Wednesday, July 2, 2014

Choice of slicer for hollow printing...

People occasionally ask me which slicer I use... the answer really is "it depends". It depends what I'm printing. Over time I've found that different slicing packages are good at different aspects of printing. A good example of this was when I tried printing this Worldcup Trophy. It's quite a large object and some reported it taking up to 6hrs to print and consuming around 10m of filament, even with a relatively low infill percentage. I felt printing it hollow was the best approach. This would considerably reduce the print time and material consumed and should be achievable.
Worldcup Trophy, standing about 22cm high including Alzibiff's base.

From experience of different slicer programs I've tried out, I've found Ultimaker's slicer "Cura" to be the best at printing hollow objects that close in at the top. When you slice a large object with Cura and set it to 0% infill it 'scribbles' support material on the inner walls when the walls close to a shallow angle as it nears the top. It can be seen as brown lines in Cura's Layers View Mode (below).
This additional sidewall support works well and allows a hollow object to close in completely without any internal infill or internal support construction. The successfully closed in top of the trophy print can be seen in the picture below. The print is hollow.

To complement the trophy, a nice base was designed and shared by Alzibiff, incorporating some nice raised text. I printed it in contrasting green and gold by simply "guesstimating" the length of green needed for the first part, then feeding some gold, then feeding some green to conclude the print. If the print rate is slowed down, as is possible with the speed slider control in Repetier Host, it's possible to watch the cut filament disappear into the extruder then manually feed the next colour into the extruder by hand until the hobbed bolt grips the newly fed filament.

One point of note if you are trying out Cura to slice for a RepRap printer is that Cura calculates Extrusion distances in "absolute" measures, where as RepRap printers generally expect "relative" extrusion distances. To accommodate this simply place an "M82" command in the Start.gcode section of Cura. M82 makes the extruder interpret the extrusion as absolute. M83 sets relative extrusion.

Thanks for viewing!

Tuesday, April 29, 2014

Makers Meetup... local Fab Lab event.

A recent local Makers Meetup brought a broad mix of skills and interests together, with talks from the worlds of photography, graphic design, ceramics and 3D printing.

Fab Lab Limerick promoted and hosted the event. The general aim was to ensure a presentation mix of creative and technological disciplines, to stimulate thinking, and discussion amongst the group, and explore how the different disciplines might complement each other. It was an interesting and enjoyable evening.

(Above) I spoke on the topic of 3d printing, focusing on how more accessible it's becoming, and showing many examples my 3d printed work. It was enthusiastically received and generated many questions from the group.

(Above) David Hunt, a keen photographer and Raspberry Pi exponent, showed how he has combined his interests by building a motorised time-lapse rail controlled by a Pi board. There are some great examples of 'time-lapse in the Irish landscape' on his website... http://www.davidhunt.ie/gallerys/timelapse/ , well worth checking out.

(Above) Claire Jordan, a local ceramic artist, talked about her work, and how engaging with the Fab Lab has helped her explore new directions. With help from the Lab, she's currently exploring the methodology and potential of 3d printed 'cookie cutter' style tools, as productivity aids for some porcelain ornament design lines she has in mind.
Above is one of the experimental 3d printed hand-tools Claire has devised in cooperation with staff at the Fab Lab.
Lucia Poliakova and Mariel Mazan, recent Visual Communications graduates, talked about how they have utilised the Fab Lab resources such as the laser cutter/engraver in creative ways, as they get their new design agency under way this year. The Lab is an invaluable resource in support of new start-ups, bringing creativity, technology and knowledge together with very positive results.

Finally, I brought my Mendel90 along on the evening and demonstrated it in action. It drew much interest. The Lab has some 3d printers as part of it's tool set, and has plans to add more printers soon.

A big thanks to Javier and Michael at the Fab Lab for hosting the event and providing the photos for this blog post.

Thanks for viewing!
NumberSix


Wednesday, April 23, 2014

New Fab Lab opens locally...

Some local news worth sharing for the Irish readers of this blog. Limerick, Ireland, sees a new Fab Lab location launched recently. http://fablab.saul.ie/

There's a Makers Meetup event at the Fab Lab location (7 Rutland Street, Limerick, Ireland) on Thursday 24th Apr 2014. I'm bringing my Mendel90 along, and giving a short talk on my experience and the ever increasing accessibility of 3D printing. I'll also show some printed items, and engage in a bit of Q&A. Promises to be interesting.

I'm delighted to see the establishment of a local Fab Lab, giving a focal point for meetings, events and perhaps workshops. I look forward to meeting other 3D printer enthusiasts from the region, at the location over time.

NumberSix

Sunday, December 8, 2013

Santa Sleigh...Ho Ho Ho!

It's that time of year when we turn to printing Christmas things! The range of published designs seems to grow and grow each year.
This year I took sleigh parts from various sources and combined them in to a new Santa and Sleigh combination (above). It's made up of sleigh runners from the CreativeTools Sleigh, which I separated from the sleigh body for easy printing. This also allowed these parts to be printed in a different colour to the sleigh body for a nice contrast. The sleigh body was re-drawn in Sketchup by simply extruding a profile which matched the gaps in the runners (side parts). I then recessed a seating area within the sleigh body, to give Santa somewhere to sit!
(Above) Parts laid out in Sketchup. There's a left & right runner because it's not a uniform thickness.

The reindeer were from Chefmaki's Sleigh, a sleigh I printed last year (see here). The deer were imported into Sketchup and scaled up to match the new sleigh size.
(Above) Six reindeer print nicely in one go, along with the supporting bar. 200mm x 200mm print bed.

I trawled for a suitable Santa to sit in the sleigh and settled on this one (photo below) which I extracted from this Candle Holder using Meshlab, tidied it up in SketchUp and sliced in Cura. Cura has a neat feature which sinks an object into the platform, creating a flat bottom on the base of an object so it sits well. Support was enabled for the arms and hat.
The sleigh body (red part above) was printed on it's side. The top wall needed support when printing in this orientation. Removing support material can often be a challenge, and the ease with which support material breaks away can vary greatly between slicing software, and settings chosen. For this project I found Kisslicer had the best support material and the easiest to remove, but you may have your own favourite. I chose a coarse Support setting with a .2mm horizontal gap. I've included a short video (below) of removing the support material from the sleigh body, for anyone that might be interested.

Once all the elements were printed the runners were glued to the sleigh body, leaving the body recessed slightly for best effect. The reindeer were attached to the support bar, all with dabs of super-glue. The final touches were added with some embroidery cord for reins and plastic gems for the reindeer. 

This is a nice Christmas Ornament and can be printed in many colour combinations and decorative styles.
 Version above with gold sleigh and red runners.

Files published to Thingiverse: http://www.thingiverse.com/thing:198381

Technical Notes:
It is worth trying different slicing software when printing new objects, as they all seem to have their own ways of plotting the print. In the case of the narrow swirling sleigh rails, I found Cura performed the best, filling in the gaps between the close perimeters of the rails very neatly. Both Slic3r and Skeinforge left gaps in the narrow rails, even after much experimentation with settings.

A .3mm layer height gave a good finish for all the elements of this print. The reindeer had a 25% infill. Anything less risked the top solid horizontal layers gapping or dipping. Santa was printed with hollow, giving a nice translucent look with the gold filament.

The above was printed in 3mm PLA, to a heated glass bed with a light PVA/water coating on the glass. Nozzle tempeature of 185Deg C, bed temperature of 60 Deg. (if using a Prusa HBP you may need the bed temperature set slightly higher because they are typically fitted with the heater on the underside, and there is a 10 to 15 deg difference between the underside and the top of the heated bed.)

 I use a .5mm j-head hotend, with active cooling on the PEEK, and variable speed cooling on the work. The printer is a scratch build Mendel90 (not from kit).

Happy Christmas printing!
NumberSix

Monday, November 11, 2013

Having a Vase Phase! (with video)

Earlier this year Slic3r introduced an experimental feature called "Spiral vase". I took some time recently to explore its capability, and was very satisfied with the results.
Above... Dandelion Vase from Thingiverse.

I've often noticed people printing vases and other similar shaped objects and asking questions about how to make them hollow, what wall thickness to choose or how best to avoid seams and and other such issues. This "Spiral vase" check-box in Slic3r simplifies the whole process and produces great results.
Above...Slic3r, Print Settings Tab, Layers and perimeters... Spiral vase check-box.

Once the "Spiral vase" box is checked, Slic3r will set a single perimeter, ignore any Infill settings, automatically making the object hollow, ignore support settings if enabled, and will not print a top solid layer. 
Above, my first vase, standing 200mm tall which is the full printing height of my Mendel90. I set a layer height of .2mm, width of .5mm matching the nozzle width of .5mm. I set 5 bottom layers to give a good base. It printed the base layers quickly (60mm/sec) but once it started into the wall it slowed right down. I'm unsure why it seems to ignore the speed settings once printing the wall commences.
(Above) The first one printed so well, I printed some more, all in PLA, with default fan cooling enabled within Slic3r.
My next object was a Gear Vase by Halalan. It's part of a set of vases which have been cleverly generated by Python script. I simply downloaded the Gear.stl file but changed it's Z scale reducing it to .75, making it shallower to become an LED tealight holder. The single wall thickness allows the light to shine through, with the shape giving it unexpected strength.

What the photos don't show is how the "Spiral vase" feature in Slic3r handled the Z movement of the printer. In typical 3d printing, when a single layer has been completed, the Z motor(s) move by one layer height and printing then resumes. With the Spiral vase box checked in Slic3r the Z movement is actually continuous, so that in the time the printer takes to print a full layer (or vase circumference) the Z height has risen by one layer. The best way to illustrate is with a short video.

This short video (below) illustrates the continuous upward Z movement. For each 360 deg. travel around the object's single wall perimeter, the Z axis rises one layer height. In the case of all the objects in this post it was a .2mm layer height. Also of note at the end of the short clip is the retreat of the print bed so the large cooling fan can do its job. 
With one Gear Vase printed I thought it would be a nice idea to have a second one with the "swirls" going in the opposite direction. The handiest way I could find to do this was to set the X Scale to "-1" in Repetier Host, then slice the .stl file. (Illustrated below.)

The completed pair of tealight holders is shown below... The flickering tealights give a lovely effect through the thin single wall.

Finally, this is the Double Twisted Vase (again from Thingiverse), the blue PLA contrasting nicely with the yellow flowers (the flowers are real!). There's a little glitch in the upper section of the vase. Slic3r did give warnings, but I printed anyway. If you are planning to print this object, it might be best to slice in something else or run the STL through Netfabb Cloud Service to see if that fixes it.

Technical Notes: .2mm layer height, .5mm width, .5mm nozzle, PLA at 185Deg C, heated bed at 60 Deg, with glass surface. I had just fitted new glass so I simply cleaned it with window cleaner and the PLA took to it nicely and clicked right off when the glass cooled. I'm not sure how long the "grippiness" will last.

Conclusions: The "Spiral vase" feature in Slic3r is worth checking out. It simplifies things and produces excellent results, with it's continuous Z movement approach to printing. There are no seams and no stop/start ooze print quality issues as a result. It does print slowly though, and seems to ignore the speed settings chosen in the set-up. This warrants more examination to see where the speed constraint lies.

This Slic3r feature is not restricted to "open top" vase style objects, and so if carefully selected, closed hollow, single wall objects can also be printed. An example I printed (below) is this ornament by Ben Malouf.
The continuous movement and flow of plastic, due to the non-stop Z movement employed, leads to an amazing blip and blemish free, smooth surface finish. This was evident in, and common to, all the objects I printed using this feature.

Hope you enjoyed the post. Thanks for viewing!
NumberSix 


Sunday, November 3, 2013

Print quality issue [Resolved]

With a good number of hours under my belt, a print quality issue began to show up on the new printer. You can see it evident in the side walls of the battery holder pictured below.
A closer view (photo below) shows lots of gaps and a general poor finish.

I entertained a number of possible causes: Too much "retract" when executed, resulting in extrusion not resuming flow in time for printing. I even entertained ambient temperature changes being an unlikely but possible cause of the problem, as Winter was setting in, and considered increasing the hot-end temperature as one of the things to try. But before changing anything, I set another print under way, with a slow print speed (20mm/sec), and had a close look at the printing process in action. (I've made a cut-away fan-duct just for easy inspection, which I must post about.)

On observing the "gaping" happening a number of times during the test print, it was obvious that the large gear that drives the hobbed bolt was slowing down and sometimes stopping, when it should have been turning at a steady rate. Closer observation of the smaller gear revealed the issue. The extruder motor shaft was slipping within the small gear.

I knew from past experience that simply tightening the grub screw was most likely not going to be a long term solution, as had the grub screw been resting against the "flat" on the motor shaft then it wouldn't have slipped even when it had worked a little bit loose. The reversing action of the motor would have resulted in more of a clicking noise than full slippage.

On removing the small gear, it was now clear that the "flat" on the motor shaft was not long enough for the position of the grub-screw on the small gear. I should really have spotted that on first assembly. The grub screw needs to tighten down to a flat surface on a shaft to best secure it in place.
The above photo shows how the "flat" on the stepper motor shaft doesn't extend enough to align with the grub screw in the small gear.

The "flat" was easily extended using a flat needle file. The bearing of the stepper was protected from filings with some 'blue tack'. The shaft was gripped in a small vice. (See photo below.)
The new "flat" doesn't have to be perfect, just enough for the grub screw to seat against. (photo above)

The small gear was refitted, and the grub screw tightened down, ensuring it aligned with the newly filed "flat".

I then reprinted the battery holder and the difference in print quality was immediate (photo below). The plastic flow was consistent and the print finish excellent.

What is also evident, with consistent print quality is that the z-movement on the Mendel 90 is so smooth. Each layer is laid down perfectly above the other on a vertical wall, such as that seen in photo below.
Technical Note: .2mm layer height, with a Width over Height Ratio of 1.8, sliced in Skeinforge. Print speed 50mm/Sec. Now to tidy up my rechargeable batteries!
Thanks for viewing.
NumberSix

Monday, October 28, 2013

My new printer (Mendel90)

I eventually got to take an overview picture of my new printer. Up until now, recent posts have only shown various close-ups so I thought a full photo would be nice.

It's a Mendel90, scratch built (not from kit). My other printer, a Prusa Mendel, was used to print all the plastic parts for this one. The sheet material (aluminium composite sheet), and some other parts were sourced locally. Motors and electronics were ordered on-line. I used white sheet material with black plastic parts and motors for a nice contrast in appearance. It currently has a single extruder, a j-head, but its flexible design will allow it to adapt going forward as enhancements evolve.
It prints very well and is faster and more precise than my older printer. My new electronics also allows greater automation than I've previously had. In contrast to my older printer, this one has integrated management of the heated bed, and even have automated cooling of the finished work via a large fan to the rear.

I'm very grateful to Nophead from the RepRap community for sharing his plans and build instructions. I enjoy the challenge of scratch building these devices, but can honestly say that unless you already have some tools and equipment there is little or no saving in comparison to buying a printer kit, but building your own printer, either from kit or otherwise, IS an excellent and rewarding learning experience.  

The Squirrel (Red) courtesy of MBCook on Thingiverse! :-)