Saturday, 22 February 2014

Calibrating 3D Printed Sizes in X / Y axes

Early days, calibrating my RepRapPro Mendel was a never-ending task. Little did I realize it was NOT calibrated and I was using software to fix errors that I should have actually calibrated to be correct.

One big issue I've been fighting and overcome is what a lot of people call the 'perimeter width' test. Although the perimeter width has very little to do with the outcome.

I worked out that the 'perimeter width test' from the wiki calibration page only really tested for dimensional correctness in the x axis, and I wanted a test part where I could measure the sizes achieved in x and y for male and female holes / features. Circles are hard to detect error in just 1 axes, so a male and female 10mm square 'plug and socket' arrangement seems perfect. I give instructions below on my take on calibrating for perfectly sized and shaped objects. Triffid Hunter has an EXCELLENT tutorial on setting x, y, z and e steps and calibrating the machine mathematically, but, unlike the digital world - we in the physical world have imperfections and variances that mean that as close as we might get, almost nothing is 100% perfect... You should follow this guide to calibrate your machine initially, and continue on from here if your results are not quite perfect.  It IS tedious, and it CAN take a while, but it saves so many prints from ending up on the scrap heap, it is worth the trouble.

Print this using your default, initially calibrated settings, the male piece should measure right on 10mm in x and y directions and the female socket should also measure 10x10mm internally.

Instructions for printing Male/Female Minimal Calibration Pieces

These instructions are PER AXIS (ie if your prints are a perfect 10mm in x, but y has issues, then the information below should only be applied to the y axis as the x is already correct! Although this print simultaneously TESTS x and y axes, you should troubleshoot them individually as they are not influenced by each other. 

1) If both pieces are too big, you have too much plastic being laid down on the perimeter and this will need to be adjusted to be lower OR the perimeters need to be 'inset' (I know at least kisslicer provides this function). What you need to configure here is your flow rate. This is related to your e-steps, but you can tweak the flow rate on the fly (in marlin firmware) by issuing a "M221 Sxxx" command, where xxx is the flow rate in percentage (M221 S95 will only use 95% of the plastic that would normally be used). If you notice your infill is a bit lacking after achieving correct dimensions you can turn the infill width up or down to achieve a 'nice fill'. I usually find this bit is a little 'trial and error' for myself at this stage. If you find you always use a M221 S95 to get perfect sized prints, it is probably best to update your firmware, specifically - reducing your e-steps to 95% of their current setting.

2) If the male is too big or too small and the female is correct OR the female is too big / small and the male is correct, you possibly have incorrect x and/or y steps set. Another test to prove that it is an x/y step issue before you go modifying firmware would be to print something larger - a 20mm box should do the trick. (you can measure the base of this test piece if your first few layers aren't 'squished out and fat' like they can be if your z height is incorrect).
If you find that the 10mm male and female pieces are actually 10.2mm AND you find that the 20mm piece measures 20.4 or so... You would also likely find a 100mm piece prints at 102mm - basically your print head moves a percentage MORE (or less) than it is being commanded to due to your controller telling it it needs to turn a certain amount of steps - if the number of steps it thinks it should move is incorrect, the position it moves to is incorrect, causing parts to basically be 'scaled' incorrectly.

If the parts are too large, your steps per mm will need to be lower.
If the parts are too small, your steps per mm will need to be higher.

Triffid Hunter explains how to calibrate steps in his guide - follow the instructions but instead of mathematically calculating your steps, adjust them by a small amount, retry the test and re-measure.

If your male is 10.2mm square and female is 10mm square, you hope to achieve something like 10.1mm square for both, this way you can then go back to step 1 above and reduce the width of the perimeter by reducing the amount of plastic laid to achieve correct dimensions. It is false to assume that because you are using a 2mm pitch belt with 20 tooth pulley on blah blah stepper motor that you can mathematically calculate your x and y steps. You will be extremely close, but if you want the precision and you are not achieving it - you should never assume that your motion system couldn't
possibly be incorrect.

3) If both male and female pieces are too large or too small you possibly have a scaling problem or your x/y steps are out. They may fit together, but the problem is your printer is not printing correct sizes. 2 parts from your printer will fit together, but if you print a part with a nut-trap or other feature which adapts to something it will not fit correctly!
Check first that you have any scaling options in your slicer turned off - they should not be used when calibrating. They will likely be off but some people turn them on in an effort to correct for undersize holes etc.
If they are off, the next thing to check would be x/y steps.


If the parts are too large, your steps per mm will need to be lower.
If the parts are too small, your steps per mm will need to be higher.

Saturday, 8 February 2014

3D Print Gallery

Updated 10/2/2014

This post will be an on-going gallery of parts that I've printed on my RepRapPro Mendel or pictures and videos related to the machine itself. The first section will be videos, the second shows a lot of my prints to date, including the first few prints and the third section is pictures related to the machine, calibration etc. The machine has come a long way from the blobby messes it was creating when I first set it up!


Video - 3D Printing a Screw Cup - One of my first prints!]

Video - A few layers of an Elephant shaped Cookie Cutter
(Showing off my new blue lights!)

Video - Testing Slic3rs new "Spiral Vase Mode"
If you look closely you can see the plastic as it flows out of the nozzle

3D Printed Parts:

In the beginning, before calibrating the machine.
It took me a long time in the beginning to understand why things like these holes were happening.
In this case it was just printed too hot!
Screw Cup - Natural ABS - .25mm layers
(Video here)
Swiss-Army Keys - Gold PLA - .25mm layers
Cat - Glow in the Dark PLA - .25mm layers
(Ironically for a cat, you can see IT in the dark and it cannot see YOU ;-)
Micro Heart-Gears - Gold PLA - .25mm layers - Really turns!
File Handle - Grey ABS - .33mm layers
An Antique Bicycle part replicated for a customer, the 3D printed part is the green one.
Decorative Roses - Natural and Green ABS - .33mm layers

3D Printed Lamp Base - Black ABS - 50 pieces in total

Pictures of my modified RepRapPro Mendel:

(only RepRappers and geeks need read on ;-)

My RepRapPro Mendel kit has arrived! Time to start making my 3D printer!
Machine frame and mechanics complete! Next the hot end and electronics! 
Just about ready to print now! Just have to hook up a few more connections.
Ready to begin! 

Monday, 3 February 2014

3D Design / Print Project - Ikea Lamp Upgrade

3D Printed Lamp

I've just moved into a brand new house with my girlfriend, we're moving things into the house and I've come across a lamp base that we bought from IKEA. The lamp suited the small space it was in previously, but it looked a bit anorexic in our lounge room. I wanted it to be just a little more... "bulky"

This is a CAD render of the lamp base so you have an idea of just how simple this lamp was originally.

See... VERY simple, a square plate as the base and 12mm shaft as the 'stem'.

I decided to jazz it up a bit by adding to it somehow. I have a 3D printer at my disposal so, why not use that to do something interesting! (I've wanted a nice big project to test it out on too!)


The printer I have is not large at all. It's great for parts that fit into its 200mm x 200mm x 100mm build volume, but this lamp is at least 1.2m high. The only way to 3D print something this size would be to make it in sections. I measured the lamp bases 'stem' with callipers and found it was 12mm diameter. I decided each segment of my design should 'clip' onto the stem. This seemed easiest. I sat down and sketched out a few ideas and came up with this design which I created in AutoCAD (note that I have added circular pads on the bottom which you can see in the pic below, these assist with printing and simply snap off later).

"You know they got in trouble for the 3D printed gun right? You can't go making crossbows..." - My Brother

My idea is that I will have many of these clipped onto the stem in succession, and that I can then rotate each one slightly more than the last so that they sort of 'screw' up in a helix around the lamp base... or I could just have a straight vertical strip or a zig-zag pattern, or just randomly arrange them! I think it could look neat! I was confident it would turn out good, and so after designing it I decided I didn't need to do a final render of the entire lamp, I would just go ahead and see how it turned out! At least print a few segments and see how they looked.

Preparing the print:

There are 2 main plastics I use for 3D printing, PLA and ABS. PLA is renowned for being very easy to print with, but it also has a lower melting point (a VERY hot day could make a PLA part droop or distort) and it is less flexible than ABS - Since I was after a "snap" fit between each part and the lamp base ABS is in the lead, it will easily stretch that little bit and snap onto the base. It is also plausable that the lamp would get a bit warm both in use and from hot sun coming in a nearby window, so ABS was chosen for this project.

ABS DOES have some caveats though, it tends to contract as it cools, which in turn can make it 'curl up' and become un-stuck from the build platform. This results in errors in the finished part or completely failed prints. I incorporated the circular pads on the bottom to overcome this - the pads give the part more surface area and act like suction cups or wads of Blu-Tack that hold the part to the build plate and resist the warping that naturally occurs.

There are 2 programs I prefer to use for 'slicing' the 3D models and preparing them for printing. One is named Kisslicer and is my go-to slicer. It is VERY fast, easy to use, and gives the highest quality printed parts. Printing with Kisslicer is also usually completed quicker and the machine is smoother / quiter due to its intelligent path generation. Slic3r is a good backup tool - I will ALWAYS use Kisslicer first, but if Kisslicer has problems or the part requires some really fine-tuned tweaking to work, Slic3r will often do the job. Slic3r also has a 'brim' feature which automatically inserts a brim (like a top-hat brim) around the bottom of the part which has the same effect as the circular-pads I added to aid printing.

Kisslicer showing the first 'slice' or 'layer' that will be printed.


I decided on black material, made the first part and noticed that it was a really easy print, without much detail and big long lines / curves. I could run it a bit faster and sped the time up from around 42 minutes to just under 30 minutes per part. Before starting the second part though I snapped the circular pads off the first part and went to check how it fit on the lamp base.

Snaps on perfectly!
Great! So I continued printing and got into a 30 minute routine, I would go into the printing room, remove the freshly printed part and begin printing the next. After I had printed a few more pieces I tested out my design to get an idea of how the finished product would look.

I didn't realise how dark this picture was! Might have to squint!

It looks... ok? yeah.... I think? Maybe?

I really wasn't sure at this stage! But continued anyway - and as time went on it looked better and better. Here are a few pics while it was still not quite finished, but I was trying different configurations to come up with my favourite.

After trying different variations of twists, zig-zags and random configurations (changing a few times a day for a week or so) we decided that a nice gradual helix was most appealing. I also decided the 2 lamp shades I have are ugly on this now, so, I will either get a plain white cylindrical lampshade the same diameter as the lamp base segments, OR 3D print a lamp shade continuing the design of the base up around the bulb (perhaps in white plastic instead of black). When I decide I will update the post with pics!

From concept to reality:

My 3D Printed Ikea Lamp Upgrade!