holding a part?

[Dave anderson]

Im making some little plaques they go on apartment doors for a new building . they are approx 3" hi by 5" long material is .125" 5052 aluminum . Im making 300 of these . the client wanting these only wants engraving on these no holes and such but wants them outside profiled with a chamfer mill . the problem im having is work holding ill set up to do lets say 4 at a time so a strip lets say 3.5" hi with lets say 4" on center for each . I do not have a vacuum plate ive tried double sided tape waste of time any ideas on work holding as he does not want any holes in the plates . I guess they are gluing them on the doors. they kinda look like a ford emblem you know the oval with 3 digits on each with a emblem above the digits . any thoughts on this would be very helpful thanks guys . Dave

[Dave anderson]

let me know if you think this would work lets say i contour outside with a .5" endmill but not to full depth maybe leave .020" then run my .50" chamfer mill around part then go back in with lets say a .250" endmill to finish final cut do you think this may work as chamfer width needs to be about .07" wide he doesnt mind . i can do it the conventional way with clamps but it will add almost double the time to this job and i fear anymore than 10 minutes at most a part will be taking a bath on this . i figure if i do it this way i can drill some holes between parts then bolt them down leaving approx 1" between ovals on the x axis doing five at a time .

[Fig sign]

Fast grip clamps on the alluminium plate premilled pockets (multi-part ) .

Mill left half on all the party,second setup mill right part .

HTH

[Fig sign]

Or mill one side ,change claps ,mill second ,cause you not milling all the contour depth.

You can get a lot of fast grip clamps various designs or mill yourself something from aluminium

[Bruce Caulley]

Dave,

 

Do you have access to a table router or trimmer?

 

I used to do a lot of parts on vacuum where we would not go all the way through and leave a "flash" on the back edge when broken off. We used a bench router with an edge trimmer in it to remove this flash. They are a carbide cutter with a bearing on the top. I know you don't have vacuum but you could make these as you described by screwing down a strip and leaving 10 to 20 thou on the depth and then breaking them out.

 

If you do use a trimmer in a bench router BE VERY CAREFUL as the thin material you are describing wouldn't need much excuse to turn into a frisbee.

 

I personally have done parts less than 1" square with this method. We used it so much that we made 2 router tables from 30mm aluminium with a minimun dia hole in it to suit the trimmer blade. Very stable.

 

HTH

 

Bruce

[Chris Rizzo]

Dave's idea sounds pretty good. Even buy a chepo router table for the shop.

 

Here's another quick and dirty option, a few more steps though....

-Start with .187 material.

-Put a whole sheet on your table...fewer tool changes the more you cut at once.

Cut to depth of say .130+. Make sure you contour around a bit extra width.

-Take sheet out of machine and rough table/band saw along flashing lines, to just break them into individual pieces. If you plan it right, it will be just straight rips on a table saw. 2 second operation, if you plan it right.

-Cut yer self some soft jaws & face backside of part to get your .125 depth...

follow?

[Chris Rizzo]

Oh, don't forget to engrave your shop name on the back while your facing them, if someone else is looking for similar work, they know where to go.

[Dave anderson]

thanks for the replies any other suggestions ?

[Dave anderson]

ps im using a 3 axis knee mill so i can only fit so many parts on table at once i figure strips that i can get four or five parts out of at a time .

[ytsudwas]

This may sound hard to believe at first but I've done alot of aluminum plaques this way.

Clamp a flat block of alum in the vise and attach the plate you are engraving and contouring with a quality, heavy duty, carpet tape. You obviously can't take real heavy cuts and you can't go too heavy on the coolant.

[Fig sign]

get the parts of regured depth and 3-5 mm more each side

make in alluminium plate multifixture .

Fast grip one side of them

Mill from outlide half of the part

mill half of engraving

M0

put second set of fast grips ,put some plastics

under grip or something soft ,if you will grip on the engraving

take off first set of grips .

Proceed with second half of the parts

 

+1 for tabs like routering way

 

Some other ideas

Put a plate of material on the alluminium plate

 

clamp it

drill some holes for bolts in a couple of places to make it rigid

M0

bolt it

Mill all your part from outside ,leave 0.5 mm of height ,mill engraving

with a small mill like 4 mm dia cut a proflie down under alluminium leave 3 tabs 1.5 length

take of bolts ,take off clamps ,brake parts with cutter pliers and clean tabs

[CAM-mando]

- In your sheet mill a rouw of profiles .100 deep.

- Engrave

- Mill Chamfer

- Mill Profile again a Z-.130 (Thru) but stop short of full profile leaving a small tab or two (as small as possible, just enough to retain the part.

 

- Break em off and deburr the tab.

[Dave anderson]

camando that sounds good is there a chamfer mill i can use that will do this profile without milling with endmill first so lets say i go with my chamfer mill about .110" deep if this can be done not sure there is a 45deg chamfer mill you can use for roughing if there is that may solve alot of the problem im haveing then go in after with an endmill and cut remaining of the part out.the chamfer mill i have is half inch at top and .250" at bottom let me know maybe there is different tool i can use .

[Dave anderson]

oh sorry camando i think you just posted exactly what i had said in my second post. i misread first line of your post mill to .100 deep the contours . ok that requires alot of tool changes same way i thought of doing it is there a chamfer mill that i can rough contour with as that would save one step as my machine requires manual tool changes. thanks Dave

[robk]

quote:

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is there a chamfer mill that i can rough contour with as that would save one step as my machine requires manual tool changes

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Is this what you need Harvey

[Fig sign]

Or this

http://www.carboloy.com/products/milling/a...ini/default.htm

[T_MALENA]

Have you tried the Mitee-grip invisible clamp? It looks like thick wax paper. You use it kinda like double sided tape. The stuff is clamped between a fixture plate & your part, heated to 200 deg., cooled and youre ready to cut. Reheat to remove part. I've used it to mill aluminum plates, they were 6"x8"x.06 it worked great.

[Matthew]

For 300 parts, I would use 1/4" material. Grip it in a vice on about .100" of material, engrave, mill the oustide and chamfer, them mill softjaws to grip the part on 100" on the outside profile and mill the back down and chamfer.

[Jim at Gentex]

The idea of leaving tabs is what I do most often when I need to fabricate a small thin part. As Iskander suggests, you can mill almost through leaving a few small tabs of material, snip the tabs away with cutting pliers, then deburr the edges. Works like a champ!

 

Another method I often use for small parts is to use thicker material as suggested above in this thread. What I do is start with a sheet of material that is at least .12 thicker than my finished part and I lay out the parts in an array so I can put tooling holes wherever I want between the parts. I mill a .1 deep pocket that is wider than each part to start, then I mill / engrave / chamfer or whatever using the floor of the pocket as the top surface of the part. Then I fill the pocket in with a 2 part resin called "Like-Wood" which 'captures' the part in the sheet by replacing the removed material with the Like-Wood. (One caution here. Sometimes I use a coating of mold release on the part at this point depending upon the type of material being cut. This makes the later step of removing the Like-Wood much easier if it doesn't bond fast to the part itself.) I then skim cut the excess Like-Wood level with the top surface of the sheet, flip the sheet over, and pocket each part to the correct depth to form the bottom surface of each part. The Like-Wood holds the part in place as long as I don't try to hog too aggressively. Then I bandsaw the rest of the sheet away which gives me the individual parts, then I chip away the Like-Wood from each part with cutting pliers, deburr, and inspect. A time consuming process...but works every time!! Also a great method for small 3D parts when all other methods of holding them don't work.

 

Jim teh been there done that many times!

[Chris Rizzo]

quote:

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small 3D parts when all other methods of holding them don't work

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I've got some of those...Do you apply the "like wood stuff" larger, and while it's in the machine, then re-cut it to establish a reference plane for subsequent flips?

[Jim at Gentex]

Yep...you got it. Works like a charm. The Likewood takes the place of the material you removed with a solid resin that will match the exact shape of the part when you pour it in, and hold the part suspended in the block of material when it hardens so you can machine the bottom surface(s).

 

You can apply it in or out of the machine, but I prefer in b/c sometimes the block of material will flex a bit when you release clamp pressure if you've removed a good amount of material. It takes about 20 min to 1/2 hr for the likewood to cure, then you can machine the top of your block of material to establish the reference plane then flip it over.

 

Info on the Likewood is found here

 

I use the #8007 which comes in 1 Gallon A and B kits and is great for holding most plastic and aluminum parts.

 

[A-ron1286490684]

We used to use this "Hotglue process" a long time ago at an old shop then I brought it to the last shop and it worked like a charm. It actually changed the way the guy bid the jobs after we got the process down. It's a long read but worth sharing and trying I guarantee!

 

 

The hotglue process involves the sandwiching of two pieces of material to eachother. One of these pieces of material, for the sake of discussion, we will call the "pallet". The pallet, I've found, seems to be most effective when made out of Mic 6 or double disk ground aluminum. This will start the job with a nice flat and parallel base to wich the work piece will be glued onto. The pallet will eventually have to be replaced after several sessions of machining if there are different type jobs to be glued down and machined but not after producing many many parts. If the pallet is located with an exact stop with the same toolpaths repeating the pallet can be used indefinately since the drill cones and profiles are never changed. The beauty of this glue down or hot glue process is the fact that the pallet allows you to hold jobs and profile right to depth without having to take the workpiece out of a vise and remove the material that was held onto by the vise jaws in a second operation. Also the part is free from bowing or torque that might distort tight tolerance jobs. It also allows you to machine jobs that might be otherwise impossible or at least very difficult because of the material thickness (or lack of it). Obviously there are limitations to the type of jobs that can be hot glued down. Any type of teflon will not stick to a pallet, most plastics will not stick properly or could have there characteristics changed, (if they do stick), by being heated to 300 plus degrees. Also there has to be some reasonable amount of surface area to the part to be machined for the glue to stick. I have hot glued materials as diverse as G10 fiberglass, 302 .012 thick shim stock to 17-4 ph stainless steels. Naturally there are limitations when doing steels or thick aluminum jobs that might make a convetional approach more practical.

 

The hotglue process starts with a prep to the sides of the pallet and the workpiece that involves a scoring step which is easiest with an 80 to 100 grit sanding to increase the surface area for the glue to adhere to. After the scoring a cleaning must be performed usually with uncontaminated acetone or denatured alchohol on a rag and a second swipe with a fresh side of the clean solvent soaked rag depending if there are cutting oil residues or other greasy type substances still left on the workpiece. Then the two pieces are heated to between 300 to 350 degrees on any type of hotplate or even range top. As the workpiece and pallet approach the melting temperature of the glue the gluestick will start to glide across the surface freely. It seems to work best if both the pallet and the workpiece are coated with the glue. The glue is a very common high strength glustick used in glue guns. It is important that the gluestick is the clear or semi-tranlucent type which resembles the color of dried silicon sealer. We have found that the ultra high strength gluesticks with the opaque creamy color are too brittle and have failed and tend to fracture off the pallet and or workpiece. After applying the glue to both sides of the workpiece there needs to be a squeezing step which I found worked best with a thick flat piece of aluminum for a base and an aluminum pressure plate for the top which not only draw the heat away but keep the pressure from the press or clamps from compressing the two pieces unevenly. These two pieces will last indefinately (the pressure top plate and the base plate) and require only occasional swipes with a razor blade to remove the glue wich is expelled from the sides of the sandwiched pieces between them. The remaining glue usually is a consistant .003 to .006 thousanths thick. After machining, the pallet should get a quick rinse with simple green and water so that the cutting fluid does not comprimise the next glue down on that pallet. Then simply put the pallet on the hotplates again, heat up till the glue releases and set the finished part or parts in a standard stoddard type shop solvent. The glue will dissolve within hours (or a bristle brush with some gloves will speed up this process). After the first glue down is performed on the pallet just wipe off the excess glue after heating and prep the workpiece as mentioned above.

 

A couple things to remember... the glue will become brittle if overheated it will turn brown and start to smoke. Usually the hotplates, rangetop, oven, or whatever is being used to heat up the pieces to be glued, will vary in temperature and a mark on the dial or a Raytech infar red temp gun will allow for consistent odor free gluedowns. Also the scoring and cleaning is critical to the process. This may seem at first like quite the involved process but will become second nature after a couple successful gludowns. Eventually, as we found, this will become a valuable tool in your arsenal of shop processes that changes not only the way jobs are approached but also the type of jobs a shop can consider bringing in the door.