Engraving aluminium question

[AdeV]

Hi All,

Right, I'm wanting to engrave a logo onto a fairly small piece of aluminium (approx 95x40mm). Due to the size, there's some fairly intricate detail, to the point where it looks like I'm going to need a 0.3mm cutter to get decent quality. The engraving BTW is going onto the cam cover of my Jaguar engine; and that throws up its own complications: I don't want to have a separate stick-or-screw on piece; I want it to be part of the cover itself. Whatever cutter I use has to stick approximately 2" out of the spindle nose, if I'm to be able to use the bulk of the 95mm width (actually I've got nearer 100mm, but I've taken 5mm off to cover spindle clearance issues).

I reckon there's 3 ways I can approach this, using in all cases a 0.3mm end mill:

1) Mount end mill in a home-made holder, in a standard DA collet holder. Upside = cheap and easy, Downside = potential cutter-killing runout, max RPM=4000, very slow cutting speed
2) Buy a spindle-speeder, mount cutter in spindle speeder collet. Upside = accurate, 20krpm top speed for faster cutting, less likely to kill the cutter. Downside = £2150 + 20% tax....
3) Make a dremel holder that fits on the spindle sleeve. Mount cutter in dremel. Upsides = cheap, high rpms, accurate if rigid. Downside = complex to make, tool breakage if I accidentally raise the spindle too high...

I must admit... I'm leaning towards #3...

Any other thoughts/ideas entertained.

PS: it's got to be a physical engraving. I intend to cut the logo, paint the entire cam cover British Racing Green, then mill off the paint around the engraving & across the rest of the patterned top, leaving the logo in contrasting BRG with a silver background.

[RobWilson]

Hi Ade

I used these http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Engraving-Cutters#Solid-Carbide-Engraving-Cutters with good resultes at 4300 rpm in the we denford cnc mill , ruff out with a 1.5mm end mill and finish with the engraving cutter . Still slooooow going 

Rob

[Spurry]

Ade
I've used a piece of silver steel of a diameter to suit a collet, say 12mm or 1/2", then drill to suit the smaller diameter cutting tool. Depending on how accurately you can make the hole on whether you need a spot of Loctite to secure.
Pete

[AdeV]

Hi Rob - I've seen a few places offering those "D" style engraving bits; are they reasonably strong at the sub-0.5mm size? As in, stronger than a typical PCB routing bit, for example?

I did contact a company who sells end-mill style bits at 0.3mm diameter (with 0.6mm flute length), G-wizard suggests I can push these reasonably hard, although I'd still expect to be sitting around for a few hours waiting for the results.

Pete - that was kind of what I was thinking. The PCB bits usually have a 4mm or 6mm shank, so I'd drill a suitable hole in a piece of steel, of a set depth, then cut down the outer diameter to suit whatever handy DA collet I have lying around doing nothing; in theory, I can do this without disturbing the work in the lathe so concentricity (provided I can spot the hole accurately) should be fine. I guess I'd need to ream it to size to get a perfectly round hole. Final ops would be to drill & thread a side hole for a grub screw, then each PCB bit would need a flat ground onto the side to lock it with said screw. That should, in theory, mean that if I do snap a bit, I can replace it without disturbing the Z-axis setting, given the likely small depths of cut, that would be important I feel. Balance at 4000rpm shouldn't be an issue, but if it's more than say 0.0001" out of concentricity, I'm sure I'll be snapping bits left right & centre at such slow speeds

That was my Plan A BTW... I was hoping to get some info from the company that makes/sells the bits before I splash out the £11 per cutter for a 0.3mm size... 

[philf]

Ade,

I second the use of a proper engraving cutter rather than an end mill. They are much more robust and, particularly if you buy them from China or HK, are very cheap. I have made them out of broken carbide end mill or drill shanks and they work fine.

How deep do you want to engrave? Obviously the diameter increases with depth and if you want a 0.15mm radius max engraving 0.5mm deep the tip would be very small.

Why does the tool have to stick out so far?

Cheers.

Phil.

[RobWilson]

Hi Rob - I've seen a few places offering those "D" style engraving bits; are they reasonably strong at the sub-0.5mm size? As in, stronger than a typical PCB routing bit, for example?

Hi Ade , yip there fairly robust as Phil mentioned  , I was using them on MS and SS  so Ally should be no problem , the thing with small milling cutters is getting rid of the chips,more so with ally  , its not a real problem with a single lip cutter .

If your engraving is large ,knowing you it will be    , may I suggest doing it sections ,just a thought .


Rob

[AdeV]

It's not a massive engraving - fits within a 95mm x 40mm box - but to get the level of detail I need I do need to use a tiny cutter - 0.3mm tip is the biggest I can use so it cuts the entire area. I could possibly rough it with a 0.5mm then use the 0.3 to finish off, I'll have to see if CamBam supports doing that.

Depth just needs to be deep enough to hold paint & allow me to take a tiny skim cut at the end - 0.1mm should do it. Or, I could skim it first & then engrave & paint, I'd just need to be careful not to let paint stay on the top surface. I was originally thinking 1mm deep, but I could get away with 0.5mm or thereabouts. The end mill I was looking at would do 0.6mm DOC.

Phil - the reason for the ridiculous stick-out is because I'm engraving directly onto a cam cover, which has a big lump sticking up to cover the drive sprocket - right by the bit  I want to engrave. I only have a 100mm flat space between the sprocket cover & the start of the ribbing, so I need to get within 1/2" (or less) of the bit that sticks up... since the spindle on my mill is quite large (BT30), getting close means a long tool...

[modeldozer]

Hi Ade.

Maybe one of these ER11 chucks,
http://www.ctctools.biz/er11-20mm-x-150mm-long-nose-shank-chuck-f66/
no afiliation, just a happy cutomer.

Abraham

[philf]

Ade,

I can picture your problem now.

An ER11 Straight Shank Collet Chuck would give you the reach for not too much money.

http://www.arceurotrade.co.uk/Catalogue/Collets/ER-Milling-Collet-Chucks-Straight-Shank

12mm Dia 150mm Long with only a 16mm nut diameter. Gets a bit more expensive if you haven't already got the ER11 collets. With a single lip engraving cutter you could set the cutting point to suit any runout - something you can't do with a spiral multi tooth end mill. (As you have already pointed out you would need to be within a midges.)

Have a look at http://www.ebay.co.uk/itm/10Pcs-3-175mm-10-20-Degree-0-1-0-3mm-Carbide-PCB-Engraving-Bits-CNC-Router-Tool-/371423014591?var=&hash=item567a896ebf:m:mul23ugmKRspv9PNAHQtCtw Cheap as chips.

As for setting the height I made a height setter for my CNC which seems very repeatable. The most simple of these is a piece of pcb sat on top of your work and the tool touching it makes a circuit. There's no give so you have to be very careful. Mine allows 2mm overtravel but breaks a circuit when the tool touches the top. I use a Mach3 routine which approaches it quite slowly until it sees an open circuit. It then backs off a little and approaches even more slowly.

Good luck.

Phil.

[Edit: I see Abraham has suggested something similar whilst I was typing.]

[efrench]

Would etching be a better choice for this?

[AdeV]

Would etching be a better choice for this?

Hmmm... that's an interesting idea.... I hadn't even thought of that option.

Time to go look at etching methods.... thanks! 

[rowbare]

A bit late to the game here, but another option might be a pencil air grinder.

bob

[polecat]

a bit late just read this engrave and use meths to cool rough out first and then do your final detailed cut fill the engraving let it dry and then linish off with wet n dry paper go down the grades the polish with solvol autosol should look great and be on there forever
polecat

[nrml]

Why not use your die sinker EDM?


Edit:Just realised when the original post was made. Apologies for the now pointless contribution.

[Beone]

I engrave cast ally house plates  .040 deep with 40 degree engraving bits with no problem. I have a great air bush set up to blow air with a very fine mist of plain water at the bit to cool it. Can't stand any lube as my router is wood.

[AdeV]

Thanks everyone for the further contributions. As is usual with my projects, I've not made any progress with this one just yet... so all additional ideas & concepts will be welcomed

nrml - I can't use the die sinker as I can't fit the cam cover into the tank... and I don't really want to go with a stick-on plate as it'll spoil the effect I'm looking for, i.e. I'd like it to look like it was engraved in the factory, not afterwards. Jaguar simply stuck a plastic sticker on there, but I'd like to think that if they'd had some wiggle room in the budget, they'd have gone with an engraving...

[nrml]

How about two or three colour anodising? It wont have the etched look, but it will look better than a sticker. The coloured cam covers could tart up the engine bay if you choose leads, tubes and bits to complement it.

[cwelkie]

Hi Ade - I'm late to the party and a long ways from expert on engraving but do have a touch of beginner's luck.

I wanted an engraved name plate for my 1/4 scale Gnome rotary (attached to the crankcase).  The letterings was going to be very small and on an arc.  Cambam made easy work of that - all the layout work was done in Cambam.

I used a shop-made engraving cutter (pointed ver; about 0.01" tip/10 degree angle).  A test on aluminium went pretty well to try and set depth-of-cut.  As long as I kept a steady stream of cutting fluid present and helped clear the swarf, my shop-made (Momus) router did a great job.
Here's a photo of the end result with a scale to help with size.

Good luck with your Jaguar project ... I drive an '86 XJS 5.3L - summers only!
Cheers
Charlie

[DMIOM]

Ade - please see your PM

Dave