How to succeed: Printing in PLA

Ready to throw in the towel?

PLA, such a source of joy with two parts frustration. No doubt you are reading this after spending countless hours scouring the web and trying a million different configurations in your firmware and slicer. Well hopefully I can restore some sanity by telling you what worked, what didn’t and send you on your way to success.

PLA Facts

PLA as a material will always contract whilst cooling. This is physics at play and there is nothing you or I can do about this. However – the trick with PLA is ensuring that we cool it as FAST and EVENLY as possible.

Lets pause and think about this for a moment. Does this mean that getting accurate prints from PLA is a non-starter? Absolutely not – I have had some fantastic prints from PLA.  If we are able to cool PLA fast, then it sets in that shape that it was laid in. The longer it is left in a molten or malleable state, the more prone to curling or shape shifting it is.

The first layer

Nothing, I repeat, nothing is more important than your first layer. In fact the future success of your print depends on it. Here are the rules that I use for PLA – work on each one independently – it is unlikely that there is one magic rule that will fix everything – your success depends on getting each setting correct:

1. Print SLOWLY – I print at 10mm/s for my first layer. Going slowly for this layer is a must as it will improve the chances of the PLA adhering to the print surface.
2. Print MORE – what do I mean by this? Most slicers will have a setting allowing you to print the first layer at a reduced height (Slic3r and Simplify3D shown below. This allows you to squish (technical term) more PLA into less space improving the adhesion to the printer bed.
   

   
3. Print HOT – I have my PLA set to print at 220c for the first layer and then decrease the temp to 210c for the remainder of the print. You do not want to print at a higher temperature for the entire print as this will result in overheating issues (such as deformed struts or columns) or worse you will experience curling – where the edges of your corner turn horn like and start knocking your nozzle. If this does happen you are printing too hot from your second layer upwards – knock it down 5-10c – this wont fix it on its own however – read on.
4. COOLING FAN – this is a golden rule – do not use a cooling fan for your first layer – we want it to be sticky until we start to apply our additional layers on top. You can find these settings in your slicer typically under “cooling”. Once your first layer is down you’ll want to stoke the engines and give it all you’ve got – turn your fan(s) to 100% – this will change your world and GREATLY increase the quality of your final print – just look at the difference here – you can easily identify the one which user a cooling fan and the one that didn’t:
   

   
   This felt like a chicken and egg situation – I needed to print a mount for a cooling fan but I couldn’t achieve a good enough quality print – so here was my short-term fix. Also note that the blower style fans put out a LOT more airflow than standard fans:
   

   
5. Printer surface – You will read lots of different things about glue sticks, hairspray and other magical messy adhesives. The good thing is you don’t need any of it, I’ve used the following decision tree with 100% success:
   1. If you have a heated bed – set this to 70c for the first layer ONLY. Tell your slicer to switch it OFF for the remaining layers – you do not want your PLA in a warm state where it can change shape during your print. Keeping it sticky whilst laying down your first layer is a GOOD thing.
   2. If you do not have a heated bed – get yourself some masking tape (that’s what we call it in the UK). You can go posh with 3M blue painters tape but I’ve found the usual pound store exactly the same (it just doesn’t look as cool).
6. Always print a skirt – this will ensure that the nozzle is primed and flowing well before you even start the main object – it also reveals any uneven beds very quickly! 2 skirts for small to medium objects and 1 for large will suffice.

If its still not sticking read on – you have other problems.

Additional troubleshooting for the first layer

Is your filament curling around the nozzle or getting dragged around the bed?

Your printer nozzle is too FAR from the bed – start by lowering (or on a DELTA increasing) your Z height by 0.05. After each change try to print a 40 x 40mm calibration cube.

Does it look a gloopy mess?

Your most likely OVER extruding. This means that every time your printer is told to extrude 1mm of filament, it is actually extruding more. Go back to basics and set your E-steps per mm. There are lots of great articles on how to do this so I wont cover this here (unless you want me to – leave a comment).

My filament isn’t being laid on the bed / nothing comes out?

If nothing comes out your printer head is:

1. Too close to the bed – ever tried to push a letter through a closed letterbox? This is exactly what happens in this scenario. The pressure will build up and likely result in your filament being grinded away at the extruder.
2. Clogged – raise the head away from the surface and head the head – try to manually extrude filament – does it come out in a clean straight drop? Or is it curling as its extruded? If its curling in free fall than you have a tiny blockage (many times not visible to the eye) that is affecting your nozzle. Either:
   1. Change the nozzle to a new one (easiest)
   2. Clean it with acetone (overnight) or use a small strand of electrical cable to push through the nozzle whilst heated.

I’ve tried everything and it still wont work

Start again – I have been in this position twice, at my wits end and each time it was something that was out by 0.1mm or a setting in the slic3r that I had overlooked. Re-visit each item above and you’ll achieve success. The very last thing is that the filament you have bought may be terrible. Get some decent filament from the likes of 3D Prima or E3D. (I am in no way affiliated to either of them – these are simply places I have purchased from and it worked).

 

Thanks for reading and happy printing!

Duet 0.8.5 – A major upgrade

After successfully configuring the RAMPS 1.4 controller and having months of successful printing I decided that I would upgrade to a board that has more expansion capabilities such as dual extrusion plus a more powerful 32-bit MPU to deal with the overhead of delta printer calculations.

I was nowhere near the limit of the RAMPS 1.4 board and, to be fair, the only signs of it struggling with the overhead of delta calculations was the slow update of the LCD screen – so purely cosmetic. I plan to create a second PLA only printer using RAMPS 1.4 so it was carefully removed from my kossel and stored for safe keeping.

I ordered my Duet from Think3DPrint3D as I am based within the UK and was pleased to receive it quickly.

There is a strong community behind the Duet board and I could quickly find the information I needed in order to get it wired and configured. One word of warning – be sure to have an Ethernet cable or wireless bridge nearby. You’ll be wanting to use the web interface as your primary method of control.

There are regular updates to the Duet firmware and it has been stable for me with no issues – as of writing I am on version 1.09x-dc42 (2016-03-13).

I found the interface to be responsive and intuitive, however, it didn’t seem to work on with Safari on my iPhone so I grabbed chrome for iOS and it worked great.

A future post will review the user interface of the Duet and the results of my prints post-upgrade.

Thanks for reading!

Setting up the Raspberry Pi as a Wireless to Wired Bridge

This may seem slightly off topic however most of us have a Raspberry Pi floating around somewhere. I have been busy upgrading from the RAMPS 1.4 3D printer board to the Duet 0.8.5 board (new post on the way) and I needed a way of connecting it to my wireless network.

I already had my Raspberry Pi next to my 3D printer so this got me thinking, would it be possible to connect the Duet via Ethernet cable and share the network via the existing WiFi connection?

The answer is yes! It’s surprisingly simple – here are the commands you will need to run on your raspberry pi.

1. Open up a console or SSH session
2. Type “aptitude install bridge-utils”
3. Type “ip addr show” and take note of the two connections you would like to bridge. In my case I wanted my wifi and wired connection: wlan0 and eth0
4. Type “sudo brctl addbr br0” – this creates a logical bridge interface – at this point nothing is connected to it, so lets go ahead and connect wlan0 and eth0
5. Type “sudo brctl addif br0 eth0 wlan0” – this tells it to add the eth0 and wlan0 interfaces to the br0 logical bridge

And that’s, easy !

I wanted all my network interfaces to use DHCP, but if you want them to use static IP simply open up your network interfaces configuration and edit the interfaces as shown below:

1. sudo nano /etc/network/interfaces
2. edit the iface for the appropriate network interface to manual. For example to eth0 interface command will look like “iface eth0 inet manual”
3. When you are done hold ctrl and press x – nano will ask if you want to save changes, simply type Y and hit enter.

I hope this helps! A bridge is a nice simple way of sharing connectivity between interfaces, there are other methods but this one took me less than 5 minutes and does the job! Hope this helps!

 

My first upgrade, the hotend

Well, it wasn’t long until I started to look for some upgrades for my basic Kossel mini kit. I started doing some research and came across the highly reviewed E3Dv6 hotend from E3D. It was able to extrude a wider variety of materials than the standard hotend that was supplied with my kit. It is also classed as an all metal design – which means it holds the heat much better than other designs – something that is important when printing accurate parts, especially on the longer prints. The kit is available in a wide variety of configurations and can also be purchased fully assembled.

In order to fit the new hotend I had to print a new delta effector – the piece that the arms connect to and secures the hot end. A quick search on Thingiverse revealed a variety of effectors, in the end I opted for simplicity and lightness with a basic design (http://www.thingiverse.com/make:192370).

This was a very simple upgrade that dramatically enhanced the quality of my prints. One observation was that I had to increase the amount of retraction due to the increased PTFE tubing as I relocated my extruder to the side of the delta unit. After many tests I finally settled at 4.5mm retraction. This could be reduced if I was to shorten the length of the bowden PTFE tube.

Overall I would say this is money well spent and I look forward to printing a variety of different materials in my future builds.

My first 3D printer – Kossel Mini – Delta

After much deliberation, I decided to bite the bullet. I didn’t want to spend large amounts of money on my first 3D printer as who knew what lay ahead. Would I grasp the concepts? What about this slicing malarkey? All I knew was I wanted one. So after much research into the multitude of shapes and sizes one particular model caught my eye. The Kossel mini.

The Kossel mini is classed as a delta printer, none of that mattered to me – it looked cool, was fast and more importantly there is a strong user community for me to call upon if I were to have any issues. With that I bought a Kossel mini kit – The basic kit cost me about £145 + £20 shipping. I was happy that this was a low-risk investment if I were to hit any barriers along my 3D printing journey.

14 days later my kit arrived! Well packaged and with plenty of communication along the way I was very happy! Now the fun part… assembly.

I was anticipating poorly translated instructions which would need to be interpreted with common sense and of course trial and error – however I was pleasantly surprised. The instructions were more akin to those of Lego – with pictures showing assembly and visual cues to illustrate the components required. After approximately 8 hours of assembly (I like to double check everything and also ensure that my measurements were accurate) I was ready to power my fully finished Kossel Mini.

Firmware, calibration and fine tuning.. wow lots of stuff to do before I am able to start my first ever print. OK here goes – luckily for me I have been using Arduino for many years so the Arduino interface is nothing new, however I understand that some of you reading this may not have seen it before. Here is a quick primer:

1. Grab and install the latest copy of Arduino IDE (the software interface for flashing your 3D printer board (RAMPS, SKS, etc.) from here: https://www.arduino.cc/en/Main/Software
2. Open your firmware (if you haven’t got one read the next section) in the Arduino IDE. You should see many tabs across the top, including the most important one configuration.h (shown below):
3. The most common error is selecting the incorrect board. Almost all of the 3D printer boards out there run on the MEGA2560 chip (you’ll likely know if you are using something different such as the Smoothieboard or Duet). Select the Arduino/Genuino Mega or Mega 2560 board. You can see which board is selected in highlight #1 above.
4. The next most important selection is then telling the Arduino IDE how to connect and communicate with your board. Plug the board in via USB and it should show up in your port selection (same menu as above but 2 options down from board.
5. Once you have nailed these basics you are ready to push the latest firmware to your board! You can test that you have no errors in your code before uploading by clicking the verify button (#2 in the screenshot – step 2) then finally upload the code using the upload button (#2 in the screenshot – step 2).

Firmware, firmware, firmware… so many choices?

It bewildering – Marlin, Repetier and others.. Which one should I choose? You’ll read so many different opinions online. Put simply there is no right answer. I chose Marlin in the end as it was the default firmware shipped with my printer board (SKS mini).

You can grab the latest versions of each firmware from these locations:

Marlin: https://github.com/MarlinFirmware/Marlin

Repetier: http://www.repetier.com/documentation/repetier-firmware/

I wont go into detail on how to set these up in this post – but if this is of interest to you then please leave a comment and I’ll put a 101 post together!

Configuration

Once you have decided on an appropriate firmware (you can easily change between them at a later date) it’s time to tell the firmware some details about your particular printer. The most important measurements are shown in the diagram below. I used a micrometer (look online they are cheap) as this gave me accurate measurements. These are really important – the more accurate you are the better your prints will be. In fact – if you are too far out bad things can happen like scratching your glass printer bed or worst catching the print head on mechanical pieces like your belts. The more time you spend here the less time you spend trying to work backwards as to why crazy things are happening.

I found the above illustration referenced in a YouTube video from Electron Hacks – credit to them for a nice visual reference!

Slicers?

We now have to choose a Slicer – these are the brains that take a 3D object and “slice” it into a series of layers and hot-end movements to construct that layer. There are many around and I used Repetier-Host as this contains easy access to three slicers (Slic3r, CuraEngine and Skeinforge) so that I could try each one out and see the strengths and weaknesses of each one. CuraEngine is probably the easiest on to start with as it doesn’t have as many options as Slic3r for example). One key rule for me was to make sure that my first layer was printer nice and slowly (10mm/sec). This rectified issues I had previously with warped prints or simply the print sliding off the bed on the upper layers.

First print

At this point I now have a fully constructed and configured 3D Kossel Delta printer. Time to try the first print – I fully recommend that you download a 10mm x 10mm x 10mm calibration cube. Its a great way of checking the accuracy of your printer. It also allows you to check if you are over or under extruding (feeding too much or too little filament). You’ll notice blobs or uneven layers when either of these is true.

Once you are happy with your cube I highly recommend that you move onto the retraction cube test.

 

Retraction

This is hugely important for accurate smooth prints – set it too low and you’ll end up with messy strings between parts, set it too high and you’ll possibly cause a jam in your hotend. 2mm is a good starting point. Don’t believe the myth that you can suck molten plastic through your hotend – you cant – its not airtight! Play around with your settings until have eliminated the stringing.

Here are the results of my first tests. https://www.thingiverse.com/make:192419 – you can clearly see that my initial retractions settings were too low for my set-up. I incremented these in 0.5mm increments (in the slicer) until the stringing was eliminated.

Non-print travel move speed

This is also very important to stop stringing. A speed of 150-250mm per second is likely a good place to start for most 3D printers. The longer your hotend takes to get from one point to another, the higher the probability of it oozing out remaining molten plastic on the way there!

Rather than go into the detail here is a great post that I used when learning about removing Oozing problems: https://www.matterhackers.com/articles/retraction-just-say-no-to-oozing

Summary

After producing some of my first prints and then a prototype case for a separate project I was convinced by the power of 3D printing and amazed at the quality of print that the standard Kossel Delta was able to produce. The more eagle eyed readers would have noticed some upgrades on my delta printer. I will write about each on of these in further posts and detail how these impacted my printing experiences.

Thanks for reading and I hope you found this useful! I’m happy to add more detail to any of the sections so if you have any questions or feedback please feel free to share!

Happy Printing!