CAD Design and Drawing

In this page you will find basic introduction of CAD modelling and also how to use slicer programs to prepare your model for printing in 3D printer.

This topic is shared into 3 parts: 

Off course there are many different 3D modeling and 3d printer slicer softwares. Every program has its own special features and some extra tools, but a lot of their core functionalities are the same. Like for example text programs MS Word and Libre Office – their working principle is the same. To make complex 3D models you have to learn every program very well and it takes a lot of time and practice. Usually you need many different training courses and a lot of practice to master some program. 

In this chapter we will learn basic engineering concepts and workflow of 3D printing. The main purpose of this paragraph it to understand most common programs and software what is used to make models and print them in 3D printer. 

In general terms, all programs witch are used in 3D printing are devided by two - modelling and slicer software.

In the study material below, you will find:

Engineering and designing ABC

Every thing what you see around you or touch is somehow manufactured.  Almost all the machines consist of many smaller details and parts - for example modern passanger car engine has over 200 independent parts!

All of them have to machined and fabricated somehow.  There are various ways to fabricate some detail - casting, milling, drilling etc... 

Usually all the parts and inventions starts with someone's idea-  there is necessity and demand for something new or some design have to be improved. After design is calculated, some kind of prototype is made and all the design is then evaluated and also changed if needed. 

Historically wood, clay or plastic molding was used as main materials for building prototypes. But manufacturing them was almost mainly manual labor and all the process - design idea to final product - was very time consuming and according to this- quite expensive.

Cycle helmet prototype - it takes many days to make and big changes are time consuming to make!

CAD designed helmet- changes can be made very fast and when 3D printing is used as prototype - relatively quick and a lot ef cheaper.

First prototypes are made with plastic and using 3D printing. When design is revised, metal moulds/dies will be made and manufacturing can begin.

Waterpump flow analysis.

Designing gun laser sight cover- first very rough-then inspected and modified- then final product

Car frame stress analysis.

Nowadays almost all industries use CAD - computer aided design- modeling environments and programs to make prototypes and new designs.

CAD drawing and modelling method is very quick and it needs usually only one person to do. When some kind professional software is used, then there are many different ways to analyse your design- calculate strength or even air/water flow rates. These functions off course need very advanced knowledge and programs, but gives vision what is possible with CAD programs and how real life engineering and prototyping is done.

Why it is more beneficial to use additive manufacturing (3D printing) in prototyping?

Its cheaper, faster and easier. 

Steps of 3D printing

Now as we know overall ideas of engineering, lets look closer 3D printing process. 

Off cource you dont't have to follow up and think threw every step very professionally, especially if you are just learning and making fun figures and printouts.  Steps mentioned below are intended for real prototyping and reverse engineering applications. 

Lets make small overview for each step. If you are using 3D printing more often and making real working models, then you will pay more attention to each step.

As you already know, all the designing process starts with somekind of demand- wether it is big engineering task to solve some major problem or it is just a humble wish to have new astronaut toy - all the design process is the same. Even if you don't know the exact outcome and final product design, you start to manufacture something. The more conditions and restrictions you use in your design, the more precise and accurate model you get- that's called engineering!

2. Develop 3D model using CAD software

Next and maybe most labor intensive step in 3D printing is making a 3D model. There are many programs for that and we will discuss their specific characteristics them in further topics.

If you need some special design, you have only one way do to that- model it yourself! But if you wish to have something such a complicated as a detailed astronaut model, be ready to make it several days!


joonestamine.mp4

Simple Solid Edge (very simple and basic) clamp design.

cults_example.webm

Downloading premade model. Look carefully working flow- please evaluate and sort out real printable files. Also are they print ready or need to have to have some extra work.

One possibility when you need something more common and not so special (e.g. astronaut figure), you could use some premade models witch are found in some special oriented community pages. Few examples are cults3d.com, thingiverse.com, free3d.com  and  yeggi.com etc....

Like always with free things, be vise and look carefully what to download.  Pages mentioned above are just few of many, but can be trusted and no commercials or viruses has not been involved so far. 

Also when downloading, don't let nice pictures to distract you. You have to keep in mind your printer and filament quality and capabilities. Many colored designs are painted afterwards or used multi colored 3D printers. Some designs also may include many little parts- you have to assemble them after printing. Offcource there are models witch you have to pay some money- they should be advanced and more thought out. 

3. Export 3D model to .stl/.obj format

Whatever 3D modeling software (Solid Edge, Solidworks, Autocar, Tincercad, Fusion360 etc.. ) you are using, they all have some special features build in program. If you save your 3D model in whatever program own file format, then you always add some extra info - model material, color,  measurements, tolernces and many more...

In 3D printing, you basically need only your 3D model "outer shell" . That's why  mainly two file formats are on use- .stl and .obj    

They are neutral file formats, witch can be opened in almost every program.  

.stl - format uses a series of linked triangles to recreate or reproduce surface geometry of the 3D model. The more triangles used, the higher resolution the 3D model will have. STL file is widely used because it is simple, light and easy to be handled by 3D machines and software.

.stl is bad, because files saved in this format, cannot be changed or edited afterwards- only size can be changed.

.obj- is used as universal format for the wider field of 3D modeling. The OBJ file contains data that not only describes the shape of the 3D model, but also its geometry, texture and the original mesh with which it was created with. Its important, because main difference with .stl is, that .obj file can be changed afterwards. So its very useful when sharing files or if you wish to make some changes.

For conclusion we can say, that modern file sharing platforms and computers can handle .obj files also. But because you can edit them, .obj should be preferred as 3D model file.

How to save .stl or .obj?

This only needs basic computer skills. If you have reached so far in this webpage, then it seems like you are more than capable of doing that 🙂

Whatever CAD program you are using, you just have to choose "save as"  and suitable file format for 3D printing - .stl or .obj format.

objstlsave.mp4

4. Use slicing software to prepare file for 3D printer- making G-code

As we already mentioned, 3D printer only needs information about your 3D model outer shell and overall shape. Aall 3D printers need G code for their operation. To convert your CAD modelled detail into G- code you need SLICER program.  Like name says, this will make the conversion of a 3D object to specific instructions for the printer.  To make it simple- they are coordinates, moving speed and printing specs (filament speed, nozzle temp). 

G-code is a language that humans use to tell a machine how to do something.

astronautGcode.mp4

Creality slicer software-  3D model is converted to "lines" and coordinates for 3D printer. 

If you look carefully, you can see in the video how changes of infill is done. Infill is web like structure inside model- more infill, stronger model but more added printing time!

5. Printer setup

This is one if not most important part of 3D printing. 

Good comparison in this case are cars- BMW and some cheap car are both cars- they drive the same and they have all the same controls. Nevertheless they don't feel the same and drive in same quality. Even same BMW models don't drive the same- they all have some special additions and functions. Also, well tuned cheap car with good driver is deffinetly faster than new and powerful supercar with bad settings and driver.

Same is with 3D printers. You have to get to know with your 3D printer and its special settings. Whatever printer you have, there are a lot of web pages and communities for different settings and help topics. Just google and test them. Very common are "3d benchy"  models- small but demanding figures witch show you some mistake in overall settings. 

3DBenchy, the tiny boat- designed for internal testing purposes at the Swedish 3D solutions provider Creative Tools, is now the most 3D-printed model in the world. 

Here are basic "things" you have to check before every print!

They are little bit different things, but affect printing progress in makes same manner. If filament nozzle is too far away, extruder don't "push and melt" layers together. Different plastic strings are visible and they don't melt together. If nozzle is too close, then you will scrape heatbed or glog up the nozzle. Modern 3D printers have automatic bed level adjustments, so you are free of that problem. But its good to know the idea and make a little adjustments if needed.


Too far/ok/too close nozzle.

Different problems - too far/all ok/too close/too fast.

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Automatic bed leveling. Image source: bit.ly/3M3Sgd9 

There are various different types of filament (plastic whats melting and becoming your model). Different filaments have different purposes and characteristics. 

Most common material for 3D printing is PLA. Its melting temp. is about 210C.  Little tip: every roll of filament has a sticker on it, witch tells you the right temperatures. You almost cannot fail at the beginning when you use PLA and 210C. Different temperatures comes with different materials (e.g Flexible TPU) and settings for this material are very individual for different 3D printers and need just trial and error method 🙂

SIMPLIFY 3D table for different filaments guide.

A heat bed is part of 3D printer- platform on what 3D model is printed. Because we use melting plastic, we need to keep temperature as good as possible. 

Heatbed is needed because: 

6. 3D printing

Actual 3D printing process seems at first glance like very hard and important part. In real life that's the time where you as operator has very little to do. 

If you made your model slicer program thoughtfully and choose right filament and its temperature, then you just have to press start button!

Its good idea to stay aside when printing is doing its first layers. Most of bed leveling/filament/temp/settings/heatbed ashesion(sticking) problems will occur then and you can make adjustments. If something is really bad, you can simply start over.

video-121baec5-05a7-4329-8b3a-0c7d52d64d5c-1664196783.mp4
grip3D.mp4

3D printing is quite time consuming progress- print on the left took about 11 hours to make, to the rihght about 7hr.

7. Post  processing

Post processing depends what model are you printing and where you use that. Usually it means to remove some extra material (supports, edges) and maybe file something down. 

To change shell, you can use small blowtorch and "melt" outside layers. Also if you are expert you can use somekind of chemical "melting" with acetone. But remember-  be careful and you have to be expert to to that, because it needs a lot of experience!!

TIP! If you are making holes and openings, be advised that they aren't precise. A thumb rule is, that outer shell and extrusions are about exact size.

Holes and openings are usually nozzle size smaller (standard 0,4mm). This all is mainly depending on your print quality and settings.

Some examples of post processing!

8. Usage

This is maybe most exiting step- you can see real outcome of your 3D printing progress.  

At the beginning its recommended to do lot of different models and in small sizes. Then you will get to know of your printer and its settings and also you are able to find most suitable settings in your slicer program.

When prototyping, then after printout you look and evaluate your design in real life and environment. Then you can make some changes and improvements and printout new detail...   until you find suitable design! Or you just give astronaut to a customer and wait "daddy, its broken, make new one" sentence 🙂

3D printed Clock 17 red dot laser sight cover- first rough model- then modified and improver- final product (printed with flexible plastic)

Just different examples and printouts to finetune your printer.

Can you name steps of workflow when using 3D printing?