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Jonathan Keep
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GCODE SLICING - CURA

I have realised that I have documented setting up Repetier-Host but now in fact I use Cura. So this is my suggestion to setting up the Cura Software to slice your .stl file to .gcode for the JK Delta and printing with clay.
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On the Cura download page find 'View all versions' as this description is for the old version - I have not yet got my head around the recent 2.. versions.
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Download a 15.. version, available for Windows and Apple. If you get a download wizard chose 'other' as your machine and the next image shows the parameters for a JK Delta.
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First set up your Machine on the 'Machine' tab, top left. The max width and depth is 200mm (The JK delta will only print about 180 mm diameter) Max height 300mm. You must tick for Machine center 0,0. Also ensure you change the drop down for build area shape to circular. Press OK and you should have a visualisation of the size and shape of your build area.
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You load a .stl file from the icon marked 1 in red. It will then automatically get sliced according to the settings we are about to set up. You get a rough indication of print time. Save your .gcode from the icon red number 2. If you have a SD card in your computer and you press save it goes direct to the card. (SD appears on the icon) If you also want to save to your computer right click on icon. Out of shot top right are some more buttons you might explore. I use the bottom drop down button as it gives a visualisation of the layers. If you right click on the object you are slicing you get a dropdown with useful options of which one is delete for when you want to slice a second object. If you left click on you object you get a bunch of tools to edit your object and scale is useful.
Left hand panel setup - First Tab 'Basic'.
- Layer height = slice height (I work between .5 and 1.2 mm dependant on scale of print that also influences choice of nozzle size)
- Shell thickness = the thickness of the wall. With clay this is determined by the clay extrusion so for simplicity set it to 1. If you want two or more shells, or two or more extrusions of clay to make up the thickness of the wall then multiply the 'Nozzle size' setting (that we are still coming to) by this layer thickness. In other words the 'Shell thickness' is calculated by dividing the thickness that you state by the given nozzle thickness.
- Enable retraction = do not tick it is irrelevant to the JK Delta.
- Fill Bottom/Top thickness = I print onto a prepared slab of clay for a bases so I set to 0. If you are going to print a base I suggest print onto a porous surface such as plaster of paris. Printed bases look nice but have a habit of cracking later when drying and firing but give it a go.
- Fill Density = makes internal support structure. I make vessels so I set to 0.
- Print speed = this is the speed the head moves when printing. 28 mm/s is a good starting point. You can print faster but it all gets a bit frenetic.
- Print temperature = this must be set to 0 or there will be a .gcode given and you machine will hang waiting for this temperature. So a big NB/Note Well this must be set to 0.
- Support = I have not got involved with Support so None.
- Filament = This is irrelevant as we are manually controlling the clay flow with the air pressure. (If you do have a printer with auger or screw type printhead then these parameters control the motor on the printhead)
- Nozzle size = set this to 1 for simplicity for now. In time you might make this more real but as it affects the shell thickness calculation 1 is an easy number. Note: In my photos 'Nozzle size' is in my next photo as I have an even older version of Cura
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Advanced Tab
- Nozzle size = set this to 1 for simplicity for now. (See above for confusion)
- Retraction = Irrelevant
- Initial layer thickness = this can be set smaller than you slice layer to get a good first layer contact.
- Initial layer line width = 100%
- Cut off = 0
- Dual extrusion = Irrelevant
- Travel speed = the speed the machine goes from home to begin printing and if your print is broken the rate the head moves between points of extrusion. If the path of your extrusion is very broken keep this low or your print will get distorted. Set between your print speed and up to 80 mm/s.
- Bottom speed = should be your print speed so I think my image is incorrect.
- Other speeds irrelevant unless you are involved in those functions.
- Cool = Irrelevant
(Note: I do nothing with the Plugins Tab)
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Start/End-Gcode Tab
You will see you can select the start or end .gcode - upper left. This is like the header and footer that gets added to your gcode file. A Gcode file is very basic and can be read in a text editor. The end selection is ok but writes more .gcode than we use.
Note: The Cura default start.gcode is much more than we need but on the whole extra is not a problem. When out teaching and having students set up their own Cura we have run into a problem and that is with the G28.
G28 is the gcode that tells the machine to go to home. Your Delta will rise up to the end switches at the top of your tower. In the Cura default they set x y alternatively that pulls the arms of our machines all over the place.
The fix is you only need one G28 code in your start code and it should have nothing written after it, no x or y values.
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This is the last setting I get involved in and it is under the 'Expert' navigation along the top, click and drop down to 'Open expert settings'. Most of this panel is irrelevant except for 'Skirt' and 'Black Magic', of course black magic is what we want!
- Retraction - Irrelevant
- Skirt = This prints a start up line before your real print. Set to 0 it is switched off but if you like the idea it offers how many and how far from the print you want this 'warm' up extrusion to be.
- Cool = Irrelevant
- Infill = Irrelevant until you get involved in infill
- Support = Irrelevant until you get involved in Support
- Black Magic = 'Spiralize', tick this box if you are printing a single skin or shell and the extrusion will slowly rise with no visible z point rise. It will not work wit two or more skins/shells and must be switched off if you want to see the layering visualisation.
- Brim = I have no idea
- Raft = Irrelevant
- Fix horrible = When running workshops I have found if when you check the layering visualisation (Selection at the bottom of a left click drop down on icon top right of main screen) there are layers missing if you tick the 'Keep open faces' check button it will fix.

Finally your last selection of settings will be retained when you close your software and reopen it. However under the 'File', top left, drop down to 'Save Profile ...' and it is best to save your settings or profile. You will see there is also an 'Open Profile ..' so I could have just sent you a profile but now you know how to do it yourself. Good luck with printing.







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DELTA DIAGONAL ARM LENGTHS – I am often asked how long the diagonal arm rods should be on a delta printer but I work on the suck it and see principal that obviously works but really I have no idea. So if somebody can say what the optimal angle should be that would be good and then the arm length can be calculated for any size of printer. The photo is of printers of various sizes that all work fine for me but as you can see there is some variation in arm angle. The more vertical the angle the better horizontal reach you get but the taller the tower needs to be. The flatter the angle the shorter the arms and more height you will get in your print but the horizontal reach begins stalling. There must be an optimum angle, any thoughts? Also do you think there is an optimal focal point height for the nozzle? I have moved nozzles up and down with no noticeable difference. In short I have found what might be considered a precision machine to be very forgiving.
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Hi +Tai Rogers - I can't help you with the alignment of infill  but a while back I did a series of works around Ant Hills and wanted to work with the outside form and inside structure so got involved with infill. The forms are generated from Langton's Ant that is a Turning Machine  or cellular automata that I have coded into three dimensions. I am using Cura as a gcode slicer. (The stand alone version and not inside Repetier Host). I find Cura is easier to set up than Slic3R. What I did want to say is that to print good infill you will probably do best with a printhead that will stop/start the extrusion flow as there can be quite a bit of non print crossing. The nozzle measurement in your settings also becomes more vital as the gcode slicer needs to knows what gap to allow between joints, parallel lines and overlaps. Good luck with it and let us know how you get on.
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Dries was asking after documentation of auger/screw printheads so this is what I am using. My design priorities have been to keep it simple, easily exchangeable with the old cartridge system and easy to dismantle for cleaning. I have found printed plastic parts not to be strong enough so have made use of a single cylinder of engineering nylon plastic that is drilled out and in which the screw sits. The clay feed container I got from this guy on eBay but I see it is currently unavailable - http://www.ebay.co.uk/itm/New-G-S-Boilie-Gun-The-Nighthawk-6kg-Carp-Bait-Making-/151767083097. The stepper motor is the same as I use on the printers. Otherwise I hope the images are self explanatory as there is no blueprint and I just build the printheads around whatever materials and parts I can find.
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For anybody interested I will be at the London iMaker Store from 3pm to late tomorrow 3rd March saying nice things in support of the WASP ceramic printhead – well really I will be more than happy to talk to anybody about any ceramic 3D printing if you can make it. The iMaker Store in Clerkenwell is having a half day ‘Desktop 3D Printing Show’ and WASP are promoting their 4070 Delta – 40 cm wide by 70 cm high build area, plastic or clay. (I apologise in advance for the blatant promotional tone to this post and hope Dries is not going to blacklist me for it)

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Return pulleys - Hi Laura (A new thread so I can add an image), obviously the function of this bit is to keep tension on the belts and yes the return pulley needs to run freely. Often if the two bolts that clamp the mount plastic plates (any material would do) to the vertical rods are not drilled flush up against the rods as you tighten the nuts and bolts the clamp plates also tighten onto whatever return pulley you have made. Then as you have found you do not get good movement of the belt and the steppers skip. In the photo bottom left is a solution I have used. Two small bearings inside a short piece of rubber pipe. Then washers either side of the bearings and so if it clamps up on the washers the bearing hub is stuck but the bearings keep turning. Two bearing the same outer diameter as the pulleys on the motors are simpler than my small bearings sheathed in plastic pipe - they happened to be some small bearings I had. Basically engineer it so the return pulleys do not stick. 
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(Tom asked after the screw I've used and to answer with a photo it needs to be a post and can't continue as a comment)
The three left hand screws I have used in the WASP printhead. First two are standard roofing screws. The third one along is a masonry drill bit (with the end cut off) and I was interested to see if it could cope with rough clay that it has but I have not used it for long to see how it wares. Interesting it has a double thread to it. All these screws fit snug into the nylon housing that carries them.
Tom asked where I get the screw from that is down the centre. I grind it out of the screw/bolt to its right that I get from a local builders merchant. The blade of my angle grinder is just the width of the thread so I grind and turn, grind and turn - no smart machinery in my studio.
Meant to say in my previous post that by taping the end of the nylon barrel, the body of the extruder to a standard 1/4 inch thread it will take the Luerlock fitment (right) but other glue gun ends as well for fatter extrusions - cut to desired size.
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To work with the motorised Screw Extrusion Head that I have shown in posts below there are changes I make in the Marlin firmware and then I use Cura (currently version 14.12.1) to prepare the print gcode. I am not trying to say that this is the only or correct way but it works for me.

So first the mechanical stuff. The wires from the printhead stepper go into E0 on the Ardino/Ramps board (just above the x motor slot). For me the wires are the other way around from the x y z motors to get the extruder screw going in the correct direction. Then in Configuration.h in the Marlin Firmware (viewed in Ardino software) the #define EXTRUDE_MINTEMP 170  needs to be change to 0. (Just over half way down the page and just before mechanical settings) If not changed the printer just hangs once the extruder is plugged in.

This is the only change I make in the firmware. Next is to set up a Machine profile and slicing profile in Cura for the extruder. The machine profile is strait forward but  the slicing profile you will need to balance for yourself as it depends on the size of screwed, consistency of clay, size of nozzle and speed of print but I offer a good starting point.

Machine Profile
1. (Top line) Machines -> Add New Machine to set up your machine profile. In wizard,' other' as kind of machine -> Custom as other machine information -> Give a machine name, width/depth the same 200, height 300 , all in mm. Nozzle size I put 1 mm. Do not tick heat bed but do tick centre 0,0,0 (RoStock)
2. (Top line) Machines -> Machine settings, check through settings. For E-Steps (rate of clay extrusion, filament for plastic) I set to 0 then Cura uses the value in the firmware. (not that I know what it is in the marlin Firmware) Change Build area shape to Circular. Gcode remains Marlin. Print head size I keep all at 0. Communication settings keep as AUTO -> Ok.
3. (Top line) Expert > Open expert settings. Familiarise yourself with these settings. I do not worry about Retratction. Skirt, it is a good idea to get the nozzle extruding, line count 1, distance 3 mm. Forget about Cool. I do not get involved in Infill. Support is ignored as set in basic Cura settings. Black magic, switch on Spiralize if you are printing a single wall. If wall double/two skins it will not work. Ignore follow mesh surface. Brim, Raft and Fix horrible are ignored > Ok.


Slicing Pofile

- Basic Tab
Quality
Layer height   .6       (I work between .5 and .9 mm)
Shell thickness 1    (Cura divides thickness by nozzle to give number of shells)
Retraction un-tick  (I have just not got involved in retraction)
Fill
 Bottom/Top 0
 Density 0
Speed and Temperature 
 Speed 28
 Temp    0 (Set to 0 so no M109 code is generated as if not it hangs my firmware)
Support
 None
Filament
 Diameter 1
 Flow 100

- Advanced Tab
 Machine
   Nozzle 1
  Retraction
   Speed  NA
   Distance NA
Quality
   Initial layer .6 (up to you)
   Initial width 100%
   Cut off   0
   Dual       0
  Speed
   Travel 80
   Bottom 28
   Infill NA
   Outer 0
   Inner 0
  Cool
   Min NA
   Enable un-tick

- Plugins Tab
    Nill

- Start/End-Gcode
  Start.gcode
 G21        ;metric values
G90        ;absolute positioning
M107       ;start with the fan off
G28   ;move to endstops
G92 E0                  ;zero the extruded length
G1 F200 E3              ;extrude 3mm of feed stock
G92 E0                  ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing...
End.gcode
M104 S0                     ;extruder heater off
M140 S0                     ;heated bed heater off (if you have it)
G91                                    ;relative positioning
G1 E-1 F300                            ;retract the filament a bit before lifting
G1 Z+0.5 E-5 X-20 Y-20 F{travel_speed} ;move Z up a bit and retract
G28   ;move to endstops
M84                         ;steppers off
G90                         ;absolute positioning

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