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No shrinkage factor in UI


tapirath
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Posted · No shrinkage factor in UI

Hover over the (i) in the Setting Visibility dialog, and you will get a somewhat cryptic hint for the reason why the setting is hidden even though you checked it. This is true for more settings (eg when you don't enable supports in the settings, most support-related settings are hidden and get such an (i) icon and explanation why the setting is not visible).

 

In the case of the shrinkage factor, that setting is just not ready for prime time yet in the current version of Cura, so it has been disabled for all printers. I believe it will be enabled in Cura 5.0.

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Posted · No shrinkage factor in UI

I can see where this is difficult to implement.

 

When designing molds I would design the part to it's exact dimensions and then scale the part up by the "shrink factor" of the particular material the production part would be made of.  The scaled part would be subtracted from a block, and I'd have my scaled mold cavity.  The toolpaths would be generated to cut that cavity.  This worked because shrinkage would be consistent throughout the production part in the X, Y, and Z.

 

In FDM since the toolpath is the toolpath, it would seem that shrinkage might only occur within each "line width" rather than being cumulative across the entire model.  For some materials (Ex: ABS) the shrink factor may change with height off the build plate.  The geometry of the model may well come into play.

 

Consider a 25mm cube that is being injection molded.  If the shrink factor is 8% then the walls of the mold cavity would measure 27 x 27 x 27.   If I intend to print a mold for that part (using Cura), then that would also need to be the model size.

If I intend to produce the same 25mm cube using an FDM printer (at a 0.4 line width) then do I really want the toolpath scaled up to 26.6 x 26.6 x 27(?) or do I just scale the line width to .043?  All the line widths or just the Outer Wall?  Do I leave the Z alone?  Should just the top layer be scaled?  Is  the Z scale different than the XY?  How about around these vertical holes?  Then there this is this partial horizontal cavity?  Decisions, decisions.

 

In the end, I think it will still boil down to the experience of the operator.  "This type of shape requires shrinkage to be applied here, but not there, and with 1/2 as much applied over at this other place.".  That pretty much puts it back into CAD.  The slicer can then "just print the damn part".  Prototyping will never go away.

 

 

 

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  • 2 weeks later...
Posted · No shrinkage factor in UI

I'm just trying to find if Cura automatically calculates shrink in relation to the material that is being used. It seems like the details of shrink have been left out. Recently, I have been heating 3d printed items for 12 hours in my precision oven as an experiment.


Tim

 

 

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    Posted · No shrinkage factor in UI

    Heat treating your 3D prints eh?  Time for a story.

    My friend was a mold maker.  Occasionally a customer would bring a mold back for re-work due to a change in the produced parts, or for repairs.

    The molds were aluminum and some were quite large.  Heat transfers very well through aluminum so to weld the large molds they needed to be heated up to around 370°C.  A old commercial gas stove was used for that.

    So a new employee gets tasked with heating up a mold.  He throws it onto the stove, cranks up the heat, and goes to lunch.  When he got back the stove looked like a Salvadore Dali painting with the aluminum melted down all over it.

    They scrapped the $1500 stove, the $30K mold, and the new kid shortly after lunch.

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    Posted · No shrinkage factor in UI
    39 minutes ago, GregValiant said:

    Heat treating your 3D prints eh?  Time for a story.

    My friend was a mold maker.  Occasionally a customer would bring a mold back for re-work due to a change in the produced parts, or for repairs.

    The molds were aluminum and some were quite large.  Heat transfers very well through aluminum so to weld the large molds they needed to be heated up to around 370°C.  A old commercial gas stove was used for that.

    So a new employee gets tasked with heating up a mold.  He throws it onto the stove, cranks up the heat, and goes to lunch.  When he got back the stove looked like a Salvadore Dali painting with the aluminum melted down all over it.

    They scrapped the $1500 stove, the $30K mold, and the new kid shortly after lunch.

     

    Sounds like a serious oven. I have a Memmert oven, only goes up to 300C.

     

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    Posted · No shrinkage factor in UI

    It wasn't an oven (although come to think of it it did have an oven on the bottom), it was a old commercial gas stove they bought from a restaurant.  It did have serious burners though.

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