Tag Archives: 3d printer

How Does Your 3d Printer Know What to Print.

what does your 3d printer understand

Believe it or not your 3d printer is a dumb machine. It needs to be told exactly what to do and when to create those wonderful models you require from it.

So how does your 3d printer know what to print: The file you create with your slicer tells the 3d printer exactly what to do and when to do it. It contains commands to move the printhead and how much material – if any – to place on the build plate and the heat the bed and nozzle need to be kept at.

Your 3d printer contains mechanical parts – the stepper motors- which need telling what to do. You also have heaters which need to know what temperature to be at…

What tells your printer what to do 

Your 3d printer is a bit like the old paper printer in the respect that it needs another computer to tell it what to do.

You can think of your 3d printer in the respects of the paper printers.

how a slicer works

Think of a pile of paper sat next to the model you want to print.

If you could push the pile of paper into the model then each

piece of paper would have a slice of the model on it.

If these are printed out in the right order then what you get with your 3d printer is a finished model.

If they are not printed in the right order what you get is a mess of plastic….

What are slices

As shown above you can have a pile of paper the same height as the model to represent each individual layer of your model.

But you can change this – within reason- with the size of your 3d printers nozzle.

The larger the diameter of nozzle the thicker the slices can be.

So instead of paper think cardboard….

A lot less slices.

But with that comes a lot less detail.

So if you are printing a plain box with little detail, would you use the finest nozzle you can or the largest nozzle to get the job done quickly…

I know i would be using the largest nozzle…

As i said you can control the thickness of the slices, this is done in a slicer program on your computer.

What does the slicer do

A 3d printer slicer does the same job as those meat slicers in the butchers.

Place the model in where the lump of meat goes .

butchers meat slicer
by Flickr

Dial in how thick you want the meat ….

And slice it off layer by layer.

That’s where the analogy stops as the slicer has to recognize what is an outside layer.

How thick have you set the wall thickness to be and what infill do you want.

It is a pretty complex program which takes your model and cuts it up into slices and works out where to position the nozzle and how much filament to extrude at that time.

And when it is moving between printing areas to turn off the extrusion and move quickly to prevent oozing and start printing again.

As the inside of the mode is not seen it doesn’t have to be full of plastic, so can be printed with an infill of a certain percentage, just to support the structure as it grows upwards.

You can adjust this infill, right up to full, to allow the parts to be used mechanically.

To allow the material out of the nozzle it has to be heated up so that it becomes runny, but not overheated…

So the slicer tells the printer that the nozzle needs to be at this temperature and the printer adjusts the heater until it reaches it. The printer now controls the nozzle temperature until told to change it.

The same with the bed temperature to help the model stick to the buil platform.

Every little move, very little extrusion must be listed in a file to control the various parts of the printer correctly.

So the final push of the slice button may, on a complex model take a few minutes to create the file for your printer to create the model from the screen.

What is g-code

The file the slicer produces is in a format called g-code.

This was invented to control CNC machines – or even further back for manufacturing pcbs.

The pcb’s conductive layer is in effect a single slice of a model, and can be printed using conductive filament…..

As CNC can work in 3 dimensions this format was thought to be ideal for adopting for 3d printers.

There is a move to change the format to one which is more suitable, but the adoption is slow…

So…the g-code – what does it look like….

example of gcode

This just looks like a bunch of numbers with letters in front – and that in essence is g-code.

It tells the printer where to start and then how far to move in the x direction and y direction, how fast and how much material to extrude over that time.

Then at the end of the layer is tells the z axis to move up to the next layer.

And it follow this file step by step until is reaches the end.

Where it switches off the heaters for the extruder and bed, makes the stepper motors go silent and waits to print the next model.

What are the main codes in a g-code file

The file commands th printer to go through a process.

The first command usually is to home the printer (G28), so that it know where it’s printhead is.

Then it heats up the bed and then the nozzle( M140,M104 and M109).

It usually raises the nozzle and goes to the start point for printing(G0,G1).

And now goes through the move and extrude commands in the file.

Even for a simple 25mm square calibration piece you have thousands of commands, depending on the layer height.

How do you get the file to the printer

There are three main ways to get the g-code file to the 3d printer and they are :

  1. SD card
  2. Usb cable
  3. Octoprint

Copying the file onto an sd card and inserting it into the printers card slot allows you to select the file to print.

There can be issues with sd cards not being read– with the shaking that the 3d printer does and the card slot being on the casing can make the contacts intermittent and fail to read the next command, in which case the print fails.

This can happen at any height, but with the anet a8 it usually happens as the model grows in height and the slightly unstable frame rocks a bit more.

But it is normally a reliable method of file transfer and means you can power down your computer or use it for other things while printing without worry.

If you decide to use the usb then you need to make sure the computer does not go to sleep while printing.

Or update any software to make it reset – a common problem with windows….

It also means the computer needs to be located close to the printer  – not always convenient to use at the same time.

And you need to not overload and stop the usb from communicating as the printers are not overly intelligent and will crash with too many commands.

Alternatively you can add a raspberry pi with octoprint to control your printer.

You can communicate with it wirelessly – sending the file over for the model and then this is sent onto the printer.

You can get feedback on how the printer is doing, how much longer the print has to go and other information that means that you can locate the printer in a remote part of the house if desired.

And finally….

So you now know how your 3d printer takes the file from your slicer.

Where you have set the height of the slices and what the filament needs.

Which the slicer finds the paths of the model to create the outer skin and the infill.

In the background it is a very complex process, but on the surface one which is getting easier to use.

And hopefully in the future even easier, with the slicer embedded into the printer itself.

Then it will be download or create the model and select the quality and hit print….

At the moment you need a few more steps and to follow a workflow.

Getting used to going through a process will prevent you from making too many mistakes -we all make them don’t worry…..

And being happy with the newly created model from your printer is what this process is about.

Understanding a little more, when you see the g-code now it may not be all confusing as you start to see a pattern or use craftware to view the model before you print and see the holes and start to know what to alter to repair them.

If you have any questions about this process please leave them in the comments below and i wish you good printing.


 What is 3d Printing Workflow

3d printing workflow

 What is 3d printing workflow

How do you get from the concept to something in your hand with an fdm printer….

What is 3d printing workflow: 3d printing workflow is the method of taking a concept of what you want and turning it into a finished model that does what it is intended to do. 

Let’s break down the workflow into it’s what is actually happening – and this happens for each print you do, whether you follow these exact steps deliberately or just merge them in your head.

3d printing workflow

There are multiple steps within the workflow and these are broken down as :

  • Concept : what you want to create – be it a broken piece or a new design
  • 3d cad: design the article in 3d cad to suit the concept- taking into account 3d print design rules
  • Stl translation: translate the 3d cad file into a mesh file that is necessary for the slicer
  • Sliced: taking the mesh file and creating a layer file for the 3d pritner to be able to print
  • Gcode check: always worth examining the gcode to see if it will look anything like what you want.
  • Print: always a nervous time for the first layer but the exciting time to see the model grow
  • Post processing: removal of supports, stringing, if necessary holes enlargement painting.
  • Done: sit back and look at what you have created…..

let’s look at these in a little more detail.

Model concept

Something breaks, you find that you need a hanger for something,

board game piecesyou have an idea that will revolutionize the beer drinking world, a missing piece from a board game….

All of these will spark off a need to build something.

So you buy a 3d printer.

It may happen the other way around – that you get a 3d printer and print a few models, get disappointed with some of the results and put it into the corner.

But sooner or later you find something that sparks that ‘i have something that will make that…’

You now have something in your head you want to bring into reality.

The first thing to do is to sketch it down with pencil and paper.

Look at it, can you imagine it doing what you need it to do.

Does it look like what you imagined.

Turn the paper, redraw it from a different angle.

Happy, well we can now commit to drawing it in a computer

3d cad programs

To some, now is the scary bit.

3d cad drawing

But 3d cad programs have come a long way to helping the user.

Some of them have basic building blocks – square, cone, ball, and a few others .

With these simple shapes you can build up hugely complex models.

Or if you are more of an organic person there is software that starts out with a ball and you can pinch, extend, add blobs and mould to get the final model.

If you are used to cad programs at work – there will be similar ones – freecad, fusion 360, openscad or similar.

So you can create your model in the cloud or offline to the level of detail you want and the measurements you take.

You may need to come back to this later after actually printing it and adjust it slightly to make it fit – it is normal in industry to go through a few iterations or designs before the final model is accepted and this is what 3d printing excels at.

Stl file translation

To get the cad model into a form that your 3d printer knows what to do with takes a two stage process.

The above model from the cad program needs saving in a format that can be passed through a slicer – don’t worry this is explained below…

But slicers need models in a certain format.

So the cad programs can export the model as a mesh.

Think of the surface of the model, the skin being made up of triangles.

So a curve looked at through a magnifier would consist of loads of triangles rather than this smooth curve.

And all these triangles need to be the right way round for the model to be watertight – yep it means what it says – another word for it is manifold.

The model needs to have no gaps or meshes the wrong way round or the next process gets confused.

You can use a lot of the cad programs to see the meshes to check them or there are specific programs to check the model – like netfabb

The exported file is in the form of a stl file – yep those are the ones you download from places like thingiverse.

These are the files sent onto the final processing before getting to the physical model.

They are processed in programs called slicers….

3d Model slicers

To get the mesh models to print on a 3d printer you need to simplify what the outside or the surfaces are like.

The 3d printer is really a 2d printer that can be raised in height, so

3d printer slicer softwarealmost a 2.5d printer building it one layer at a time.

It can’t turn the extruder upside down to print things underneath, so it needs a process that formats the surfaces into layers.

Or slices…..

Hence the term slicer  – they convert your model into a number of slices that can be built up.

Understanding what slicer software can do, what you can change and what they have hidden is one of the keys to getting good 3d prints.

There are a few slicers out there, not all very user friendly and i hope in the future they will be built into the printer itself to make them easier to use…

We will see…

But in the meantime it can be one of the stumbling blocks for a 3d printing.

If we take one of the most common slicers, cura, and look at what you can adjust – currently ( april 2020) there are over 200 parameters in expert mode with everything turned on that you can adjust….

I don’t want to think of the number of permutations of changes you can make, but it will be in the billions.

This is one reason for quick and dirty prints, i keep an old version of cura ( all the old versions are still available) with it’s simple interface ( makes it a lot quicker to setup and get the file for printing as well)

I am also looking at another slicer with interest called slic3r, which prusa used to copy and add their own mods to, but they have now gone in their own direction and i will explore that one as well in the future.

But getting a slicer that works well with your printer makes your job here a lot easier.

This is the point where you are combining your cad with the material and the printer parameters.

You setup the materials, the rate of flow for the material, the layer height, the speed of the printer, and a few other settings.

Then you press slice, and it takes the model and creates a stack of 2d layers for the printer to understand.

This is the reason you get that characteristic ridged surface on the 3d printed model.

One thing i really would advise you to do is to check your gcode file ( this is the output of the slicer to be passed onto the 3d printer).

If you open the gcode in a program, you are not printing blind.

You can see what the printer will do, where it will start layers, where it will travel between printing parts, what it thinks is an inside surface and an outside face.

In small areas whether it will fill in the details or it will miss parts.

All of these can be sorted in the computer, within the limitations of the technology.

And there will be less failed prints and frustration…..

It is quicker and easier to make changes to the slicer now rather than waiting for the printer to finish…

Once the file has been checked and looks ok on the computer it is finally time to get it out into the world…

3d Printing

These have been around for a while now, they are getting better and easier to use.

The printer is in effect a 3 dimensional robot which lays down

3d printed cloth vase
cloth vase
by Sashko- thingiverse

material when commanded.

So the gcode file the slicer creates is the one that needs to be loaded into the printer for it to replicate the original model.

This can be done with a computer interface ( making sure the computer doesn’t go to sleep as printing times can be quite long ) or it can be transferred to a sd card ( always my preference)

I do smile when i read in forums that the print got to 90% and the computer decided to carry out an update to windows…..

One way around this is to put your internet connection on a metered connection and windows will always ask to update itself……

So you heat the hotend, insert the material you want the model in, select the file for the model and wait…..

The heat bed heats up, the hotend stabilises…and the nozzle moves towards the bed…..

And with its familiar dance across the print bed it starts to lay down material.

And questions start to arise in your head from memories past.

Will it stick to the build plate, did i level the bed enough, when was the last time i cleaned the bed, will i have another power cut…..

But fortunately in this case you have learned that to have the nozzle a little too close to the bed is better than too far away…

And you can cope with the little bit of squish to trim off after.

I always watch the first layer to gauge whether the model will stick.

And yes sometimes it does go wrong, but if you are there for the first layer then you can abort the print, clean the bed and start again.

Maybe even leveling the bed a little before stopping the print….

I do normally pop back to see how the model is going – i am fascinated with seeing it ‘grow’ from the print bed.

As the nozzle and the bed do their dance to create material in the right place to form what has been programmed.

And looking at the screen and seeing 100% with the nozzle lifted away and silent always puts a smile on my face.

And with a sigh i take the scraper and starting at a cornertry to remove the print from the bed.

And move forward to the next and final stage of the 3d printing workflow…

Post processing

Getting the model off the bed is not always an easy job…

I have seen numerous glass plates with chips out of them where the model has stuck and pulled a piece of glass form the plate.

Or in my case with the paper tape on the metal bed, i have ripped up the tape to remove the model from the bed, only to not be able to remove the tape from the model.

But with the model removed you can now hold it up, turn it  around – start to examine it .

Does it look like what you originally conceived, has your mind vision been translated into physical reality.

If it is something to replace a broken part, now is the moment of truth….

Does it fit…..

A lot of time you do need to fettle (technical term for filing, cutting and adjusting the size) things like hole sizes, depending on whether you left enough tolerance for the print.

This is where you will learn what your printer is capable of at the moment and can go through adjustments in the cad program and forward in the workflow ( so reducing the amount of material extruded ) to get a piece you know the size of.

Do you want a smooth finish, does it need a little more curvature.

All these post processing procedures can be now carried out on your model.

Smoother finishes can be material off or filling in the layer lines.

Then spraying with a finish.

More curvature can be change the cad file, or in the case of pla…

Place in a up of hot water – leave for a few seconds – remove and gently adjust  -hold until cool.

But now to have something that a little time ago was just a thought in your head, or a broken article that now has a new lease of life.

With a file that can be shared with everyone around the world to make.

For me it is one of the more magical moments.

I have made a few pieces for childrens doors, and the looks you get when they see it for the first time is really priceless.

Making lithophane lamps, which portray their favourite characters when lit up.

Or giving to grandparents an image of the grandkids when lit from behind.


There are endless possibilities to create and repair things with a 3d printer.

Once you have got bitten with the bug you may never stop.

And you may not stop at one printer.

This is mainly due to the time it takes to create the prints….

So one becomes two….two become three…..you know how it is…..

But this workflow is something you get used to.

It looks a lot, but  lot of the time you will download the model in stl format, so shortening the workflow.

It relly is worth checking the model for manifold, and then after creating the gcode to reduce the disappointment.

And keeping your printer in good working condition, rather than waiting for something to break before repairing it.

You can’t cover everything and they will go wrong or need parts replaced.

So keeping spares in stock reduces the frustration of not being able to print now….

But i hope this has shown you a little of the workflow of 3d printing and has inspired you to give it a go…..

What ….no 3d printer….are you going to let a little thing like that stop you…..

Nowadays you can design the 3d model and order one online from 3d printing shops.

The model appears in a few days through the post.

You can then see how close you are to your vision.

So no excuses and it might make you take up the hobby…..

Thanks for reading


3d printer project ideas: salt grinder repair

While looking around for 3d printer project ideas, I had said to myself that I would make, as far as possible, useful bits!

So I am starting a series of ‘how to design’ repair parts, how to think 

3d printer project ideas : tall grindersthe problem through. How to use the software to get the desired results.

This may be what you are already thinking through, without realising it or you may be just downloading and printing. Either way is good, but if you can design simple parts to repair items that have broken – even better.

We have a tall salt and pepper grinder – two separate items.

A while ago while using the salt grinder a small piece of plastic fell onto my meal.

I didn’t think anything of it until I went to fill it up.

The bottom fell out!!

The rod with the grinder just dropped. It had never done that before!!

On closer examination the piece of plastic that had landed in my meal was a keeper which, when the top nut was undone kept the center rod from falling through.

We had a smaller one to use in the meantime and the tall one was put to one side – other than that it worked ok, the important piece was in good working order so why throw it away?

It is now about 12 months later and it is time I looked at the salt grinder.

Turning it over there are two screw holding the lower piece in.

Removing these the lower piece drops out.

3d printer project ideas: inner pieces

The screwed in bit is made up of two pieces, an outer plastic piece and the inner ceramic grinder part.

The outer plastic piece is not really any use any more – just holding it there are pieces falling off. The salt has completely corroded it. Not the normal corrosion but it appears to have changed the structure of the plastic and it is crumbling away.

Now being careful, I extracted the inner ceramic piece without

3d printer project ideas: salt grinder piece brokendamaging the outer too much.

I need to draw up the outer, to remake it in 3d printed plastic. Will this survive the salt atmosphere? Don’t know – there is very little data on the survival rate of PLA in salt water. Although it is made from corn starch, I am still a little wary of contamination. But it will be a useful exercise to draw up the outer and at least print it off in readiness for more suitable material.

Taking out a note book and pencil – it’s still easier and quicker to do this, unless you have an all- in-one with integrated scanner – then you have the advantage over me. Just scan the object – make sure it is now hollowed out correctly then print it!!(well that’s the theory at least!!)

Up until the time I worked out it was a separate part I was looking to add a strap across the bottom, fixing it with the two screws. I would have rotated the strap through 90 degrees from the screws and affixed it onto a ring around the bottom.

3d printer project ideas: quick sketch

See quick sketch for details.

So using Google Sketchup how do we draw up the piece?

Turning the piece around you can see it is made up of discrete shapes. Tubes, rings, flat pieces so nothing too difficult – except it is the most complex part I have made with Sketchup.

A couple of quick sketches and I think I can simplify the piece from what is there, and thicken up the lower wall, always a bonus.

With things like this you need to look at how you are going to print them, if you get it wrong then there is a good chance an overhang will droop or even worse break. So with this piece print it from the bottom up with the strap at the base and it should be possible.

So taking a break from here until I have drawn up the piece I will post this and get back to you with the drawn up piece.

To be continued

How would you have designed the piece – if you have any ideas then please leave them in the comments box below. Have you any 3d printer project ideas you would like to see me make, leave a reply in the comments box below.

Many thanks for reading