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LePaul

Any really good drawing tutorials, for making objects to print

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I've gone through a few various tutorials for SketchUp, SolidWorks and even tried Tinder (but can't seem to create an account or get in using my AutoCAD one...its broken really good).

SketchUp seems to have a template for the Makerbot Replicator, I wonder if there is one for the Ultimaker / Ultimaker 2?

That said, minus an in depth studio of CAD, I was searching for some tutorials that might give the end user a guide on how to draw a part for printing. I know there are many things we need to be aware of for quality prints, but wondered HOW to draw a part AND have it be optimized for printing

Have any of you encountered any such tutorials/videos that do this?

While I enjoy Thingiverse and Youmagine, I would like to get better at drawing things for my printer to print :)

 

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#1. Years of CAD experience, and I'm still revising the way I design for 3D printing. There's an art to visualizing a project and how it needs to be designed for 3D printing. They say an artist sees the final result of his work before he even starts... he just needs to go through the actions of turning it into reality. I fing it's a lot like that when designing for 3D printing, so be patient, it's a skill that comes with a lot of practice. Tutorials will help you learn the software, but there's no substitute for trial and error, hitting the forums, experimentation, and hands on experience.

#2. About 80% of the files people send me that have been designed in Sketchup have strange problems with the .stl's. Things like objects they didn't design in just floating off in space, parts not touching each other (such as a door handle 1mm away from the door), scaling issues, orientation issues, and the list goes on. I don't use Sketchup so I can't speak to the correct workflow (if there is any) for designing a rock solid .stl for 3D printing. If you plan on using Sketchup I would recommend making sure you're not picking up bad habits that will make for poor .stl's.

#3. Every part is different. What kind of drawing are you asking about? There's organic modeling and mechanical modeling. Mechanical modeling can then be broken down into parts or assemblies. Assemblies need tolerances built in, so It's a lot like designing several parts at once because each part relies on the others in the assembly.

 

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Then I would say... How large? How strong? What material? Are you going to split the hollow rectangle to overcome bridging/overhang problem at the top of the square? If you're going to split it, are you going to design in a way to attach the 2 pieces together?

:p

If it's just a simple hollow rectangle, and you don't care that the top is going to look like crap becasue of overhang, then....

Wall thickness can be printed in anything over the nozzle diameter (well .42mm and on because Cura seems to skip .4mm walls). If you're going for maximum efficiency, then you can design your wall thickness to be a multiple of your nozzle diameter. For example, a nice strong wall may be 3.2mm ( or 8 passes of the nozzle if you set your wall thickness to 3.2mm in Cura). Most people don't do this of course, but if you're printing in something like T-Glase, or Bendlay, where transparency is key, then you don't want any fill, just nice even lines that run the perimeter. Setting shell thickness to 3.2 in this case would be very beneficial.

To throw a wrench in this thinking, the wall size has to be divisible by .4mm, then divisible by 2. For instance, our 3.2mm wall would have 8 passes, divide that by 2, and you get 4 pairs. If you were to try a 2.8mm wall, or 7 passes, 7 passes is not divisible by 2, so you're left with 6 perimeter lines, and one fill line in the middle (the 7th line). The fill may be fine for some parts of the model, while other parts it will try to fill in a diagonal pattern, which would degrade optical quality.

You might try and start with a cube that has been hollowed out to leave 1.6mm walls. (again 1.6/.4=4.... 4/2=2 ...good to go)

You can set your shell thickness in Cura to 1.6mm and it will print quickly and efficiently.

As for Z height, you would need to make sure that you're initial height plus the layer heights = 1.6mm. For example, .2mm initial layer height, and .2mm layer height would work becasue .2mm initial layer + 7layers at .2mm = 1.6mm.

If you have your initial layer set to .3mm, and your layer height set to 1.2mm, then your end result will not be 1.6mm. Cura will either delete a layer, or add a layer, depending on how close it is to rounding off to the next layer.

To get even more technical, for dimensional critical Z measurements, the printer needs to be tuned to print good. Then you'd print a test cube and measure the Z height. In other words, you have your printer printing great, and you proceed to print a 10mm test cube. The XY measurements measure out to 9.98mm x 9.99mm . Awesome, but your Z measurement is 9.85mm. You Have 2 choices here. You can accept that you need to add .15mm in to your design, or you can adjust the bed level to gain the .15mm. Designing the added .15mm in is like a carpenter who adds in the kerf of the saw bade (where the saw blade removes material), so adding .15mm is nothing new.

Then there's strength, where you DO want the diagonal infill. It's a lot like plywood, where each layer of wood is glued in a different direction to add stiffness. In this case, a thin shell of .4mm ~ 1.2mm would leave the rest of the wall to be filled with diagonal fill.

Let's not forget complex parts, where there may some aspects to the part that need to be printed absolutely perfect, whereas other parts of the print can have time consuming fill, extra travel, etc... For instance, if you your hollowed out rectangle had a feature in it that was more critical than the size, strength, or optical clarity of the rectangles walls, then you might set your shell thickness or layer height to print that feature better than the walls.

Almost forgot material. If you're printing in ABS, Nylon, Bendlay or other shrinkage-prone materials, then go ahead and plan on some shrinkage if your hollowed out rectangle needs to be dimensionally accurate then a 30mm x 40mm x 20mm rectangle might print out to 29.6mm x 39.6mm x 19.9mm. Again, printing a test cube and taking measurements from that will lend you insight to design changes you need to make. A 10mm solid test cube is not ideal for this. You're better off printing a test object with walls that are spaced further apart.

And now for splitting. If you are going to split the part, then you need to design in a small gap where two pieces fit inside each other. Think round peg in a hole. If you design in a 10mm hole, and expect a 10mm peg to fit in it, think again. Either the peg will need to be smaller, or the hole will need to be larger. Same goes for all tolerances, not just round holes. I have one machine that prints good with .15mm tolerance for a snug fit, while an older machine needs a .35mm fit. Materials can have an effect on tolerances as well, so again, do a test print and take measurements. I believe there are coin tolerance test models you can download, where you print the part and see if your coin will fit into the part. A more accurate method is to use machinists tools such as drill blanks. You could take a 8mm drill blank, for instance, and model a simple 4mm thick block with several holes, starting from 8mm and working up to 8.5mm in increments of .05mm. When it's printed, try and slide the blank into each of the holes and make notes on the sizes and how they fit. There are 3 types of general fits... Loose, Close, and Tight (we'll omit press fit for now) So if you blank fits into the hole that was designed at 8.25mm nice and snug but slips in and out with slight force (close fit) then you can start designing in +.25mm tolerances into your model when a close fit is needed. You may not need to model in gaps along the Z axis however, as the printer is much more accurate along the Z axis than the XY axis. This depends on the surface finish of the top layers, and weather or not you have designed layer heights in that correspond to Cura settings for layer heights. So,again, if Cura rounds up a layer, then you're tolerance in the Z axis will be too tight.

MAN! A lot to take in, and rather very difficult to sum up in a couple of paragraphs. Like I said earlier, there's no substitute for trial and error, experimenting, and practice practice practice. Make sure to take several notes along the way. Good luck!

 

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IMHO Solid Print is making it sound harder than it really is. E.g. material? Not an issue - for beginners it'll always be PLA. The finesse stuff can be learned as you go along.

What really matters is (1) is what kind of object you intend to print - e.g. arty curvy stuff (faces?, horses?), or engineering shapes (boxes, cylinders). And also (2) what your background is, e.g. do you have any programming experience? or CAD experience?

Personally, I have lots of programming and engineering experience, but my artistic qualities are sadly lacking.

I have tried many 3D design packages, but the only ones that struck a chord with me were OpenSCAD - which has a scripted approach for creating engineering type shapes by combining simple solids, and also SketchUp, which I love for woodworking plans but unfortunately while the image looks great it's hard work to create watertight models which you need for 3D printing. You can create watertight shapes with SketchUp but the software itself doesn't enforce it, so you have to be quite disciplined yourself. I believe there are third party plugins that can test a SketchUp model for validity.

I went from 0 experience with any kind of 3D design software to creating my own model within a couple of hours of encountering OpenSCAD. I thoroughly recommend that you start with that (it's also free).

 

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Or you can do the rectangle project in 3 steps like this with some of the better CAD programs.

Step1 - create a sketch and give it XY dimensions

200

Step 2 - Extrude the sketch in the Z direction

201

Step 3 - Hollow out the rectangle using shell or similar tool.

202

Finished

203

If you want simple, it doesn't get more simple than that. It literally took me 30seconds to build a hollow rectangle.

 

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I have a feeling that "one of the better CAD programs" may be beyond LePaul's budget.

For fun, here's a parametric OpenSCAD script for a shoebox :-

 


wall_thick = 2;
x_size = 200; // external dims
y_size = 100;
z_size = 110;

difference() {
translate([-wall_thick,-wall_thick,-wall_thick]) cube([x_size,y_size,z_size]);
cube([x_size-wall_thick*2,y_size-wall_thick*2,z_size-wall_thick*2]);
}

 

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