Plate milling with cutouts

Racecar · May 17, 2018

I am milling 6061 aluminum 1" thick on a Haas VF2. I'm starting with a square plate 10x10, the outside of part ends up being almost oval, there is some pocket milling in the middle, but no holes.
I can clamp down the corners and mill the pockets, then cutout the oval exterior shape, but when the cutter make the last pass, the part will be free and may bounce off the cutter.

Any ideas appreciated on how to hold down this part, when it is cut free from the clamped corners.
The only idea I have is to make that final cut half way around, then stop the machine and swing a big clamp over the middle of the part.

What do you do when a big part is going to be cut free of the clamps, and you can't put any holes in it to hold it down.

Thanks

CGornet · May 17, 2018

I know a lot of guys that use an elastic low to mid viscosity super glue for workholding. Have never needed to try it myself, but have a project coming up that I plan to try it.

Mstcnc · May 17, 2018

I use vacuum to clamp Al parts.
Even quite small ones will do just make final cut thin.
Or leave tabs which will removed manualy after machining.

Regards Mika

706jim · May 17, 2018

Or possibly make up a plug that fits one of the pockets and can be used as a clamp to a tapped hole or two on a fixture plate below the part.

HuFlungDung · May 17, 2018

I use ordinary strap clamps and M0's. Yes, you can clamp with M0's

First mill the outer profile down to leave maybe 1/8" material at the bottom of the groove. Mill this profile groove somewhat over the width of the tool so as to provide clearance between the tool and most of the waste for the next phase when you cut the part free of the waste.

Start with 3 strap clamps to hold the part and mill the first quadrant and have the machine pause with M0. Move one strap clamp at a time so as to clear the pathway for the next quadrant. You can also add extra strap clamps to hold the waste if not cut completely free. Always have at minimum, 2 clamps applied to the part to keep it from rotating under cutting forces.

DMF_TomB · May 17, 2018

Racecar said:
I am milling 6061 aluminum 1" thick on a Haas VF2. I'm starting with a square plate 10x10, the outside of part ends up being almost oval, there is some pocket milling in the middle, but no holes.
I can clamp down the corners and mill the pockets, then cutout the oval exterior shape, but when the cutter make the last pass, the part will be free and may bounce off the cutter.

Any ideas appreciated on how to hold down this part, when it is cut free from the clamped corners.
The only idea I have is to make that final cut half way around, then stop the machine and swing a big clamp over the middle of the part.

What do you do when a big part is going to be cut free of the clamps, and you can't put any holes in it to hold it down.

Thanks

.
.
double sided .030" foam tape stuck to 1/8" masonite board. at least it works for me usually the past 40 years machining. if nothing else cutting into 1/8 masonite you wont cut into table or parallels

DavidScott · May 17, 2018

Since I get to have design input on most of the parts I make I radius the outside edges where I clamp them on the first op. I also really like vacuum but the size of your plate at 1" thick will be pushing it. It may work with but keep your cutting forces as low as possible, smaller diameter free cutting end mill, say 3/8" 3 flute Destiny Tool Viper would be my pick. I absolutely would not rely on vacuum to do the rough work, you do not want to helicopter that size of plate!

Vacuum would work fine to finish the outside profile IF you locate the part with the pocket on a fixture so you only rely on the vacuum to hold the part down. You should be able to get around 1000 lbs of down force with vacuum. Vacuum and good fixtures will allow you to do a lot, for best results I keep the parts about .0005"-.001" smaller than the fixture pocket, you do not want them to move around.

greggv · May 17, 2018

On a 10 x 10 plate the pockets can't be too big, I just machine them away. No problems with pieces getting loose and breaking something, which would probably pay for the extra time involved.

dandrummerman21 · May 17, 2018

Racecar said:
The only idea I have is to make that final cut half way around, then stop the machine and swing a big clamp over the middle of the part.

What do you do when a big part is going to be cut free of the clamps, and you can't put any holes in it to hold it down.

How many do you have to run?

Do what you said. Don't mess around with tape or glue, vacuum table would be overkill and might not hold it well enough anyway for that last "cutoff pass". Just position clamps where they won't get hit, run around half of it (I usually do left+right first, then top+bottom), M0, move clamps (put NEW clamps on where you cut already, then remove old clamps after the new ones are there), and hit cycle start. E-Z

Clamped on bottom and top, to cut left and right

Cut left and right, move clamps so we can cut bottom and top

Cut bottom and top, and drilled the holes.

keep it simple.

carbonbl · May 17, 2018

If your plate is being milled down from the starting thickness, and you are doing multiple parts, it might be worth using Talon Grips (from mitee bite) or some similar clamps and soft jaws to cut the profile and pockets in one operation, then flip into the soft jaws and face mill the plate to final thickness. I do this all the time if my starting stock is at least .060 thicker than the final stock and flat/rigid enough. If you don't want to buy the whole talon grip jaw set, you can buy the small clamps separately and, depending on part geometry, mill pockets into your soft jaws so both ops use one set of jaws.

AARONT · May 17, 2018

Leave a .01" foil on the bottom of the part. This will be enough to hold the part in place, but will also be thin enough you can punch through it and pull the exterior material away. A quick debur and you're done.

Racecar · May 19, 2018

Wow, A lot of great ideas there. That gives me plenty of methods to try out. Thanks to everyone that contributed.

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Plate milling with cutouts

Racecar

Plastic

CGornet

Aluminum

Mstcnc

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706jim

Titanium

HuFlungDung

Diamond

DMF_TomB

Diamond

DavidScott

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greggv

Hot Rolled

dandrummerman21

Stainless

carbonbl

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AARONT

Stainless

Racecar

Plastic

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