Tag Archives: stereography

Evaluation of Preform 0.8.1

As I was explaining in my previous post, the form1 printer software is still a work in progress. Some bugs have been squashed with the 0.8.1, but some remains and I’d like to go though the some of the current challenges that a fellow formers might encounter. The first ones are the most critical in my opinions…

Object skin is not always sticking to the filling

[I’ve submitted this bug #1123 to the community board]

I’ve chosen the impossible heart brain teaser available in Thingiverse to see how very simple and smooth pieces would print… First it was not a brilliant idea to print it without supports. I had to use a clamp to pry apart the pieces from the platform and in the process damaged a bit the puzzle surface.

impossibleHeart_plateAndAssembly

But the real issue was, as some of the Reuleaux spheres in my previous post, the perimeters on some of the pieces didn’t stuck and I ended-up with a ugly result. What you see behind are the back and forth inside filling profiles. My hunch is, depending on the pealing direction, the perimeters might not be completely merged with the filling leaving a weak spot in the structure…

impossibleHeart_peallingPerimeters

If I was Formlabs, I would try to extend the filling paths so that it overlap at least the last perimeter to make sure everything is correctly glued together.

impossibleHeart_extendedFilling

[.form file]

25 microns prints non sticking to the platform…

This point a a bit a hit or miss. I’ve followed the advice in the community forum that using the “grey 25 microns” material profile was increasing the chance of sticking and so far I had 2 out of 3 prints working. The sticking might be affected by the location of the print on the plate and the orientation of the base platform. If you have a long platform, turn it so that the peeling starts on a small side.

To solve this it would be great to have more control on the laser, like being able to set the speed of the scan, the number of repetitions, the number of perimeters. That would open quite a few possibilities and for the most advanced users it could be a great way to experiment.

Overlapping supports are creating pockets of uncured resin

[I’ve submitted this bug #448 to the community board, and it’s marked as closed]

That one is strange but apparently it’s already fixed for the next revision. The problem arise when the software decides to place 2 supports so close that they are overlapping. In this case the internal filling back and forth of the laser is missing at the intersection. That will create a hole of uncured resin and I it’s safe to assume the support strength is gone…
[.form file to test]

supportsHoles

Peripheral loops are overlapping on very thin walls

[I’ve submitted this bug #1124 to the community board]

Preform is drawing 3 loops around perimeters. These loops are continuous and when the geometry has a very thin wall, these perimeters will get inverted and even create filling outside of the geometry… (Yes I know it’s not clear, just look a the picture to understand the issue…)
[.form file to test]

outsideFilling

That’s all for today 🙂 If you have any comment or extra bug to report on this release please comment I’ll investigate them!

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First steps with the Form 1 Printer

So here it is after many months of waiting the Form1 Stereo printer is sent to backers! and I received a few days ago my puppy, and now the 3D touch has some serious competition.

More on that later, but I’m thinking on selling my 3D touch printer with ~15 filament spools of various colors/materials. So If you are interested mail me, free training included if you are in the bay area 🙂

I will not do a full tear down of the printer, but if you are interested to see the guts of the form1 Bunnie’s blog has an interesting post.

cartboardWith3dTouch

The cardboard boxes are massive and Formlabs decided to avoid foam or bubble wrap to lock the printer in place. The printer was held by 2 plastic films, but you can see in the picture under that during transport it shifted out of the slot. Nothing serious in my case but I have already read some reports of people complaining they received their printer damaged. I’m not exactly sure if this packing method is completely fool proof, especially if the box are rotated during transport/handling.

InsideCartboardBox

The unpacking was really easy, just a few tape pieces to remove… But dang, that’s a sharp looking printer! I’m especially impressed by the build quality. As you can see in the following pictures, they didn’t try to cut on the details. The only small remark I’ve is that the printer detect when the orange hood is closed using a hall sensor and from time to time the magnet is not completely aligned so you need to fiddle/move a bit the hood to get it detected.

Form1ReadyToOperate form1BuildQuality

Now let’s move onto the printing. The samples I’ve seen during the Maker Fair were great but I have to say I feel the Preform software (V0.8.1 at the moment of writing) is still somehow limited and you need to practice a bit to understand how to get the best out of your printer.

My first test was a 25 microns print of one of the Cyvasse game piece but for some reason the support (surface of ~ 2 * 1cm) was not sticking to the platform and the cured resin ended up floating in the tank… So after 2 tries and a fishing party to retrieve the layers, I decided to start with something easier and stick with the default 50 microns layers for the moment.

My first success was with a pocket monster figurine by Andreas. I’ve scaled it down to 50% (.form file) and the result is quite stunning when you are used to the FDM quality. Once cleaned from the resin with alcohol and dry the pieces are a bit cloudy and not very shinny (left picture). I used a Varathane Gloss polyurethane water based spray (interior / Heavy Use Formula) to get a great shine (right picture). With one layer, the details are not lost and you really have the impression that it’s made of crystal.PocketMonster

After that, I was ready to test the limits of the printer. So I tried the simplest structure I could find on George Hart math page. When processed by Preform, the Goldberg polyhedron (.form file) had a large red/unsupported ring area but I decided to print it anyway…goldbergSphereError

It didn’t worked out and I could just  clean up the mess after. golbergFailOnTheTray

As you can see the resin is rather flexible and not fully cured after print. I couldn’t remove the remaining of the sphere from the support without tearing the sphere in half. So lesson 1 is: don’t pull 1mm thick walls… Maybe I should have tried to wash the result and wait until dry?golbergFailFlexibleResin

I was surprised to see how flexible the resin is after print, so I’ve put some of my failed pieces outside in the sun to see how the resin age. As you can see under, after the prints, the parts are white, but just 2 days outside (gyroid – top right) and the resin is much harder/cured but with a yellowish tint. After 4 days (sphere – top left) the tint is even stronger and  all the flex is gone, the cured resin is actually very stiff.form1_aging_resin

Now let’s have a look at print defects that you can get with the form1…

I’d like like to stress that Formlabs team is making progress and the new Preform software revision (0.8.1) is actually solving one of the issues, each layers had a visible seam but the new cleared that point.

seam_form1_defects

Visible seams in Preform 0.8 (Releaux spheres print in 50 microns)

These seams were visible but you couldn’t feel them on the surface so it was more a cosmetic defects. The real issue comes when some parts of the print are not cured properly. In this case the end result is rather ugly on some sides…

reuleaux_form1_defects_0-8-1

Reuleaux Spheres printed with 0-8-1 (50 microns, default generated supports)

To conclude this post, I have to say the form1 is an impressive printer, the details of the parts are great and the build quality is stellar. That said, I know being an early adopters has its disadvantage and even if the printing process is not yet “plug-and-print”, I have high hopes for the future!

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Introduction to 3D scanners

Our brain is able to reconstruct volumes and perceive the shape of an object by relying on multiple sets of clues:

  1. Motion parallax  and perspective give a relative sense of the position of objects in the scene
  2. Focus and field of view
  3. Stereoscopic effect (slight view difference between two eyes)
  4. Experience and familiarity with the object fills the remaining gaps (by recognizing an object we expect it to have a given shape)

[Click on the image to see the animation]
narita13
This couple of stereo-images gives enough information for the brain to reconstruct the depth of the scene. (source: http://www.stereomaker.net/sample/ani/ani_e.htm)

As a side note, the fact that all these simultaneous information are used by the brain means that, beside holography, there is no possibility to display great 3D information without causing motion sickness or nausea to some people.

A 3D scanner using all these passive clues would be complex to build and probably not very accurate. So most of the current scanner rely on active methods.

Active scanners can use laser for direct distance measurements:

  1. Time of flight: these videos shows how to use laser to scan the Sphinx or drive autonomous cars in the DARPA challenge
  2. Or displacement in the case of some industrial sensors. These sensors can achieve amazing accuracy in micro-meters over a range of a few centimeters

sensor_configuration(source http://www.measurecentral.com/technology/semiconductor.php)

These sensors are unfortunately very expensive and not accessible to the hobbyist, so, to build a home scanner we have to rely on triangulation. The principle is to send a coherent pattern on a object to extract its shape from the deformation of the shadow. A great introductory course is available here.

shadow-2
(Source http://mesh.brown.edu/byo3d/source.html)

After examining all the 3D scanner option I’ve chosen to use a laser to project a line and cameras will capture the line deformation. The line sweep will be performed using two galvanometers used in the laser show business. This is the perfect occasion to go and explore the world of laserists…

galvanometer
Two galvos are used to deflect the laser beam on the X and Y axis
(Source: http://www.zamisel.com/SSpostavka2.html)

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