Left hand helix endmills for thin floor parts and difficult slot?

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Hi Everyone, do any of you have experience using left hand helix endmills for thin floor parts? I am about to make a housing that is .020" thick on about 80% of the part. 1st op will be cake but the 2nd where everything becomes aluminum foil is concerning. I have made plenty of parts that have large thin floors that are .060" thick but never .020" over such large areas(4 x 4 in. roughly) I am planning on making a fixture to support every area that will end up very thin and was going to use some harvey downcut endmills to finish the floor after roughing it to about .08 thick with regular tools. I am just wondering if there is any secrets to using these tools. I attached two step files, THIN FLOOR is the one i am talking about and SLIT has one of the most messed up slots I have seen on a part. I would really appreciate any advice on these two parts I haven't really made anything quite like these before.

SLIT.STEP

THIN FLOOR.STEP

[gcode]

I've never done a .020 floor, but the downcut endmills make sense

I think I would run a decent corner fillet on the endmill and spiral out from the inside

I'd take a hard look at a vacuum fixture as well though at .020 thick

the channels  in the fixture might leave witness marks in the finished surface

 

[gcode]

5 minutes ago, gcode said:

the channels  in the fixture might leave witness marks in the finished surface

maybe a 2 piece vacuum fixture ???

the part sitting on a  plate with a .100 square grid of .050 holes which connect to a vacuum chamber below

that way there are no channels or o rings to distort the thin floor

 

 

[[email protected]]

Thanks, the guys on the floor mentioned doing a vacuum fixture. I haven't made a vacuum fixture before. somehow I have 13 years in this trade and have pulled off all my thin parts with fixturing, mitee bites, double sided stick and/or clay(for cavities). BTW this is a one off prototype i should check the quote to see how much time I have in the fixture before commiting to a vacuum fixture but in the end I am going to have to do whatever it takes to make it in tolerance.

[CEMENTHEAD]

I've done many of these. although really need to know the material.  makes all the difference. what is it Alum ? (cause aluminum foil comment) Titanium? Inconel? honestly tho. either way would do a .060 envelope outside flip .030 env inside, flip finish outside, flip finish all walls to the +.030 depth, then spirial inside thin floor pockets ramping in from center out, small tools and small radial step over. the .050 floor thickness is your rigitity. IMHO the area is too small to waste time on vacuum. you have nice walls to support the sides once you get there.

GL HTH.

[[email protected]]

Thankfully it's just 6061-T6. Cementhead, to do what you suggest would I be making a fixture for the ".060 envelope" op to sit in for cutting the ".030 env inside" op? I'm guessing that when you say .060 envelope you mean leaving .06 stock on all surfaces for that side? Anyway I appreciate the advice, did you happen to have any recommendations on the SLIT part as well... Right now my only guess is to use a .04 thick slitting saw 1st then place a shim in the .04 slot and clamp the tab down somehow before cutting the back of the tab thin.

[crazy^millman]

Thin part answer is yes that is what they are meant to do. I was exposed to them years ago. They were making different thickness pie shapes in a part in plastic. Thinnest one was .006 up to .035 in thickness. That side I wouldn't worry about that kind of en endmill on that part. I would rough that section within .1 thick and then leave that area for last. Then do a pocket toolpath helix start in the very most center and then Parallel Spiral out from there at the .02 thickness and call it a day. Use the strength of the .100 thickness to help you where you need it.

EDM the slot don't try to cut that with a slitting saw. I am afraid it will warp up that section. EDM will do a better job of keeping the heat and stress out of the part. You have no other choice then make sure to use WD-40 on the slitting saw and keep the SFM low. Get a Jewelers Saw that has many teeth on them verses a standard slitting saw. Keep the feed rate less that 5imp maybe not more that 1000 rpm.

[CEMENTHEAD]

17 hours ago, [email protected] said:

on the SLIT part

We have a bunch of Wire edms they slit quite well. Our burr depot has gotten real good at removing the recast.  

(I did attempt to finish thin floors with the wire before as well. but the heat deformed the floors "dished them")