Engraving coconuts

[Mike Null]

I have the opportunity to do a fairly large job of engraving a logo on coconut cups. The logo has to be color filled and there are 1600 pieces. The cups are part of a promotion by a rum distributor.

The coconuts are irregular in shape though close in size. They have a base glued to the bottom of the bowl and it's of question durability.

I can engrave these with my laser but the logo will be smaller than requested. I can also engrave them with my Newing Hall rotary/mechanical machine but I'm concerned about holding them securely without breaking the base.

I'm looking for ideas and any experience you might have had. I need to do the samples this weekend.

The picture just321582 shows the shape.

[Scott Shepherd]

A 4" lens would help on that shape a lot Mike. I can't get it to in time to try for the weekend, but I'll gladly send mine if you want to try it.

[Mike Null]

Steve

Thanks for the offer and idea. I'm thinking that I'll do the colorfill (white) with paint sticks as I don't believe they can be masked due to the shape and texture.

I've turned down 3 jobs this week where a Speedy 500 or even better a 1500 would have been required.

[Matt McCoy]

Mike: For best results, please be sure to put the lime in the coconut.


https://www.youtube.com/watch?v=aA9OqUuA6a0

[Mike Null]

Matt

Obviously, an important point.

[Scott Shepherd]

I'm thinking that I'll do the colorfill (white) with paint sticks as I don't believe they can be masked due to the shape and texture.



Might be able to do a liquid frisket on that, depending if they are smooth and painted or just raw. Then you could just rub off the frisket once it's painted (airbrushed).

[David Somers]

Mike,

I am not familiar with the Newing Hall so I am guessing. But if I were trying to do something odd like this on the wood lathe I would trap the piece between a cone shaped chuck on the head stock and a hollow cone on the tail stock and rely on friction to rotate it. The hollow cone would be hollow at the widest part of the cone, with the narrowest part of the cone ending in what amounted to a dowell that I could grab with a tail stock mounted jacobs chuck, or with a bearinged receiver in the tail stock that could take a regular 4 jaw chuck. Either way, the tail stock side can freely rotate.The head stock cone will take whatever diameter opening the cup has. I usually glue or tape a thin foam on the head stock to protect the interior of a cup like that and to provide some friction.The tailstock hollow cone would fit over the base of the cup and contact the bottom of the cup itself. The shape doesnt have to be an actual cone so long as it can fit over the foot of the cup and still contact the body of the cup. Even a hollow cylinder with a dowel like tail to it would be fine. This way there is absolutely nothing touching the foot, which is of questionable durability in your description. Again, a bit of thin foam to protect the cup surface is fine. You are basically using friction to hold both sides. You dont need much since you are not actually spinning the cup like you would in a regular lathe operation. Instead you are rotating it slowly like you would with the rotary on a laser.I use this kind of setup to hold a hollow form when I am cutting spirals into the piece. Again, the piece is not being rotated like regular lathe work. Instead it is rotating slowly as you cut the spiral. The lathe is more of a holder than a lathe in this case.

Not sure if that helps.Dave

[Kev Williams]

Ironically, I have nearly 400 coconut cups out in the garage shop myself- While the one in your pic looks all nice & smooth, the ones I have here are anything but! They've been cleaned up and clear coated, but they haven't been sanded smooth at all..
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They're all different-- heights, diameters, shapes- running a couple on the cylinder attachment in the LS900 I'm getting over 1/2" of variance between the high and low points as it turns, and that's only 1/2 circle's worth. I just have to laser a logo (mostly lettering that goes around nearly half way), fortunately no color filling! (I wouldn't even if they asked, these are too rough!) Some are very dark, won't be much contrast on those...

I'm still trying to figure out how to run these without stopping to re-focus each one 3 or 4 times! (I do have a 4" lens, but I'll have to McGuiver something up to make it work in my LS900...

Sorry I'm of no help, but I can relate to your pain! http://www.engraver1.com/gifs/nilly.gif

[Ross Moshinsky]

Sandblast and color fill?

[Mike Null]

Thanks for the suggestions. I have retired my sandblasting gear and am about to give it away. In my opinion sand blasting would add too much cost to this project though it would probably work.

I would prefer to laser them but they are irregular in diameter height and shape. Still that might be my best option.

The Newing Hall will rotate the cup back and forth and it will work but holding the cup between the cones as Dave mentioned carries some risk of breaking off the base.

[David Somers]

Mike,

See if my silly drawing below makes sense. If you used a cylinder as your tailstock, one that is larger in diameter than the largest foot of any coconut cup, then you could use that as a friction chuck on the base. You wouldn't need to touch the foot in any way so you shouldnt get any damage there. The cone friction chuck in the head stock will automatically center the opening of the cup. The cylinder on the tailstock will center the bottom of the cup with just a touch of adjusting, if any is needed at all.

I use a vacuum chuck now for this kind of work. But in the past I have used this type of friction chuck for the kind of shape you are describing.

Hope that explains it better.

Dave

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[Keith Winter]

The 4" will help with divots as Scott said. However a 4" won't cover that much curve, you're going to need a rotary for that big of a curve.

[Ross Moshinsky]

Thanks for the suggestions. I have retired my sandblasting gear and am about to give it away. In my opinion sand blasting would add too much cost to this project though it would probably work.

I would prefer to laser them but they are irregular in diameter height and shape. Still that might be my best option.

The Newing Hall will rotate the cup back and forth and it will work but holding the cup between the cones as Dave mentioned carries some risk of breaking off the base.

If you're just going to color fill it, I question whether a silk screen or pad printing wouldn't be the best way to go. Other than that, a sticker of some sort seems another obvious choice.

I just don't see how you're going to engrave those being so irregular. Relatively minor inconsistencies can cause engravers fits. These things are all over the place. If you must engrave, a big focal length, rotary, and literally sorting them into different runs might work. Still seems like a lot of work and an incredibly frustrating job.

[Kev Williams]

Pics of another one in my rotary, one of the darker ones. View from left, top, and right.
Notice in the top shot how far the left side bulges out vs the right side. That's likely beyond even a 4" lens focal range!
The other shots show that nothing about these equals "round" or "consistent". And this is a "good" one!
They're not even assembled straight, at least as far as engraving them goes-
They ARE assembled so that when sitting on table, the top opening is reasonably level.

They're easy to laser, if you like 'babysit' work. Whichever one of us runs these, will have to keep
an eye on the lasering itself, when needed the machine will be paused to autofocus.
I figure the average will be 2 stops per cup. Even so, the engraving I'm doing is all of a minute,
so not too bad. And the end customer is thrilled that I can even do them at all, gotta love easy-to-please people! :)

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[Keith Winter]

I'm continually amazed by your ingenuity Kev! Very clever way to hold those!

[Scott Marquez]

I'm continually amazed by your ingenuity Kev! Very clever way to hold those!
I think if he used the same cup design as the top, on the bottom it would take the "off centered" base out of the picture and it might spin pretty true.
???
Scott

[Kev Williams]

Keith, thanks, but don't blame me, blame good equipment! Great cylinder unit, comes with lots of accessories.
And it works with all the newer Gravograph machines, I can use the same unit on my IS400 and IS7000 tool machines :)

Scott, I tried using a cone on the cup-top and a 'dish' on the bottom, doesn't make much difference!
But I got to thinking about what I said above, that the cup ENDS are relatively flat to each other, so,
I turned around the big dish, AND my small cone (the groove in the back of the big cone is in the way),
so I can hold it flat-to-flat.

!321630321629

Once I find a relatively evenly round section of the side to start from, I can look straight down and
eyeball side-to-side center, then close the clamp. Might take a few extra seconds to load, but
I should make that time back in less stops to refocus...

(Mike, sorry for the hijack! ;) )

[Keith Outten]

Mike,

Can you grab the inside of the cup with the chuck on your rotary?

If you don't have enough reach from the chuck jaws you can turn an ID / OD disk on your wood lathe and cut it into segments to extend your chuck jaws. Make sure that you cut a groove in the disk so you can use a rubber band to hold the segments to the chuck jaws.

[Mike Null]

Guys, thank you all for your suggestions. Kev, you didn't hijack the thread, your ideas are relevant. My NH has a very similar rotary device to yours and I'm quite sure I can route them using cutters like these. http://www.antaresinc.net/EngSTD.html This process will be slower, more expensive and will probably entail more breakage.

Dave, your idea is a good one and similar to what Kev is doing except he put the cylinder on the other end. I should be able to find a cup around the shop that will work--if not I can turn it on my lathe. (actually I'm going to use a piece of pvc pipe taped to one of my cones.)

Keith, I believe you're referring to a rotary device for my laser which I do not have.

[Kev Williams]

Hey Mike, I was assuming you had a rotary for your laser, my apologies!

I'm not sure what holding jigs you have for your NH, but assuming you have a self-centering clamp and no issues holding the top of the coconut, to get around the issue of the cup's base, could you make from wood another v-cup, with the center hollowed out to clear the base? It would take a good size chunk of wood, but I'm sure that's not a problem! :)

this way it'll support the cup and the base will be untouched. This assumes you'll have enough engraving area remaining after you size it to work...

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[Joe Hillmann]

Does it have to be laser engraved? Due to the curve in both directions as well as slight inconsistencies in shape and size I think pad printing would be the best way to go with that or depending on the size of the image maybe loose screen printing.

[Keith Outten]

Mike,

I knew that you didn't have a rotary for your laser engraver but I thought you had a 3 jaw chuck for your NH rotary. Most 3 jaw chucks can be used to hold objects from the inside diameter or the outside by reversing the jaws.
.

[Mike Null]

Keith

You are right but my chuck is relatively small and I doubt that I can hold the nut securely enough to rout. I may pad the fingers with some sponge or rubber for better grip. I'm thinking I'll have to make a .010" deep cut to be enough to give me an outline for a freehand fill.

Joe, I think pad printing might be the answer also. The concerns are the course texture of the nut and the irregularity of the shapes. I don't know how much texture can be handled with pad printing. Everything I can recall seeing has been on a smooth surface.

[Kev Williams]

I'm finally putting a laser beam to these coconuts--

My setup is as described above, except that I turned the tailstock cone around so the narrow end fits inside the cup bottom. Turns out many of the bottoms are too big for the flat side of the cone, and this is working out nicely.

Note the lens setup- I'm using a 4" lens installed in one of my Triumph lens holders. The lens and holder is on the machine upside down, the lens is just under the mirror at the clamp. To get the clamp to hold I had to wrap a couple of layers of tape around the tube end. Hey, it works! The other thing I did was make a new auto-focus plunger rod out of some delriin. It works too!

The 4" lens is the saving grace on this job! As noted above, I just find a relatively consistent 3" sweep area on the coconut, put the starting point straight up, then eyeball the side-to-side center as best I can- They're running flawlessly, no stops, and the engraving looks great, very consistent- even with the lens upside down! (I swear, with certain materials and jobs I get better results with an upside down lens).

-I'll show the engraving if I get permission to... :)

http://www.engraver1.com/erase2/cocoengrave.jpg

[Joe Hillmann]

How far + & - out of focus can you be with that 4 inch lens and still get good results?

[Kev Williams]

I haven't tested it, but according to this webpage: (which has some cool laser & lens info, check it out!)
http://www.parallax-tech.com/faq.htm
(http://www.parallax-tech.com/faq.htm)
--the depth of field of a 4" lens is .200" (5.6mm), which is quite a bit. This means from dead-center of the lens's focal length, the work can be nearly 1/8" closer OR farther away and still get pretty good results! The trade-off is the beam's spot size is bigger, so that has to be taken into account. But hey, I'm engraving coconuts! Spot size isn't really an issue!

This is a table from the website, showing the beam spot size and depth of field for different focal length lenses...

http://www.engraver1.com/erase2/lensinfo.jpg

[Mike Null]

Just a quick update. I was able to get a good quality engraving using my Trotec and two focus settings. Even though the engraving is good I can't figure how to colorfill without getting paint outside the engraved area. Masking is not possible due to the rough surface and I've tried a paint pen and a small brush. A syringe might work but it's too tedious for 1600 pieces.

I think I'm going to tell my customer no fill is available.

[Bert Kemp]

Mike how bout a liquid mask would that work?Plastic dip or something like it?:rolleyes:

[Mike Null]

Bert

These are in their natural state and so rough that no mask can be used, The liquid would work up to the point you tried to remove it then it would be too time consuming.

One of my customers is a promotional products company and I am going to consult with them today. If they have a solution I'll turn the job over to them.

[David Somers]

Mike,

This is a silly question. But have these cups with the rough coconut husk exterior actually been made yet? Or are you dealing with a few prototypes? If the latter, can you explain to the potential client that a smooth coconut would be doable but a rough coconut would be better left unadorned?

Another silly thought just came to me. If they are rough husk exterior I assume they were not meant to be used with any frequency, if at all? Display items only in other words? If that is the case, how about not actually engraving them but cutting fully through the shell to the interior? Just a wild thought. Not sure that would have any bearing on the design. Just brain storming.

Dave

[Jay Selway]

Wow, that job sounds like a huge pain in the butt.

I might try and run this one using a 4" lens and put a bunch in jigs and try to run flat (calculating the curvature).

[Mike Null]

These coconut shells were imported from the Philippines. The customer's customer is keen on a white image. I sent the samples back today--one with a sloppy colorfill and the other just engraved. I advised them that I would not do the colorfill and that engraving would be $2.00 each which I am fairly sure is beyond their budget.

These are likely for a one time use at a promotional event.

[Kev Williams]

now for an easy question, Mike-- do they look like those I'm engraving? (these are from the Philippines too)

These I have are lasering quite nicely, but the last thing I'd attempt to do is paint the engraving! Bumps and ridges and grooves-- I doubt these could even be pad-printed with good results...

[Mike Null]

These appear to be identical to the one you have pictured. The other thing about these is the varying and rather thin thickness of the shell. My engraving depth was about .040" and I was afraid to take it any deeper.

[Bill George]

These coconut shells were imported from the Philippines. The customer's customer is keen on a white image. I sent the samples back today--one with a sloppy colorfill and the other just engraved. I advised them that I would not do the colorfill and that engraving would be $2.00 each which I am fairly sure is beyond their budget.

These are likely for a one time use at a promotional event.

I did a 3D print of a birdhouse and then made a nice looking label from what I had on hand, the Rowmark LaserMag plastic in silver. It was super glued onto my project.... how about something like that? Or the Black in Script or Times outlined vector cut and glued?

[Kev Williams]

These things run the gamut between size, shape and finish! They've been sanded somewhat, and clearcoated with something that has zero smell (like enamel or linseed oil would have).

Any kind of painting or printing on these would take way more patience than I have!


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[Scott Shepherd]

I think you guys are on the wrong end of the transaction here :) You need to be the one ordering a drink served in a coconut :)

[Mike Null]

I sent the coconuts back and was forced to use a very common glass for my maple syrup old fashioned.