My Large Kossel build: Feedback encouraged

Hi All

I've owned a Mini Kossel from think3Dprint3D for about six months and have been loving it. Over that time i have made alterations (as you do) and I now have it running very reliably on Duet electronics and dc42 firmware. I use the printer mainly for my hobby of flying models first person view: Quadcopter, Plane and Ground Station parts mainly, more recently I've started collecting vitamins for a piclop 3D scanner. This has meant the 170mm print bed of the Mini Kossel is no longer big enough, I need a bigger printer. Luckily, the Mini Kossel IS big enough to print parts for a larger Kossel! So for now the scanner project is on hold and bigger printer has begun....

My lose targets are:
300mm build area minimum
300mm build height (at edges) minimum
Better stiffness using 2040 for towers
Better layer resolution below 0.2mm
Multi extruder (I plan 3 being as deltas lend themselves to multiples of 3)
As much of the electronics hidden as possible
Not having too big a foot print
Make use of the mountain of M3 fixings i already have

So far I have been finding and collecting the best source for the parts while trying to stick to within a limited budget and making some preliminary designs for the printed parts I'll need. I really want to mount the 2040 towers to make the most use of the stiffer wide size but nothing on thingiverse fits the bill. Being as I also wast multiple hot ends the effector will naturally be bigger so between wider carriages and bigger effector i can widen the distance between the diagonal arms, hopefully stiffening things up even more. I've also got my eye on a 330mm bed heater that fits the bill and will make a fixed size I can build the rest around.

This has timed nicely with dc42 latest blog post about his large Kossel build and he has raised some interesting points from his build experience that I will be taking note of. In the blog dc42 links to robotdigg.com a new site to me and if they can supply what is advertised it should be a great resource for more unusual parts.



Here you can see where I'm at with the 'corner' design, they don't extend out as far as if I used stock Kossel ones and the orientation of the 2040 is (in my mind) the correct way round. Interestingly, for a 330mm bed the horizontal extrusions work out to also be 330mm with my corner design. My plan is to use the newer carbon reinforced filament that had been coming to market in the hope that it does what they claim and add stiffness to parts. I'd really appreciate feedback here.

I intend to make the top horizontals 2040 too, again hoping for extra stiffness.

To give me space below the bed for as much electronics as possible, i intend to let the vertical extrusion protrude below the main 'deck' and then use another set of 'top corners' on the bottom to add stiffness. This also gives me an adjustable amount of space for the electronics. If you get the idea? I'll post a picture soon...

I've got a rough design for the three end effector but its gonna take more time to refine, I'm most familiar with SketchUP and even so I'm rather limited so the more complex shapes are taking me some time.

I will be using 0.9 degree steppers as recommended by dc42 in order to improve sub 0.2mm layer heights.

Extruder wise I've found the rep rap mini extruder as supplied on the Mini Kossel to be just fine, i like the large gear to be able to feed filament by hand when needed. I like the E3D V6 hotend I'm currently using but i may go with clones or the Lite6. We'll see what i can afford.


So thats it for now, all feedback/advice welcome and more from me to come......

Good luck with your build! I have a few suggestions:

- That 330mm diameter heater you link to is only 120W, which I am fairly sure will be nothing like enough power for that bed size to reach ABS printing temperatures.

- My build is very rigid despite being 1m high and using 2020 extrusions. I think the metal corners help a lot, so perhaps does the use of 2060 extrusion for two of the lower horizontals. The Robotdigg corners won't fit your proposed 2040 vertical extrusions. Johann is offering some sheet metal corners here [groups.google.com] that look interesting.

- Effector tilt is likely to be an issue if you use 2 or 3 nozzles. See the topic I have just started.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
- That 330mm diameter heater you link to is only 120W, which I am fairly sure will be nothing like enough power for that bed size to reach ABS printing temperatures.

Was what you've used something like these? [www.omega.co.uk]

Nice find! I see they don't have thermistors embedded like the other silicone ones i've seen and that could be a good thing from dc42's experience. Would sandwiching a thermistor between the silicone and the Ali be a more accurate solution? SRFR-12/10-P-230V would be the obvious choice here.

On the effector tilt point, I could easily start off with a single extruder and upgrade as i go. The less complex variables to start with the better until its reliable, then add more.....

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wayno complaino
Nice find! I see they don't have thermistors embedded like the other silicone ones i've seen and that could be a good thing from dc42's experience. Would sandwiching a thermistor between the silicone and the Ali be a more accurate solution? SRFR-12/10-P-230V would be the obvious choice here.

Yes indeed but they are quite expensive and a 6 week lead time

I got mine from Silicon 300 mm 500w 220V AC heater it took about 2 weeks to get here and it is the second one that I have ordered from them.

Note that the Thermistor is in the centre of the pad (I think looking at DC42's photos of his that his is offset somewhat and is closer to the edge than the Centre) also there is nothing stopping you from fitting a thermistor between the heater and the bed as long as any wiring can cope with the temperatures generated and is well insulated.

Doug

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wt

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dc42
- That 330mm diameter heater you link to is only 120W, which I am fairly sure will be nothing like enough power for that bed size to reach ABS printing temperatures.

Was what you've used something like these? [www.omega.co.uk]

Mine came from here [www.aliexpress.com]. They will make a heater to your size/power/voltage specifications, with or without thermistor.

If I want a more accurate thermistor, I will attach one to the margin on the underside of the aluminium plate.

Edited 1 time(s). Last edit at 06/04/2015 09:43AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

All good info guys.

I discovered that my corners were slightly too big for my Mini Kossel to print so slightly amended, will print a test tonight just to see how it comes out. I'm keen to stick with the 2040 mainly as I've not seen one built in this orientation so it'll be an experiment others can learn from (even if its a "don't bother")

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wayno complaino
All good info guys.

I discovered that my corners were slightly too big for my Mini Kossel to print so slightly amended, will print a test tonight just to see how it comes out. I'm keen to stick with the 2040 mainly as I've not seen one built in this orientation so it'll be an experiment others can learn from (even if its a "don't bother")

Interesting - I'm in the early stages of trying to plan a delta build (with zero previous 3d printer experience), but on looking around I'm sure I saw a few in that orientation, and wondered why no-one had done it with the long side pointing towards the centre. Then I found the latest Cherry Pi had done it that way.

So both orientations seem plausible. Whether one is actually better than the other, I don't know.

Given most smallish builds seem to use 15x15 happily, I'm currently tending towards ~300mm sides (+end plastics) and 600mm verticals in 20x20 v-slot, as they cut nicely from lengths of 1500mm. Though I have also considered 20x40 for the verticals (as I'd get 10x300mm from 2x1500m, and then 500mm verticals from another 1x1500mm) but I think that came out a bit poor on print height compared to diameter.

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wayno complaino
All good info guys.

I discovered that my corners were slightly too big for my Mini Kossel to print so slightly amended, will print a test tonight just to see how it comes out. I'm keen to stick with the 2040 mainly as I've not seen one built in this orientation so it'll be an experiment others can learn from (even if its a "don't bother")

Kossel%20Large%20Corner%20Design2.png

Actually Wayne there is a design on Thingiverse that uses makerslide 20x40 in the same orientation as yours see Snowstock Delta I was considering this for my Large delta build but didn't think his mounting of the Verticals would be solid enough so went for a Cherry Pi XL/4 or whatever you wish to call it (Thread is called A larger Slice of Pi) Didn't quite work out for me due I think to my corner print's were rubbish so I am now doing it with std 20x20 V-Slot from OpenBuilds and robotdigg Aluminium extruded corner brackets.

Doug

Quite right Doug, now you've linked to it i have seen that delta design before. Its quite different to a 'Kossel' though and i was looking to keep it as Kossel like as i could being as it a proven design. I'd say I'm remixing the kossel, not making anything new in any way. The belt semi inside the extrusion is an interesting feature though.

I left a corner to print last night, its the longest time print i have done so far and it showed a problem I've not come across before. Near the top of the print one of the belts rode over the edge of the flanged bearing and got stuck meaning the effector was miles over the side of the bed (and table) so i now have a nice tangle of used filament on the floor. Doh! I've worked out that on one tower the belt loop is slightly longer than the other two and so for the same belt tightness that top corner is slightly higher. This makes the whole top a slight angle and so the belt is very slightly to the inside flange, over the hours of printing one print (and many previous hours printing) it has worn the edge of the belt, eventually leading to it riding up and over the flange. I also have belt tension springs on the belt that must have given it the ability to 'stretch' over.

Live and learn. Looks like a rebuild and more precise belt measurement is in order and ditching the springs. Or closed loop belts.

Edited 1 time(s). Last edit at 06/05/2015 08:52AM by wayno complaino.

Should be able to put an order in for the 2040 this week so i can try a printout to make sure the tolerances are good enough......

In the mean time here is the initial and simple plan for the top although there is no belt adjustment like the Mini Kossel, i think i will add that to the Carriage.

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wayno complaino
Should be able to put an order in for the 2040 this week so i can try a printout to make sure the tolerances are good enough......

In the mean time here is the initial and simple plan for the top although there is no belt adjustment like the Mini Kossel, i think i will add that to the Carriage.

Kossel%20Large%20Top%20Corner.png

Wayne

Where are you as I have 3 x 1000mm lengths of 20x40 Motedis extrusion doing nothing now?

Doug

Milton Keynes, UK

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wayno complaino
Milton Keynes, UK

Ah I am in Chesterfield Derbyshire though am coming down to the Smoke next week Carravaning at Lee Valley.

I'm in the process of planning a similar build, based on a wolfstock (which is a 2040 makerslide based mini kossel). Printed parts are similar to yours, although the corners aren't as wide. As it's makerslide the orientation of the vertical extrusions are like yours (not sure why anyone would orient it the other way though?)

At the moment the dimensions are sized for a readily available 265mm heated bed, with 2040 for the base horizontals and 2020 for the top. I don't quite like the common mini kossel way of mounting the top pulley though, it seems to me better to have a fixed structure all adjusted to be true, with independent pulley mounts. I'm playing around with simply using a separate copy of the top vertex (without the horizontal "wings") which would hold the pulley and be able to be bolted onto the rail on both inner and outer faces.

Edited 1 time(s). Last edit at 06/18/2015 04:21AM by rocketwiz.

nice find, i'd not come across the wolfstock before. i'll have a good look into it.

sounds like a good option for the pulley mounts, i was thinking the same thing about having the frame built true then tension the belts in another way.

wish i didn't have so many projects on the go at once as my 'toy budget' keeps getting blown on other stuff......

Hello,

I'm actually working on Sketchup PRO v15 for my new 3D Delta printer.
My requirement are identical than yours :-) so I'll follow your project with attention.

For now, my choice about controller is the Duet controller (already ordered to [www.replikeo.com]) with PanelDue touch-screen controller and Mini height sensor board (ordered to DC42 on this forum)
I already have in stock E3D so I'll use this one.
About NEMA, I'll choice 0.9° (400 steps) for accurate precision.

When I'll have more time, I'll post more information with pictures :-)

V-Slot and mini wheels on the way from ooznest......

V-slot is here and i've been trying to print some corners in ABS. Ether i need an enclosure or i stick to PLA for the frame parts.

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wayno complaino
V-slot is here and i've been trying to print some corners in ABS. Ether i need an enclosure or i stick to PLA for the frame parts.

I had to do 2 things to get successful ABS prints from my Mini Kossel:

1. Use Kapton tape to shield the nozzle area from the draught produced by the hot end fan.

2. Put 2 plastic bags over the printer to provide a temporary enclosure.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Were the bags enough? I remember seeing a picture on another thread.

Did you use any insulation under the kapton tape?

Ive only just looked at the thread where you suggested the sheet metal corners, probably a better solution long term. I'll have a chat with the tutors in the engineering workshop and see what they can make. It takes away from the RepRap printers printing printers philosophy though so i will persevere with the printed ones first.

Yes, the bags (2 of them, one over the other to mostly give an air space between them) were enough. But I intend to build a proper enclosure, because using the bags was fiddly.

I didn't put any insulation under the Kapton tape, I just used it to mostly seal some large gaps between the nozzle and the fan duct.

Have you considered using 60mm high bottom corners, and 2060 bottom horizontals? That is what I did (except I used 2 x 2020 extrusions on one side so I could put the mains input connector, switch and fuse between them). It adds extra stiffness, because the 2060 horizontals act like 60mm corner braces, and gives more room for electronics, power supplies etc. under the bed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yep, the bottom will be 2060, I have a 1.5m length here ready to machine to 330mm lengths once i'm 100% sure 330mm is correct. If i go for a different corner style (like the sheet metal brackets) then that length may need to change.

Nipped out to B&Q this afternoon and picked up some hard board and silver 'bubble wrap' insulation, gonna make an enclosure, I wanna nail this ABS printing. Gotta find something transparent and cheap to use as a window so i can see in though.

my build ended up going this direction... i used 8020.com 1020 extrusion for the head and base and the columns are makerslide. My corner connectors are printed but i chose to build my motor mounts and idler pulley mounts seperate and out of 16ga sheet metal.



Its a full 1m tall since thats what the stock length of the makerslide came in.

my build area should be around 250mm dia x 525mm tall.

my spool mount



motor mount

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Freebird01
my build ended up going this direction... i used 8020.com 1020 extrusion for the head and base and the columns are makerslide. My corner connectors are printed but i chose to build my motor mounts and idler pulley mounts seperate and out of 16ga sheet metal.

Looks nice! However, the bed looks small compared to the length of the horizontals. I too have 1m vertical extrusions. My horizontal extrusions are 355mm, the bed is 330mm diameter, and the printable diameter next to the towers is 300mm. What length are your horizontal extrusions?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

the horizontals are 20 1/2" (appx 525mm) the build glass is 14" dia. (appx 355mm)

Im already there as far as build surface etc. 120w is enough to reach 105c on the bed for sure, my stock 12 x 12 heated PCB bed with a 2mm layer of aluminum and a glass mirror on top is enough. Using a DC-DC boost converter to bring up to voltage to 14v or so will reduce heat up times to under 10minutes. I only print in ABS, no PLA here ever. But I can say that even when tuned properly the printer really needs a heated chamber to exceed a 200x200 build in ABS. You idealy want to go into the 40c range.

If you want any more info PM me or check out my blog in signature and also check out my youtube channel. My latest video shows how my printer is built. [www.youtube.com]

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My Personal Blog. Build blog.
[engineerd3d.ddns.net]

Modicum V1 sold on e-bay user jaguarking11

Enclosure.....





Got to seal the top and bottom then add a door. Got some clear plastic for the door, just hope it doesn't melt. Then its back to making large kossel parts.

Don't know why the thumbnails are rotated, click on them for original the correct way up.......

Enclosure 'finished'




Not perfect by any means but well enclosed. There are gaps in both top and bottom so there will be air being pulled through as it rises but hopefully no drafts just on a smaller test print opening the door at the ens it feels pretty toasty in there. It has made the whole printer more noisy though and the fiberboard resonates, shame as it was very quiet compared to any other printer ive seen in person.