Automated-Symbol Engraved On Hard Irregular Shapes(How-Who?)

[MitchJi]

Hi,

We need to engrave the folowing symbol on quite a few Irregularly Shaped Hematites:


Hematites:

A mineral form of iron (III) oxide that is highly paramagnetic

Hematite has the same crystal structure as corundum (ruby).

We've been hand engraving them with a Dremel which is a hassle. They are pretty hard and probably brittle. Another difficulty is the rounded and irregular shapes but we only need to put the symbol on about 20% of the Hematites, so we can select relatively easy shapes to work with.

If anyone has any suggestions on a procedure we can use to do them ourselves (preferred) or the best procedure (CNC, Water Jet, Laser, Plasma Cutter etc.) that we can hire someone to do for us I'd really appreciate the advice. Recommendations for who to hire would also be good.

Another option is if someone wants a job doing this for us please let me know. I considered posting this in the Classified Section.

 

[jonathanm]

you need a spring loaded diamond "drag" tip in either a cnc or manual engraving machine...

they are very common now and most engravers use them.....

EDIT: or laser engraver would also work....

 

[jonathanm]

http://www.2linc.com/engraving_mini.htm

see the animation on that page......

 

[bigmoose]

Sandblast them with silicon carbide. You can make photo masks. This link might help http://www.scmsysteminc.com/

 

[MitchJi]

Hi Jonathan and Big Moose,

Thanks!

 

[jonathanm]

there are a million different types and prices.....

If this is all you want to do, and you don't have to do thousands of them, you could probably get away with a small hermes type without a motorized spindle. In which case you can maybe pick one up for $1-200 on ebay or even for free if you ask nicely at an engravers (a lot still have them kicking around unused)

http://cgi.ebay.com/NEW-HERMES-ENGRAVER-SER-M47809-/320729970937?pt=LH_DefaultDomain_0&hash=item4aacfef8f9

If you want a more consistent finish / speed / higher quantities, then look for something bigger/stronger, with a spindle....

http://cgi.ebay.com/New-Hermes-Engravograph-Rotary-Engraving-Machine-MORE-/390331687155?pt=LH_DefaultDomain_0&hash=item5ae194e0f3

The way these things work is you make a scaled up template version of your symbol on a plate of metal. Then you trace it out with a stylus on the end of an arm....the linkage moves the engraving head through a reduced version of the same movement.......

http://en.wikipedia.org/wiki/Pantograph

EDIT: oh, the question disappeared!

if you're going for any quantities or more symbols, you'd be much better served with a cheap cnc machine......

 

[liveforphysics]

I have a CNC machine, but if I had to do this job, I would buy a plotter for $350, and cut masking stickers that just expose what I want etched into the surface. Then, like Moose said, sand-blast would be fine, but I would experiment a bit with some glass etching acid pastes.

Apply masking stencil sticker. Swipe q-tip with glass etching paste over it. Wait a couple hours. Dump them all into a bucket of baking soda water and leave over night. Remove and clean them up.

 

[MitchJi]

Hi,

Luke and Big Moose:
Thank you very much but setting it up sounds like too big a project (for me).

EDIT: oh, the question disappeared!

there are a million different types and prices.....

If this is all you want to do, and you don't have to do thousands of them, you could probably get away with a small hermes type without a motorized spindle. In which case you can maybe pick one up for $1-200 on ebay or even for free if you ask nicely at an engravers (a lot still have them kicking around unused)

If you want a more consistent finish / speed / higher quantities, then look for something bigger/stronger, with a spindle....
(sold for $450 + $95 shipping)

The way these things work is you make a scaled up template version of your symbol on a plate of metal. Then you trace it out with a stylus on the end of an arm....the linkage moves the engraving head through a reduced version of the same movement.......

http://en.wikipedia.org/wiki/Pantograph

The question disappeared because before your post, based on my own ebay searches I thought these were all to expensive but free to $550 are well within my budget. Thank You Very Much!

How feasible is a non-motorized spindle for hard (feel like metal) stones?

How much might it cost (rough ballpark) to have a template made?

What do you think of this older New Hermes Unit? I think its either in good condition or needs minor repairs. Are they fairly simple to repair and are parts available/affordable?
http://www.publicsurplus.com/sms/all,ca/auction/view?auc=594219

Auction #594219 - New Hermes Engraver with Engraving Material

This New Hermes engraver comes with a full package of engraving material to make those snazzy looking office placards. This New Hermes engraver is perfect for all of your engraving needs.

Condition: UNKNOWN

Thanks Again!

 

[jonathanm]

Well I haven't really used one but I have had a play around with one.

Gotta love publicsurplus.com. If that's in your area I would go for it. There's not much can go wrong with them, they're pretty simple mechanically. That one has a motor and spindle on it. The motor might not work, or you might need to replace the belt, etc.

I know that some people don't use the motor, basically doing "scratch engraving" most of the time. You might need to pass the engraver back and forth over the same bit a few times to get the depth you want. Even just scratch engraving works on most metals and even glass.

Also, you may not even need a diamond tip - carbide might be fine.....dunno anything about your material.

Why not try scratching one of them by hand with a carbide drill bit and see what happens? If it looks like it will work then you could get a machine, try scratch engraving and rotary with a cheap carbide tip and move to diamond if it warrants it.

Like anything else, you are gonna have to experiment a little bit unless you can find someone who has engraved that specific material before.

As for the templates - I dunno but I wouldn't expect a lot - any local shop should be able to make it easily and cheaply. To get started with your experiments you could just make something yourself and carve it out of a small piece of wood or plastic..

Good luck!

 

[jonathanm]

According to this, hematite is 5-6 on the Mohs hardness scale. Diamond is 10, and tungsten carbide is around 8-9 I think.

EDIT: whoops forgot link.....

http://www.mineraltown.com/infocoleccionar/mohs_scale_of_hardness.htm