MakerGeeks.com Mini Kossel Kit - Junk!

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shadowphile
...For this reason alone I have seriously toyed with converting to 1.75, although that eliminates any possibility of flexible materials...

You can certainly get Ninjaflex in 1.75mm.

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shadowphile
I have since realized that the standard 170 diameter plate is too small for many of my desires; if I have the patience (and cost of different parts), I would definitely move up to a 220 or bigger.

One of the nice things about the delta design is that you can easily use a large bed without having to worry about how to move it, or how to power the bed heater - you can use mains power and an SSR, without the safety concerns of flexing wires carrying mains voltage. I now have a 330mm bed with 300mm printable diameter. It has a 240V 350W silicone heater. The SSR for the heated bed and the 12V 100W PSU for the rest of the printer are under the bed. I'll publish more about this design in my blog (see link in my signature) when I have finished the conversion to 2020 extrusions and metal corners.

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shadowphile
I am curious though how you worked out that the the electronics combo you mentioned (which comes with the MakerGeeks kit and NOT one of the issues I've had) is under-powered.

This is well-known. There are plenty of people running deltas on Arduino Mega/RAMPS, but you need to get the number of delta segments per second just right (low enough not to overload the processor, high enough to avoid serious artefacts at the highest print speed you want to use), and you can't run a 12864 mono graphics LCD at the same time.

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shadowphile
If I decide to just buy a working assembly how much can I expect to use it vs doing maintenance? Should I bother with a delta or stick with conventional cartesian? It seems like the biggest attraction for most people is 'It looks cool'.

My Delta is maintenance-free, although I expect the Traxxas joints will wear out eventually. My Cartesian printer requires regular oiling of the threaded rod Z drive, occasional adjustment of the bed levelling screws (even though I use auto bed compensation on large prints), and occasional oiling of the smooth rods. I have never had to clean out the hot end in either printer.

However, I don't think you are too far from getting a working machine. My machine works well despite the leaning towers (the auto calibration is a great help here), and the metal corners should sort that out (you already have 2020 extrusions, so it is an easier conversion for you). If you can sort out the extruder issues, you will be printing.

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shadowphile
Does anybody have suggestions about working out the jamming issues? That is the scary part for me because it is so hard to get feedback about what is happening. Either it is sticking to something, or the hole is clogging, or the filament flow properties have changed somehow. Trying to troubleshoot all three seems to reduce to: try,try, try! Maybe there is better forum or thread for this issue? It's not really delta specific.

I don't have any experience with 3mm filament, so this is theoretical. I have already found that extruder stepper motor current is a compromise. Too low, and the motor will skip steps at high feed rates. Too high, and when the nozzle is temporarily obstructed, the motor will chew through the filament, and then it won't feed any more filament until you push the chewed section through the extruder drive. A 3mm filament requires nearly 3x the feed force, but provides less than 2x the diameter to grip. So,other things being equal, the compromise is probably slightly more critical with 3mm filament than with 1.75mm filament.

If you can't find that compromise, then I can think of a few things to check:

1. Is the hobbed bolt in good condition, and is the shape of it appropriate for the filament diameter? A hobbed bolt that is clogged or has blunt teeth will have less grip on the filament and be more inclined to chew through it.

2. Is your hot end temperature high enough?

3. Do you have sufficient cooling to the top end of your hot end?

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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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Dark Skunk
... I replaced the extruder mechanism with a more powerful one (it's a beast)...

What did you actually find? I'd like to look at your beast. Another junky piece I have to replace. In my kit the pivoting part of the plastic clamp had a hole much too large for the screw necessary to go through into the stepper motor, which is where ALL the stress is. Really? Rotate all that heavy clamping stress around a soft printed-plastic hole much too big for a long thin threaded screw? I was told there was nothing wrong with the printed part. This is beyond poor quality; it is criminal negligence that can hardly even be called 'design'.
RobotDigg has a solid looking product for $40, can't tell much from the picture.

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dc42
You can certainly get Ninjaflex in 1.75mm.

I've read that trying to push 1.75mm Ninjaflex through a bowden tube is too difficult to control the feed (at least the softer varieties). I can believe it.

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dc42
One of the nice things about the delta design is that you can easily use a large bed without having to worry about how to move it, or how to power the bed heater - you can use mains power and an SSR, without the safety concerns of flexing wires carrying mains voltage. I now have a 330mm bed with 300mm printable diameter. It has a 240V 350W silicone heater. The SSR for the heated bed and the 12V 100W PSU for the rest of the printer are under the bed. I'll publish more about this design in my blog (see link in my signature) when I have finished the conversion to 2020 extrusions and metal corners.

I've built stuff like this at work using same SSR, so yeah, solid approach. Some people aren't comfortable working with mains though. I also don't see any insulation under your heater pad.
Doesn't the overhead thermal plate cause a lot of heat build-up? I found some 1/16" inch cork sheet with adhesive at the local hardware store for lining shelves, and it is PERFECT for slapping a couple layers of thermal insulation on the bottom side of the heater plate. Despite that, there will still be heat build up, plus those hard-working steppers inside as well. I've been thinking about the need to force air through the space just to keep the steppers cool.

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dc42
... metal corners should sort that out (you already have 2020 extrusions, so it is an easier conversion for you)...

I looked at the RobotDigg parts; a full set of anodized vertex parts for $55? That is a no-brainer. Thanks for the reference! In fact I am looking at the metal carriages and their extruder mechanism as well. Alas, it would all ship from China. I've been leery of Chinese parts so far due to reputation of quality, although I know even Apple has their parts made there. I've been told that if you do some hard baby-sitting you can get quality out of China, but not as a default. I had a friend engineer who flew their several times to set up manufacturing and he was very under-impressed with their factories.

(funny story: I was using a German lab-grade micro fluidic diaphragm pump in a design at work that didn't need any real pressure, and if the output was blocked the very high-pressure of the 'quality' pump would blow out the internal tube fittings. It cost over $100. At the behest of my Taiwanese boss we bought a whole tray of pumps from China for $9 each! Although I still think their reliability will prove to very poor, they happened to be so weak they would easily stall at a low pressure when blocked. Har! How often is a low-quality part chosen over a high-quality part other than to save money?)

Edited 1 time(s). Last edit at 05/19/2015 06:50PM by shadowphile.

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shadowphile
I also don't see any insulation under your heater pad.
Doesn't the overhead thermal plate cause a lot of heat build-up? I found some 1/16" inch cork sheet with adhesive at the local hardware store for lining shelves, and it is PERFECT for slapping a couple layers of thermal insulation on the bottom side of the heater plate. Despite that, there will still be heat build up, plus those hard-working steppers inside as well. I've been thinking about the need to force air through the space just to keep the steppers cool.

It's not in the photo. but I have a double layer of corrugated cardboard under the bed heater, with aluminium foil on top of the cardboard. I have a sheet of cork that is waiting to replace it. My stepper motors run cool at present (they are running at 1.0A out of a rated 1.6A), so heating is not a problem. When I build a heated enclosure for the printer, I will add a fan under there as well, mainly to cool the power supply.

I'm not sure quite what you mean by heat build-up. When I heat the bed to ABS temperatures, there is no significant overshoot even though I am using bang-bang control. The bed does take a long time to cool down, but that is no bad thing. The biggest problem is that the thermistor is buried in the silicone instead of being in contact with the aluminium. I have to command it to 140C to print ABS, which gives me about 115C-120C on the aluminium and 110C on top of the 4mm glass. I may epoxy a thermistor to the bottom of the aluminium and use that instead.

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shadowphile
I looked at the RobotDigg parts; a full set of anodized vertex parts for $55? That is a no-brainer. Thanks for the reference! In fact I am looking at the metal carriages and their extruder mechanism as well. Alas, it would all ship from China. I've been leery of Chinese parts so far due to reputation of quality, although I know even Apple has their parts made there. I've been told that if you do some hard baby-sitting you can get quality out of China, but not as a default. I had a friend engineer who flew their several times to set up manufacturing and he was very under-impressed with their factories.

My Robotdigg corners are OK except for the drilling on one side of one of the top vertices:



The two holes on this side are 1.5mm above the centreline, which causes the top frame to distort when it is assembled. As it is a top vertex, I will file those two holes into an oval shape. If it were a bottom vertex, I would send it back.

I bought the metal carriages and effector too. The carriages were a waste of money for me, because they are intended for endless-loop belts. There is no facility to terminate two belt ends on the carriage. The aluminium effector looks OK, however as my diagonal rods are 350mm long, I think I ought to increase the rod spacing to increase stiffness and increase the vibrational frequencies - which means that I will need a larger effector.

If you do use the Robotdigg corners then you will need this hardware:

M4x10mm button head screws to attach the horizontal extrusions
M4x8mm countersunk screws to attach the vertical extrusions
6x623ZZ bearings for the idlers - looks like 3 of them could be flanged bearings, but ordinary ones work OK for me.

Also check that your extrusions are compatible. The spigots in the square holes for the verticals are 5.65mm wide. The Motedis I-profile 2020 extrusions have slots only 5.25mm wide, so I had to spend a lot of time enlarging them with a Dremel.

Edited 2 time(s). Last edit at 05/20/2015 01:33PM 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].

dc42, how long did it take to get those RobotDigg parts (and are you not in the US?)

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shadowphile
dc42, how long did it take to get those RobotDigg parts (and are you not in the US?)

Both Dave and myself are in the UK and my parts arrived in approx 7 days and there were no issues with Mine.

Doug

Mine took about 7 days to arrive too. Apart from that one top vertex, they are OK. I might email them the photo and ask for a replacement anyway, just so that they know they need to improve their QC.

Edited 1 time(s). Last edit at 05/21/2015 10:24AM 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].

I received my RobotDigg vertex parts today. They are fairly good looking, only a very very slight hole offset on one part of the top pieces. It will be very comforting to have a no-compromise rigid metal chassis.
But..I am very annoyed that it is designed for M4 screws. My Kossel mini used M3 or M5 on everything. I can't run to the local hardware store and buy M4 t-slot nuts (I'm stocked on the M5s). Besides, I'm boosting the chassis strength with metal parts but now I am supposed to use weaker screws? I am fairly sure I will be drilling these out. (sigh)

(one Makergeeks thumbs-up was he sent be a big bag of M5 t-slot nuts for free because I couldn't find what I wanted online)

..I think the only things I have left from the original kit are the aluminum extrusions and the motors. Oh, and the glass bed. What a waste of $800!
I used a local makerspace's drill press so drilling out those 45 M4 holes to M5 in the RobotDigg vertex parts went from a headache to a trivial task. This new chassis is a tank! I thought about upgrading it to a larger width while it was all torn down but decided to keep my life simple and make the existing design work first. I'm getting comfortable with tear-down and rebuild.
BTW, did Dave or Doug notice that the upper vertex parts have no facility to adjust the belt tension? At this point I'm redesigning everything so it doesn't matter and I never liked the concept anyway. I want to put the belt-tension adjustment right in the stage carriage where the two belt-ends meet. Stick 'em in then pull tight with a screw, don't know why it wasn't done this way in the first place.
A tank I tell you! I am delighted with how much stronger (and square) this thing is. Yes, it's heavier, so what. Resonant frequencies have probably skyrocketed and I eventually want a multi-extruder design that will benefit from a stronger chassis.
Now the hard part: get a working cold-end up. I haven't had much luck finding an off-the-shelf direct-drive 3mm airtripper-style mechanism. If I am going to keep using 3mm I need to design a very strong drive and bowden tube assy or the required forces during successful operation will blow something apart. I wonder if too much force inside the hot-end might cause a back-flow of molten plastic that will cause jamming? (shudder) The thermal model of the hot-end is rather complicated with the filament phase-change and all, still trying to work that out in my head.

Ugh... I wanted to purchase the Anodized parts from RobotDigg (They're definitely worth the $55), and had a few other small things in my cart for a total of $76.10 before shipping. But then I received a shipping quote of $40!!!!!! That's crazy!

So I cancelled my order... The shipping quote nearly doubles the cost of the corners. I'm just going to fabricate my own corner braces instead. Sure, they won't be as pretty as these gorgeous anodized corners, but oh well.

I don't understand why they can't ship it 'slower' for at least half the quoted shipping cost... GRRRRRR!!!!! ANNOYING!!!

Jeff

Not sure either . . . the last order I made about 6 weeks ago shipped standard, non expedited for $6 . . . .

- Tim

Edited 1 time(s). Last edit at 07/13/2015 11:16PM by tadawson.