Replicator 1 vs Replicator 2x vs Replicator 2, an engineer's caliper wielding comparison.

[Elbot]

I will print some more parts on the Rep 1 that are identical and compare the two later, but here are my preliminary results and photos;

Part is a rectangle 10x10x40 mm. Rep 1 is red ABS and Rep 2 is green PLA. Measurement is of 10mm diameter. Statistical sample is 5 measurements.

Rep 1 = 30 mm/s, 210 C, 0.2 mm layer height.
Rep 2 = 40 mm/s, 210 C, 0.2 mm layer height

1. Replicator 1 = 9.91 +/- 0.02 mm
2. Replicator 2 = 10.25 +/- 0.025 mm

Part was supposed to measure 10 mm.

Also, from the pic, the holes are also oblong with the Rep 2 while the Rep 1 gives more circular holes.

Full disclosure, the Rep 2 is a stock Rep 2 from a new owner on this forum. The Rep 1 is mine and I've given it every mod imaginable while I've also had 6 months experience with mine while the Rep 2 owner is a newbie.

Mods on my Rep 1;
1. Dave's (avidquestion on this forum) enclosure for heated build volume.
2. Custom made temperature controlled with digital thermometer air regulation fan and air filter to filter out the stinky abs fumes and regulate temperature inside the build volume to exactly 104 deg F (40 C for you Europeans!). Improved airflow mods to improve airflow to mightyboard to hopefully stave off another blowout. Fan guard for extruder fans The minimalistic extruder mod for more reliable printing. The lcd backing mod to prevent a short circuit blowing out the mightyboard. Spool guard mod to prevent tangled filaments. Custom spool spindles for plastic filament from Octave. I like Octave due to their competitive pricing and sealed silica dessicant packaging with circumference and circular consistency measurements with deviation (like I did here for you) of their filaments (diameter = 1.75 +/- 0.1 mm, roundness = 1.75 +/- 0.07 mm).

Enjoy!

[Doogiekr]

30 mm/s? That would drive me nuts to go back to...

As far as the rest, interesting comparison, but I really think there are FAR too many variables that can effect prints like this for comparison purposes.

[Elbot]

Stay tuned. I will also do more measurements and even a structural integrity to failure test. I'm gonna put one ABS item under a big iron weight and put the other PLA item under another weight and keep adding weights until they crush/deform. This is to test the relative strengths of PLA vs ABS. I've heard conflicting reports of the strengths of the two materials on the internet so I want there to be some definitive measurements that are objective, not subjective.

In one youtube video, some guy puts a PLA part in a needle nose plier and said that it was impossible to crush. Then, he put a ABS part in the pliers and crushed it easily.

However, I read on some wikkipedia page that ABS is 30% stronger than PLA, so I don't know what to believe. I'm gonna test it and report back a definitive and objective answer with statistical measurements like I did here!

Enjoy!

[Eighty]

Well, the term "stronger" could mean a couple of different things.  In the world of structural engineering, these are the most important strength-related properties:

 

Modulus of Elasticity:  How "stiff" something is - i.e., how much it will deflect.  For example, steel is approximately 2.9 times stiffer than aluminum (for the same cross section). 

 

Yield strength:  How much stress it can take before permanent deformation occurs (in bending, tension, compression, etc.).

 

Ultimate strength:  How much stress it can take before it breaks completely.

 

I haven't studied up on the differences between ABS and PLA, but I'm guessing this could be the source of the conflicting statements.  One person may gauge strength based on bending it, while another may judge based on when it snaps in two.

I have considered putting some test PLA prints to a strength test.  I'd be interested to see some results. 

[Elbot]

I'm not an engineer. I don't design engines nor fix 'em. I fix people in the E.R. for a living and this 3d printing stuff is just my hobby.

So, my definition of "strength" is very simple. If it deforms and/or breaks, then it is past its strength limit. The reason is because if an engineer designed something to be exactly 10 inches wide, then it should be 10 inches wide. I don't care if it didn't break but got temporarily bent. If it's supposed to be 10 inches and square then it should not bend NOR break.

I will also test how bendy ABS is compared to PLA because there are designs for springs on thingiverse, but if PLA is too brittle to print a spring, then people need to know just how bendy PLA is so designs could be adjusted for printed springs within the bendiness of PLA so it doesn't break but bends when you print a spring.

[MacGyver]

I'm hoping you'll be making some videos so we can see your tests.

[Sean Tu]

Brings up memories of the .505 tensile and Rockwell hardness tests I had do in college labs and never touched again after passing the class :-)

Not to sound negative here, but, given the nature of the 3d printers you are using, environmental issues, differences in the plastics between prints (even on a single roll), and your instrumentation, I would expect a pretty large variance in your results. I would suggest a very large sample size. With a big enough data set you can get something good enough for what you need.

Also wondering if anyone has a new(er) edition of The Handbook of Chemistry and Physics? (For engineering students in the late 80's it was known as The Bible) )My 24 year old edition is too old but I believe they have added a section on polymers. Just wondering if they have tables for polymer mechanical as well as chemical properties.

Enjoy!

--
You received this message because you are subscribed to the Google Groups "MakerBot Operators" group.
To unsubscribe from this group and stop receiving emails from it, send an email to makerbot+u...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.
 
 

[Dan Newman]

Sean Tu wrote:
> Brings up memories of the .505 tensile and Rockwell hardness tests I
> had do in college labs and never touched again after passing the class :-)

Ahh yes, the things we used to put in the Eng. Lab's Instron machines.
(All in the name of Engineering Education, mind you.)

Dan