D-Bot 3D Printer

[tekkydave]

I have replaced the mini-v wheels on the y axis with linear rails. I used the printed parts from here and used these MGN12 rails.

The reason the rails are on the underside is that how the thingiverse parts are designed. If it is an issue I can swap them but I will need to shorten the rails by 20mm.

I also took the opportunity to replace the GT2 belt and idlers at the same time.

Movement seems to be a lot smoother and the mesh levelling has improved. I now plan to do a similar thing to the x-axis once I have designed some parts.

 

[Dr_Ju_ju]

Funny you should do that upgrade, as I was also thinking the same type of upgrade for mine, as my belt bearings have worn out, making a horrible screeching noise, and was looking at other improvement, while I'm at it fixing the noises.....

[Gina]

I've been interested in those linear rails and wondering how well they work.  I know the cylindrical linear bearings had problems and I soon got rid of them in preference to V-Slot rails.  I shall shortly be building a new printer to replace my Mini with the idea of maximum precision for printing smaller parts so if these modern type linear rails are good they would be well worth considering.  I look forward to seeing how well you like them Dave.

[tekkydave]

I'll have to see if it makes any noticeable difference to print quality. I think the mini v wheels are starting to wear. I got black dust out of some of the ones I took apart today.

I want to do the x-axis next then possibly the z too. The printer needs rebuilding as some of the sections are no longer 100% square or parallel. If I rebuild from scratch I'll do the z axis at the same time. The 3 z motors need better mounts in the base so lots to think about.

[Gina]

I've noticed black dust in the V-Slots in my printers too.  I think the Delrin wheels do wear with extensive use and I do make extensive use of my printers!

Edited November 19, 2019 by Gina

[Dr_Ju_ju]

You have to be careful with the sliders, as they also use ball bearings, like the cylindrical bearings, that can also drop out, making them as problematical as the cylindrical ones.

Thomas Sanladerer, recently did a modification upgrade on his Mk3 (

 

For him, this proved inconclusive on any benefits...

I've always used the Igus linear bearings, and apart from a quick clean up, now & then, I've had no issues....

Edited November 19, 2019 by Dr_Ju_ju

[Gina]

Interesting but the Prusa printer is quite different from mine and indeed from the D-Bot so the comparison may not be valid.  OTOH there are situations where a rigid construction can produce conflict as the system is constrained in more than one way at a time.  Pretty much what he said in fact.  I need to think about all this.  I guess some flexibility is needed somewhere.

Edited November 19, 2019 by Gina

[Dr_Ju_ju]

Yesterday, I did a stupid thing & 'serviced' my Prusa Mk2, resulting in the bed rails being just a tad stiffer than they were, resulting in print failures.

Loosening things up a little, has returned everything to normal...

[Gina]

His Prusa Mk3 seems to produce very good results but I don't know how fast (or slow) he prints.

[Dr_Ju_ju]

My experience, with my Mk2, is that the quality of the print, stays the same whatever mode is selected.

Quality, also relies heavily on the slicer used; for me its either Simplify3d (Paid for) or the preferred PrusaSlicer (free). I have multiple profiles configured for printers\filaments etc. which means I can usually send the print to any of my printers, depending on the size of object etc.

[tekkydave]

11 hours ago, Gina said:

Interesting but the Prusa printer is quite different from mine and indeed from the D-Bot so the comparison may not be valid.  OTOH there are situations where a rigid construction can produce conflict as the system is constrained in more than one way at a time.  Pretty much what he said in fact.  I need to think about all this.  I guess some flexibility is needed somewhere.

There is still a small amount of 'give' in the D-Bot y-axis even with a rail on both sides. This is with no belts fitted. Maybe this is less on the better quality rails. I don't think the ones I have fitted are of the highest quality - that costs £££

Once the belts are fitted and correctly tensioned there is no discernible play. I haven't printed anything yet 😮

 

[tekkydave]

1 hour ago, Dr_Ju_ju said:

My experience, with my Mk2, is that the quality of the print, stays the same whatever mode is selected.

Quality, also relies heavily on the slicer used; for me its either Simplify3d (Paid for) or the preferred PrusaSlicer (free). I have multiple profiles configured for printers\filaments etc. which means I can usually send the print to any of my printers, depending on the size of object etc.

I have been using Cura for about 6 months having used Slic3r 1.3 dev for a long while before that. The latest releases of Cura seem to produce inferior results so I tried the PrusaSlicer again last week. Much better results so I have switched to that. It has come a long way since being forked from the Slic3r project - well worth another look if you are in the market for a different slicer.

[Chriske]

I always use selfmade linear-bearings. It's nothing more then a little (printed) block in which 6 small ball bearings are mounted. Two of them(in each linear bearing) are adjustable to rule out all play on all axis. For the X , Y axis and the extruder-unit I need 36 ball bearings. My first printer still runs without any problem and need no maintenance. And there's no wearing-out at all.

[Gina]

All this has got me thinking again.  Whilst the V-Slot extrusion and Mini V-Slot wheels look fine for my bigger printers (Concorde and Giant) they seem rather "chunky" and not all that accurate for my new Mini printer where I want the very best performance, sacrificing build volume to achieve this.  I don't really have the time to produce self-made linear bearings with lots of small ball bearings like Chris and I'm thinking the MGN12 rails might be a reasonable compromise.  At least they are metal on metal.  Alternatively, a combination of the Chriske method and linear rails may be an option.

[tekkydave]

Having a go at printing something; some amended parts so I can reinstate the y-axis optical endstop.

The printer overall is quieter. The old y axis seemed to amplify any vibrations for some reason.

Also the mesh compensation map is better. Before there were dips at the corners despite the bed being rigid. I concluded this was due to some springiness in the 3-wheeled y carriages. It is almost dead flat now.

 

[Gina]

WOW!!  That is a wonderfully flat bed.  My Concorde bed seems to curl up on one corner by a few tenths of a mm!

Are you using the new linear rails for all three axes now?

[tekkydave]

24 minutes ago, Gina said:

WOW!!  That is a wonderfully flat bed.  My Concorde bed seems to curl up on one corner by a few tenths of a mm!

Are you using the new linear rails for all three axes now?

No, just the y axis. The x axis has 4 wheels and the z has a 3-wheeled carriage at diagonally opposite corners.

[Gina]

For greatest benefit I think all axes need upgrading particularly the X axis.  I think the Z axis may be less critical.  I'm wondering if a single slider on the X rail would be sufficient to hold the extruder and hotend plus fans etc.  Is there any adjustment in the sliders to take up slack?

[tekkydave]

Yes, I think you're right; the x carriage needs sliders above & below. There is no adjustment built into the rails/sliders themselves. I'm currently using the Re-X Carriage by NickRimmer which is designed for the D-Bot & Titan Aero. I also use this alternative motor mount to hold my piezo device.

There isn't a rails version of this so I will have to design my own.  Could be an interesting FreeCAD project. I'm gradually getting more proficient

 

[Gina]

I've just ordered a 300mm one of those linear rails to examine - arriving tomorrow.  This will be long enough for one of the Y rails on my new Mini printer.

Edited November 21, 2019 by Gina

[Gina]

The linear rail and runner seem excellent so I've ordered 5 more, making 2 each X, Y and Z rails.  I also have X and Y drive rods and the crossed extruder and hotend rails on order.  See Blog for my Mk2 Mini 3D Printer.

[tekkydave]

I have been beavering away for the best part of a week designing a new x carriage for the D-Bot. This will allow me to use the same linear rails as I used on the y-axis. There will be rails top & bottom even though my design is balanced with the motor below the 2040 extrusion. I have designed it to re-use some parts of my existing carriage such as the motor holder which also contains the piezo sensor. It also re-uses the belt clamps. I have based the design on the existing carriage which is the Re-X-Carriage by NickRimmer and modified where necessary. I will probably lose about 20mm of z travel but that's not an issue. The D-Bot will go to 300mm in z but I never print anything that high.

Here are the designs from FreeCAD. Front view:

And the Rear View:

The small PCB on top is the Precision Piezo Universal PCB which eventually will have a small cover.

The yellow part is the existing motor holder / piezo sensor. The Titan Aero bolts to the front of it. I should be able to just take this intact from my existing carriage and insert it into the new one

The only parts I need to print are the front & back panels (blue) and the top & bottom block holders (green). I have also added some extra holes on the front panel to take a cable relief (currently being designed) and a filament guide. I may change the filament guide into a filament motion sensor at some point in the future.

The parts are printing at the moment...

[tekkydave]

Nearly done...

[Gina]

I probably said, I'm designing and building a completely new printer using these linear rails.  Just a little one but more complicated.  I'm still working on the design.

[tekkydave]

A quick mock-up this morning to check the parts take the existing extruder assembly (motor/motor holder/extruder/piezo).

Looks like a perfect fit. Now ready for those rails

I need to do a spell of nut insertions first (ooeerr  )

 

Edited December 1, 2019 by tekkydave