CNC engraving
- Thread starter mrpercysnodgrass
- Start date
Help Support UKworkshop.co.uk:
Sporky McGuffin
Light entertainer
Yes, as long as the machine has a proper z-axis and you know the curvature of the surface. And have the right software.
I think I'd approach it by machining the curve using the CNC machine; in CAD you'd then project the logo onto that curve. I use Rhino3D and MADCAM and you could then either V-carve the logo (so the wider strokes are deeper) or pocket it which gives a flat bottom. You could probably get close to matching the bottom of the pocket to the curvature of the top but that'll depend somewhat on how much time you're willing to spend on it and the geometry of the bit you use.
I think I'd approach it by machining the curve using the CNC machine; in CAD you'd then project the logo onto that curve. I use Rhino3D and MADCAM and you could then either V-carve the logo (so the wider strokes are deeper) or pocket it which gives a flat bottom. You could probably get close to matching the bottom of the pocket to the curvature of the top but that'll depend somewhat on how much time you're willing to spend on it and the geometry of the bit you use.
mrpercysnodgrass
Established Member
Thank you for those replies. I have two problems, one, I have only ever seen a CNC machine on the telly but guessed that would be the machine to do the job! Two. Words like CAD and Rhino and surface mapping mean nothing to me! oh, and three I have already made the disc, for the reason it is reworked antique ivory and the only piece I had that was big enough to do it without a join. I had to know I could make it first as there are no spares!
What I need to know now is, can it be done and can someone do it for me with the knowledge that if it does not work getting more ivory would be problematic.
The photos below is the piece I have made showing the curvature, the diameter is 38mm.
What I need to know now is, can it be done and can someone do it for me with the knowledge that if it does not work getting more ivory would be problematic.
The photos below is the piece I have made showing the curvature, the diameter is 38mm.
Attachments
getting more ivory isn't the issue it need be - you would test I assume on a copy in cheap wood until it works and then do a final run on the ivory?
from the sound of it you need a professional firm to do it as you would presumably want them to take liability if it went wrong?
from the sound of it you need a professional firm to do it as you would presumably want them to take liability if it went wrong?
Phill05
Established Member
I would be inclined to find a hand engraver now you have the finished item.
mrpercysnodgrass
Established Member
“getting more ivory isn't the issue it need be “
please don’t climb into Longleat on my behalf
mrpercysnodgrass
Established Member
More good suggestions thank you. I like the idea of getting a hand engraver so I will do a search this evening and see who is out there.
So just to add first laser engraving may be an option as Ollie78 has mentioned but I am not sure if it is a material that can easily be laser machined, Secondly you say you have made it but does it need to stay exactly as you have made it or could it be altered ever so slightly?
It could be CNC machined IF that were possible, from measuring the actual piece you should be able to create a dome shape that was very close but probably not exactly the same, run the finishing pass for the done that was created in the software would then give you an exact shape to run the other toolpaths to cut what needs to be engraved.
It could be CNC machined IF that were possible, from measuring the actual piece you should be able to create a dome shape that was very close but probably not exactly the same, run the finishing pass for the done that was created in the software would then give you an exact shape to run the other toolpaths to cut what needs to be engraved.
mrpercysnodgrass
Established Member
It could be reshaped, the shape I have is one created by eye on the lathe so cnc would be an option providing it would just skim the surface. What sort of cutters are used on a cnc? Would it leave a surface that would just need sanding with say 240 then 400?
Henniep
Established Member
Hey, you guys from another planet. Way over the top of my cranial capacity. Best of luck, really hope you come right!
Ollie78
Established Member
Just thinking about this. I wonder if you could use some kind of etching method. Where you create a mask of a sticker or as we did a art college wax. Then expose it to acid or even a sandblaster like they do on glass and granite and stuff.
Ollie
Ollie
mrpercysnodgrass
Established Member
Im not sure using an acid would be the right way to go. Ivory is essentially dentine, Im no expert but I think acid would eat into it and spread out.
I think I will try to find a hand engraver as the ivory works very well with hand tools, so should be the safest method of transferring the design.
I will keep you updated and post a photo of the finished patera.
I think I will try to find a hand engraver as the ivory works very well with hand tools, so should be the safest method of transferring the design.
I will keep you updated and post a photo of the finished patera.
I do CNC engraving for work (check out the 2d section on my site - www.thebeast.co.uk )
The part you have has very little curvature. You don't need to model the profile, a proper engraving spindle (as opposed to a v cutter held in a standard spindle) will follow that amount of curvature, and more, without issue.
I had to do some gearsticks once for a vintage car job. They had way more curvature than what you are needing.
Again, a proper engraving spindle will follow the surface mechanically. The code itself needs to know nothing of the change in z.
The part you have has very little curvature. You don't need to model the profile, a proper engraving spindle (as opposed to a v cutter held in a standard spindle) will follow that amount of curvature, and more, without issue.
I had to do some gearsticks once for a vintage car job. They had way more curvature than what you are needing.
Again, a proper engraving spindle will follow the surface mechanically. The code itself needs to know nothing of the change in z.
Sporky McGuffin
Light entertainer
Ah - so the engraving spindle floats? My PCB machine does that but only a couple of millimetres.
Ollie78
Established Member
Fascinating I had no idea about this type of spindle as I only do wood butchery mostly on mine.
Is it a completely separate head or an add on bit for a conventional spindle ? Does it "float" in Z only ?
Ollie
Z only. So you won't get rotation around the curve of your part, but, if you look at similar parts, gear stick knobs, etc. very closely (and you may have to remove the infill to see) you will see this is normal.
Z travel could be whatever the designer wants it to be. But there is probably no point in it being that much as if the curvature is enough to warrant that much z travel than the angle of the cut staying in line with the z will probably start not to work. But for limited curvature of your part it is the solution without doubt. As I say, I've done similar.
Oh, one more point... You will need a nose cone on the spindle with a swiveling end. Without that you won't get proper reference to the surface. You can buy them for all the major spindles.
A final point to note - with this type of arrangement, because the spindle references off the surface by contact, you can run into issues with abrasion, especially as chippings build up.
I will not, for example, engrave non anodised brushed alloy. The surface is too soft so as to withstand disruption to the brushing from the swarf.
Ghosting (an echo of the cut) can occur on other substrates but this can usually just be polished off. It's mainly an issue where a specific surface texture (like brushing pattern) must be maintained.
For your job, I don't think there will be an issue, but give it some thought.
My spindle is an off the shelf gravograph, but the rest of the machine is custom. The z travel comes from a tiny precision ball slide table. I think it probably has 30mm of travel but I never use more than a couple of mm of this.
The pivoting nose cone that I mentioned in the last post is somthing that I use for flat work all the time also, as, if you are making a very fine / shallow cut in a "flat" material and there is any tiny deviation in flatness, then a standard nose will lift the cutter and, with a shallow v cut, alter the line width noticeably. With a swiveling nose cone this variation is, to all intents and purposes, averaged out / eliminated.
Sporky McGuffin
Light entertainer
Ta! My PCB CNC has float on the Z for engraving and a funny rubber-tipped shoe, so I'm guessing yours is a more advanced version of the same. Most interesting - if'n you have time, a photo would be grand.
