Cracked rings

[Mike2]

John, I had seen this all the time when I was doing PTM's. I used Microstar and I used to pour 900g's at a time. The rep told me I was crazy because I shouldn't be mixing such large batches. Anyhow, it was very common with the 300g ring to have hairline cracks before pressing, but they wouldn't split in the pressing cycle. When I did encounter this issue it was always to short of bench set outside the rings. My parameters were 15min in ring and 1 min out for 100g, 20mins in ring and 2mins out for 200 gram rings and I believe 25mins in and 3mins out for 300g rings. I would place all my money on steam cracks as the culprit. As a sidebar, are you sure that the powder isn't settling out in the machine, how often is it added? I like the single serve, they can be shaken and all components are mixed before adding to the liquid. One other possibility is the liquid, sometimes there are bad batches, I know you had done some alloy rings, but were they as big of rings and were they full casts? More to burnout ='s more expansion. I know you probably know all this but I would try a little longer bench set outside the ring. For the money, I think Microstar is by far the best investment out there and you can count on Jensen solving these issues for you, Terry is a great guy and very knowledgeable. If you want, you can call me and discuss further, I am sure somebody knows how to get you my e-mail???

 

[JohnWilson]

Hi Mike,

Just an update, I ordered new everything from Ivoclar yesterday after all the head aches. The old plastic parts for my rings seemed a bit beat up and rough from the investment over time. After thinking about how the rings were cracked I started to wonder if perhaps when the rings were being separated that the plastic parts were possibly putting some stress on the ring while removing them after the 15 minute set. I am sure I am just grasping at anything now but in any case we still invested with Formula one today but from a fresh bag and fresh liquid and bench set it 5 min longer than normal and had 100% success. Still had a few small hairline cracks in the pattern but no problems in the pressing oven

I still have the ivoclar investment coming its just really pricey but if it gives me a trouble free life its well worth it..

Thanks so much for all the tips and suggestions guys I appreciate it.

 

[TheLabGuy]

Yeah John, I think being it's winter (although I know CA is beautiful this time of year) you need to let it set longer. Like I said previously, I let my Formula 1 set up for a 1/2 hour. I think you're getting steam cracks like someone else mentioned, makes sense.

 

[desertfox384]

After you pull off the silicone ring, bench set 3 minutes. That will dissipate alot of moisture.

Exactly, after you break the ring out of the former place it on the bench for a few minutes, pick it up and look at all the moisture underneath where the ring was sitting, it needs to release that moisture or it will crack.

 

[amadent]

ring failures

John, I had the same problem with Formula 1. I spoke to the trouble shooting dept about my problems. This was involving patterns for porcelain copings. I would get cracked rings and some times blowoff in the burn out furnace. This is what I was told. After removing the investment from the ring former to grind the top of the ring and then let it sit on the counter for at least seven minutes for a 200 gram ring. It worked most of the time. If there were too many patterns (coping) in the ring, 8 was the limit for a 200 gm ring. If they were all at the same exact height and in a row it could happen , and it did. I am not knocking them, I switched investments. Could not take the uncertainty. Also, If I mixed 500 gms at a time , BOOM. Small consolation to your problem ,but I hope I am of some help. cracked and blown up rings = no money + frustration NOT WORTH GETTING UP TODAY. Al

 

[Mike2]

John,
I know you have the speed investment on the way, for the money I think Microstar is better. You cannot beat Jenesen's support, in addition in the long run all labs try to cut and save on materials etc., in my experience at a large lab(100+) they would step over dollars to pick up dimes daily. The most frustrating was when they patted thierselves on the back for it. Investment only comes out to a very small percentage of the cost, especially if you are grouping units. If you want to save on devesting labor please e-mail or call and I will give you some info., maybe a product to bring to market. respectfully-mike

 

[capickettcdt]

OK guys here is where I jusmp in! Humidity can effect the set time and the moisture release from the ring. We need some of the moisture to act as a heatsink and reduce the thermal shock to the surface of the investment. too much and you get cracks.
If you see these cracks, next time wait the 15min (which is a minimum bench set) pop it out of the ring and bench another 3-5 for 100gr/5-10 for 200gr and the same for 300gr. Heat in these rings gets up to 185F while sitting on the bench. If you didn't get that kind of heat there is somthing wrong...CALL ME!!!! If the cracks continue...CALL ME!!

 

[oaktra]

Are the 200g rings being placed flat in the oven? I had this problem with bigger rings until I tipped them on old ceramic trays in the oven so the wax and gases didnt bubble back into the ring during burnout and cause it to blow up.Also I found out the same way you did that 15 min. bench set on the 200g ring needs to be about 25min.

 

[paulter317]

“We have been on the bulk program with Whipmix so the investment comes in big bags not 100 Gram packages
A side note ee invested and cast 5 ceramic alloy rings today with no trouble or cracks with the same batch of investment”


Hello from NYC to every one! I’m new here. You guys did excellent job. I get a lot of tips from you. Big thanks!

In my opinion in this circumstance, John should stir powder of investment very well from bottom to the top, because investment comes in big bag not 100 Gram. In my experience this way resolve the problem. By the way, cast 5 alloy rings went well cause was covered by metal rings, If you use ring less casting alloy, I thing it’s going to same cracked result.