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December 13, 2018 ...


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Topic: Calibrating towers to the build plate (Read 6883 times) previous topic - next topic

  • BobC
  • [*][*]
Re: Calibrating towers to the build plate
Reply #30
Sigh.  This entire thread is about trying to paint a turd gold. It may look better, but it will still be a turd.  A shiny turd.

It is important (and also critical and vital) to realize that the 101Hero pylons, bed and arms DO NOT FORM A RIGID STRUCTURE!  Precise mechanical calibration is totally useless.  Close enough is good enough.  Custom g-code won't make calibration any faster, better or easier.

Just the act of removing a print can bork the tower alignment.  Changes in room temperature affect the entire printer structure, both in dimensions and stiffness.

That said, there are mitigations that are simple, cheap and effective.  Please read my posts in other threads for the details.  I'd recommend limiting the total investment in 101Hero upgrades to well under $20.  Any more is just paint on the turd.

The next step would be improved firmware, but the printer is hardly worth the effort, since the gains will be small.

The 101Hero is an amazingly awesome set of ideas with very poor execution.  There's no way to turn it into a great printer without replacing all the plastic parts.  Such upgrades could be a great hobby project, but would also be a terrible return on investment compared to getting, say, a $99 BuildOne.

Edit: Well, that sounds pretty dismal, right?  I want to emphasize that I LOVE  my 101Hero!  A better printer would not have permitted me to learn nearly as much as I have about the many ways prints (and printers) can go wrong, and the things that can be done to remedy the situation.  This, to me, is truly the best and most awesome way to get serious about learning the nitty-gritty of 3D printers and 3D printing without making a major investment.
  • Last Edit: 22 Nov, 2017, 08:28:30 AM by BobC

  • BobC
  • [*][*]
Re: Calibrating towers to the build plate
Reply #31
Some miscellaneous notes on keeping the 101Hero printing at its best:

1. Use glue stick.

The thing to take into account here is that the nozzle can easily push into a glue stick layer if it has to, and freshly extruded filament will still stick to the glue stick layer even if the nozzle isn't quite down far enough.  I tend to keep my glue layer about 0.2 mm thick (one layer in draft mode), which seems to make mechanical alignment (and drift) much less of an issue.

2. Put acrylic sheets between each pylon.

This is the simplest single modification you can do to your 101Hero that has massive dividends.  The acrylic sheet should be clear and thick enough not to easily flex (2.5-3 mm).  The pylon has a V-groove the sheet can slide into, but the edge will need to be beveled for it fit snugly. Make a gig (or use a router) to shape the bevel, so it will be consistent on both sides of each of the 3 sheets.  I started with the sheets slightly wide, then worked the bevel until I got a snug fit on all 3 sides.  Make one side slightly looser so it can be raised and lowered for bed access.

Calibrate the printer once, and you'll only need to do it again if you drop it!

Once installed, the sheets not only make the printer much more rigid, but it also makes it much quieter, and reduces the effects of drafts in the room.

3. Use these glass plate clips:

Taking parts off the bed is the easiest way to knock the 101Hero out of alignment.  Using these clips makes bed removal and installation effortless.

4. Print Calibration Towers


Both of the above include OpenSCAD files and Python scripts.  I highly recommend using OpenSCAD to modify the prints, and avoid the Thingiverse Customizer.  The scripts can be used in any version of Cura, but for me they were easiest to use in 15.04.6.

I print a temperature tower for every new spool, and/or when a spool has been sitting for a while.  The main issue is that the temperature sensor on my 101Hero is not at all accurate (it has it's own private unit of temperature), so the temperature ranges printed on the spool are useless to me.  I don't care what the temperature setting number is, I just want it to be whatever lets me print with high qualtiy:  I just use the value indicated by where the "sweet zone" is on the tower.

I do a speed tower whenever I change anything mechanical, including both hardware and settings, or if I unexpectedly get a lousy print.  All my prints to looked terrible after upgrading to Cura 3, the main problem being the pylon stepper motors were skipping steps despite printing at the same old speed that's worked well for me for months. The speed tower made it clear I had forgotten to reset the Cura 3 accelerations from the default of 3000 mm/sec^2 down to the 101Hero limit of 500 mm/sec^2.

These calibration towers should be your most frequent prints.  They provide a consistent reference to help you find and fix problems.  Be sure to keep all your old towers for comparison.

It will take some learning to create a custom STL in OpenSCAD, and to use the script to make the towers print easily and consistently.  See my posts elsewhere in this forum for details.  Though I use Cura 3 for all my regular prints, I still use Cura 15.04.6 for the calibration towers to keep everything consistent, and I don't use Cura 15.04.6 for any other prints.