Grinders keep burning emax and breaking tools

[HygienicBee]

I've been having a problem with my AG wetmill where my orange grinder 1.8mm keeps on burning material and as a result, stripping all of the diamond off the grinder.
Called support, told me it was coolant.
Changed coolant, steam cleaned, and greased collet.
Ran coolant cycle. Milled 1 crown, came out great, second crown burned halfway through and stripped the diamond off of the grinder tip.

anyone else ever have this problem and find a solution? This is starting to become a real problem and money pit for me.

 

[deadhead]

what kind of restoration are you trying to mill when the tool burns out, and what mill are you using. We have had this issue before with our Motion2(1st generation) mill, and it ended up being a mixture of dirty coolant, and the way the restoration was nested. When nesting make sure your connector is near bottom of restoration and where the connector meets the restoration make sure it doesnt form a 90 degree angle. Also make sure that the unit you are milling is all the way to the back of the block. If you put towards middle or front tool will get too hot due to all the material it has to mill away(unless you have the Motion2 DNA with the carving mode then it really shouldnt matter where the restoration is as far as placement but connector still cant meet unit at 90 degree or else the tool will jam in that spot and get heated up due to lack of coolant being able to hit the tool and restoration at the same time. Also we noticed if we were trying to mill a unit that was a crown going over an MDI implant or even a screw retained crown, the 1st generation Motion2 cant mill these due to the fact that there is only 2 nozzles that the coolant comes out of to cool the tool and work piece, which isnt enough when milling these kind of units because the coolant cant get into the hole when it mills to keep things cool which in turn will burn the unit and bust the tool, but with the Motion2 DNA this mill has 3 nozzles and a beefer spindle which can handle these types of units. here r 2 pics showing correct placement and incorrect placement. hope this helps
correct placement




not correct placement

 

[HygienicBee]

I was milling a pretty simple crown, on the straumann M series mill.

The coolant was fresh as can be, and this was only the second crown being milled after fresh coolant was put in.

I've added my nesting below, it mostly follows what you've mentioned, although my co-worker advised I put the sprue on the lingual side of the crown. I'm not sure if that would be my fatal flaw here

If I still had the block I would upload a photo, but it did fine trimming the material during the first phase, milled out the interior fine, as soon as it tried to mill the outside is when it left a large burn streak as well as broke as it was grinding near the sprue. Looked as though it had gotten jammed in a spot where coolant was unable to cover the grinder.

Thank you for the information as well, I do believe these two machines follow very similar strategies.

 

[Toothman19]

I know this might sound dumb, but we had this problem once. Somehow the old burs got mixed in with some new burs and the same things happened to us....Just double check

 

[HygienicBee]

I know this might sound dumb, but we had this problem once. Somehow the old burs got mixed in with some new burs and the same things happened to us....Just double check

I wish that were my case, the last bur I used went straight from the package into the machine

 

[2000markpeters]

Maybe your feed rate is too quick. I mill glass st 60%, and have no issues. Get about 35 crowns before burs are dull

 

[Techy]

Sounds silly, but make sure you are using correct tool....if it requires "taper" and your tool in straight, this could cause it!
Just thought I would mention it....(also double check tool paths)
Adam
Streamline Dental

 

[HygienicBee]

Thank you all for the advice, I will make sure to look back here the next time I have emax to mill

 

[RypeSnicks]

Still having issues? We occasionally have that issue but usually cleaning the collet and keeping up on our (custom made) regular maintenance helps!

 

[omsk]

what kind of restoration are you trying to mill when the tool burns out, and what mill are you using. We have had this issue before with our Motion2(1st generation) mill, and it ended up being a mixture of dirty coolant, and the way the restoration was nested. When nesting make sure your connector is near bottom of restoration and where the connector meets the restoration make sure it doesnt form a 90 degree angle. Also make sure that the unit you are milling is all the way to the back of the block. If you put towards middle or front tool will get too hot due to all the material it has to mill away(unless you have the Motion2 DNA with the carving mode then it really shouldnt matter where the restoration is as far as placement but connector still cant meet unit at 90 degree or else the tool will jam in that spot and get heated up due to lack of coolant being able to hit the tool and restoration at the same time. Also we noticed if we were trying to mill a unit that was a crown going over an MDI implant or even a screw retained crown, the 1st generation Motion2 cant mill these due to the fact that there is only 2 nozzles that the coolant comes out of to cool the tool and work piece, which isnt enough when milling these kind of units because the coolant cant get into the hole when it mills to keep things cool which in turn will burn the unit and bust the tool, but with the Motion2 DNA this mill has 3 nozzles and a beefer spindle which can handle these types of units. here r 2 pics showing correct placement and incorrect placement. hope this helps

I believe AG now sells a separate nozzle plate for the older Motion 2 so it has 3 nozzles like the newer DNA versions.

 

[HygienicBee]

Still having issues? We occasionally have that issue but usually cleaning the collet and keeping up on our (custom made) regular maintenance helps!

Yes, I'm still having issues, I did a very thorough maintenance sweep, scraped the water reservoir, steamed and greased the collet. For some reason the part of the grinder that goes into the collet was under so much stress that it snapped. Should be having a Straumann tech come take a look soon

 

[notifyme]

Hi, any luck in resolving this issue which is peculiar to 1.8mm bur and emax blocks? We have been experiencing significant wear-out issues for this particular bur whenever we mill emax blocks to the point we have seen the tips wearing out in just single veneer.

 

[Slimboyphat]

i had the same issue although i haven't had a burnt tip after chicago.. here's what i learned:

you can add in a bit more coolant than is called for. maybe 1.5 bottles.. if you haven't cleaned the coolant tank in a while then emax slurry remnants can get pushed through and blasts onto the tool and causes heat..

another tip(refer to pic) - in this view, tilt the crown mesial/distal 14-20 degrees - this will get the tool to use its side a little more rather than tip.

 

[Brett Hansen CDT]

i had the same issue although i haven't had a burnt tip after chicago.. here's what i learned:

you can add in a bit more coolant than is called for. maybe 1.5 bottles.. if you haven't cleaned the coolant tank in a while then emax slurry remnants can get pushed through and blasts onto the tool and causes heat..

another tip(refer to pic) - in this view, tilt the crown mesial/distal 14-20 degrees - this will get the tool to use its side a little more rather than tip.

View attachment 44480

We don't mill emax, but if we did, I would find this post very helpful!

 

[tuyere]

That is indeed handy, thanks.
RE: coolant issues, we've found that we have to change coolant significantly more often than the manufacturer recommends (this is for a PM7 running pure emax),especially if we're using high-finish toolpaths- they're extremely sensitive to any grit or crud in suspension in the coolant. I think we change it every 25-30 units or so?
Also- it never hurts to purge your coolant lines, over time they can clog with dried coolant crud and reduce overall through-flow and nozzle pressure, both of which are bad for irrigating the worksite. Get some very hot water and pump it through the coolant loop for a good long while- use a bigger volume of water than the tank holds so it doesn't cool off too quickly, and ideally you can change the water at least once to replace it with a new batch of very hot water, or else drop an immersion heater into the temporary reservoir. Run it for at least half an hour, but sometimes running it all night or longer is called for, especially if the lines have never been purged this way. After a good hot water clean-out you'll be surprised at how much your coolant situation can improve, you forget how it was when the mill was brand-new.

 

[Foggy_in_RI]

Hated milling e.max
Too much scrap / high cost to keep running

 

[notifyme]

Thank you Slimboyphat. This resolved my longstanding issue - was able to mill over 30 e.max CAD blocks in a single bur

 

[notifyme]

i had the same issue although i haven't had a burnt tip after chicago.. here's what i learned:

you can add in a bit more coolant than is called for. maybe 1.5 bottles.. if you haven't cleaned the coolant tank in a while then emax slurry remnants can get pushed through and blasts onto the tool and causes heat..

another tip(refer to pic) - in this view, tilt the crown mesial/distal 14-20 degrees - this will get the tool to use its side a little more rather than tip.

Could you please help me understand what's wrong with this nesting - the AG tool (Bur) is breaking with this nesting. This is the third bur that has broken. Please advise so that I can avoid the mistake in future.