Precision taper/polishing job

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

=========== 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.

don't show 1-1/8 S7 high shock, but its available. FYI see Stress-Proof is also widely used in these applications

see

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).

Here is a link to the "time-saver" lapping compound.

Roger

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

Mold steel, machined nitrated and polished.

John

Can't you order it from the US?

Wes

They don't answer eMails. Maybe I'm in their filter? :-))

Nick

Their website indicates they ship worldwide.

Wes

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

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