Engraving Bit Feed speeds

[WCSG (Unregistered Guest)]

I'm using a .010 engraving tip 30 deg angle carbide bit. I'm cutting thru some gravotac 1/32" thick on top of burshed aluminum. Naturally the cutter will go slightly thru the Gravotac engraving the outline of characters and symbols into the aluminum, but when it does it's not turning out to pretty.

I have my SB set to 24K RPM's and .50 inch/sec anyone know if that's to fast or to slow? Or is this just the result

[paco]

Hi WCSG! (C'mon... don't be shy... Join in!)

What's wrong?... just a thought but 24 K RPM at .5"/sec. is VERY cautious approach... maybe too much... though you're using a probably very brittle bit...?

[WCSG (Unregistered Guest)]

So to slow a feed rate or rmp?

[paco]

WCSG,

my feeling is too fast a RPM and too slow the feed (depends; how is the chips from the kerf? Dust or small chips? How does it sound? Chattering?)... still, can't you share what is wrong about your current result so I (we) could help more... pics?!...

Small engraving on metal IS an interesting field...

[WCSG (Unregistered Guest)]

Here's some pics

http://www.thesignindustry.com/miscstuff/alum1.jpg

http://www.thesignindustry.com/miscstuff/alum2.jpg

http://www.thesignindustry.com/miscstuff/alum3.jpg

[bleeth]

I think the .010 may be a bit heavy. Talk to the folks at bits and bits. www.bitsbits.net (http://www.bitsbits.net)
I would try a .005 end and check my Z-zero very carefully.

You don't have to be going very deep into the aluminum to be cutting a pretty wide swath which considering how thin the aluminum is would tend to tear it like your photo shows. You also may need a little cooling lube down there and I think Paco is right that you are spinning fast.
Brady: You out there?


Dave

[paco]

Hi Eric!
(Now I know who you are!)

WOO!! Ask for pics and you get 'em!!!

Re-reading your first post (which I should have done before... I now realize that you're actualy cutting plastic... right?... trying to avoid touching/machining the ALU... right?), your problem seem to be related to Z height accuracy (your or machine accuracy?!)... you sure want to ensure A FLAT HOLD DOWN; probably vacuum...

Still, for cutting plastics (soft) you could feed some more and slow down the RPM.

[egastelum@westcoastsignco.com]

So say 20,000 and 1 or .75/sec?

[Brady Watson]

Yeah...I had to work today...Imagine that!


Yes...change your depth of cut to .005" and your RPM to 13-15,000. If you can, squirt either AlumaTap or WD40 on the surface to keep things lubed nicely. Your move speed will probably want to be in the .5 to .8 IPS range. Listen/watch the tool and it will tell you where it wants to be for speed using the above depth and RPM.

For material hold down, the easiest way is to use carpet tape with fiberglass cloth in it (at depot Duck brand ~ Either hi-traffic or indoor/outdoor) As long as your AL sheet is not bowed all over the place, you should be fine....but don't overdo it with the tape...you may not be able to get it off without bending the AL. You'll see what I mean.

-Brady

[WCSC (Unregistered Guest)]

Hmmmm,

okay have to try those speeds. So your saying instead of cuttin the 1st surface (Gravotac) at 1/32" change to .005"?

For a hold down I use double sided tape.

[Brady Watson]

Yes...run .005-.007" stepdown per pass. Also, it helps to run some type of coolant/lube on the surface ~ Which easily is washed off with Cascade and warm water solution to prep for paint if necessary (in the case of WD40).

-Brady

[WCSG (Unregistered Guest)]

k, will do

Thx all for all your output.

Paco! I don't use my name because I'm trying to dodge certain people :p

[paco]

Sorry for that...

8-o