Print settings for case mold for high internal detail

[Onesome 0]

I am making a PLA printed case mold so I can pour silicone into it.

 

I want the highest detail on the inside but it is not necessary for the outside. I used a miniatures setting but it was a 4 day print, I realized half way in I didn't need high detail on the outside.

 

Any advice?

[nallath 995]

You could try to invert it; Print a positive in PLA, create a mold over that by casting it and then use that mold to cast your final positive.

 

You could also try to cut the model up into parts; A thin model that sits inside of a casing for support. You print the inner "sleeve" at a very low resolution and the sleeve very rough.

[geert_2 524]

The two-shell concept of gr5 might be worth considering, at least for those areas that need most detail. In injection moulding this is also used: the main mould gets a cruder finish, while areas that need lots of detail, like fine text or optical lenses, are done with a smaller insert with high quality finish. It do not need to be complete sleeves covering the whole model, maybe a smaller area is enough, depending on the model.

 

I have made several PLA moulds for casting silicones. The most important aspect is to remove layer lines as much as possible. They act like a zillion of tiny undercuts, and make it very hard to remove the cast. Any layer lines are also terribly visible in the cast, and they make the cast sensitive for dirt.

 

(You are probably well familiar with the other normal moulding aspects like: no undercuts, venting openings, alignment features, clamping features, etc...)

 

Chemical smoothing might also be an option: I sometimes use dichloromethane. See my recent post here on PLA and PET smoothing with dichloromethane. This greatly reduces layer lines.

 

One of these models is chemically smoothed, reducing the layer lines; the other is as printed.

 

 

[Onesome 0]

Thanks for the replies. Geert I will check your smoothing post.

 

The mold itself is already inverted and a 2 shell solution won't work, I tried that before.

 

Does Cura have an inner wall quality setting? I adjusted the speed for outer/inner but Cura gives a warning about speed differences.

[Smithy 998]

You can set the speed for inner and outer walls. Maybe the setting is not shown by default. But use the search field above the settings, this shows also hidden settings.

[egarstang 0]

I’m also looking for help on this topic. I need to reverse the printed envelope. The default setting makes the yellow face accurate to the model. I need to make the blue face accurate to the model. In other words the wall thickness needs to sit to the outside rather than the inside of the STL shape.