Kossel Delta 3d Printers

posted in: 3d printing | 3

Update (January 26): Autoleveling is working.

Update (January 27): Added packaging photos.

Update (February 5):  Extruder Challenges

Hello everyone,

(I’m sure nobody actually reads my blog, but I don’t mind listening to myself talk.  It’s especially entertaining in the shower.)

I’ve recently acquired a delta 3D printer kit from RenRen3D on Aliexpress and would like to talk about my experience with it and how it compares to the Makerbot 2 I last touched.  But there are a few things that I must get out of the way before I talk about that.  After all, this is just part of the introduction section.

Introduction to 3D Printing

3D Printer Toolflow

3D Printing is the method of getting a computer model to your desk.

You start from a model created in a 3D editing program such as Solidworks or AutoDesk Inventor.  You export it to an .stl file.  You take the .stl file and do transforms on it using your slicer software such as Slic3r or Cura.  This slicer software then generates a .gcode file for your 3D printer.


Why get a 3D printer kit to build and configure at great expense to my personal time?

Well, if you haven’t heard of my recently acquired personal time (at great expense to my social life), I guess I’ve been hiding it fairly well.  So there’s that; I now have time to build the printer.  The horrible thing is that I would rather sit at home and 3D print things than go to lectures.  Oops, hopefully I can make up my missed time by the time the midterm comes around (Thursday, January 28th 2016).

But really, I just wanted a 3D printer so that I can 3D print the various parts that I design on Solidworks.  Let me see if I can find a few samples of what I’ve done in the past:


Hopefully, my numerous 3D models is enough to justify my use of a 3D printer.  Although, I don’t know why I never got a picture of the completed IEEE quadcopter frame.  I also don’t know where my carbon fiber rods went.


Date Completed Thing
January 18, 2016. 3D Printer Arrival, Building The Frame
January 19, 2016. Frame Completed, Hooking Up HotEnd and Electronics
January 20, 2016. Electronics Finishing, Printing with the Printer, Endstop Calibration
January 21 – 24, 2016. Extrusion Calibration, Eiffel Towers
January 25, 2016. New Firmware: Marlin 1.1.0-RC3

At the time that this section is written, it is January 26th, 2016.

Challenges Faced

PrintBed Retainer Changes

The printbed instructions handed to me had brass standoffs; however, the new design calls for nylon spacers instead.  I was confused by this for a while until the 3D printer kit manufacturer handed me the updated instructions.

Electronics Mounting

I couldn’t find out where to mount the electronics until I was given the new instructions for how to mount them.

Marlin Software

The software included with the 3D printer has some odd bugs in it (that really didn’t affect printing performance anyway).  One of these bugs has the odd effect of making the LCD screen show random symbols when it should be showing negative numbers.

I don’t actually know what Marlin version is included either.  It seems to be a branch that eventually supported automatic bed leveling and then disappeared.

Much of the unknowns of this version of Marlin suggested my update to Marlin 1.1.0-RC3.

Newer Marlin

A newer Marlin firmware didn’t support automatic bed leveling (ABL) in its “stable” repository (1.0.x).  So I was going to use Marlin 1.1.0-RC3 which did support ABL.  However, a possible bug with the run_z_probe() function causes it to abort before actually touching the printbed with the Z probe.  I had submitted a bug report about this.  I eventually figured out that the solution is to make sure that the limit switches that I actually use are left as noninverting.  The switches that I don’t use or use for bed leveling are left as inverting.  This causes the endstop logic to recognize that the unused switches (and “pressed” bed leveling probe) are not triggered.

The probable bug is in how Marlin handles the endstops.  The code has a bit too many precompiler directives for me to read and edit confidently.  So my non-kosher fix should be good enough for now.  If it works, it works.

The printer also tried to move at 200mm/s when it homed the first few times I ran it.  I have since changed its homing speed to something more reasonable but still quite fast (60mm/s).  This is much faster than the original firmware’s speed of 40mm/s.


For whatever reason, I cannot find a good retraction setting that would allow for me to have adequate retraction for whiskers not to form.  I have tested many, many prints.  I think the reason they don’t turn out too well may be with the 3D printer PTFE tube holder.  I’ve recently observed that the one closest to the extruder slips while the retraction cycle happens.  I’ll replace it someday, but it’s not a big issue for now.

Retraction Testers

Manual Leveling

Leveling isn’t too hard and is accomplished by using shims under the build platform.

Leveling Guide Printout

Automatic Bed Leveling (ABL)

Automatic leveling is where the difficulty arises.  Much of this is caused by the software either supporting or not supporting ABL and exactly which version to check out and program onto your printer.

Extruder Malfunction

Eventually, the pneumatic fittings that attach to the PTFE tube will fail.

I first noticed that the fitting closest to the extruder stepper motor started to become loose.  (This is why my Eiffel towers always look so unclean.)

The next thing I knew, my filament was stuck and I couldn’t tell why.  What had happened was my filament got caught in the metal shrapnel generated by the spring that had broke in my pneumatic fittings.  The most likely cause of this is metal fatigue whereby metal eventually weakens over time when exposed to cyclic loading.  Metal fatigue is a serious concern in many applications (and apparently one of them occurs in my room).

Okay, so it’s broke.  What now?  Buy another one from a local retailer (or China for that matter).  I ordered McMaster Carr part# 7880T368 which is a pneumatic fitting with a 4mm OD tube on one side and a M5 x 0.8 male thread on the other.  I was able to get the part from McMaster Carr’s Los Angeles warehouse, and I accidentally ordered it as will-call.  The part more or less functionally replaces my old pneumatic fitting.

I have noticed a strong mark on my PTFE extruder tubing, and have mentally noted that it may need to be replaced or cut slightly shorter someday.

Prints Printed

Although I have many things designed on Solidworks, the only thing that I designed and printed was my fit-test plugs.

These are parametrically modeled and are evaluated in Solidworks as a specific size before exporting as an .stl file and then printing.

Parametrically Modelled Plugs


Comparison with Cartesian 3D Printers

cartesian versus delta printers

Here’s a photo of a set of test cubes with the cartesian printer’s cube on the left and the delta printer’s cube on the right.

Notice that a cartesian printer actually makes a better edge.  (The finish on the cubes is an effect caused by the 3d printer filament.)

I’m not sure where this would be a concern, but you’re less apt to cutting yourself with the edges on a delta printer’s printed part.

How Everything Arrived

Equipment Photos

Please excuse the mess!




Parts Already Printed


Although it has been a strange journey, I regret nothing.  Worst case scenario, I end up applying to every 3D printing company ever because I lose interest in schoolwork!  Whoops.

3 Responses

  1. Avatar
    TISSERAND jean-Claude

    Hello Brandon,
    I’m glad to find your blog, and I’d like to congratulate you about it’s pertinence of informations
    and nice pictures too. Cool
    I have bought the last month, the same 3D PRINTER KIT kKpssel Pro K800 from renren3d (Aliexpress)
    and like you, I encountered few problems…with the extruder too, but also with the thread lenght of the quick pneumatic element of the hotend, which is too short after insertion on the effector part, to be correctly fixed.
    One of the eight eyelet carbon rods is also slightly more rigid than the other one.

    But, despite of those litlle mecanicals problems, the maajor actual difficult that I meet is with the configuration
    of the 3d printer.
    Fully assembled and properlly wiring in 2 days, actually, 3 weeks later this nice 3d printer refuse to print anything!
    it stop is process after homing postion and reaching asked temperature, and seem to be waitting something…but what?
    Now, I have replaced their old version of marlin firmware for the new one Marlin 1.1.0RC3 and same for Arduino version, in order to try avoid few previous errors messages generated with their rr3d config.h include on their firmware….

    So, to make it short, and because this blog could not be made for this type of exchange, I would be sincerely grateful to you, if would like help me by sending me your working configuration files by email, in order to compare all your values with mine, and hope to find where is something wrong.
    I’m French, so, sorry for gramatical mistakes.

    There is my email adress: jct54@free.fr

    Best regards.

  2. Avatar

    Hello Brandon,
    Finally, I have found your configuration.h following your link “Bugg report”
    and Uploaded these values into my 3d printer, and Oh Miracle! all encountered problems disappeared.
    So, a big Thank to you from France and “Bravo for the setting configuration”


    • Avatar
      Brandon Lu

      Hi Jean-Claude,
      Sorry I haven’t responded in a while. This is kind of my “low maintenance” blog. I haven’t posted anything new since January. Yikes!

      Oh, thanks for telling me that it’s a K800. I’ve been wondering what the equivalent model is. This will really help when I describe the printer to other people.

      I’m glad that my configuration file was helpful. If you have problems with the hotbed causing “thermal runoff” like me, it is probably safe-enough to turn it off for now.

      Meanwhile, I most likely won’t touch Marlin 1.1.0-RC4 for a while. I seem to be very busy with university work this quarter.


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