Cracks!

McTeeth

McTeeth

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Hey Guys,

This is the 1st time with this result. I'm a rookie at the long-spans. Cracks where the supports are, 4-5 of them. 3.0mm diameter supports. Program specs in attachments. Nabertherm Bottom-loading sinter furnace. Probably have too many supports, but this strategy was what solved another long span bridge case from warpage.

Pics might be not clear, but they basically cracked in a circle around the support. One crack started to run up towards the incisal.

Uggh,

Sean
 

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McTeeth

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Doing some research, I should of used this strategy?
 

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CoolHandLuke

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WAY too many supports.

the supports are pulling in the direction they face, and so supports pulling in too many directions creates stress in many directions. in this case 4 or 5 supports will suffice.

the strategy in your 2nd post tries to ensure the horizontal force and vertical force is equal (so no warpage)

thats the strategy that you should use. balance out the directional forces either by pinning 15-11-24, or with 4 supports at 16, 13, 21, 24.

try to pin just copings, but it doesnt really matter.
 
zero_zero

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I usually leave 3 or 4, 4 if the bridge is thick and even and sinter standing on the support structure.
20170601_151222_.jpg
As for the program here's my recipe: 7C/min to 1000C -- Hold 2 hours -- 2C/min to 1530C -- Hold 3 hours -- 2C/min down to 1000C --- 7C/min down to 250
 
McTeeth

McTeeth

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WAY too many supports.

the supports are pulling in the direction they face, and so supports pulling in too many directions creates stress in many directions. in this case 4 or 5 supports will suffice.

the strategy in your 2nd post tries to ensure the horizontal force and vertical force is equal (so no warpage)

thats the strategy that you should use. balance out the directional forces either by pinning 15-11-24, or with 4 supports at 16, 13, 21, 24.

try to pin just copings, but it doesnt really matter.

Awesome, thanks man. I'm in the learning phase of this stuff.
 
McTeeth

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use 3-4 connectors and make them 1.5 -2mm thick

Yeah , I should dial it back. I used 3mm because I popped one off it's stabilizer at 2mm. But I just learned not to use low speed to cut supports or it creates "chatter", which is what I did
 
RCKSTR

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Next time, call me first Sean ;)
 
JohnWilson

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