Milled Bridges Rocking Again

N

NickB

Member
Full Member
Messages
74
Reaction score
10
We solved the bridge issue we were having a while back, but its now happening again. Ive been using the stabilizer bar feature in Sum3D, and it seems to help somewhat, but these little bastards have begun to rock again. I suspect its the same issue as before (waxers carelessly spruing).....so I decided to leave the connectors kind of long when cutting the bridge off of the wax ring......this allows the waxers to sprue the bridges without getting their hot wax too close to the bridge itself.

It seemed to work for a while. But now they rock like crazy again. Also having issues with the cement gap, as one setting doesnt mill out enough, it the dies wont seat and I have to use a high speed to dig it out. Then the next setting they fit a little loose after we make an adjustment. Its getting frustrating and the guy who came here to teach us this stuff from Zahn was kind of a goof ball and simply could not help us with any tips.

Starting to winder if this stuff was even worth it. Any help from your experience would be appreciated.
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
refresh my memory, what design system and what milling system and what cam calculations are you using.

it is possible that the design parameters do not match the capabilities of the cam calculation software, which in turn produces poor units.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
refresh my memory, what design system and what milling system and what cam calculations are you using.

it is possible that the design parameters do not match the capabilities of the cam calculation software, which in turn produces poor units.

We are using a Roland DWX-50 along with 3Shape scanning software and Sum3D milling software. By design parameters, are you speaking of our settings regarding
cement gaps etc? When the wax is placed on the model, usually the wax bridge fits well. But once in metal, its terrible many times. Plus, the margins are open and sometimes
a bit extended in metal, while in wax, they fit like a glove. We've changed our run up settings in our burnout furnace and triple checked our ratios with investment. Handwaxed
units fit well. So I doubt its the investment ratio.

Can you give me an example of how the parameters not matching could cause a problem?
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
handwaxed units fit well post-cast, but computer designed ones seem to have problems once cast...

then you may need to consider the wax itself as problematic. try a new supplier. wax pucks are dirt cheap.
 
user name

user name

Well-Known Member
Full Member
Messages
6,960
Reaction score
1,633
Or...youre casting with too much metal. You should have minimumal/no button left; just some of the runner bar. With too much metal youre shifting the heat center of the casting so the button draws metal from the runner bar/reservoir instead of your pattern. Distortion every time.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
Or...youre casting with too much metal. You should have minimumal/no button left; just some of the runner bar. With too much metal youre shifting the heat center of the casting so the button draws metal from the runner bar/reservoir instead of your pattern. Distortion every time.

We used proper amounts of metal. We also ensure that the waxups are not at the center of the ring for cooling purposes. We used to have investment breakdown with flash all over our metal units, but we fixed that by slowing down
our run up times in the furnace.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
handwaxed units fit well post-cast, but computer designed ones seem to have problems once cast...

then you may need to consider the wax itself as problematic. try a new supplier. wax pucks are dirt cheap.

And we did try new wax pucks. Multiple ones actually. All rocked still.
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
And we did try new wax pucks. Multiple ones actually. All rocked still.
then you are indeed processing incorrectly.

whoever is providing your alloy should also have recommended an investment and provided full instruction on using that investment. otherwise they are doing you a disservice.
 
user name

user name

Well-Known Member
Full Member
Messages
6,960
Reaction score
1,633
Photo of a casting before you cut it off...?
 
JMN

JMN

Christian Member
Full Member
Messages
12,205
Reaction score
1,884
Don't know how your waxers are spruing, but what I saw caused a lot of bridge issues is how much/how far the wax had to be built to reach the copings.

If you have a high variance on height, even it out and let it cool before adding onto the bar. You should only and barely "glue" the bridge to the bar, if you are adding 2mm of wax to reach one and the other is already attached the cooling wax will contract and warp your bridge that used to fit perfectly before casting.
 
kimba

kimba

Active Member
Full Member
Messages
478
Reaction score
58
In my experience , all , or the vast majority of problems with rocking bridges is in the pattern before it is invested. Maybe the waxers are heating the pattern up too much when spruing? not taking as much care with milled patterns as they perceive they are more robust than handwaxed patterns? The cynic in me sometimes thinks that some metal workers will try to find problems in milled patterns because "there is no way a machine will do it better than them by hand" I do lower my expansion ratio for bridges , but I don't think this is your problem if hand wax is fitting and milled are not. Have you personally milled , sprued and cast to see the results? I had this problem with a metalworker who swore blind it was the investment, so I got a different investment for him. same problem . This went on until we did a challenge . Me wax 2 bridges , him wax 2 bridges mill 2 bridges. We each sprued and cast 3 . Guess what .. mine all fitted , his a mix. sorry for the long winded response , but I think its in the spruing for what its worth. Hope this helps
 
JMN

JMN

Christian Member
Full Member
Messages
12,205
Reaction score
1,884
In my experience , all , or the vast majority of problems with rocking bridges is in the pattern before it is invested. Maybe the waxers are heating the pattern up too much when spruing? not taking as much care with milled patterns as they perceive they are more robust than handwaxed patterns? The cynic in me sometimes thinks that some metal workers will try to find problems in milled patterns because "there is no way a machine will do it better than them by hand" I do lower my expansion ratio for bridges , but I don't think this is your problem if hand wax is fitting and milled are not. Have you personally milled , sprued and cast to see the results? I had this problem with a metalworker who swore blind it was the investment, so I got a different investment for him. same problem . This went on until we did a challenge . Me wax 2 bridges , him wax 2 bridges mill 2 bridges. We each sprued and cast 3 . Guess what .. mine all fitted , his a mix. sorry for the long winded response , but I think its in the spruing for what its worth. Hope this helps

I really like the method you used to test. That was an excellent non confrontational proof positive way to find the facts.
 
kimba

kimba

Active Member
Full Member
Messages
478
Reaction score
58
I really like the method you used to test. That was an excellent non confrontational proof positive way to find the facts.

I thought so , but to this day he still thinks I am a pri-k!!! go figure
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
it happens. to some, i appear condescending and confrontational. to others, i'm the lone member of the DLN Hall fo Fame for being non confrontational.

*shrug*
 
Sevan P

Sevan P

Well-Known Member
Full Member
Messages
3,413
Reaction score
641
Seems to me this tech just wants to get done with the work load, and doesn't care. We had a ceramist that broke a full round house Zr bridge in 2 spots while doing a first bake cause she that all bridges are fired the same from 3 unit to 14 unit. WTF!!! I asked here would she fire a full arch metal lingual bridge in the same program as a 3 unit frame pfm bridge? She said no, then I said why would you not do the same on a Zr bridge? I don't know she said...................... unfortunately old techs are stuck on old ways and don't get it sometimes. But the investing parts has never changed, talk to the high up on the food chain and let them know this is what is causing the issues and if the techs can't get in gear then maybe it is time for some replacements.

Water to liquid and sprueing of round house pfms are so crucial for fit not everyone should to it. maybe train and hone a single tech to be responsible for them narrowing the chances down a bit and if it happens again you know exactly who to go to.
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
In my experience , all , or the vast majority of problems with rocking bridges is in the pattern before it is invested. Maybe the waxers are heating the pattern up too much when spruing? not taking as much care with milled patterns as they perceive they are more robust than handwaxed patterns? The cynic in me sometimes thinks that some metal workers will try to find problems in milled patterns because "there is no way a machine will do it better than them by hand" I do lower my expansion ratio for bridges , but I don't think this is your problem if hand wax is fitting and milled are not. Have you personally milled , sprued and cast to see the results? I had this problem with a metalworker who swore blind it was the investment, so I got a different investment for him. same problem . This went on until we did a challenge . Me wax 2 bridges , him wax 2 bridges mill 2 bridges. We each sprued and cast 3 . Guess what .. mine all fitted , his a mix. sorry for the long winded response , but I think its in the spruing for what its worth. Hope this helps

That is what I personally suspect. The waxers, for the most part, dont speak much English (although they do understand it fairly well) and they take personal offense when you try to correct them.
But yeah, I think Ill try to sprue it myself and see what happens. Typically, when investing, they always pour the investment to the top of the ring former.....yesterday I had them stop pouring the
ring completely full, only ensuring that they covered the wax patterns with at least enough to dry grind the tops. This means the wax patterns will be further away from the center of the ring.

Ill post photos later of the milled bridges while in wax form....and post photos tomorrow once they've been cast.

Nick
 
N

NickB

Member
Full Member
Messages
74
Reaction score
10
What investment do you guys use for your milled wax? We use microstar HS. I doubt its the investment.....I think microstar is very good. Just wondering if there is another investment
meant for any milled wax in particular.
 
JMN

JMN

Christian Member
Full Member
Messages
12,205
Reaction score
1,884
it happens. to some, i appear condescending and confrontational. to others, i'm the lone member of the DLN Hall fo Fame for being non confrontational.

*shrug*
That happens when your service patches are installing and have noncritical functions offline.
 
CoolHandLuke

CoolHandLuke

Idiot
Full Member
Messages
10,078
Solutions
1
Reaction score
1,411
That happens when your service patches are installing and have noncritical functions offline.
no it happens BECAUSE YOU'RE A BUMBLING NINCOMPOOP

4d9d54325e920f7e3c559e24c839e1f7.jpg
 
Top Bottom