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! :-)


Tuesday, October 22, 2013

Insulating the heater block... more data!

I recently posted on the topic of Insulating the Heater Block and a few days later received some great data (graphs) from Alzibiff, a Mendel90 owner and keen RepRaper. Alan (Alzibiff) was in the process of insulating his J-Head heater block with some silicone tape, as per Nopheads design improvements, when he kindly captured some before & after data. This is great data in many ways. I hope I can do its interpretation justice...

{By the way, Alan is the proud owner of that 'pin-up' of 3D printers, the Black Dibond one with the Christmas Tree, which famously featured on the cover of the Mendel90 build manual for some time!)

The target temperature for all graphs was the same, 220 Deg C. The power resistor in the J-Head v5b, running on 12v, had no difficulty bringing the heater block up to temperature in all tests. The significant observable differences between graphs was in the average % power draw, the blue line along the lower (green) graph in each case. Alan has two fans on his x-carriage, one ducted under-carriage PEEK cooling fan (same as this), which I'll call the "Upper Fan". He has a standard M90 work cooling fan, which I'll call the "Work Fan". The latter fan duct was unmodified, no insulation cooling hole (another of Nopheads mods.)

Small Tech Note: I've checked that the power draw of the fans do not impact on the power graph. It only shows % power draw by the heater.

Figure 1. No (heater block) Insulation, Upper Fan ON, Work Fan OFF. 45% power to maintain temp.
Figure 1

Figure 2. No (heater block) Insulation, Upper Fan ON, Work Fan ON. 55% power to maintain temp. This is interesting because it's suggesting there is extra power needed to maintain temperature when the Work Fan is on. There must be air drift from the downward facing cooling fan that is impacting on the heater block, causing it to draw more power to maintain temperature.
Figure 2

Figure 3. Heater block insulation fitted (Silicone Tape), Upper Fan ON, then Work Fan ON at the '31' mark, so both fans on for the latter half of the graph. 38% power (Upper Fan ON), 48% power (both ON), approximately.The power draw to maintain temperature after the insulation is fitted to the heater block is nicely reduced. The insulation is doing it's job. But, once the Work Fan cuts in the power usage increases again slightly. This suggests that cool air drift from the work fan is cooling the heater block somehow. I expect the heater block would benefit from some insulation on it's base also, to further improve the insulation, but the nozzle probably doesn't protrude enough to permit this with the present j-head design.
Figure 3

Figure 4 is probably the most impressive. It shows the insulated heater block in operation with both fans OFF. To me it's the most impressive because the power draw (green graph) is barely above 25%. It shows that the silicone tape is a very good insulator, and really outperforms my skinny Teflon jacket. I must add that this particular test (Fans off) did unease Alan, and he didn't run it very long as he has had his share of extruder jams in the past.
Figure 4

Quick Conclusions:
The silicone tape is an excellent insulator, and an enhancement worth considering.
Indirect cool air (air drift) from fans has a greater impact on the power required to maintain hot-end temperatures than one might think, due to the cooling effect of such air.

Thanks to Alan for the graphs. Hope folks found it of interest. Questions and comments welcome as always.
Regards,
NumberSix


Sunday, October 20, 2013

Print Bed levelling: 3 versus 4 support points...


The importance of a well levelled print bed can not be emphasised enough. The lower the layer height you print with the more critical having a perfectly level print bed becomes for trouble free adhesion of the first layer. The use of a Raft or even altered first layer width or thickness is often a compromise for imperfect bed levels or surface flatness. This is functionality accommodated within slicing packages, e.g. Slic3r. I've never had much success with rafts as they have always proven difficult to detach from the printed object. Rafts are commonly used in commercial printers and also successful on the UP! printer, but the secrets of good raft separation still seems to elude the OpenSource community, it being theorised to be perhaps both material and software related as discussed here by Nophead, although Chris' desire to get to the bottom of this does extend to having good peel-away support, not just raft.

I think, in printers where the print bed is typically un-clipped to remove the finished work, the precise levelling of the print bed can't always be guaranteed so rafting is a good compromise. If you don't want to use rafts or alter the first layer width/thickness then a very level print bed is essential for good contact of the first layer.

I opted to use the Helios Heated Print Bed (HPB) in my scratch-build Mendel90, instead of the more popular Prusa HPB (typically red). I have a Prusa HPB already so its interesting to compare.

My initial expectation was that the Helios would be even more suited to 3 point support and the inherent ease of levelling that brings. The Helios board is twice as thick as the Prusa board. However, I think my expectations have risen over time, and in borrowing a dial gauge to level the new M90 Print Bed I was disappointed by not being able to get it as level as I'd hoped with just three points of support. The problem came down to a slight warp in the HPB, which can't really be described as a fault, as the the deviation is only about .2mm along one edge that was only supported in the middle.

Perhaps if I used thicker glass then the clamps would pull the board straight and leveling would be fine with three point levelling, but I am happy with my light glass (1.3mm thick), as it keeps the overall print bed weight and inertia down.
The Helios comes with long M3 counter sunk screws, some washers, spring washers and nuts. I like the ease of adjustment that spring loading the bed brings, but you have to use strong springs here to avoid wobble.
Photo showing counter sink screw, washers and bolts that come with the Helios board. I use a strong spring (also shown). The Helios fittings are stainless steel which conducts less heat, a good think in this situation.
An essential prerequisite is that the x-axis has been levelled with respect to the printer base. This can be done with a vernier callipers (see photo above), moving the callipers from left to right and turning the Z leadscrews independently of each other, until the x assembly is perfectly parallel to the base.

To hold the dial gauge to the x-carriage I printed off Nopheads dial gauge holder. If your dial gauge has a narrower (8mm shaft) this other clamp may fit better (http://www.thingiverse.com/thing:92852).
You don't have to have a dial gauge to level the bed but it's more time efficient if you have access to one. You can level the bed by using a sheet of paper or feeler-gauge to set the gap under the nozzle at various locations around the bed, and adjusting the bed height until the gap is consistent.

I did some video recording while adjusting the bed level, and generally checking the level after adjustment. I'm sharing an edited down version of my recordings below. It is not intended as an instructional video so don't view it as such. In the first section you will see me adjust the nuts to raise or lower the bed. There is only .1mm between each of the visible numbers on the dial gauge, and the smaller incriments are just .01mm, but what I concluded by the end of the first section was that I was not going to level the bed on the right hand edge. The second section of the video shows how well I was able to level the bed with four adjustment points (each corner). If you observe the movement in the dial gauge as it moves around you will see that the bed is levelled to within a very tight range, estimated +/- .02mm!
Conclusions:
4 adjustable points of support will (most likely) be better than 3 if the print bed top layer consists of the HPB board and thin glass.
3 points of adjustment is easier to level, but the board or glass must be rigid and flat.
A dial gauge makes bed levelling easier and quicker.
A well levelled print bed enables consistent printing of first layers, giving good print quality and reduced risk of print warping or detachment during printing.

Hope it was of interest!
NumberSix