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My hexagon hot end to davinci project.
#1
My goal is to install the Hexagon hot end into the Davinci 1 with all new carriage that places the hot end in a position to retain the Z travel. It also uses the linear bearings instead of the sleeve bushings.
It is designed around most of an MK8 extruder which has a decent size and function.
I would like to hear any comments or if anyone has any input on the design I would appreciate it.
Here is my first draft render of the assembly.







[Image: newhexcarraige1.jpg][Image: newhexcarraige2.jpg][Image: newhexcarraige3.jpg][Image: newhexcarraigeairflow1.jpg]
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#2
Design looks cool. few things I would pay attention to

- Raising the extruder to maintain the Z height may cause issue with running into bar across the front of the printer that the Y-Axis belts run around
- Closely enclosing the Stepper motor without any direct cooling my cause you heat issues with the plastic. I definitely wouldn't use PLA for that. Might get hot enough to give you heat creep issues from the stepper heat only.
- Having fixed holes for your bearings/bushings for both rails may cause you issues getting it to fit. Typically you see one rail going thru a fixed hole, and the other rail in an open channel so it can float a bit to accommodate tolerance issues. I'd suggest opening up one of the rail holes to give yourself a little slop
- Don't forget a method to fix the carriage to the belt. Don't see how your doing that
- Don't forget a feature to interact with the opto-endstop. Unlike a mechanical endstop, your going to need to have something that will fit into the opening of the opto-endstop
- I believe the wire connector for the Da Vinci stepper motor is located on a side, which means I don't think you have any openings to plug into the stepper motor.
- If your going to print PLA, you will probably need a layer fan. not sure where that will fit. The existing one won't be sufficient, in my opinion

My $0.02
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#3
I measured the interference with the Y bar and it clears at the maximum printable distance.
My latest draft has open holes in the stepper area on the sides and top for ventilation and for the wires.
The fixed hole issue isn't a problem. My Davinci extruder carriage has fixed bushings on one side and the slotted area for the bushings on the other side. The bushings in the slotted area were glued in place from the factory. I think they did it for ease of carriage removal instead of a floating bearing arrangement.
The belt retainer is an easy fix. I am getting the bearing alignment and bore size correct before finishing the details.
The problem with printing something like this is that each machine will print a model a little different. I am having to print the bore size for the bearings at 15.9mm to fit a 15mm bearing. I plan to put the finished files on thingiverse when I get a working model, but like everything else the files my need to be modified to work with other printers.
My Davinci has the ramps /arduino electronics and the opto ends stops are now mechanical end stops.
Hopefully there is enough clearance around the hot end to allow some of the air to hit the layers as they are printed. If not I can add a fan.






[Image: newcarraige1.jpg][Image: newcarraige2.jpg][Image: beltgrip1.jpg]
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#4
Here it is with the bearings

[Image: newcarriagewithbrng.jpg]
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#5
You also need to think of a where to put the breakout PCB that comes with the stock extruder, since you'll still need that too.
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#6
Na, you don't need the breakout PCB on the carriage if you don't want. Plenty of places for it in the rear of the box.

Chris -

I think your mis-understanding my comment about leaving one rail bearing feature open. You said it yourself, "each machine prints a little difference" It doesn't take much more than a few thousands of an inch off to have your carriage not slide smoothly on the rails because the center-to-center spacing of the bearings/bushings isn't perfect. That is why nearly every carriage in the machine has one side fixed and the other side slotted and glued in place. If you include a slot and plan on gluing in place, it's nearly guaranteed that your carriage will work. If not, your at the mercy of the printing tolerance of your machine, and possibly the warping of the part......
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#7
That's a good point. If the hole diameter isn't printed perfect it can be reamed to fit but if the hole spacing isn't printed correctly it cant be made to fit easily. I will change the design to the slotted arrangement for this reason.
I don't use the PCB on my Da Vinci but I can add some holes to allow it to be mounted somewhere. Once I have a working carriage I can see where there is enough room to mount it.
I am in the middle of a 12 hour print of the first carriage and crossing my finger that it goes well. :cheer:
Thanks for the replies,
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#8
Slotted carriage
[Image: newslottedcarraige1.jpg]
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#9
Finished the second print of the carriage. I too have the problem with the Davinci printing out of round holes so I have to fiddle with the measurements to accommodate. I'm still printing the small parts and hopefully will have a working extruder and hot end by tomorrow.




[Image: DSC02931.jpg][Image: DSC02933.jpg][Image: DSC02934.jpg]
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#10
Mounted and printing.






[Image: DSC02935.jpg][Image: DSC02936.jpg][Image: DSC02937.jpg][Image: DSC02939.jpg]
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#11
Chris - Following your project with interest, curious what led you the Hexagon vs the E3D? While both seem to be good hot ends there seems to be more reviews on the E3D although, I know it's a bit bigger.

Great Job on the design, seems to be well thought through. Can I ask was 3D Modeling software you used?

Look forward to your print results and your eventual Thingiverse post. Thanks!
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#12
Price.
Also the Hexagon hot end will do everything I need which means printing with PLA. Adapting a E3d to this carriage should be direct with the mount plate style and depending on the overall length and diameter of the E3d, the only issue would be if the bed will adjust enough to accommodate the longer or shorter e3d hot end which ever the case may be. The Chinese MK8 extruder is very cheap on eBay and works quite well. You just need to toss the MK8 hot end and heat sink. The MK8 heatsink and fan screws are re-used for the new assembly.
I probably could have purchased a knock off e3d hot end for cheaper but I decided on the Hexagon.
The difference in print quality between the Da Vinci and the Hexagon was immediately apparent. Prints just looks better in every detail. The most obvious difference is the accuracy of the nozzle bore. The Da Vinci says it is .4mm but you can throw a cat through it compared to the Hexagon .4mm nozzle.
The software is Solidworks


[Image: expl1.jpg][Image: expl3.jpg]
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#13
Here are some pictures under the microscope. The accuracy of the new hexagon hot end is more visible. Both prints are ABS done at .25mm layer height.
Da Vinci top


Hexagon top


Da Vinci side


Hexagon side
[Image: davtop.jpg][Image: Hextop.jpg][Image: davside.jpg][Image: hexside.jpg]
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#14
The serrated grip for the drive belt is printed separately from the main carriage to allow for better printing quality. I used acetone to glue it in place on the carriage once I made sure the fit was good and the belt fit was also good. Acetone is the best glue in the world for ABS.
I printed the serrated piece with the serrations up so I could get a better result. After gluing the piece into the carriage I ran some small screws through the serrated piece and into the carriage to squeeze the opening of the serrated piece against the belt. The belt isn't going anywhere.
I also ran a screw and washer in the carriage to prevent the linear bearings from escaping.
[Image: DSC02945.jpg]
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#15
Parts hardware list:
10ea 3mmx16mm socket head cap screws
2ea 3mmx20mm Phillips head machine screws (from the MK8 extruder)
4ea 15mmx8mm linear bearings
7ea 3.5mmx 7mm sheet metal screws
4ea 3.5mm flat washers
1ea Hexagon hot end kit
1ea MK8 Chinese extruder
2ea 1/4"x1.25" nylon machine screws
Screw holes have to be tapped to 3mm and 1/4" U used bottom taps
Various clean up has to be done on the right angles, holes etc.
The carriage is designed to be printed on the right side when looking at the fan. It is completely flat on this side and makes for a better print. It places the bearing holes up for better print results.

Thingiverse files http://www.thingiverse.com/thing:665620
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#16
Just finished a successful 12 hour PLA print and starting another. I am very happy with the way this turned out. I could not print more than a few hours with PLA before.
The 12hr print was done at .35 layer, 80 speed, 180c hot end temp, 70c bed temp





[Image: DSC02946.jpg][Image: DSC02947.jpg][Image: DSC02948.jpg]
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#17
Added a file to Thingiverse for a carriage that uses the Davinci bushings instead of the linear bearings.
http://www.thingiverse.com/thing:665620
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#18
Any chance you could share the SLDPRT files? (Or STEP/IGES) I tried opening the STL in SW but it is pretty terrible with STLs and I can't make open it as a solid body to do modifications. Thanks!
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#19
Did you try selecting .STL from the file type drop down then changing the options to mm and solid body?
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#20
Yup. Won't let me open it as a solid body saying the model has too many surfaces. It suggest I open it as a graphics body, but you cant modify a graphics body.
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