Sub MandrelParticipant @submandrel]

So a diamond drag cutter is just a metal bar with a diamond point on the end, and you just pull it around uder its own weight. Interesting – I wonder if my printer can pull hard enough? I'd imagined using my little electric engraver with a counterweight so the pen drive can lift it.

Neil

[John Stevenson 1Participant @johnstevenson1]

Neil,

The diamond I use is a 1/8" diameter rod with a diamond in the end that has been sharpened to a point 90 degrees and 120 are the usual angles. It's spring loaded into a holder and you zero it onto the top of the work and I usually use 2mm as depth of cut.

It obviously doesn't cut 2mm deep but that depth puts the pressure on via the spring load.

Bit of experimentation is needed as regards materials depth of cut and spring pressure.

Doesn't't take a lot to pull it in X and Y but Z needs a bit of force to overcome spring pressure.

I currently use an old Roland PNC2200 engraver which is a gutless wonder and moves the carriage via fine bowden cable and capstans so I wouldn't worry too much about X & Y movements.

**LINK**

[Sub MandrelParticipant @submandrel]

Hi John,

That looks more robust than THIS which is what I have got, less the pens. It also uses bowden cable, but the pen is at the end of that long, unsupported arm. I once used it to print a double sided circuit board using a dalo etch pen! It's great for technical drawings, if slow, but a nightmare for text.

I might stick with photo-etching for the time being

Neil

[richardandtracyParticipant @richardandtracy]

Reminds me of the A0 pen plotter in use when I first joined the company I work for. That plotter used a rolling bed for the paper and drew the lines in completly random order, doing one corner then randomly flitting to another corner to draw part of the text before whizzing elsewhere. It was as fascinating to watch as a shaper. And just as slow.

Regards,

Richard.

[Sub MandrelParticipant @submandrel]

Hi Richard,

You be interested that modern rollerball pens work far better than the various original pens. Nice consistent line and clean lift-off.

Neil

[richardandtracyParticipant @richardandtracy]

It is hard to believe, but even with things as old & established as pens, there have been amazing advances in the last 10 years.

I got my first Chinese made fountain pen in 2008, and it was .. let's just say 'poor'. Five years on, one of my regular carry pens is a £14 Chinese re-interpretation of a £435 Parker pen, and it is every bit as good as the Parker.

Regards,

Richard

[BazyleParticipant @bazyle]

I do so little hand writing these days sometimes all I have written all week is my signature on an electronic receipt pad. Yet I have a nearly full bottle of ink on a pile of papers just behind my desk which has been there for a year or two. Not sure where my Parkers are now as I haven't used them for about 35 years.

edit : well I'm blowed . Found them right in the drawer they were supposed to be in. helps to keep thinhgs in place if you don't open the drawer every decade.

Edited By Bazyle on 04/06/2013 15:36:53

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