why CAD/CAM restoration have space in heavy chamfer?

[PinAn]

Hi guys, My scanner is D900L and milling machine is 350i the CAN Is sum3D
I don't know why if abutment have heavy chamfer , chamfer or shoulder
there will have a space in the chamfer part!
I means margin is fit! but there are space after margin
I can see the space with fit check and micro scope ,
Does anyone know why? and how to improve it?

Thank you

 

[Patrick Coon]

Try increasing your distance of spacer to margin line. This parameter should help.

 

[PinAn]

Hi what is your value in 3shape?
I have try to control it to 0.001
But it didn't help

 

[user name]

@PinAn

Im not sure if I understand. You are saying your margin is nice and accurate, but inside the crown you have too much cement space? Unless you cut a crown in half, how do you know theres space there?

 

[Patrick Coon]

You ant to increase your distance to margin line, not reduce it. This stops your spacer from getting closer to the margin. So 0.5mm stops the spacer a half millimeter from the margin and 1.0mm stops the spacer 1 millimeter from the margin. With more parallel preps move the spacer closer, with more tapered preps, you can move the spacer further from the margin to tighten things up.

Sent from my SM-G935V using Tapatalk

 

[PinAn]

@PinAn

Im not sure if I understand. You are saying your margin is nice and accurate, but inside the crown you have too much cement space? Unless you cut a crown in half, how do you know theres space there?

Sometimes margin will chipping and I try-in the crown with 12.5x microscope and the shoulder didn't have red marker

 

[PinAn]

You ant to increase your distance to margin line, not reduce it. This stops your spacer from getting closer to the margin. So 0.5mm stops the spacer a half millimeter from the margin and 1.0mm stops the spacer 1 millimeter from the margin. With more parallel preps move the spacer closer, with more tapered preps, you can move the spacer further from the margin to tighten things up.

Sent from my SM-G935V using Tapatalk

Yes... I use cement gap 0.001 and extra cement gap with 0.015, and distance of margin is 1.0
I can see the shoulder is fit in cad software, but it's not fit in reality

 

[user name]

My guess is youre not getting an accurate scan. Do you use any sealer on your dies? It could look ok in the CAD, but maybe not actually representative of the die. False imaging.

 

[PinAn]

My guess is youre not getting an accurate scan. Do you use any sealer on your dies? It could look ok in the CAD, but maybe not actually representative of the die. False imaging.

Yes I have use sealer but also I have use DFS spray,
But the space is huge... I feel it have 0.05 I can see in micro scope
And what is your. Value setting in 3shape? I know every machine need different value,
But it will be helpful

 

[user name]

Stop using sealer and stop using spray.

I quit using 3Shape.

 

[CoolHandLuke]

nothing wrong with scan. everything to do with cam strategy. simply, the margin is overmilled for some reason. call the provider of your cam and find out if overmilling is calculated into your strategy and how to undo that.

 

[CoolHandLuke]

the thing is, sometimes you design a line in space that is simply not millable. a margin too highly detailed. consider that the cam program is making slices at a certain thickness, and using only a certain diameter cutter, no not all that detail can be milled.

secondarily, .001 mm is difficult to acheive even when you arent doing anything.

when you physically touch an object in space, it has micro air gaps between it and your fingers because thats how science works. nothing ever truly touches because if it did it would fuse.

i suggest the following: design a straighter margin and get comfortable in the fact that peaks and valleys less than 20um in size cannot be cut by your machine, let alone by even the most in-tune laser ablation system around. its not happening. so loosen your settings to at least .01/.03 and be cool.