SLA 3D Printer Project Log 8: Why cut butter with a broadsword? Or alternatively, the AMD Athlon 5350 APU!

Around two weeks ago, I took delivery of a new PC; a machine that is Ivor the Engine to my Gordon of a CAD/Gaming rig and my Edward of a laptop (Peter-Pan Syndrome?  Perhaps...).  This centres around an AMD Athlon 5350 APU, which provides an all-in-one solution to CPU and GPU at least halving power consumption.  The current testing setup is shown below:

I would say that desk space is too mainstream, but I have no desk space ;(

I originally intended for touchscreen operation, sadly the monitor's touch didn't work, neither could I find drivers.  Perhaps a wireless keyboard with built-in touchpad?  Also note the brightness of the projector - that is from a 2200 lumen bulb and the image size is roughly 12.8cm x 8.0cm, or my target print area (the plywood panel is 30.5cm square).

Note the presence of the RAM, or it's stealth capabilities in any case.

Before we move on I just have to sing praises about noise levels - that mini fan on the APU is 50mm across (smaller fans are notorious for noise), yet it can barely be heard with my ears 15cm away.  The fan on the PSU doesn't even spin and I suspect it may not need to given that it's a 300w model and the fan begins at 120w.  Compare that to many budget laptops which can be heard across the room and only feature Celerons and Intel Graphics (for those not in the know, both of those are considered bottom-of-the-barrel).

For the sake of tuning I ran a few tests with the APU running stress-test programs to max out power consumption on both CPU and GPU, varying the Windows power plan each time:

1. Power Saver:  Idle = 17.0w, Max Load = 36.4w
2. Balanced:  Idle = 17.6w, Max Load = 36.9w
3. High Performance:  Idle = 17.5w, Max Load = 36.4w

Astonishment is a perfectly apt way to respond - I know I was!  None of the power plans made any significant difference, and temperature was similarly unaffected:  Idle was around 12 Degrees Celsius (sub-ambient cooling from an HSF?  Black Magic!) while Load topped out at 37 Degrees Celsius.

Idle state on Power Saver (admittedly I replaced the TIM on the cooler with Arctic Silver 5)

Load state on High Performance, with Furmark on the left (the other stress test was Prime95)

So you say "This is stellar news!  But how well does it *actually* work?".  That is a very good question with a compromising answer, in other words, my CAD rig will do a much better job but this will do us well especially given the reduced power consumption - my main rig will sap 150w from the wall at idle!

That gives a crude representation of the UI in action, with an 800x600 resolution (not great) and a highly complex mesh (may be quite common in my line of work, but oh well).  I also managed to get a representation of how the image will look when printing is underway:

That gear was indeed 60mm across, just as designed.

So all in all, a promising start; still have to figure out how to stop the projector from curing resin during start-up or when idle (the desktop extends to the projector in these cases), but I believe this is a much easier and user-friendly solution overall than the Pi even if you suspect I'm being lazy... which I am...

Until duty calls again...

SLA 3D Printer Project Log 7: Underframes? Thought I did those in Creo...

I've been working on underframes, I know, it's a bit soon to resume work on the wagons but I'm on about the mounting system for my 3D printer; until now I had components floating in space - not an ideal proposition for accuracy.  That has now been fixed, and I was in for some wake-up calls.

Don't worry, there'll be 10mm bolts holding the basin in place.

The dimensions were envisioned as a worst-case scenario of 1m³, which would give me plenty of wiggle room to add insane features like gull-wing doors and water-cooling for the built-in pc, but the dimensions as they stand now are 412mm x 380mm x 626mm.  I reckon I can now aim for a desktop model, and this means a few changes:

• I'll probably ditch the case, and just use a black cover when not in use to prevent the resin from curing - this will probably save me a lot of bother when maintaining my printer.
• A Mini-ITX PC is essential - I can no longer use the bulk of the unit to house an ATX motherboard.
• Get more sensible with the design - I (and possibly you) am going to use this printer frequently, I need something serviceable.
• Mounting the touchscreen just got a lot harder...

A few ancillary developments have happened in my life recently; I've got a new job at a composite manufacturer running cure checks for them, and one of the things I observed is that the Autoclaves run standard PCs alongside their massive built-in computers to run the UI; maybe I shouldn't follow the leader, so to say, but it gives me reassurance that my plan to use an x86 PC to control this thing isn't insane after all.

As much promise as the Pi had, I am not a coder, and Raspbian didn't run how you'd call slick (Risc OS did, but it doesn't support wireless internet which makes things a hell of a lot harder these days); if I'm going to use it everyday, which I may do for a few weeks of each quarter, I'd prefer a rapid system as well as one which has a GUI.

I intend to install Windows 7 Basic to run Creation Workshop by PacManFan, a program which can slice the STLs as well as operate the printer with the help of RAMPS board.  This program uses little CPU power, so the Pentium E2160 I possess can be used (I bought it for a secondary gaming rig, to use whilst home from University), but it does use a lot of GPU power in it's Model View, which runs on OpenGL; I bring up OpenGL because it means that Workstation Cards, designed largely for OpenGL-accelerated CAD programs, could give stellar performance.

I'll expand upon this further when the time comes, I'm getting tired in one of my few windows of time I have to do CAD and blog, in spite of the much-needed money.

Regards.

SLA 3D Printer Project Log 6: The Up of Sketch

Creo Elements Direct is fantastic, it's similarity to Pro/Engineer and Solidworks make it an instant transition for someone in the CAD industry that's used something less archaic than AutoCAD and it basically operates on an Additive/Subtractive modelling principle rather than vertices and points like the free version of Sketchup (Sketchup Pro has Solid Tools which afford the same functionality, but costs $590 or ~£350 at time of writing).  Model Railway wagons are a no-brainer using this method given how many rivets and tumblehomes and other assorted chamfers and blends make it impossible to attain high resolutions under Sketchup.

However, It's use as a design tool for machinery like the SLA 3D Printer Project and the Reprap is severely curtailed by it's lack of visualisation features and it's very modelling system:

Initial design for the Resin Basin, made from 12mm Cast Acrylic.

As can be seen, it's a grey box with a flange, not even remotely looking like the clear acrylic intended for the production model; I also wanted to raise the flange to a level where the top of the flange will be at resin level, allowing me to make a 12mm Calibration Sheet to place in the mount to calibrate the projector - in Sketchup, this is as simple as selecting all faces you want moved, then raising them to the required level, whereas Creo will need you to delete the part, raise the hole locations on the workplanes (all four of them in this case) and then re-extrude the parts.

With this in mind, I have transferred all the geometry to Sketchup by way of drawing them again (I dread having to do this for a locomotive...), and I've made further progress by constructing a prototype for the Print Bed:

I say prototype because I seem to have blocked off the bed to the projector o.O

That's the spot!  Now we can make out which bits are Plywood, which are Acrylic and which are 3D Printed.  I know I ought to have taken the projector into account seeing as it is the most vital part of the machine, but that's okay because it's an iterative process, CAD; furthermore, it is far easier to amend a model than a drawing, which I should know given how small I like to make my concept drawings.

Until next time...

SLA 3D Printer Project Log 6: Quick Snippet

Since the last post, I have been giving thought to my projector mount - long story short, I believe it will be too flimsy with all that weight resting on an 8mm thread (wrt the vertical adjustment).  As a small update while I figure out what to do from here, I have some basic drawings to clue you in on some ideas for two of the Sub-Assemblies:

I don't draw so well...  I'm not the best calligrapher either...

I have now opted for a tighter design utilizing 3D Printed clamps on the 8mm Steel Rods; I can now drastically reduce the distance, and hence the moment arm the projector will enact upon the structure, enabling a smaller frame overall.

Never one for freehand...

This is an initial design for my Build Platform, consisting of a suspended steel grate (a fine pattern to help grip the print) suspended from four LM8UU linear bearings to stabilise the platform, taking moment stresses off of the 8mm threaded rod, which in turn positions the platform.  I have literally just thought of using two motors like the Reprap as long as I can overcome synchronicity issues.

Another thing of note is that I managed to make the Resin Basin in around 30 mins in Creo:

...Which is why I'm a CAD man ;)

So, not a complicated job, simply laser cut from 12mm cast acrylic to allow the use of heavy duty cleaning agents (Extruded Acrylic has microscopic stress marks which the agents can penetrate and cause further damage); the holes in the end and the bottom (not the flanges, I'll cover them later) are sized to take G 1/4" threads commonly used in PC Water Cooling equipment, the one in the bottom drains the tank of all fluids while the side holes act as fill levels for the Salt Water and the Resin on top - Procedure for filling is as follows:

1. Close the Bottom Valve.
2. Open the Lower Side Valve (the Upper Side Port will have no valve).
3. Fill the tank with Salt Water until it flows out the Lower Side Port.
4. Close the Lower Side Valve.
5. Fill with resin until it flows out of the Upper Side Port.

A similar procedure is done for draining:

1. Remove any Prints.
2. Open the Lower Side Valve.
3. Let The remaining Resin drain out.
4. Open the Bottom Valve.
5. Let the Salt Water drain out.

All fill leveling is therefore done by the tank if the correct procedure is followed, I have it calibrated for 20mm of Resin on top of 110mm of Salt Water, giving 120mm of Z axis Build Area alongside a proposed upgrade of 192mm x 108mm build area once I source a 1080p native projector (once I've sifted through all them "1080p" projectors with an embarrassing native resolution of 800 x 600 >:(  ) .

The other holes on the flanges are simply mounting holes to suit M10 bolts, and another idea as of present is to make a calibration sheet from more 12mm Acrylic set to the same height as the resin to position the projector accurately.  I propose using L plates for accurate positioning of the basin.

Take care :)

SLA 3D Printer Project Log 5: 200 Step Program

I've recently obtained a Raspberry Pi (and instantly overclocked it - reached 900MHz CPU, 500MHz GPU and 600MHz RAM with an overvolt of 8), as skeptical as I was at first, this £25 Set-Top Box with pretensions to being a Linux PC is giving me some real inroads in this project.

I've already got it to run a NEMA 17 Stepper Motor through an EasyDriver V4.4, and my coding prowess is as extensive as the Waterloo and City Line; I did this via WiringPi, a library for the Pi that enables you to use the GPIO Pins without using Python or typing sudo (super-user do) ahead of every command.

The commands entered were:

• gpio mode 1 pwm - this assigns Pin 1 to PWM operation
• gpio pwm-bal - this enables Balanced PWM, which is SoC default
• gpio pwmr 100 - this sets the range to 100, or 0.1ms per unit
• gpio pwm 1 - this sets the duty cycle to 1, or 0.1ms out of 10ms

Keep in mind it is possible I am hideously wrong at this stage, I don't own an oscilloscope and with that in mind I am a cretin.  I frequently used PicoScope in Electronics class in College so that'll be my first port of call.  I believe I also need to vary the frequency to change the speed, not the duty cycle; maybe that'll need a dedicated board...

In other news I have finished my Projector Mount for the SLA 3D Printer, images below:

Frontal View, the width of the frame (sans handles) is 580mm.

Isometric View.

Rear view, showing the main frame.

A side-on shot showing the guts of the traverser.

I'm slightly doubtful about the 8mm steel rods I'm using to support a Projector which may weigh up to 5kg, so let's do a few Beam Bending Equations :P

Let's assume that the projector is positioned dead centre of the supporting rods in both axes, and that it weighs 5kg, it's centre of mass is spot-on in the middle of the Traverse Plate and 100mm above it (to account for an early, heavy and highly bulky DLP projector).  These are the crucial dimensions (for moment calculations):

• Horizontal Rods are 560mm long, so 280mm is the moment arm
• Vertical Rods are 565.5mm long, gives a moment arm of 282.75mm
• There is 62mm from the Horizontal Rods to the Traverse Plate
• This falls to 13mm with respect to the Vertical Rods
• On the Traverse Plate there is 170mm between the centres of the bearings (for the vertical axis)
• 317mm is the distance between the Horizontal Bearings

In order to find the deflection (which will cause uneven projection distance and hence ruin our prints), we need to find the moment arms and hence the force experienced by the beams at their various points; we know the Mass of the Projector is 5kg, this multiplied by 9.81m/s² gives us 49.05N of force, which for the sake of simplicity we will disregard for the vertical axis for now, and focus on it's effect on the horizontal axis.

Mooching around on the internet found me these highly useful formulae:

Thanks to Andy Ruina of Cornell University for this PDF so I didn't have to format this pile of symbols

The formula at the end is of greatest interest to us, and the symbols are as follows:

• P = the deflecting force:  what we are hunting for
• l = the length of the beam in question
• E = Young's (Elastic) Modulus = ~200GPa for Mild Steel
• I = Second Moment of Area, details below

There are many formulas for the Second Moment of Area, as it's highly dependent on the cross-section of the beam in question:  we'll be using (Pi*r⁴)/4 since that corresponds to a solid cylinder.  Our cylinders are 4mm in radius so (3.14*0.004⁴)/4 = 2.011x10^-10 m⁴ , there being two rods so double that to 4.021x10^-10 m⁴

With this information gathered, we can deduce that the denominator of this fraction is 48*200,000,000,000*4.021x10^-10 = 3860.39 GPa.m⁴ (Dimensions will be useful later); the numerator will be 49.05*0.560³ = 8.61N.m³, therefore we get a δ_max of 0.00223m or 2.23mm down in the centre.  Keep in mind this doesn't take moments into account nor does it account for the bearing spacings.

Wow, this really is looking like 200 steps!  I didn't expect to go back into my university course this soon, but it did highlight the fact that I may need to review my reliance of Reprap-derived mechanisms especially since I don't want my threaded rods to take on an undue amount of mechanical strain.  I'll end it there for today and continue with this lark at some other point, just because I'm tired of entering HTML mode to put in ^{(Superscript text here)} constantly.  Time for a kip...

SLA 3D Printer Project Log 4: A projector mount with traversing features, potential as a garden railway traverse table?

Aside from experiments in salt, I have been working on a mounting method for my projector; one which offers versatility both in terms of adjusting projector distance to vary the build area/resolution balance and also to make way for projector upgrades.  Given that I am building a top-down design this is no easy task considering that gravity threatens to either collapse my construction or slowly inch the projector down and out of focus.  So far, this is my design which as of yet only features the vertical axis:

Looks very Reprappish, and that's because it is :D

I am keeping to Reprap parts as much as possible since every 3D printing enthusiast and their Budgie has a Prusa Mendel of some kind, so relevant parts will be cheaper; the central rod is a M8 threaded rod and the other two are 8mm plain steel rods for support and guidance, SCS8UU bearings are used throughout due to their cast metal housing and built-in M4 threads.  Another thing to note is that the Traverse Plate (highlighted in green) is not what will carry the projector - I intend to make another plate bespoke to the mounting requirements of my projector and users can make bespoke mounting plates for their respective projectors.

The bearings for the horizontal guide rods can clearly be seen.

The Backplate may look a bit skeletal for some, but this is made out of 12mm plywood; 6mm plywood may be used to allow for simplification of manufacture with other parts like the Traverse Plate, with 12mm parts made of two 6mm parts epoxied together (this also allows for half-engraved features without half-engraving, which could bring potential de-lamination issues to a single 12mm sheet).  The large amount of space also allows for a high degree of nesting to occur, saving material and space on the laser bed.

Trusses added for stylistic reasons ;)

This is the mounting cross for the Traverse Plate, where the plate interacts with the M8 rod to allow the plate to move vertically; this is done via two M8 nuts located in slots (just visible above), of which one or both may be a nylock nut to provide friction when traversing is not required.  This is made from a 12mm (or 2 x 6mm) plywood cross which interfaces with a 3D printed nut mount to create the mounting cross.

Reprap inspiration is found again...

Finally, we have the clasps for the plain steel rods that guide the Traverse Plate.  Not much to mention here other than it's 3D printed, I've decided to use Shapeways for my prints since it's WSF printers offer almost infinite flexibility in the shape of my objects within reason and my Reprap is giving me constant trouble right now, so much for saving money by printing at home :(

Good news is that design should be straightforward from here, since I only need to replicate the parts I have made here in the horizontal axis with a few minor tweaks.  Pity this is only one of five sub-assemblies I am slated to design (Projector Mount, Resin Basin, Z axis with build plate, the Mounting Frame and the Case).

SLA 3D Printer Project Log 3: Salt and Spot-GP

So I finally got around to conducting an experiment in how much salt is needed per unit volume of water to buoy the 3D resin.  Overall results were:  Flotation, Frustration and Fiery throat...  well not quite, but 3D resin does get it's vapours in there and make it sore.

I filled a measuring jug with 500ml of water and an unspecified quantity of Spot-GP (around 75ml I believe, which in a 14cm x 9cm basin is around 6mm of resin), As before the resin sank to the bottom of the jug:

That's not another menacing fluid in that beer glass, that's Robinson's Orange & Mango.

I then proceeded to add salt in 10g increments, observing the water as it took on a misty opacity and more blobs of Spot-GP found their way up:

Sadly at this point, the blobs would still choose gravity as their mistress...

When I got to 60g of salt, I chose to adopt the more efficient method of weighing the salt bottle, dumping salt in, weighing it again and finding the difference; at 75g the resin was buoyed but over time it took on a form that would doubtless terrify any sea creatures below:

I suspect Archimedes will come in useful when ascertaining salt content for the actual tank.

Once 120g was reached this behaviour ceased, but the resin was still too heavy for my liking, so I added 30g to make 150g and that was my final amount - 1 Litre of water to 300g of salt:

Still have no idea why that step was there...

That isn't a final number - I couldn't test the planned 20mm of resin due to the constraints of the jug and Archimedes states that the force uplifting the less dense fluid is equal to the mass of the denser fluid displaced, thus it becomes easy to calculate the salinity required for a 20mm layer of resin in a 14cm x 9cm basin (with some cheeky help from here):

• 140mm x 90mm x 20mm = 252,000mm³

• Water is at 50C to account for exothermic heat from resin curing and summertime conditions.

• The density of Spot-GP is around 1050kg/m³.

• Hence the mass of the fluid is 0.2646kg.

• For the same volume of Saline Water to buoy this resin effectively we need a density of 1200kg/m³.

• At 50C worst case scenario therefore we need 270g of salt per litre.

• I plan to allow for up to 150mm of Z travel in my design, so basin depth will likely be 200mm with 180mm of Saline Water, giving a volume of 2,268,000mm³ which requires 612g of salt.

While this amount may be alarming, it shouldn't hit the wallet too hard since salt costs around 30p for 750g, which is staggering considering 500g of Sylgard 184 costs £50 and to fill the whole tank with Spot-GP will cost a humbling £230 just to fill the tank.

Other observations of note:

• Cured resin tends to float in the absence of a build plate, which should be good for build quality but presents a challenge for finding a suitable build plate material.
• The resin stuck well to a stainless steel teaspoon I had on hand (I used a cigarette lighter blue LED to do the curing, 3 cheers for professional equipment), and the part did not loosen even when stirred vigourously through the fluid.
• Some bubbles of water were present in the resin even after salt was added, so a through mixing may be useful before printing, perhaps with an electric whisk.
• Some of the salt came to rest at the bottom of the fluid even after stirring, so take that into account when mixing the Saline Solution.
• Natural UV light pollution from the room cured some of the resin around the edges of the jug (image below), so a "Dark-Box" will be necessary and the printer cannot be open-frame.

Quite a day today, especially since I did some science for once!  To cap it off, here are two ancillary images from the experiment:

A clear ring of resin is to be seen, there's another one at the bottom if you look closely.

Two of the test "Prints" done via blue LED.