centrifuge casting and torch

[adamb4321]

A good torch is essential. My old Perkeo torch was a nightmare, precious bonding metal needed super heating for a full minute to get a full cast and believe me blasting your alloy for 60 seconds when it's already molten is quite counter intuiative.

I'm now using degudents torch which is much better, it melts really quickly and only needs 10 seconds or so of super heating, ask C&J about it I think they stock them.

Gas regulators for your oxygen and propane are a must and I would get some flash back arrestors too.

You'd defo need a well for a centifugal spring machine or health and safety will go nuts, I've got an old Degussa motorcast it's a self contained electric motor powered machine and works like a charm. It'd be worthwhile checking out Milnes Bros to see if they have any used ones knocking around.

 

[paulg100]

Yep the casting arm is in a bench top well so thats gonna be fine.

Im trying to get a replacement spring for it at the minute and then i can start looking at torches, so thanks for the info, ill keep it in mind when im ready to order one. :top:

 

[hydent]

Good stuff guys, I've been thinking of adding a small casting dept to my 1 man removable lab just for repairs and sub frames to start off with. Do any of you have any tips on casting non precious with a broken arm machine? also tips on casting a partial framework? I have books that show how but they are ancient, the more info the better as I'm not sure this will be a good idea yet. It's just getting a custom partial would sure be a lot nicer if I could wax it to my specs and not have to try to explain what I want and in the end get something that isn't exactly what I want. Obviosly a induction casting machine for the small amount of work that I will use it for would not be a good investment. Thanks in advance.

 

[paulg100]

OK i have since found out that no parts are available for the bench top unit we have so that is a dead end.

Also in the UK centrifuge's like this are not approved by health and safety any more, but since it will only be me using it then im not to concerend about that.

I have someone looking for a second hand unit for me but in the mean time i came across this on ebay:

NEW Dental Lab Centrifuge Casting Machine Apparatus CE | eBay

Maybe if i sit this in a bench top well, this would work OK?

Any thoughts..

 

[TECHARTISAN]

a different kind of centrifuge

Certainly not the budget minded solution youd had in mind....but in a compact setup....I find Ti-Research's systems to be quite interesting.

They even have a recessed version....

Of course, the price is a bit daunting, especially when you can buy a chinese built induction unit for near the same money.

 

[paulg100]

Interesting find!

But those rings are HUGE also, dosent look like they do smaller ones. Will keep a note of the site though.

I cant find anywhere in the UK now that sells new centrifugal setups due to helath and safety.

Im really not interested in an induction unit. I Keep getting told that centrifuge/torch type is the most accurate method, as you have more control of the metal melting.

 

[TECHARTISAN]

Interesting find!

But those rings are HUGE also, dosent look like they do smaller ones. Will keep a note of the site though.

.

The rings are huge in comparison to a traditional casting setup..seems more suitable for "batch casting" which should be more efficient then single unit work....though a greater loss when casting fails.
Their solution for smaller "loads" is a sectioned ring, in which castings and investment is only located in the U portion of the ring. The metal plate you see opposite the U is the counterbalance.


As for torch vs induction...I have only used induction so I cannot say which is better...but I use a digital optical pyrometer that measures the temperature of my melt..I dont know how much more control I would need.

 

[paulg100]

"but I use a digital optical pyrometer that measures the temperature of my melt..I dont know how much more control I would need."

yep we had one of those with the camera, our Heraeus one...it was junk, we down graded to their semi auto which they still use in our production lab.

"I dont know how much more control I would need."

Enough to get sub 40um margin castings
The accurate waxing/pattern resin under mag is the easy part, seems to me its the casting thats screws the margins up. If i send highly accurate patterns for casting at our main lab, the castings NEVER come back the same as the wax/pattern resin was. Cant tell you how frustrating that is.

Only way im gonna get the fits i want is to do it myself.

 

[TECHARTISAN]

I have a ticomatic caster. I wasnt impressed with its built in control so I use mine manually polling temperature with an extek 42570 handheld. I find it works quite well and has the added benefit of allowing me to check the temperature of the investment as well. Its a handy tool around the garage as well LOL.

 

[adamb4321]

"

Enough to get sub 40um margin castings
The accurate waxing/pattern resin under mag is the easy part, seems to me its the casting thats screws the margins up. If i send highly accurate patterns for casting at our main lab, the castings NEVER come back the same as the wax/pattern resin was. Cant tell you how frustrating that is.

Only way im gonna get the fits i want is to do it myself.

You should get good fits, what investment do they use and is it weighed out properly, how long between waxing and investing? maybe the patterns have distorted due to heat or the guy who is sprueing and investing is mishandling your patterns.

You get great results when you press, so you should get equally as good results if casting (though some alloys do "creep" a bit on the margins which can spoil the fit) which alloys do you use?

 

[paulg100]

The main lab is a prodution lab.

There is no real control going on, its just full of poeple wanting to get out the door on time with no real passion for what there doing, so it is no suprise that there is no consistancy.

Ill not be beating my self to death to change that, its easier just to get my own casting equipment on site.

4All from Ivoclar is the NP we use
Esteticor + is the precious alloy we use.

I know NP wont cast as accurate but i do not beleive the variable i am seeing are due to this.

As i cant find any new centrifuges in the UK (health and safety preventing sale?) ill have to give that china one a try by the looks of it. It looks a bit cheap and nasty but we will see.

Im pretty anal about everything i do here as far as ratios, protocols etc, so im pretty sure all these problems are gonna dissapear once im up and running. Im planning on using fujivest platinum.

 

[cheadlemick]

Have you tried the Rotojet or similar?

 

[paulg100]

HI Mick

No never heard of that. After a quick google it looks interesting, but availability seems to be real scetchy for europe.

Only place is italy and their website is all in italian :/

Maybe ill try a translator and contact them for pricing.

Thanks for the heads up.

 

[adamb4321]

Hi Paul,

I vaguely remember Metrodent doing a motor driven machine and Skillbond have the rotojet for 2k.

Have you tried Milnes Bros for 2nd hand spring machines? Jeff Halagan in Birmingham might be worth a try too as he sells 2nd hand gear.

Contact DHC Products

I've got a Nessor E4 vertical machine that I use as a back up, not pretty but it does the job, you might find these about too

found this too, looks like the same machine your link points to.

Centifugal Casting Machine - Centrifugal Casting - Dental Lab Equipment - Dental Equipment - Dental Instruments Sale Online Store

 

[cheadlemick]

HI Mick

No never heard of that. After a quick google it looks interesting, but availability seems to be real scetchy for europe.

Only place is italy and their website is all in italian :/

Maybe ill try a translator and contact them for pricing.

Thanks for the heads up.

hi Paul you can buy them from Skillbond they are very good!

 

[paulg100]

Thanks guys, ill look into that.

TBH for what those little units are comming in at, i might just take a punt!

If its no good then ill have to look at these dearer units.

 

[ALPHA]

I never used gloves but for the rings in the back of the furnace you have to grab them fairly quick or youll singe the hairs on your fingers. Done that alot but never burned myself.

Al, I also gave up using glove to cast my rings, bulky fit. Learn to grip the ring fast of feel the heat and something smell of chicken feathers burning...Cast like that for about 25yrs b4 coming to a Cad milling center where my fingers are pretty and always get hand cream. )

 

[sndmn2]

I use a casting tub with a broken arm machine. The blue one from Degussa. I hope the spring never goes because I don't know where to get a new one. I welded up a stand and bolted it to the floor. I use the Renfert casting torch. I really like the little soldering tips. I think they are sweet to work with. If you go with the Renfert torch you"ll need to take it to a local welding supply dealer and have them convert the threads to standard because it comes metric.

 

[pingvin]

sndmn2, I have the same one! Spring broke 2 (or was it 3) times already. It can be repaired, you simply shorten it (it brakes at the end where one screw holds it). It then goes a few more years. I also would like to know where to get a spare one!

 

[sndmn2]

sndmn2, I have the same one! Spring broke 2 (or was it 3) times already. It can be repaired, you simply shorten it (it brakes at the end where one screw holds it). It then goes a few more years. I also would like to know where to get a spare one!

Thanks for that info. I bought this off of fleabay 12-14 years ago. I never have had to replace the spring. But by what you tell me about cutting the spring I should be good for some time. Again Thanks.