Thursday, 1 January 2015

Putting it all together

With some time off work it would be a good time to fabricate the frame parts and put it all together.

The BOM so far is as follows:



- 3 lengths of 30x30 aluminium extrusion for the uprights.
- 6 x 12mm linears rod for the carriages to run on
- 12 x 3D printed 12mm rod end supports
- 6 x LM12LUU linear carriage bearings
- 12 x 21mm external circlips to lock the bearings
- 12 x 10mm diameter N42 magnets
- 6 x 10mm diameter x 8mm bore carbon fibre rods
- 16 x 30mm right angle brackets
- 4 x 47mm Nema 17 steppers, 1.8° step, 47 N.cm
- 3 x  right angle brackets for mounting the steppers
- 6 x T2.5 16T sprockets.
- 6 meters T2.5 polyurethane timing belt with metal reinforcement
- 9 x 625zz bearings for the stepper shaft supports and belt idlers
- 3 x laser cut 6mm plates for the bas, bed and roof
- 1 x custom all metal hot end
- 1 x 3D printed end effector
- 3 x 3D printed linear carriages
- 3 x 3D printed stepper shaft supports
- 3 x 3D printed adjustable belt tensioners
- 1 x 40w heater cartridge
- 1 x ptfe bowden tubs, 2mm ID
- 1 x 5XC Smoothieboard
- 1 x LCD panel for the smoothieboard
- 1 x 5v voltage regulator for the smoothieboard
- 1 x 24vdc power supply
- M4, M5, M6 and M8 bolts, caps screws and nuts
- blue loctite to keep things from coming loose

Still to purchase are the end stops, themistors, extruder drive wheel and extruder nozzle and I still need to print the extruder parts.  I like the 5:1 extruders so will go this way I think.  the extruder that RichRap uses has been proven to work well so a good place to start.

I am still undecided on what type of heater bed I am going to use.  A 240vac version will be much easier and draw less power and I am steering towards a silicone heat pad at present but we will see.

Frame Uprights:

The three 30x30 frame uprights are just under 1,100mm in length and were cut using a mitre saw.


Then, since each end of the extrusion will be bolted to the floor and roof plates I drilled a 7mm hole then tappped an M8 thread into the extrusion.  The important thing here is to ensure there are no burrs as this will cause the extrusion to not sit flat when bolted to the plate  and therefore introduce the  wobble in the frame.  


Floor, Bed and Roof plates:

I opted for 6mm thick aluminium plate for these parts.  The original plan was to drill all the holes using the mill and DRO but sinve my mill only had 250mm in the Y axis it would be inpossible so  purchased the plate and sent it, together with the .step files over to my local laser cutter to cut.  the results were outstanding and given that Delta printers rely on acuracy, this was the most important thing for me.  Cost wise the 3 plates cost $110 to cut but well worth the money.  

Assemebly and drive parts:

Having the base, bed and roof plates laser cut was one of best things I could have done as the accuracacy is second to none.  Once the smooth rods and vertical extrusions were cut to the correct size it was jsut a cose of bolting the peices.

I started by bolting the vertical extrusions to the base plate first, fitting the stepper motor shaft end supports into the extrusion then fitting the 3 stepper motors.  This was much easier to do without the bed plate fitted.  The stepper motor shaft supports have a 625zz pressed into them and a 5mm nut and cap screw which goes through the bed plate.  This allows for adjustment of the bearing centre height to suit teh stepper shaft.  The idea behind the supports is to stop deflection of the stepper motor shaft when tensioning the belts which will stop premature failure of the shafts.

supports with 625zz bearings 

fittind to the alloy extrusion

motor removed after locating the bracket so the cap screws can be tightened

all mounted

stepper shaft captured by the support
Next to be installed was the bad and roof plates, linear shafts and carriages.  The bed plate is supported by six 90° angle brackets which allow for adjustment of the plate.  The roof plate is bolted to the vertical extrusion and has three angle brackets.  The 12mm linear rod passes thought 12mm clearance holes in the plates and are secured with 3D printed mounts that are bolted to the plates.  All in all it make for a very strong and rigid structure.
90° angle brackets

12mm linear rail mounts

bed plate fitted
fitted linear carriage

12mm linear rod before mounts were fitted


  Belts and Tensioners

he belts used as mentioned earlier are T2.5 polyurethane steel reinforced  running on 16T sprockets.  I opted to use sprockets also for the idlers to ensure the belts are not stressed when going around the diameter.  The tensioners were 3D printed with 2 x M5 bolts and nuts fitted for tensioning and an angles slot to allow quick removal of the idle pulley.  Like the stepper shaft supports they are also made to slot into the alluminiun extrusion profile for added rigidity.  The pulley is supported each end with a 625zz bearing so runs very smoothly with little friction. As seen in the picture below there are also 2 M4 cap screws going throught the body of the tensioner to stop the printed part ever delaminating under load.

close up showing the idler pocket

fitted to the roof plate 

2 longer bolts are the belt tensioners.  

The belts were then fitted to the carriages and cut to length.  Since this is a custom build this involved removing the alluminum upright to gain access to the rear of the carriage.  Once done the upright was re-installed and the belt tensioned.  This was repeated for the remaining two towers

Diagonal rods and rod ends

The diagonal rods are made from 10mm OD x 8mm ID carbon fibre tube that was cut to length using a jig to enable all the rods to be the same length.  

The rod ends were made from M8 mild steel bolts.  In the lathe I turned the flats off the bolt head, then using a 10mm ball nose end mill cut the pocket into the bolt.  By using rocol cutting fluid it is possibel to get a near mirror finish on the parts.  To ensure all the pockets were the same depth the bolts were pucher hard against the lathe chuch, and a stop was fitted to the tool pust for teh drill chuck to hit when home.

The treaded portion of the bolt was then cut off leaving a 27mm shaft plus the head.  This provides plenty of metal for the magnets on the effector and carriages to hold onto.  The metal rod ends were then cecured into the carbon fibre rods  with epoxy glue.  To ensure they are all the same length a jig was used consisting of 10mm balls and my mills x axis table and DRO. 

pocket after drilling

end stop for the drill chuck

finished rod end and one inserted in the carbon rod
(not the rod is not cracked, it is just the light reflection)
These were then fitted to the linear carriages and end effecto and finally it is starting to look like a 3D printer.  



Endstops

For the endstop  am using small mechanical switches bolted so custom mounts with M2.5 bolts.  The mounts are fully adjustable via a bolt that goes throught the roof plate and again slide in the alluminium extrusion.  There is also a bolt to lock the mount to the extrusion when happy with the position..   The limit switch arm is activated by the top of the carriage.  The wring for the swithc is run inside the extrusion keeping things neat


M2.5 cap screws securing the switch
back side showing the switch and extrusion locking bold


mounted to the upright
switch location when fitted


All assembled

All assembled ready for the electroinics

The printer stands 1100m high and is 540mm wide.  Weight wise it feels around 25kg.



Next to my Up Mini printer


Smoothieboard

After much research I bought a smoothieboard 5XC controller from Robotseed and couldn't be happier.  Admittedly  this was the part of the build I was most worried about especailly after reading some have spent weeks trying to get their printers to work.  Well, my worries were unfounded and the Smoothieboard has surpassed all my expectiaions in build quality and easy of uses.  


The guys at Smoothie have done a great job with the instructions and almost every question I had could be found online.  Also the SD card that is pre-installed in the board has all the files, software like Slic3r, Cura and Pronterface, plus masses of documentaion to cover everything one could imagine.  The user forum located here was also great for getting questions answered fast by the developers. 

The kit I bought had all the conections pre-soldered but the user still needs to install the crimp connectors and fit them to the plugs for your steppers, end stops and other parts.  To be doubly sure there was a good connection I also soldered the wires to them

The installation guide located here covered pretty much everything I needed to know and within a few hours I had the printer up and running.  There is no firmware to muck around with and if anything needs to be changed it is done by opening the config file in a text editor, changing the value, saving the file and rebooting the board.  

For a delta printer a few extra lines are codes need to be pasted into the text file.  This allows the input of the ARM_LENGTH and ARM_RADIUS.  I also altered the max stepper current which I set at 1.3A, although my stepper have a maximum current of 2.5A.  This has not affected their performance and my initial movement tests at 150mm/s proved that. Other settings that need to be changed are steps_mm, speeds for homing, and possibly the motor direction.  

You also have the option of downloading other peoples config files for delta printers and use their config but this would be more useful on generic printers, not custom ones.  Most of these can be found on GitHud.  

Anyway, I wired the motors and enstops and loaded the supplied Windows drivers for the Smoothieboard.  The baord was then connected the board to an external 24vdc psu and the board plugged into my computer USB port.  The best thing to do here is to eject the printer via the "Safely Remove hardware" icon to avoid any hangups.  I found if left mounted Proterface would freeze occasionally.  Then go into device manager and set the USB port speed to 115200 to match the smoothieboard.  

I opened Pronterface and connected to the smoothieboard via com6.  A few settings in Proterface needed to changed like build area etc and this will be different for every printer.  Pressing the console home icon casued the carriages to head upwards until they hit the end stop switches, then they backed away and moved up slowly for a second more accurate position.  I was not happy with the fast homing speed so I redued the fast_homing value in the config file,  saved and rebooted the board.  A second test was much more to my satisfaction.  

Bed height was set by homing the printer with a G28 command,  and loweing the carriage down manually using the pronterface console until it was a sheet of paper thickness off the bed. Then send the command M306 Z0 followed by M500 to save it.   This is not a complete calibration but enough to move the head up and down without crashing and more than sufficient to allow air printing for motion testing etc.  A more complete configuration guide can be found here 

The video below is a motion test at 150mm/s . I printed a pen mount that fits the end effector so I could see what is was doing when printing.  The result was fantastic.


                                 


I also have the full function LCD for the smoothieboard that needs to be wired in but I first need to work out which pins need to soldered to the board for it to run.  I have the V1 shield but there is a V2 shield ariving soon.

I will try and print an extruder thisafternoon if all goes well but will need to wait until some thermistors arrive to test the extruder properly.  

Thanks for looking