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Anonymous Poster #1

Cold Isostatic Pressing System

09/24/2015 3:23 AM

I have a large size Cold Isostatic Pressing system having 385 mm diameter x 1550 mm height(internal). Now when we are pressing any hollow round or square tube in this press, we got it so nice & good, but if we press any solid round or square article with Alumina Ceramic or Zirconia Ceramic powder in this same mould, always we got it broken. So what is the reason? What we should do to get good solid article article? What should the pressing increase & decrease rate for 22000 PSI pressure?

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Guru

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#1

Re: Mr

09/24/2015 4:35 AM

Are you making coffee cups? Rock solid ones!

Sorry there is not much to tell you with the given information!

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#2

Re: Cold Isostatic Pressing System

09/24/2015 5:32 AM

I know absolutely nothing about this subject, but, just guessing.

Have you tried increasing the pressure much more slowly?

Is there a way to introduce vibration into the mould whilst pressing: I'm suspecting that you may be experiencing problems with "stiction" between parts of the material.

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#3

Re: Cold Isostatic Pressing System

09/24/2015 12:52 PM

Where are the kracs ? How dos it brake ? In fact when you press the particles have a complex movement not only in axial direction. Thus my question, if you have a picture it be even better. I was confronted with similar problems but at lower scale.

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#4

Re: Cold Isostatic Pressing System

09/24/2015 11:57 PM

Triaxial compression (freely moving ceramic powder charge and rubber mold) in your isostatic vessel tends to fracture the preform during the decompression cycle, because of the grip between the re-expanding mold and the permanently compressed, fragile preform.

Tubular preforms are reinforced by their grip on the shaped center mandrel (generally metal) so they resist tensile failure.

Solid preforms do not enjoy that same reinforcement by compressive grip on a mandrel - there is no mandrel - so they will suffer tensile failure during decompression, as the mold returns to its original dimensions.

The best solution is to redesign the mold for solid pieces, restricting its long axis against movement in compression and again in decompression. Then, simple biaxial compression in the same chamber will yield perfect, unfractured preforms, whether solid or tubular.

You will need to understand the extra local strain on the rubber mold where it attaches to the restricting hardware. You will need to understand the distortion of preform shape very close to the restriction points.

Mark Bingham

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APIX Pilot Plant Design Project - Member - Amrut Patel

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#5
In reply to #4

Re: Cold Isostatic Pressing System

09/25/2015 3:52 AM

Dear Mr. Mark, Thanks for understanding my problem and giving me your valuable suggestion. But still i am not clear about the solution. So kindly, guide me with some simple way. So that i can understand and get my problem solved. If you can provide me with your email id, I can send you the pictures of mould and product. Thanks, Regards Amrut Patel

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#6
In reply to #5

Re: Cold Isostatic Pressing System

09/25/2015 4:55 AM

I have emailed you through your website contact info.

Mark

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#7
In reply to #6

Re: Cold Isostatic Pressing System

09/25/2015 5:11 AM

Thanks.

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#8

Re: Cold Isostatic Pressing System

09/26/2015 2:58 AM

This may have to do with the angle of repose (internal friction), which can be quite large for both the materials specified. This limits the extent of pressure penetration. This is why the thin components come out alright but not the solid ones.

Very little can be done on this other than adding a binder and sintering later.

The other option is to do this in layers. I am not too sure if the adhesion subsequent layers will be sufficient for the intended end use.

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#9
In reply to #8

Re: Cold Isostatic Pressing System

09/28/2015 7:13 AM

What about adding some ultrasonic vibration to the liquid to overcome the friction during the increase in pressure?

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#10
In reply to #9

Re: Cold Isostatic Pressing System

09/28/2015 7:39 AM

"What about adding some ultrasonic vibration ... ?"

The particle size distribution in such materials is useful to gain the highest apparent density of the load, prior to application of pressure. That distribution exists in the ceramic being added to the mold. A nice spread ranging from golfballs to dust, which packs efficiently and reduces the needed compression factor.

Vibration tends to separate the particle sizes, commonly sending dust to the bottom and golfballs to the top. This results in non-uniform loads, hence non-uniform preforms.

Mark Bingham

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#11
In reply to #10

Re: Cold Isostatic Pressing System

09/29/2015 4:50 AM

Thanks.

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