FFF/FDM (Fused Deposit Modelling) vs SLA (Stereolithography)

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I spent the last few months producing over 100 prototypes for an exhibition which is showing at NUS Museum at this moment (It was also the work I showed at my graduation show at RCA). In practical terms, this meant that I pretty much sat next to the 3D printer the entire time tuning it. The conclusion? I NEVER EVER WANT TO RUN A RAPIDFORM SHOP THAT PRINTS THINGS FOR OTHER PEOPLE. Whatever the advertisements tell you about the miraculous magical instant dream of 3D printing – ITS A LIE. There are still many material limitations.

I have also thought very seriously about selling off the UM2 (FDM printer) to get the Form 1+ (SLA printer), but have come to the conclusion that it is not worth it. Here are some of my thoughts on both types of machines:

FFF/FDM PRINTER

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FDM stands for Fused Deposit Modelling but technically Stratasys owns the term FDM, so an alternative term for it (if you care about the legal semantics) is also FFF or Fused Filament Fabrication. The reason for so many cheap FFF machines is that the patent has expired on this technology so many cheap and DIY version of FFF machines have been developed.

Imagine a tiny jet extruding tiny blobs of plastic which solidify into a larger solid – which makes your object. Its that simple. I’ve been using the Ultimaker 2 so far, as it has had some of the best reviews. Although the UM2 technically can do up to 150mm/s, 50mm/s is usually the top speed that I can go if I want really high quality and no risk of unexpected under-extrusion. Most times if I see a “difficult” portion coming I might even tune the speed down slowly.

Printing notes:

1. Slowing down the first layer helps: If a print lifts off the heated bed on the first layer with a newly calibrated bed, I sometimes stop the printer and force the printer to start the first layer at a face-slappingly slow 15-20mm/s. This actually seems to make all prints work better in general. If the print is not well stuck on the first layer, the whole print may be problematic.

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Fused Deposit Spaghetti Machine – first layer failed to stick to bed

2. Level the print bed: You can mislevel the bed such that if you are doing 4 prints on the same bed at each corner of the bed, then just one or two of them will be less “stuck” to the bed. So levelling the bed is important. At times, it just seems impossible to do right!…

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Three were fine but one had a terrible and stringy brim

3. Don’t print multiple prints too close to each other: If you print multiple objects on the same bed at the same time, sometimes the heat from the nearby prints can cause general warping or for parts of the “foot” of a print to curl up from the bed. I try to print objects one after another, not all at once, it seems to work better.

4. Increasing the temperature by 5-10 degrees can help – but only for a while: Raising the temperature slightly can help some prints along at times. But if you set the temperature too high for too long, it will burn the filament (it will turn brown in parts) and cause a filament jam.

5. Get some good lubricant: You’re supposed to oil the machine once in a while. I ended up buying Ballistol which is suitable for use as a gun parts lubricant. I’VE TRIED MY BEST, IS THAT STILL NOT ENOUGH FOR YOU, MACHINE?

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6. Check for random problems: Finally, I had a period where all my prints weren’t working for a few days and it turned out that the colorfabb roll has a design which makes it snag on the especially long M3 screw I had sticking out of a new material feed that I had installed. AARGHHH! There was no choice as my local hardware shop only sells M3 bolts in a few fixed dimensions and that was the only one I could use. There was no way to stop it from accidentally snagging, and I couldn’t find replacement bolts immediately, so I eliminated the filament spool entirely and unrolled it out. Actually, after this I managed to print without A SINGLE FILAMENT JAM for a few solid weeks. MIRACLE!!!

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Who cares if this looks like crap on the table if it works

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Countless ways to do it wrong
Basically FDM printers can seem frustratingly temperamental because they won’t tell you exactly what is wrong with them, so you have to figure out what went wrong. Most of the time the under-extrusion problem can be due to filament jam (mechanical issues), temperature problem, speed problem, etc.

SLA PRINTER

In Stereolithography, laser shoots through a photo-reactive resin/polymer bath and solidifies parts of the liquid into a solid, then the print emerges from the liquid bath like terminator.

The main reason why I never got an SLA printer in the first place was because the 3D Printer was going to live in a home environment. But since George and I moved to a big new house in March I thought for one brief moment of madness that maybe, maybe, I could allocate some space to a Form 1. But the problem is that I still cannot justify having a machine with such toxicity to humans and environment, as the prints would require curing treatment, which can also affect the size of the print (possible shrinkage/curling). And although SLA prints would have the potential to have thinner walls and higher detail without as much overhang problems, the type of materials and colours in which I could print with would be much more limited.

My assessment is that as a user I mainly want:
– large range of colours
– large range of cheap materials
– a dry work room (no “dirty” sinks)
– not having to potentially contaminate my living/working space with fumes

So FFF/FDM wins over SLA.

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Maybe I will just have to embrace the UGLY OVERHANG aesthetic…

I also don’t know how our pet snails feel about having the 3D printer next to their tank. There is no precedent for this even – I can’t simply google for “Are snails disturbed or traumatised by stepper motor sounds? Or do snails enjoy the vibrations from 3D printers?”. Anyway, more on our friendly domestic slimeballs in the next few overdue updates of this page…

A Meeting with a Land Surveyor

This weekend I was very fortunate to meet Mr KL Loh, a land surveyor who has been working for over 40 years in land surveying (and an avid collector of Killifish and moss expert!). He was very kind to invite me over to his house, and to tell me more about his work as a land surveyor, and we also looked through the symbols I’ve been collecting for the last few years. (Many thanks to Mr Loh and his family for having me over – and Caleb for introducing us in the first place!)

It was really really amazing to finally speak with a real land surveyor and to hear it directly from someone who makes official, practical marks which are being used in actual architectural and civil engineering projects in Singapore and we had many many urban stories or anecdotes to share and talk about. I will slowly process it all and write more about it in time to come.

It appears that most of what I have been collecting is not always “survey markers” but also a lot of informal civil engineering markers. True survey markers always have a plate and a reference number. The number is stored inside a big database known as the Integrated Land Information Service and anyone can retrieve information from this service (such as property titles, boundary plans, cadastral maps, control points) for a small fee.

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This is the cover plate for what would be a real control point made by a land surveyor.

On INLIS, this is a list of information that is provided:

a. Property Title Information comprising title, ownership, encumbrances, last transaction information and Land Encroachment Details
b. Property Ownership Information
c. Property Title Information – Estate and Land Description
d. Property Title Information – Encumbrances Information
e. Property Title Information with Cadastral Map
f. Historical Information which lists instruments and caveats lodged against a title or unregistered land after it has been computerised
g. Caveat Index Information which lists caveats lodged and still affecting an unregistered land
h. Land Information – Lot Particulars
i. Land Information – Lot History
j. Encroachment Boundary Plan
k. Certified Plan
l. Strata Certified Plan
m. Registrar of Title Plan
n. Road Line Plan
o. Horizontal Control Point & Vertical Control Point
p. Image of HDB Leases
q. Image of HDB Instruments
r. Image of Private Property Instruments
s. Image of Index to Land Book
t. Image of Index to Caveat Book
u. Image of Private Property Deeds

Available Graphical Information (as listed on INLIS):

• Cadastral Map
• Property Title Information with Cadastral Map
• Road Line Plan
• Horizontal Control Point & Vertical Control Point

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Trimble CU Controller

Some of the interesting things I learnt were that (1) the control points are also sometimes on turf and i have only collected ones on pavements but surveyed points sometimes aren’t always on concrete pavements or roads, and (2) the control points have the potential to go missing – KL said that many control points were made much more quickly in modern times, and as a result some of them would disappear after a few years. So when surveyors returned to look for them after many years (or when looking for other control points listed on INLIS) these points might have disappeared (soil movement might also cause their position to shift!). Apparently in the old days some of the control points were marked out with granite blocks and they were laid into the turf/ground with more time and care; a few still exist in older places such as Bukit Timah Nature Reserve and possibly Bukit Brown.

With regards to blocks that stick out on grassy turf… having read a book on LTA Guidelines recently, I have also realized that there is also much more to learn about those boxes and pipes we sometimes see on roads. I have frequently wondered why sometimes pavements have little metal boxes sticking out and it appears they are not all the same! Those little boxes or tubes serve very different purposes in monitoring different things. Here are diagrams of what some things that stick out from roads might be:

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Pneumatic Piezometer

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Inclinometer

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Water Standpipe

 

More significantly, for my work, it seems the variance in shapes and drawing depends a lot on the individual surveyor/clerk of works who is drawing it on the ground – whether for his own reference, or for his company to be able to recognise the mark. As many of these marks aren’t official survey marks, the person drawing it for their temporary reference while working on a civil engineering or road project could technically take any “artistic” liberties with it and draw almost anything so as to make the marking recognisable to himself during the duration of the project.