Cnc Pen Range Just Starting To Think Of Shapes

[richardandtracy]

Some of you may be aware I have a little CNC engraver/milling machine. It has been 6 months-ish & I'm getting a handle on what can be done with it and have had to design some pens to its limitations/capability. I have come up with some shapes it should be able to handle, and will be trying to machine them over the next few weeks. These are the pens:

 

The decoration inspired by the Duofold DNA LE pen (the near one) may not be possible in the way I have designed it - it may be too tall to go under the gantry of my machine or there may be interference with the router - I shall be making the tooling shortly. If that is the case, I'll have to resort to machining each segment as flats rather than as 41.68mm diameter arcs (machined by my biscuit joint router bit) - which will mean using the rotary axis on the machine used by the other two designs.

 

If you can think of something nice to decorate the basic pen design with, please suggest it, and I'll see if I can do it too.

 

Regards,

 

Richard.

[avlisyar]

The top one is my favorite. Very nice!

[richardandtracy]

Thanks avlisyar, it's a nice shape & fairly easy to program too. The only pen I've seen similar to the shape is the Visconti Divina, though that spirals the other way and has a different twist pitch. The one on the pen above is 252mm/turn, a very lazy spiral indeed.

 

Regards,

 

Richard.

[dfurlano]

I like them all! Good luck.

[Ted A]

They look great. How about pinstripes or a double-helix type spiral.

[basterma]

They are all great to see. Consider doing repeated or single company logos. Maybe one with the FPN emblem as a Limited edition. You might get some business from companies wanting something more substantial than the printing on a plastic Chinese ballpoint.

[Lloyd]

Have you looked at any of M.C. Escher's patterned images?

[drgoretex]

Cool. Looking forward to seeing some of these pens!

 

Cheers

 

Ken

[richardandtracy]

Thanks to ye all.

I am going to make a concerted effort to make these pens in the next few weeks. The furniture is going to be the difficult bit. I hope to make it in silver at some point, but think that brass is probably a better bet for prototypes. There will be some experimentation for the cap decal too. The first off is going to be machined in ivory polyester with a 0.3mm diameter end mill. This will then be used to make a silicone mould for polymer metal clay (PMC) to make fine silver decals as I don't think the 0.3mm mills will last very long machining either polyester or silver.

Not quite sure how deep to engrave the cap ring writing, but 0.15mm seems about right, with a 0.1mm/15degree engraver.

 

Ted A:

I must admit I didn't consider pinstripes. I thought a Barleycorn might look a little better, but haven't had time to model it yet. I tried with a Duofold style 'Lucky 8', but found that would have taken out some of the barrel threads unless the diameter was increased (not keen as the proportions look wrong). A Decahedron works though, and I may experiment with one after the others above.

Not sure about the double helix. Three pairs of grooves, 3mm diameter and 1mm between them, spread 120 degrees apart around the barrel with a tighter spiral, may look good though. I shall have to try modelling it.

 

basterma:

I am not too keen on doing work like that - I want to keep pen making as a hobby rather than turn it into a way of life. Having companies as customers makes greater demands on production rates etc. It is nice if you want to do that sort of thing, but not for me at the moment.

As for doing an FPN LE. Yes, I have considered it. I suspect that may come eventually when I have sorted the bugs and streamlined production a bit. But it would be a very limited LE.

 

Lloyd:

I have considered all sorts of engraving, but want to start fairly simple at the moment. An engraved pattern similar to Escher's cubes turning into ducks would be quite interesting & entertaining to do.

One idea I have had is to bond a metal tube to the outside of the blank and do a pierced pattern filigree through the metal and expose the coloured blank below. That is for future experimentation though, as I don't know how good the finish would be. It may demand a second blank, one for working, and the other to be put in afterwards after polishing.

 

Dan & Ken,

Thanks.

 

Regards,

 

Richard

[Ted A]

This is going to be exciting to see what you do.

[pshibb]

What shapes can you engrave? What materials can you use? I have plenty of ideas.

[richardandtracy]

pshibb,

I think imagination is the limit to what can be done. As for materials, due to the stiffness of the machine I think I'm limited to non-ferrous materials, ie aluminium, silver, brass, plastics & wood. With metals the maximum feed rate is 100mm/min or less. With lithophanes (carving plastic to make pictures) I've used 800mm/min.

 

Regards,

 

Richard.

[Shuggy]

As an engineer I can really appreciate the care that has gone into these designs. One suggestion is for a 'candy twist'. This is where you have two helical patterns running in opposite directions. These sort of patterns are quite popular for machining the bolts on custom rifles - I'll see if I can find some pictures for you.

[richardandtracy]

That would be nice Shuggy, if you could as at the moment I can only guess at what you mean. The second one down (diamond shape) is a variant on the idea I think, but with a very narrow engraving tool.

If I were to use more spirals and a 120 degree engraver 0.5mm deep, I suspect that would give a shape more like pillows on the surface.

 

I am considering writing a piece of software that will allow a profile to be defined, then apply a toolpath file to that profile, so almost any figure of rotation could have its surface engraved/machined. The software would be far from simple, but it may be nice to try.

 

Regards,

 

Richard

[richardandtracy]

Ahh. Seen a few photos.

I see about the candy twist. Full round top to the machining, 6 or 8 spirals and about a 50mm pitch.

 

Due to the fact the pen has a hollow running down the middle it would be structurally unsound to make a machining quite as deep as those seen on rifle bolts. However, if the idea were flattened a bit, it might be possible to do on a pen.

If I were to do that, I think I would have to re-design the cap. At the moment, the cap lip is a separate item with the cap-barrel thread on it (to allow for the cap ring to be fitted and for me to glue the cap lip in at the correct angle to align the decoration regardless of the orientation of threads). With the candy twist machining, it cuts much deeper, so the thread would have to be on the inside of the cap body, and then the cap ring & cap lip would slip on over that. If I didn't do that, I'd machine right through the cap in some places. This is the way Delta fix their cap rings, as opposed to the way I've done it which is similar to Parker & (I think) Onoto. It would require more thought in aligning the decoration during machining - not too hard to do, will just need some experimentation for the thread alignment.

 

I shall think on it, and maybe model up a few ideas based on available router bits to see what it looks like.

 

Regards,

 

Richard

[pshibb]

Could softer stones be used? Something like the harder soapstone used for counter tops or some other softer stones.

[Shuggy]

Well, my memory was at fault. The double helix patterns are known as 'diamond fluting' for fairly obvious reasons. Not unlike the TWSBI Diamonds in fact. Here are a few of my favourite patterns. I agree that they will be too deep or uncomfortable to hold for a pen barrel, but as you say, you could use shallower and more rounded cuts. In fact, you are only limited by your imagination and your ability to programme the CAD/CAM software.

 

'Diamond'

http://img.photobucket.com/albums/v223/baldiedave/IMG_1091.jpg

 

'Barley Sugar'

http://img.photobucket.com/albums/v223/baldiedave/sakobolt2.jpg

 

'Candy Twist'

http://img.photobucket.com/albums/v223/baldiedave/IMG_1466.jpg

 

'Fishnets'

http://www.sharpshootersupply.com/images/Accessories/flutedbolts.jpg

 

 

[richardandtracy]

Could softer stones be used? Something like the harder soapstone used for counter tops or some other softer stones.

Not on my cnc machine. It is just too flexible for really hard materials. Corian (stone dust in acrylic resin) is just about possible, but to be honest it's right on the upper limit.

 

Regards,

 

Richard.

[Scribblesoften]

This is very interesting. I look forward to seeing your results. I am a fan of faceted pens. Perhaps that is too simple.

[richardandtracy]

Shuggy,

 

Some of those are impressive, particularly the 'fishnet' ones. They could be done with something like a thread mill, or a fly cutter.

The diamond one is simply a deeper version of the middle design I showed.

The barley twist seems to be done with a ball nose cutter, and will be fairly simple to program.

 

As for imagination being the main limit - I have to agree with you. The software is less of a problem. I am comfortable writing C++ programs to output exactly what I want. Over the last 10 years, amongst other things, I have been tinkering with a 3D modeller to enable someone to make a 3D finite element model from scratch, and output the analysis file for the NISA package (also imports from Cosmos, Radioss, Nastran (I think, it certainly outputs to Nastran format), some DXF entities, STL, and Wavefront .obj format). About 90000 lines of code.

 

Regards,

 

Richard.