A new product from start to finish

[KeithB]

One of our customers wanted us to make some brackets for mounting one end of a hydraulic cylinder. The small quantity involved (about 100 or so pieces) makes production methods such as die casting in one shot or extruding and machining impractical. The only way to make this small quantity is by machining the part from a solid billet.The basic part is 1" x 1" x 2.5". Our customer wanted us to make them out of 1" x 1" stock. While that would use the least amount of material it would mean the the cutters that would cut the material away to make the ears would be spending a lot of time entering and leaving the cut. It would simply not be cost and time effective. My way to make the part is as follows:

1. Cut a 1" x 3" bar into pieces 12" long. This gives me 12 pieces from a 12' bar.

2. Drill the 20 mounting holes for 10 pieces spaced on 1.2" centers. Center drill holes along the edge of the piece on 1.2" centers offset by .6" from the mounting holes. These will be used as a guide when cutting the pieces off in the cutoff saw.

3. Flip the piece over and cut away all the material to generate the profile. Note that the root of the ears have a .12" radius and not a sharp corner. A special 1/2" diameter end mill with .12" radius corner was used for the finish passes.

4. Cut the individual pieces apart.

5. Mount the pieces in a fixture and mill the profile of the base.

6. Mount the pieces in a different fixture and mill the profile of one ear and drill a hole in one ear. Flip the piece 180 and do the other ear.

To make this piece I had to write 8 CNC program, make a special set of vise jaws, and two fixtures, one with several parts. If we make more of these we will be set. I will note that the base milling fixture required handling two 5-40 screws to mount the part. When I made the ear milling/drilling fixture I opted to make a fork clamp and screw that is held captive so no fiddling with little bitty screws.

The basic part. Looks a lot like a bracket for a bathroom stall wall. We checked. Nothing off-the-shelf available.


A screen shot of how I see a gang of parts.


A screen shot showing the parts in the billet. The dashed lines show where they will be cut apart.


Had to make a set of 12" long vise jaws to hold the foot long billet properly.


Here is a shot of the bottom of the 12" bars showing the bolt holes and cutoff center drill spots along edge.


Here is a shot of a bar mounted face up. You can see the profile and the mounting holes along either side.


Here is a corner radius end mill used to finish sides and bottom of ears with proper root radius.


Here is bar getting cut into individual pieces. Note saw blade lined up over center drill spot.

 

[KeithB]

Continued...

A simple fixture to mount individual pieces on to mill perimeter of base to size. The profile is smaller than base and raised up so cutter can cut past bottom of piece to make clean corner/edge.


Here is individual piece mounted to fixture with two 5-40 screws prior to cutting. The screws were a real PITA!


Here is part finished at this step.


Here is last fixture, a simple pocket cut into a piece of 1.25" plate and anchored upright in vise.


Here is part mounted ready to have top ear drilled and radiused. The fork clamp and captive screw make this fixture less fidgety fumbly than the prior fixture.


The part before and after finishing ears. A little deburring and this batch of parts is ready!

 

[JonB]

I love seeing your processes, and reading your excellent explanations is a huge bonus.
I can only imagine how great of a teacher you were (and still are).

 

[Pistolero]

Very nice, Keith. I am sure that the "extrude and machine" influenced your planning. Basically, since the quantities are
too small to justify extrusion, you made the extrusion from solid and then went on from that.

Cool. I haven't ever worked on this sort of production stuff, it takes a different outlook, I can see, from thinking
about making one, which is almost always what I am doing.

 

[KeithB]

Your reasoning process is correct Bill. This is our market niche. If you need a million+ you might could justify an extrusion die and a couple of special shearing/punching fixtures. If you needed a couple hundred thousand you could just get the extrusion die and do some CNC milling to make profiles. If you only need two or three you could make them from 1" x 1" stock using a Bridgeport and a belt sander. But for making 100 to 1,000 we can usually make enough simple tooling and fixturing combined with a little creative thinking to make them affordable for the customer and profitable for us.

This is for my aircraft parts dealer customer. We have done a lot of stuff for them that started out as one of a kind parts whittled out of god knows what with absolutely no thought of quantity production. But whatever it is works, and somebody else wants one like it, and then a few more, and then they come to us to figure out how to "standardize" the part and process the machining steps so it can be made in bulk at a low enough cost for everyone to be happy. And it usually works out fairly well. We hit our time estimate on this part pretty closely and our price is fair to us and our customer.

 

[Pistolero]

Occasionally, the topic of "what would it cost to make....." or "how would you make....." a particular item will
come up with friends. I make it a point to ask the first question of "How many are you going to make?"
If the answer is 1, there is a particular answer on how to make it.
If the answer is 10, it might not be different than 1, but it may be.
By the time you are making 100, the answer is definitely different than 1 (fixtures and CNC programs).
By the time you are making 1,000, thing usually change a bunch- like a sand casting or extrusion to get nearer net shape.
At the real, serious production level, things like investment casting, forging and die casting come into play, where the
up front costs are high - like many tens of thousands of dollars, even hundreds of thousands, but the cost per unit will
drop dramatically, so that the net production run, of say 1 million units, will easily pay back the up front investment in
tooling - casting dies, forging dies, etc.

I am no expert on this stuff, but have been exposed to it in my job, and we often were stuck because we rarely built over
1,000 of anything and so frequently we were doing things "inefficiently"...but the right way, really. That $100 automotive
part could easily cost $1,000 if it were made in batches of 10.

Bill

 

[freebullet]

Beyond being a top notch machinist your a great teacher, Keith.

 

[Tomme boy]

Awesome! I worked maintenance at a hot and cold extrusion plant here for about 10 years. Metform or MacLean Fogg. We had some HUGE mechanical and hydraulic presses. I used to have to fab up a lot of the feed systems for all the different parts they ran.

It was pretty neat watching a cold rolled steel rod get smashed into every type of nut and bolt, gear, ball joint, axle locks........ Their bread and butter was the 2 piece wheel nuts on every semi and other heavy duty truck or van made.

I learned more about factories and production at that job more than any other I have had since. I wish I still worked there. They had 2 lines set up for phosphate coating(parkerizing) One was a heavy coat and one was a light coat. The light coat was what most gun parts were done with. We parked A LOT of gun parts on the side on 2nd shift when I was there.

 

[Bret4207]

Nice photo essay Keith! Just out of curiosity, what happens to all the swarf and left over bits and pieces? Years back there was a market for that stuff if you could ID the material ahead of time.

 

[KeithB]

We don't produce enough chips for anybody to want to buy them. And we would have to certify that there are no other metals mixed in, and since we run mixed metals on our machines that is impractical. So they go to the dump. Solid material which can be clearly identified can be sold for scrap, the last time I sold 6061 aluminum chunks it was $0.30/lb.

You saw how much material gets cut away on this product. We make another product called a Supertrack which we mill from a 3/4" x 3" x 14-7/8" aluminum billet. My CAD system and my shop scale both tell me that we mill away 83% of the material to make the final product. We have several other products which have 60+% material removal

There is a story about a famous artist who explained that the beautiful statues he made were always there, he just had to remove everything that was covering them up. Us folks in the material removal biz can really identify with that legend.

 

[Gary]

Tremendous waste, at least it seems like a waste. I and I'm sure others here would buy some of the drops, ect .

 

[KeithB]

A while back I had a sign up list and shipped out 6 or 7 boxes of drops and scrap to some of the members here for the price of shipping only. And when we move to our new building I plan to clear out a lot of scrap and would be glad to send you (and others) a box under the same conditions. Consider yourself on the top of the list right now, be glad to send a box of stuff your way.

The waste is high, and unfortunately most of it is in the form of chips, and unless you have an aluminum smelting rig in your closet (I don't) then those are truly waste and not economically recyclable on the scale we are operating. But any of the solid pieces you are welcome to.

Edit to add: I've made this offer before and will repeat it now. If there is a project you are working on and you need some stock of a specific size please feel free to contact me. If I have a stick of anything the right size on the rack that I can cut off I'm sure we could make some kind of deal.

 

[Pistolero]

Thanks, Keith. I have several times pulled a piece of stock from that box I got from you and used it on a project.
When you are moving, put me on your list of folks willing to pay shipping for a "care package" from your scrap
bin.

It would seem like someone would be willing to melt down barrels of aluminum chips, but I guess the cost of
fuel would be more than the value of the scrap aluminum bars that were the result.

Bill

 

[KeithB]

Its the contaminants that would need to be removed.

 

[Brad]

I would think that the time it takes to keep the chips and such all separated isn’t worth the value of said chips at the scrap yard.
Time is money

 

[Pistolero]

Yes, and time plus fuel to melt it down. And as Keith says, once it is contaminated.....all bets off.

 

[Gary]

FANTISTIC!! Keith, where I live NOBODY offers to sell drops or cut offs. I'll look forward to a box of cut offs, ect. Thank you so much.

 

[wquiles]

Loved the story and photos. Nice work Keith!

 

[Ole_270]

I spent a lot of years in a machine shop doing that sort of thing, mostly aircraft contracts. 3,4 and a little 5 axis CNC milling towards the end of my time there. They would hand me prints and a computer file of the solid model part and say, "here make me some money". Pretty amazing the pile of aluminum chips you can work up running 10,000 + rpm at 200+ ipm feedrate with 1.25" diameter and larger tools. Had a lot of Makino horizontal mills tied in cell systems. 1 or 2 guys keeping 4 large machines going all day. Glad I'm retired.

 

[KeithB]

There are some amazing cutting tools available now days and if you have the horses you can indeed turn a billet into chips very quickly. I liken it to the old cartoon showing a guy running a tree through a grinder to get one toothpick.

Our next milling machine will have a10k rpm spindle, that’s just barely fast enough to run an 1/8” end mill efficiently in aluminum. Right now our mill has a 5k spindle, we could cut the time on several jobs we do by (almost) half with a faster machine.

Go much faster than that and you start having dynamic balancing problems, even to the point of needing to use shrink fit tooling.