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Machining intersecting radii/cylinder

sfriedberg

Diamond
Joined
Oct 14, 2010
Location
Oregon, USA
That sharp V bit to remove the fillet still requires the part to move to keep the tool tip in contact. If we are going down the manual route, I would be better off setting it up on my Brown & Sharpe with the head tilted every which way and geared up to mimic the lead necessary. But that would only do half the part, so I would have to machine all of them on one half and then machine the second half.
Yes, it does. That's where a shop-built machine can have advantages over something like a Gorton. Rig your part and the master to rotate in synchrony around the horizontal axis. Add a short slide motion (interlocked so it's only permitted when the rotation is at its max/min) if you need to continue the sharp inside corner down the vertical length. Maybe "lathe duplicator" (like for mass producing wooden gunstocks) is a better image than 3D pantograph, although I'd still want the reducing action myself.
 

Fal Grunt

Titanium
Joined
Aug 5, 2010
Location
Medina OH
can you share the dimensions of that drawing?
I don't have a drawing for it, its just something I made up quick with random numbers. I can dimension those random numbers if you had a thought you wanted to try? If you want I'll output it as a step and you can play with the model.
I would make that as two parts and weld or solder them together. Make them just like the mating part with a slot in the vertical cylinder to accept the side piece.
I had briefly considered making them two parts, but I guess I couldn't figure out a way to weld them together without then needing to machine them to hide the fact they are welded.
Hi Fal Grunt:
What material do you want to make these from?
Since you can't accept a radius at the intersection of these two basic shapes you have to either remove that material (5 axis with cone shaped cutter or sinker EDM) or you have to displace it out of the way (coining die).
Either way, your choice will depend on what it's going to be made from.
If the material is ductile enough to coin, the die is pretty easy to build.
Make it out of S-7.
You can probably just squeeze it in a milling vise, but if not a little hydraulic press will do it, or in a pinch, a small sledge.
When you squeeze it, the displaced metal will make it want to elongate...expect to have to trim it back to length.

So the protocol is to mill what you can, then drop it into one half of the die, put on the other half and squeeze the piss out of it to just pick out the corners, pop it back out, trim off the free end and then chop it to length.
I've done it (lots faster and cheaper than sinker EDM) and it works, but I was using a pretty ductile material (Leadloy).

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Anything heat treatable for wear.... for casting I looked at 8620 and 4140. In reality they could probably be 1018.

I don't have any experience with forging dies, but to a certain degree I guess they can't be THAT much different than a stamping die. If I had enough tonnage I'd stamp the damn things. A friend and I talked about building a little forging die, but they are so damn small I didn't have a lot of confidence in it working. Maybe I should just make a single out die and see what it does? My friend has a 25T hydraulic forging press and furnaces so that end is taken care of.

Coining the semi machined part might work just as well. I've got a 3 ton Greenerd, not great, but it works. I've got access to bigger presses, but they are all manual including a 20T Greenerd. I'll machine up a couple prototypes and make a quick and dirty "coining" tool and see what happens.
 

Fal Grunt

Titanium
Joined
Aug 5, 2010
Location
Medina OH
Here's an idea...

Instead of making just this part, how about you also make the mating part, and ONLY
sell them as a set.. If big business can do it, Why the F* can't we????
Ha! well, im hoping to make lots and lots of money selling to the people that are missing this little part :rolleyes5:
Yes, it does. That's where a shop-built machine can have advantages over something like a Gorton. Rig your part and the master to rotate in synchrony around the horizontal axis. Add a short slide motion (interlocked so it's only permitted when the rotation is at its max/min) if you need to continue the sharp inside corner down the vertical length. Maybe "lathe duplicator" (like for mass producing wooden gunstocks) is a better image than 3D pantograph, although I'd still want the reducing action myself.
If I was making any quantity that would be an approach. I used to work for a company who built production automation and specialty machines just for tasks like this. Unfortunately this job doesn't justify several hundred thousand dollars investment.
 

EMTech

Aluminum
Joined
Feb 10, 2022
Location
South Bend area
What are the tolerances you are wanting to hold?
Seems to me like it could be done on a 4th axis rotating around the cylinder.
5th axis would be easier.
It would either need a relief allowable or a surfaced finish on the radius.
Send me the .stp file. I will play with it when I have time.
 

Fal Grunt

Titanium
Joined
Aug 5, 2010
Location
Medina OH
What are the tolerances you are wanting to hold?
Seems to me like it could be done on a 4th axis rotating around the cylinder.
5th axis would be easier.
It would either need a relief allowable or a surfaced finish on the radius.
Send me the .stp file. I will play with it when I have time.
Tolerances are pretty loose, I haven't made a drawing up yet, but I think I designed everything plus/minus .002"
Yeah..that would be my approach too..fixture and silver solder them But I suppose it depends on the material and application.
You are clearly 1000 times more skilled than me at silver soldering. :D
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi All:
For those who advocate silver soldering or welding these. there are a couple of problems you would need to overcome:
- First, these parts are pretty small so fixturing them would be an interesting challenge.
Nothing that can't be overcome, but a challenge nonetheless.
- Second you'd need to make the fixture out of something heat tolerant...maybe inconel or titanium.
- Third you need something that solder doesn't stick to readily...inconel or titanium.
- Fourth your fixture needs to maintain the proper solder gap.
- Fifth, your parts need to be heat treated at some point, so you have to make them out of something that retains hot hardness like H-13 and use a low temperature solder, so you can harden them first and then solder them together.

That's a lot of problems, and you need to do it at some (thankfully modest) scale...at least 50 or 100 of these parts for the first run.

Laser welding them creates a different set of challenges;
- First, the penetration and therefore strength is not great unless you really pour the coals to it or vee the joints and use filler wire.
- Second, welding it puts a fillet at the joint...you don't want a fillet at the joint.
- Third, you have to fixture them as with soldering.
- Fourth, the quality of the weld depends on the quality of the process control, so to do it reasonably reliably you're talking CNC laser welder in an inert atmosphere and etc etc.
- Fifth, welding hardenable steels is problematic (hot cracking) so your material choices are restricted to something you can case harden or nitride, or else you need to develop the welding process so you can get reliable welds.

You can see where this is going cost wise.

Given that; casting them, coining them , EDM burning them, all start to look more attractive.
Of those coining remains the most attractive to me because the process is so simple and predictable (and cheap).
The OP can make the dies cheaply and easily and give it a go without investing much more than a bit of S-7 and a half day of time.
I wouldn't be surprised at all if that's how they were originally made 140 years ago...coining has been around for a very long time.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
Slightly oversize machine each "leg". then silver solder the two legs. polish it up in the mill and hit the intersection with a safe edged needle file?

machine as you would (your ability here way better than mine), then run a pencil path in fusion, defining the tool as a ball end <bigger* -- edited out> than the lollipop you would really use. this would undercut the intersection.

*smaller programmed mill, real mill bigger

reason, its way to late to be up
 
Last edited:

memphisjed

Stainless
Joined
Jan 21, 2019
Location
Memphis
implmex - double flow a hard silver solder should get you up to heat treatable temperatures later. Rio sells all the fancy holders for holding and soldering, they even have a playdo you can mush your part into then solder.
 

angelw

Diamond
Joined
Sep 10, 2010
Location
Victoria Australia
Hello Marcus
The fixture could be simplified by providing for a dowel location between the two components during the machining of each and the solder gap also simplified by a small solder shim and bulk solder in a controlled atmosphere furnace; in fact, you could heat treat and solder in the one operation with a suitable material; cost would be relatively minimal.

Regards,

Bill
 

Comatose

Titanium
Joined
Feb 25, 2005
Location
Akron, OH
I hate to say the A word, but have you considered doing this part additive? Selective laser sintering is all about the volume of the part, and what, 100 of these would fit in a cubic inch with spacing? Additive doesn't care about geometry. Surface finish might be limiting though.
 

implmex

Titanium
Joined
Jun 23, 2002
Location
Vancouver BC Canada
Hi comatose:
You wrote:
"Additive doesn't care about geometry"

Yeah that's all true, but the precision remains problematic.
I have some parts I did for a project a bit bigger than this one that were first 3D printed and then MIM molded and sintered.
The difference is pretty stunning:

DSCN5521.JPG

You're never going to convince me that the 3D print on the right can be interrogated accurately for dimensions...the resolution is just too poor.
So yeah...in principle...
But the reality is still a long ways from the promise with 3D printing and it really comes out when the parts are small.

BTW this project was done in 2020, so it's not that old and I haven't seen additive doing all THAT much better in the meantime.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 

mhajicek

Titanium
Joined
May 11, 2017
Location
Minneapolis, MN, USA
Early on you mentioned you could accept a clearance corner. Do that and it can be done on a 3 axis mill with ball endmills in a few setups, or faster in fewer setups with four axis.
 

Fal Grunt

Titanium
Joined
Aug 5, 2010
Location
Medina OH
Hi All:
For those who advocate silver soldering or welding these. there are a couple of problems you would need to overcome:
- First, these parts are pretty small so fixturing them would be an interesting challenge.
Nothing that can't be overcome, but a challenge nonetheless.
- Second you'd need to make the fixture out of something heat tolerant...maybe inconel or titanium.
- Third you need something that solder doesn't stick to readily...inconel or titanium.
- Fourth your fixture needs to maintain the proper solder gap.
- Fifth, your parts need to be heat treated at some point, so you have to make them out of something that retains hot hardness like H-13 and use a low temperature solder, so you can harden them first and then solder them together.

That's a lot of problems, and you need to do it at some (thankfully modest) scale...at least 50 or 100 of these parts for the first run.

Laser welding them creates a different set of challenges;
- First, the penetration and therefore strength is not great unless you really pour the coals to it or vee the joints and use filler wire.
- Second, welding it puts a fillet at the joint...you don't want a fillet at the joint.
- Third, you have to fixture them as with soldering.
- Fourth, the quality of the weld depends on the quality of the process control, so to do it reasonably reliably you're talking CNC laser welder in an inert atmosphere and etc etc.
- Fifth, welding hardenable steels is problematic (hot cracking) so your material choices are restricted to something you can case harden or nitride, or else you need to develop the welding process so you can get reliable welds.

You can see where this is going cost wise.

Given that; casting them, coining them , EDM burning them, all start to look more attractive.
Of those coining remains the most attractive to me because the process is so simple and predictable (and cheap).
The OP can make the dies cheaply and easily and give it a go without investing much more than a bit of S-7 and a half day of time.
I wouldn't be surprised at all if that's how they were originally made 140 years ago...coining has been around for a very long time.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
Great post!

I hate to say the A word, but have you considered doing this part additive? Selective laser sintering is all about the volume of the part, and what, 100 of these would fit in a cubic inch with spacing? Additive doesn't care about geometry. Surface finish might be limiting though.
I 3D printed the parts several times while I was designing them. I see a lot of people extolling the benefits of printing, but I haven’t seen it myself. Especially for steel.

Now, if I had the money, I’d make a powdered metal (not MIM) die but I doubt the place I used to make tooling for would ever run someone else’s parts. I don’t even know of a company that does that kind of work for the market.

That being said for the application, some of the higher end printers can print a hard polymer that would likely function just as long as a piece of steel. Convincing customers of that. . . .
Early on you mentioned you could accept a clearance corner. Do that and it can be done on a 3 axis mill with ball endmills in a few setups, or faster in fewer setups with four axis.
That’s likely what will happen.
 

Metalurgent

Aluminum
Joined
Feb 14, 2013
Location
New York City,
American Beauty has a range of resistance soldering equipment where carbon electrodes can be pre-machined to act as holding fixtures. I have a tweezer set that I use sometimes for little stuff. You can machine a small recess to hold a scrap of silver solder between the mating parts, add the flux, press the foot pedal and hold 'til cooked or link it on a timing relay for multiples. Slick as snot when it works.
 

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Comatose

Titanium
Joined
Feb 25, 2005
Location
Akron, OH
If polymer is strong enough (30ksi, tops?) maybe cast out of Zinc? Some of the zinc alloys are pretty strong and zinc casting is easily an in-the-shop project when it needs to be.
 

magno_grail

Cast Iron
Joined
May 29, 2014
Location
ca, US
Late to the party but is there any reason you cannot make it in two pieces, one with a socket and the other with a post and press or bolt them together?
If you have a 4th axis you could use a slab cutter and rotate the part about one cylinder whilst cutting to the intersection line, then do the same with the other cylinder.
 

precisionmetal

Stainless
Joined
May 16, 2005
Location
CA
I'd look into MIM if it was me.

Of course you'd end up with a 1000-year supply of parts, but if you can bake the setup cost into say... the first year or so of sales, then it's all gravy after that! :D

PM
 








 
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