Clay 3D Printing with Jonathan Keep...

When an opportunity arises to join a clay 3d printing workshop with Jonathan Keep, it should not be passed up! Jonathan describes himself simply as an artist and potter, but as evidenced by his own website, he is much more than that simple description. The breath and depth of his lifetime of work in ceramics, makes a workshop with him something much greater than a instructional 'how to' 3d print in clay. You just know it's going to be something special!

In more recent years Jonathan's exploration of digital technology, from an artists perspective, brought him to learn how to model and code in programs like Blender and Processing, creating patterns, shapes, even vessels in a virtual world. A next logical step for him was to explore how to bring the shapes to life in clay and fire into wonderful ceramic works. Learning from what the RepRap movement was sharing about 3d printing in plastics, Jonathan went about adapting a RepRap design (Rostock Delta) to print in clay, creating and sharing his own clay delta 3d printer with the world (2013).

His "Ceramic Delta" broke new ground, with it's simplicity of design and ease of construction, even with limited DIY tools and materials. The printer, specifically for printing in clay, was easily constructed, making it an attractive option for other artists, designers and potters to build themselves. The printer he launched and the desire for people to create their own clay 3d printers continues to be supported via a Google+ Community called  Make Your Own Ceramic 3D Printer.

The workshop...
What I'd like to convey here are some observations and explanations of the clay printing process, complemented with photos and videos from the two day workshop I attended. It was interesting from my perspective to be comparing the clay 3d printing process to that of printing in plastic, as I'm very familiar with plastics, but never before printed in clay. There were many parallels and some differences which I'll try capture. Also, this post is not meant as an instructional document, more a log of key processes followed and some notes along the way.

The Workshop took place at Fab Lab Limerick, which is equipped with a variety of 3d printers. One of these, the Wasp, has a 3d print-head and related air pressurised chamber for clay delivery. This is what was used for the workshop.

Jonathan setting a clay print on the WASP printer.

A simple hollow cylinder always forms a good test print for tuning in the printer.  Photo: Johanna Aaspollu.
Cylinder Diam 50mm approx.

It's all in the preparation...

What immediately stood out about printing in clay was the time given to preparation. In plastics the only setup time is in changing a roll of filament or waiting for the heated bed to come up to temperature. In clay, the preparation of the clay is everything. Softening the clay with the addition of water is a skilled process. The judgment of how soft to make it also requiring careful judgment and experience. Too hard and the the clay won't flow easily from the pressurised chamber. Too soft and the printed object won't support it's own weight and simply collapse. The best way I can convey the mixing process and final consistency of the clay is the share a video of the process in it's entirety.

Clay is cut in thin slices using wire, and dipped in water for an initial wetting. A fork is used to increase the water contact area with the clay. The complete softening process is illustrated in full in the video below (20min).

Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

Note: Some clay preparation guides illustrate the use of  ethyl achohol (ethanol) as a softener, mostly in place of water. The ethanol will decrease the viscosity of the clay also. It will evaporate during the drying stage and may make softening the clay an easier process, but in discussion during the workshop it was collectively felt that for health and safety reasons we would stick with water. Good ventilation and masks would be required to work with ethanol.

Loading the clay...

My observation of clay printer designs is that there's a chamber of some sort to hold the softened clay. This cylinder typically has a piston type insert and is pressurised by air or perhaps mechanical means to force the clay out of the cylinder, through a pipe, to the print head. The clay may be directly fed to a nozzle, or delivered in a more controlled manner via an auger screw driven by a stepper motor. The WASP has a motor driven screw to move the clay through the nozzle. The movement of the print head in three dimensions on a clay printer is no different to equivalent style plastic printers.

In our workshop session Jonathan took the clay and carefully loaded it into an aluminium cylinder, adding large scoops and careful to avoid trapping any air while loading. The clean inside of the cylinder received a light coating of silicon spray lubricant before loading any clay.

There isn't a single "right way" to load clay. The important point is to avoid any method that might get air pockets trapped in the clay. The piston, in the WASP design, has two rubber "O" ring gaskets. It's important to ensure they are seated well and free of clay from any previous use.

Both end-caps of the cylinder were screwed back on, hand tight, making sure the threads were clean. The air valve was opened slowly until the pressure rose to about 4 bar, and clay began to flow through the 12mm teflon tubing, connected to the cylinder via a pneumatic style push-fitting.

Above shows the air pressure control valve which keeps the piston under force against the clay in the cylinder.

Above: Jonathan opens the air valve, increasing the air pressure to about 4 Bar. Clay begins to flow at a slow but steady pace from the connected pipe. This pipe then gets connected to the push-fitting in the extruder printhead assembly.

Slicing and tuning...

With a presumption that you are able to get a 3d model of your object to STL format, the next key step for 3d printing is to 'slice' the object. This generates a 'gcode' instruction file for the printer. There are many slicing packages to choose from, and everyone has their favorite. The fact that we were printing in clay was is some ways irrelevant to the slicing process.

If anything, configuring your slicing software for clay printing is a lot easier. You have no heated bed, nozzle temperature or cooling to consider or manage. Typically also your are printing a 'vase' or 'vessel' style single walled object, so infill percentage or pattern is not a factor. A 'spiral' or 'vase' setting is usually chosen, and that was the primary choice in our workshop also. With this setting it's usual not to have any top or even bottom on your object. If a base was desired on our objects then Jonathan quickly showed us how to press a solid disk in clay and print onto that. This over-sized base could be easily trimmed to shape later once the object was printed and allowed to dry for a while. This also saved on printing time and gave good solid bases to our prints.

Above: Jonathan shows a clay base placed on an MDF disc.

The WASP printer only came with a .5mm nozzle for the clay extruder. Jonathan's preference was for a 2mm or even 3mm nozzle for clay printing. A new nozzle was fashioned from some threaded rod and drilled out to 2mm by Michael in the Fab Lab, and it worked excellently, as visible in some of the photos below.

With experience and confidence showing, Jonathan soon has the printer working well with the new nozzle, choosing to just get it printing then play with the flow setting via the printer control panel.

An easy way to tune in the printer was to print a simple cylinder, with a .6mm layer height and ~ 1.5mm wall thickness set in Cura and see what happened. Jonathan adjusted the flow rate on the machine's control panel until a visually satisfactory result was obtained. Corrections could always be made back into Cura settings later to negate the need for any control panel changes when printing in future.

This approach taken by Jonathan may be in contrast to how you might carefully research and select settings for your particular machine when printing in plastic for the first time. But clay from a 2mm nozzle was far more forgiving of 'loose' settings. Once the Z height was reasonably dialled in the clay would take nicely to the base, and soon begin to grow the object as it spiraled around.

Above: Jonathan tuning the flow via the printer control panel.

Above: Test cylinder printing in 'spiral' mode, continuous rise in Z direction.

Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

This cylinder was drawn in Blender and sliced in Cura,  Jonathan has shared  Cura settings on a Google+ ceramic printer group. 

Printer bed surfaces...

Jonathan recommended that an absorbent surface rather than a smooth surface was best for clay printing. An absorbent surface would absorb moisture, drying the base as the rest of the object also dried. A smooth surface under the base would prevent drying at the same rate as the rest of the object. Uniform drying of the clay is very important, I've learned. 

The Fab Lab laser cut some 200mm discs from MDF (9mm), and these proved ideal for printing on to. The printer was "zeroed" to the height of two discs, and as Jonathan explained in the following video, this meant we could choose to easily print our object with or without a base with no printer z-height adjustment needed. The discs were simply held in place with some 'blobs' of clay, and that gave a quick and efficient swap out of finished prints, welcome in our workshop scenario.

Above: Making a clay base for your print.

Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

First prints...

The beauty of printing in clay, was that if your first layer wasn't good due to poor initial flow or even z-height setting, you could easily start over with a simple wipe-down and print again!

Above: Restarting a print job after poor initial clay flow.

Video courtesy of Johanna Aaspollu, Fab Lab Limerick.

Above: 5min in Blender, allowed Jonathan's experience to draw this object and move quickly to get something printing to demonstrate the process end-to-end early on in the workshop. Good strategy. Impressive result.

By the end of the two day workshop, everyone had produced some prints. Keeping in mind that many of the attendees had never 3d printed in any medium, the results were very impressive, and the workshop a great success. With the majority of the participants being from a ceramics background, students and professionals, this introduction to 3d printing in clay had everyone very excited about a new direction to explore with their clay medium. 

Above: A mix of objects printed during the workshop. The majority original creations, the lower two from Thingiverse thing:969262 and thing:1063915.

A big part of the 3d learning curve, whether you are printing in clay of any other material, is 3d modelling. Some of the workshop discussion was given to this topic, since many of the participants had no computer based 3d modelling skills. While the power and potential of Blender was demonstrated, we reverted to Autodesk Tinkercad, and in my case 123D Design to begin drawing some objects we could later print. (Sadly, both programs are now being retired by Autodesk.)  Identifying and learning a 3d modelling program that meets your needs is one of the biggest obstacles and challenges in exploring 3d printing in any material.

Above: Once fired the object is transformed in strength and appearance.

To conclude, a big thanks goes out to Jonathan Keep for giving the workshop, to the Future Artist-Maker Labs exhibition and events program for funding and organisation, to Fab Lab Limerick for hosting and providing the equipment and venue, and to the Ceramics dept. at Limerick School of Art and Design (LSAD) for firing the printed pieces. Should you care to view them, some more photos of the fired prints are posted to Ceramics at LSAD Facebook page.

Thanks for viewing.

Ivor

"IvorBot", the early days...

I found some short videos of early days testing of my core-xy movement (stacked, fishing-line, rectangular format). Worth sharing I thought, as even a short video shows so much more. In the first clip you see it plot, probably doing about 40mm/sec. It was my first experience of a core-xy movement and was pleasantly surprised at how precisely it plotted, and how accurate the repetition of the same drawing was. Fitting a pen holder to an x-carriage is always a practical way to get an initial feel for movement and dimensional accuracy, in x/y directions at least. See video below.
(In the audio you can hear the poor quality groove bearings beginning to grind, which was it's ultimate downfall. The stepped nature of the circle is just the way it was drawn.)


Driving it at higher speeds didn't help the failing bearings, but you could really open the throttle on this chassis. Having no weight at all on the x-carriage helped. In this other short video clip (below) you can see the movement running at faster speeds. I used an old Gen6 board to drive the experiment, which it did without issue once I updated Marlin firmware for the core-xy support. The tests were controlled from Repetier Host. If you don't have an extruder fitted and want to trick the printer into working you need to set a dummy thermister "998" in Marlin Configuration.h, and un-comment #define DUMMY_THERMISTOR_998_VALUE 185". You can then slice something and send the gcode file, which it will pretend to print, or plot if you have a pen fitted, and no Z mechanism.



I learned a lot from this 'prototype'. I was able to draw on my existing body of knowledge and understanding of 3d printing, and build on that to construct this experimental chassis. The plans were drawn up in Sketcup primarily, which I use quite a lot for design visualisation. With some plug-ins I can export for printing (STL), and export for laser cutting (SVG).



I've also found Autodesk 123D very good also, and move to it for more complex components.














By building the physical working model I was able to get a true sense of scale, construction challenges, and mechanical performance. I was then able to modify design and rapidly improve through iteration, swapping out both printed parts and laser cut framework. I'm constantly keeping an eye to my primary design goals of compact size for given print volume (200x300x250 approx), along with dual extrusion capability with room for experimentation.

More detail of the journey to follow.
Tks for viewing.

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!

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

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 

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



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

Halloween printing fun begins!

The Halloween printing fun has begun... I hope everyone has enough orange and black! There's a great range of bits 'n' pieces out there to print or you can always draw up something of your own. I've started with a Pumpkin. This one from Thingiverse http://www.thingiverse.com/thing:134066

As I ramp up the challenges for my M90, this print tested it well. The Pumpkin is hollow inside, and top closes right in. It actually printed without support to my amazement. There was a bit of spaghetti on the underside of the roof but that wasn't an issue for this object.

Just to set off the Pumpkin, and lower the position of the LED Tealight I drew up a base in Sketchup.

For the finishing touch I put three stick-on feet on the base!

Tech Notes: 3mm PLA, .5mm nozzle. Pumpkin printed with .25 layer height, 2 perimeters, 50% infill. Speed set to 40mm/sec. Small brim and first layer at reduced speed. Temperature 185Deg C, Heated Bed at 70 Deg C. Glass with PVA solution coating. I had no warping or lifting. Clicked right off when cold.

The black base was printed at .3mm layer height and 50mm/sec. 10% hex infill. I'd slow down the top surfaces and increase the number of layers on the top surfaces if using hex infiill in future. It was slightly gapped in places as it tried to bridge a 10% hex infill.

Both parts were sliced with Slic3r. Cooling was enabled under the Filament Settings (defaults used). I have a cooling fan with variable speed on the M90. Detail on it's set-up in a previous post... here. I think it's helping greatly with PLA print quality.

I printed at about 60% of published size as a first run of this. I think the M90 could easily handle it at 100% size.

Happy printing!

NumberSix  

Active cooling of J-Head insulator...

Construction of my self-build Mendel90 continues. Recently my new J-Head hot-end arrived, the final part of the jigsaw! Experience from my other printer has taught me that active cooling beneath the x-carriage has a number of positive benefits. Placement of a small fan that directs cooler air horizontally beneath the x-carriage causes a disruption to convected heat rising from the hot-end, preventing a temperature rise in the x-carriage that might cause deformation if overheated. It also cools the PEEK insulator on the J-Head which then maintains a short thermal transition zone, essential to prevent jamming. (There is a good illustration and explanation of thermal transition zone here on Nophead's blog.)

The current (at time of posting) Mendel90 x-carriage design didn't have a mounting point for such a fan. I had been designing a clip-on fan bracket when I saw Goopy's x-carriage modification to take a direct drive 1.75mm extruder, which included an under-carriage 40mm fan mount. Goopy's x-carriage wasn't suitable for me as he had also altered the carriage opening and extruder mounting-hole positions. So I imported the original x-carriage stl into Sketchup and modified it to meet my fan mounting needs. I also included M3 nut-traps into the design, which makes fitting the fan much easier, especially after the carriage is fitted to the printer. Goopy's lower shroud (half ducting) was of use as it directed the air flow above the stock cooling duct.

Illustrated above is the design change to the M90 x-carriage. 40mm fan mount. Design shared on Thingiverse.

Photo above/below shows first fit of 40mm fan and half-ducting.

Photo below shows new J-Head V in position. 

Below is a view from beneath the x-carriage, showing the new fan in position (right of pict) and the existing larger fan ducting for cooling the work. The half ducting on the new fan redirects air nicely up and over the larger ducting.

Finally below, a side view of the new fan mounted in position. It sits flush under the x-carriage resulting in no change in the length of the the carriage.

Controlling the fan:

The fan takes it's power via the ribbon cable to the x-carriage. The Mendel90 design has spare capacity on the 20 strands of ribbon cable that run to the x-carriage. I have the fan turning on/off automatically from the the Marlin firmware. A pin on the Azteeg X3 controller board becomes active when the temperature of the hot-end rises above 50deg C. This is all set is the ConfigurationAdv.h tab of Marlin (Section shown below.)

// Extruder cooling fans

// Configure fan pin outputs to automatically turn on/off when the associated

// extruder temperature is above/below EXTRUDER_AUTO_FAN_TEMPERATURE.

// Multiple extruders can be assigned to the same pin in which case 

// the fan will turn on when any selected extruder is above the threshold.

#define EXTRUDER_0_AUTO_FAN_PIN   5 //IOS 20130914 //-1

#define EXTRUDER_1_AUTO_FAN_PIN   -1

#define EXTRUDER_2_AUTO_FAN_PIN   -1

#define EXTRUDER_AUTO_FAN_TEMPERATURE 50

#define EXTRUDER_AUTO_FAN_SPEED   255  // == full speed 

The benefit of this is the fan operates automatically under firmware control, and I don't need to add any start/end g-code to drive it. It remains on after the job has finished, but automatically shuts off once the nozzle temperature has dropped below 50, or some other temperature specified in firmware section above.

Thanks for viewing!

Comments and questions welcome.

NumberSix