avoid distortion while drying

[Mileslgr]

Hello, 

Since a few week, I am developing a project through 3D printed ceramic. The objects I'm printing need to be as much accurate as possible in terms of dimensions etc. 
The problem is that every time I dry the pieces, they start to get crazy deformations (I knew ceramic always move while drying, but I was not expecting such big distortions) 

The pieces are printed on a MDF board, covered with a piece of fabric. The fabric helps the first layer of clay to stick to the surface (the nozzle goes pretty fast)
The piece of fabric is stretched on the wood.
Once the print is done, I usually unstretch the fabric so it can shrink with the clay. Then I cover it carefully with some plastic. I leave the whole on the floor. 

I need the top of my piece to be flat, but as you can see on  my last picture, it's now bending a lot :

https://drive.google.com/drive/folders/1iwQ6TLWefRFuEQVDA_IaLFZokacUni7Q?usp=sharing


What would you advice me for this drying process ?
Does the fabric and the wood under the print soak the water faster than it evaporates from the rest of the piece ? Should I flip it immediately onto a plastic sheet ? (the problem being that it is very difficult to flip the piece while the clay is still fresh) 

Thanks for you help 

 

[PeterH]

I assume that the first picture is before drying, but the warping seems to be present.

Perhaps at least some of the warping is occurring as you free the fabric?

[Hulk]

Hi Miles, good question.
I wonder if placing the piece on onto its flat and weighting it down might serve; you'd have to wait until the form had firmed up some.

There might be a learning curve along a) placing the piece on something slick, hence slowing the transfer of moisture, and b) sliding the piece onto a pottery plaster slab, hence speeding the transfer of moisture from the contact surface (the top/flat part/roadway). When the piece is too fresh to turn, a flat surface can still be brought up on the vertical.

Good luck! Post back your findings

[Babs]

Not knowing how this clay reacts, freeing the fabric may be the cause. Why free it?

If form is not rolled onto the fabric it would not be stuck to it???

Put a piece of kitchen paper between fabric and where it is being contructed? 

[Rae Reich]

If the fabric printing surface could be set on a ventilated platform, a fine screen or punched metal, the drying could be made more uniform. I would suggest completely restricting drafts and temperature changes to dry slowly and evenly. 

[Callie Beller Diesel]

How close is the printing head to the piece as it’s squishing out the clay? (Technical terms there, I’m sure.)

I’ve seen some videos where the extrusion was a slight distance from the forming piece, and it distorted somewhat as it fell. I confess to having never worked with a 3D printer, but could the plastic memory from any possible scenario like that be coming into play?

[Rae Reich]

Looking at the photo again, I think maybe the drying/shrinkage problem is because of the design. The center portion is the weakest, that is, the least reinforced by surrounding structure. If you could change your design in that center section to have slightly thicker walls it might have a stabilizing effect during forming and drying.

Alternatively, you could make the form symmetrical when cast - with two ‘legs’ sticking up as well as two down - then cut off the upper ‘legs’ after drying. This would equalize the tension on the center section while drying. 

Edited April 29, 2022 by Rae Reich

[PeterH]

The line I've added seem to show that there is warping in the first photo you posted (IMG_2268.JPG).

Can you state if this photo was taken before or after drying?

[Babs]

@Mileslgrlots of questions lots of folk thinking about your problem.

Any feedback from you?

[Mileslgr]

On 4/25/2022 at 1:34 PM, PeterH said:

I assume that the first picture is before drying, but the warping seems to be present.

Perhaps at least some of the warping is occurring as you free the fabric?

Hi Babs, thank you for your answer, the pictures have been taken after drying

[Mileslgr]

On 4/26/2022 at 2:57 AM, Babs said:

Not knowing how this clay reacts, freeing the fabric may be the cause. Why free it?

If form is not rolled onto the fabric it would not be stuck to it???

Put a piece of kitchen paper between fabric and where it is being contructed? 

The fabric is used so that the first layer of clay stick to the surface it is printed on. Since the nozzle of the machine goes pretty fast, it is necessary to have this rough surface at the bottom of the piece. Once printed, I free the fabric so it can shrink with the piece at the same time. Otherwise the extremity of the shape start to bend like the one on this picture : 
 

[Mileslgr]

On 4/25/2022 at 6:03 PM, Hulk said:

Hi Miles, good question.
I wonder if placing the piece on onto its flat and weighting it down might serve; you'd have to wait until the form had firmed up some.

There might be a learning curve along a) placing the piece on something slick, hence slowing the transfer of moisture, and b) sliding the piece onto a pottery plaster slab, hence speeding the transfer of moisture from the contact surface (the top/flat part/roadway). When the piece is too fresh to turn, a flat surface can still be brought up on the vertical.

Good luck! Post back your findings

Yes, I have been reducing the size of the object so that I could easily flip it  down onto a piece of plastic foil after letting it dry a bit. It seems to be already better 

[Mileslgr]

On 4/29/2022 at 11:46 AM, PeterH said:

The line I've added seem to show that there is warping in the first photo you posted (IMG_2268.JPG).

Can you state if this photo was taken before or after drying?

 

On 4/28/2022 at 7:01 PM, Callie Beller Diesel said:

How close is the printing head to the piece as it’s squishing out the clay? (Technical terms there, I’m sure.)

I’ve seen some videos where the extrusion was a slight distance from the forming piece, and it distorted somewhat as it fell. I confess to having never worked with a 3D printer, but could the plastic memory from any possible scenario like that be coming into play?

Yes, very good point. We have noticed that regarding the direction the nozzle would extrude (clock-wise or counterclockwise) for the same object, the direction of the distortion would also change. So there is definitely some tensions created through the layers of clay while the nozzle "pull" on the extrusion. 

I am use to work with slipcasting, and I was shocked how crazy were the distortions compared to this technic. 

[Mileslgr]

On 4/29/2022 at 7:44 AM, Rae Reich said:

Looking at the photo again, I think maybe the drying/shrinkage problem is because of the design. The center portion is the weakest, that is, the least reinforced by surrounding structure. If you could change your design in that center section to have slightly thicker walls it might have a stabilizing effect during forming and drying.

Alternatively, you could make the form symmetrical when cast - with two ‘legs’ sticking up as well as two down - then cut off the upper ‘legs’ after drying. This would equalize the tension on the center section while drying. 

Thank you for your answer, it is a good point. Unfortunately I have no more time to further develop this design, since I made it through a residency and I am getting to the end now.
Also, the idea is to produce a large production a this piece in the future, and the people who would produce it needs the less steps as possible in terms of finition, in order to make this product affordable. 
 

[Mileslgr]

On 4/29/2022 at 11:46 AM, PeterH said:

The line I've added seem to show that there is warping in the first photo you posted (IMG_2268.JPG).

Can you state if this photo was taken before or after drying?

Sorry, the picture was taken after drying 

[Mileslgr]

On 4/29/2022 at 12:09 PM, Babs said:

@Mileslgrlots of questions lots of folk thinking about your problem.

Any feedback from you?

Yes sorry for the late answers, I had some hectic days lately. I will keep you all updated with the final results 

[PeterH]

Digital fire has a page on 3D printing, with some comments on the clay-related issues

3D-Printed Clay https://digitalfire.com/glossary/3d-printed+clay
A major challenge is making the clay set fast enough so that the next layer applied over it will have a firm base. When plastics are extruded in typical home 3D printers they simply cool and firm up, but clay pastes are soft and fragile. Additions of polymers can help set them after extrusion. Augmenting the water with alcohol (e.g. ethanol is preferred over isopropyl alcohol because it carries off more water as it evaporates) speeds evaporation. Pure ethanol and clay is flammable and the plasticity and dry strength are poor. But 50:50 water:ethanol is not flammable and workability is excellent. However, even though the clay feels cold evaporation does not proceed that quickly, it needs a fan to stiffen up fast enough. Under greater pressure stiffer pastes of lower water content can be delivered. When large objects are printed, fans and the extra time between layer delivery may be enough to enable structural integrity. In some types of 3D printing, support structures of a different material are printed with the item and these are later removed, this could be practical for ceramics also.

[Mileslgr]

1 hour ago, PeterH said:

Digital fire has a page on 3D printing, with some comments on the clay-related issues

3D-Printed Clay https://digitalfire.com/glossary/3d-printed+clay
A major challenge is making the clay set fast enough so that the next layer applied over it will have a firm base. When plastics are extruded in typical home 3D printers they simply cool and firm up, but clay pastes are soft and fragile. Additions of polymers can help set them after extrusion. Augmenting the water with alcohol (e.g. ethanol is preferred over isopropyl alcohol because it carries off more water as it evaporates) speeds evaporation. Pure ethanol and clay is flammable and the plasticity and dry strength are poor. But 50:50 water:ethanol is not flammable and workability is excellent. However, even though the clay feels cold evaporation does not proceed that quickly, it needs a fan to stiffen up fast enough. Under greater pressure stiffer pastes of lower water content can be delivered. When large objects are printed, fans and the extra time between layer delivery may be enough to enable structural integrity. In some types of 3D printing, support structures of a different material are printed with the item and these are later removed, this could be practical for ceramics also.

thanks a lot for the link ! That's really interesting 

[PeterH]

1 hour ago, Mileslgr said:

thanks a lot for the link ! That's really interesting 

In that case I'll chance my arm and mention this one as well.
A Guide to Clay 3D Printing http://www.keep-art.co.uk/Journal/JKeep-Guide to Clay 3D Printing - 2020.pdf#id.o2ieis64brlz

It's mainly directed at the DIYer, but seems to have lots of  potentially interesting test results.