Precision taper/polishing job

Excessive wear is relative to your production requirements and cost of the tools.
The suggestion of another poster to use precision tubing for the mold form seems to have merit.
A quick web search indicates stainless steel tubes are available, but small quantities may be a problem.
See
formatting link
(DocumentsInternetWeb)/A3EEB94DA5D1A68DC1256B680035B18F
formatting link
formatting link

While the tubing may be hard to obtain in small lots, pneumatic/hydraulic cylinders could be disassembled. See
formatting link

As an alternative, depending on the pressure/force used, it may be possible to use pvc pipe. The bores are generally very slick, and it is intrinsically corrosion resistant. Also, it won't produce sparks. This could be cut to suitable lengths, and movable plugs placed in one end, and a close fitting ram used to compress the form. The plugs and rams could also be nylon or pvc. The compressed form could the be extracted from the tube by either removing the support for the plug and pushing on through the tube, or in a second op, inverting the tube and pushing on the plug. One source for PVC tube/pipe is your local ace hardware. Enco has pvc/delrin/nylon rod for the plug and ram.
Unka' George [George McDuffee] ------------------------------ Watch out w'en you'er gittin all you want. Fattenin' hogs ain't in luck.
Joel Chandler Harris (1848-1908), U.S. journalist. Uncle Remus: His Songs and His Sayings, "Plantation Proverbs" (1880).
Reply to
F. George McDuffee
Loading thread data ...
yup.
I should have been more "complete" in my description of the entire machine. It exists. I'm seeking a better, more durable, and easier-releasing cavity than what's in there. In the meanwhile, I'm building a new loader for more precise filling with clumpy mixtures, modifying the pressure elements to directly measure the height of the pellets, adding a finished product stacker/orienter (for the next operation), and modifying the press cycle for better 'self cleaning' of the mould and its components. And all of this is WAY less work than building a new machine with new principles from scratch.
So, I cannot arbitrarily use "split moulds", etc. It has to be a 1.125 x 4 bored rod.
PVC won't work -- the pressures _start_ at 1465psi and go up.
The original designer made it with Ni-Tuff coated cylindrical aluminum cavities. They wear out after about twenty thousand strokes -- not economical. PVC and Delrin liners were tried, and they wore out faster. Even _with_ a degree of taper, they don't seem to hold up to the abrasion at these pressures.
The pill press fellas use steel. We get hundreds of thousands of fill/press/eject cycles from each of their punch/die sets, so I figger they've got the method... but they won't let on about what alloy, etc, they use... only the geometry. About the only things I know about it are 1) it wears like iron (*ulp* _steel_) 2) it will rust if exposed to both composition and high humidity, but if clean, it won't and 3) it loses its initial polish almost immediately, but doesn't seem to change dimensionally for hundreds of K cycles.
Our production demands are growing, and this machine is a pivot point for several product lines. It will get a twin brother, as soon as these new features are added and tested. I have the prints for the existing version, and have built replacement wear parts for it on several occasions.
I think I hear myself saying, "Buy a tapered reamer." I've never had any fun reaming aluminum, but 41L40 probably will not gall and mark as badly; no?
This is a "small production lot" project, not a one-off. But the production will continue in dozens-lots for the forseeable future.
LLoyd
Reply to
Lloyd E. Sponenburgh
=========== Ah So
Given your ongoing production, you will almost certainly be better off getting a custom reamer ground. You won't need an entire custom reamer, but one that is as close as possible reground. Shouldn't be that expensive.
I would look at using drill rod for the mold. In many cases simple W1 [the cheap stuff] will be adequate, particurarly if you can make the molds quickly/cheaply. There is also precipation hardening A1 that is considerably more expensive but heat treats well with minimal distortion. Given your requirements, most likely a good vacuum or inert atmosphere heat treat would be the way to go.
Generally drill rod machines very nicely. We used this when we made the mounting post for the quick change tool holders. Its good that you have 1-1/8 diameter as this is the largest that can be chucked in a common C5 collet.
Hard chrome or TiN in the bore would greatly increase both the wear and the corrosion resistance, but with a custom ground reamer you should be able to chuck the mold in a collet and touch up the bore as required.
For examples of drill rod see the enco urls below. Lots of places have 1-1/8 drill rod.
formatting link
don't show 1-1/8 S7 high shock, but its available. FYI see
formatting link
Stress-Proof is also widely used in these applications
see
formatting link

Unka' George [George McDuffee] ------------------------------ Watch out w'en you'er gittin all you want. Fattenin' hogs ain't in luck.
Joel Chandler Harris (1848-1908), U.S. journalist. Uncle Remus: His Songs and His Sayings, "Plantation Proverbs" (1880).
Reply to
F. George McDuffee
Here is a link to the "time-saver" lapping compound.
formatting link
Roger
Reply to
Roger Paskell
Greetings Lloyd, Aluminum can be polished to a very smooth surface. Then hard anodize to maximum coating thickness and do a final polish if needed. Another solution which may be better is to make the part from heat treated 4140 or 4340. Though a little tough to machine it's easy to get a very good finish. If the chrome moly is too tough then use 12L14, aka Ledloy. No matter what kind of steel you use have the surface coated with titanium nitride. There are all sorts of places doing this coating now and the costs have come way down. The coating has the multiple advantages of being corrosion resistant, really hard, and really slick. I'll bet that it may be the longest lasting part you could make. ERS
Reply to
Eric R Snow
Mold steel, machined nitrated and polished.
John
Reply to
John
Can't you order it from the US?
Wes
Reply to
clutch
They don't answer eMails. Maybe I'm in their filter? :-))
Nick
Reply to
Nick Mueller
formatting link
Their website indicates they ship worldwide.
Wes
Reply to
clutch
I would be tempted to machine a piece of copper to the correct taper, load it with grit by rolling it in a puddle of lapping compound on a flat surface, and using the loaded copper taper to hone the inside of the mold bore.
Joe Gwinn
Reply to
Joseph Gwinn
P20 and a CNC lathe
Gunner
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects. Lazarus Long
Reply to
Gunner

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.