Help creating a mold from an existing model

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domad
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Re: Help creating a mold from an existing model

Post by domad »

TuttleJA wrote: Mon Aug 30, 2021 9:01 pm Hi domad, That's very nice... Maybe some day I'll learn how to add color... Right now, what I need is a negative mirror image so I can 3-d print a mold of the part. Then I plan to use the mold to make rubber parts that look identical to the part you made solid and colorful. Using Boolean, I think I was able to made the part solid and then get the negative/mirror effect, but it's on the wrong side of the mat.
Hi TuttleJA, good morning to the Community!
When you have the solid (!) "Positive" (punch) available, obtaining the "negative" (matrix) is very simple, using any 3D cad, even more so with FreeCad, just apply the boolean function difference between a parallelepiped (a little more large of the "postivo") and the positive itself.
Since the "negative" (matrix) you will use as a mold, one thing to consider is extracting the printed body from the "negative" (matrix). I recommend to slightly incline all the side faces in order to facilitate the draft and to connect all the straight edges. But given the small thickness of the molded body and the material it is made of (rubber / caoutchouc) it could work even without these precautions.
Today (weather permitting) I hope to get the "negative" (matrix) and post the result. :)
The coloring of the faces (it is a very simple thing to obtain in FreeCad with Workbench "Part") was done to highlight the low thickness of the letters, certainly not for aesthetics.
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papyblaise
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Re: Help creating a mold from an existing model

Post by papyblaise »

This is the result of solidification
you don't say how to get the "solidification, I stay with a" non-solid "body
TuttleJA
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Re: Help creating a mold from an existing model

Post by TuttleJA »

Hi Domad, Your help is immensely appreciated. I don't know the terminologies in FreeCAD. I'm a player piano repairman with no training in drafting or engineering. All of what I've learned about FreeCAD is what I found at YouTube, and at 73, I'm having difficulty learning how to use the program.... :?
domad
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Re: Help creating a mold from an existing model

Post by domad »

TuttleJA wrote: Tue Aug 31, 2021 11:17 am Hi Domad, Your help is immensely appreciated. I don't know the terminologies in FreeCAD. I'm a player piano repairman with no training in drafting or engineering. All of what I've learned about FreeCAD is what I found at YouTube, and at 73, I'm having difficulty learning how to use the program.... :?
Hi papyblaise and TuttleJA, greetings to the community!
A careful analysis of the * .stl mesh with Blender highlighted the usual problems (intersections, double vertices, etc.), therefore, to avoid unnecessary headaches with direct solidification, I appropriately chose to use the "Draft" bench to get me the faces (tools Shape2Dview / Facebinder / Upgrade / Downgrade / etc.). Once the faces were obtained, I modeled and blended everything with the "Part" workbench (I could have also used "Part Design" but in the generation of the sketches I would have found myself with a myriad of spline curves with all the problems that would subsequently arise) .
I enclose the file containing all the faces that generated the "positive" solid or punch and then, as explained in the previous reply, obtain the "negative" or matrix.
Here is the link to download the ready-made solid matrix http://www.filedropper.com/matrix2

If you think fit you can make a donation to FreeCad (it will go to the @developers who with their precious time and expertise have created and continue to develop this magnificent CAD), on the main page of FreeCad all the details.
Attachments
generating_faces.FCStd
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matrix1.png
matrix1.png (240.85 KiB) Viewed 1517 times
matrix2.png
matrix2.png (362.54 KiB) Viewed 1517 times
Matrix.gif
Matrix.gif (889.02 KiB) Viewed 1517 times
TuttleJA
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Re: Help creating a mold from an existing model

Post by TuttleJA »

Hi Domad, This is amazing! Thank you, thank you, thank you!!! I'm positive I never would have been able to do this. I will make a donation to FreeCAD. Sadly, however, the base is so thick that it will cost over $300 to have the mold 3-D printed at Shapeways, and my budget is only $125. ;-(
domad
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Re: Help creating a mold from an existing model

Post by domad »

TuttleJA wrote: Tue Aug 31, 2021 1:40 pm Hi Domad, This is amazing! Thank you, thank you, thank you!!! I'm positive I never would have been able to do this. I will make a donation to FreeCAD. Sadly, however, the base is so thick that it will cost over $300 to have the mold 3-D printed at Shapeways, and my budget is only $125. ;-(
.... do not feel obliged but free (!), a greeting :D
TuttleJA
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Re: Help creating a mold from an existing model

Post by TuttleJA »

Hi Domad, Thank you again... :-)
TuttleJA
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Re: Help creating a mold from an existing model

Post by TuttleJA »

Hi Domad, Would it be terribly difficult to reduce the thickness from 20mm to 7mm?
TheMarkster
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Re: Help creating a mold from an existing model

Post by TheMarkster »

TuttleJA wrote: Tue Aug 31, 2021 10:37 pm Hi Domad, Would it be terribly difficult to reduce the thickness from 20mm to 7mm?
It will be very easy to do. In Part workbench you can create a cube primitive to use as a cutting tool. With a boolean cut the parts of the original piece that overlap with the cube will be cut away. You just need to adjust the cube's height, width, and length properties to be bigger than the part to cut away. Here I made it 13 mm tall so it would be 7 less than the 20.
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The final step is to make the cut. Select first the base object from which the material will be cut, then holding down Ctrl key select the cutting tool (cube in this case), then click the boolean cut toolbar icon to perform the cut.
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I think you could probably get away with even smaller than 7mm if you want to save some money on the printing costs.

If you need to make an stl to send to the printers make sure the stl is good before you send it. You can check it in mesh design using the Analyze tool there in the menu. Run all the tests, but do not attempt to repair if it shows problems. Repair will just delete offending parts, not really fix anything. Try netgen mesher when making the mesh if the standard mesher doesn't make a good mesh. It is much slower, but I have found sometimes it succeeds where the standard mesher fails.
TuttleJA
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Re: Help creating a mold from an existing model

Post by TuttleJA »

Hi TheMarkster, Thank you for this information. I'll try it tomorrow.
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