Mini 3D Printer Conundrums

[Gina]

I'm planning to upgrade my Mini 3D printer so that it produces more accurate and cleaner prints.  The main problem is a somewhat less than rigid main framework of aluminium extrusion so I plan to use a strong plywood box instead (like my Concorde printer).  I have already made one improvement by replacing the inductive Z probe with the Precision Piezo system as described in another thread in this forum.

Here are some photos of the current build.

[Gina]

Extruder is direct feed E3D Titan and the hotend standard E3D V6 currently with 0.3mm nozzle (I have a 0.2mm nozzle I can use too).

XY and Z motors are standard NEMA17 1.8° steppers and the extruder a "pancake" NEMA17 0.9° stepper.  I plan to replace the XY ones with 0.9°.

V Groove extrusion and matching wheels provide the running mechanism for all 3 axes.

The drive system uses high strength fishing line cord with CoreXY drive and the Z being the print bed suspended from the four corners by cord wound onto a 12mm rod at the back.

The whole printer is controlled by a Duet WiFi system which works very well.

Now for the conundrums...     

There seems to be opinion that fishing line cord is "old hat" and that timing belts and pulleys are better.  Changing to timing belts has pros and cons.  Due to the way the belts run, the X carriage would need to be taller to accommodate the fastenings for the timing belts, both above and below the X rail.  Now with the V6 hotend the bottom of the X carriage would be below the nozzle!  Or it would be with the extruder motor above the X rail as is convenient.  That would say "stay with the cord".  OTOH the XY drive drums are best horizontal and with a box instead of framework would mean the motors would have to be mounted on plates on the inside of the box with the motor bodies projecting outwards through holes in the plywood.

One possible way to move the extruder motor lower would be to mount it onto the X carriage from the back.  That would move the extruder, hotend and nozzle 25mm forward.  The disadvantage is an extended depth and also maybe rigidity problems with so much overhang.

The Z drive system is another area of possible contention.  The 4 corner support would be better changed to 3 which is something I could do.  I do find the cord drive fast and accurate and also silent.  My experience with my Concorde printer is that screw drive is slow and noisy though the Z carriages work very well at holding the 500mm square print bed level.  Clearly the Mini has a very much smaller print bed (printing area 200mm x 205mm) so this printer would need much less powerful Z drive.

I'm posting all this in a forum rather than a Blog because I would appreciate opinions and comments from other experienced 3D printer builders.

[Dr_Ju_ju]

Heath Robinson has nothing on you …...

Personally, I'd ditch the wires & replace with good quality belts & pulleys. Also, 2020, can be ok, but I'd add some better corner joiners (metal plates) & add some more back to front, at the top, to create a true box.

 

[Dr_Ju_ju]

Although I have no personal experience of a corded system, just the fact that you are winding cord at each end of travel, must mean there's a chance, that a cord will "cross-over" another cord altering the movement length (it's what I've seen on fish reels).

You've obviously seen the CoreXY\DBot variants, even the new one (BLV), so something along those lines ??

 

[Gina]

Yes, there is clearly a chance of "cross-over" but with the geometry I used it doesn't happen.

Current Mini and Giant printers are rather like the DBot but my Concorde printer has proved very good though also very heavy being based on 18mm plywood.  One possibility is a smaller version of Concorde.

[Slas]

just get an ender 3 for $190. It makes 99% perfect prints.

[JamesF]

I'd have thought the aluminium extrusion would be fairly rigid in itself.  I suspect it's the joins that are more likely to cause problems.  Bracing those with plate and perhaps adding some external diagonal bracing might improve things no end.  I guess that would achieve pretty much the same as putting it in a box, but without putting it in a box.

James

[tekkydave]

The D-Bot is extremely rigid. It uses 4020 for the corner risers but more importantly the corners are all braced by custom printed parts/brackets and also metal 90deg brackets.

 

[Gina]

That's good to know Dave.  Although I've got the plywood - a 3ft square of 18mm - I have yet to saw it into pieces, a job I don't really fancy without a saw bench.

[Gina]

If I were to go for timing belts instead of string/cord and have to mount the extruder motor onto the X carriage plate in front of the X rail I'm considering upgrading the E3D Titan extruder with V6 heatsink to Titan Aero with either the Aero Upgrade Kit or just the Aero Heatsink.  Anyone using the Titan Aero?

[Dr_Ju_ju]

I tried an Aero on my DBot, but honestly, I just couldn't get on with it.

Instead I bought an original Titan, and even though, when I bought it, it was at the time they were having bearing issues, E3D sent replacement parts, and ever since its been as good as gold.

[Gina]

@Dr_Ju_juWhat was the problem with the Aero?

[Gina]

From comments above and since this printer is working reasonably well as it is, just stiffening up the frame plus odd little tweaks may be all that's needed.  No point in looking for work!  The Concorde was a different matter, it replaced a printer that had numerous problems.

[Dr_Ju_ju]

The main problem was that the heatsink was so efficient that when retracting, some filaments (e.g. PetG) would cool, just enough to start clogging, then when you add the fan into the equation, even with it fully turned down and or temperature controlled, I'd often be cleaning it out, something I could well do without.

[Gina]

That's rather strange.  I have super heatbreak cooling (DIY water cooled block) on my Giant printer but haven't had that problem.  Mind you that is with my own design heaterblocks and 2.85mm filament, which could make a difference.

[Dr_Ju_ju]

I use 1.75, and the standard E3D blocks etc.

One thing I would also add, for me anyway, is that with the Aero fan\heatsink arrangement, I needed to provide a bottom end shroud, as the air-flow, can get to the print, where I didn't want it.

[Gina]

Yes, I can see that would be a problem.

[Gina]

I've decided I'm going to stiffen up the frame I've got.  I've got corner plates and also several pieces of 2020 extrusion 500mm long that I can use to brace the sides and top diagonally.  The base can be screwed to a plywood panel.

[Dr_Ju_ju]

sounds ideal, and there are some cheap'ish suppliers of metal plates on the bay, that are uk based, so reasonable quick delivery if needed.

[tekkydave]

I upgraded my Titan to an Aero using the upgrade kit. I also have a duplicate heatsink/block assembly so I can switch between 2.85 and 1.75mm filament easily. All the wires have in-line connectors. Once I have used up all my existing 2.85mm stock I will shift to using just 1.75mm.

I haven't had any problems with it jamming due to overcooling.

[Gina]

Thank you for all your replies everyone.  I have concluded that a total rebuild is probably not necessary and I shall concentrate on stiffening up the frame, improving the print bed and Z carriage arrangement and a few other tweaks.  If that doesn't give me virtually perfect prints I may reconsider but it's certainly worth a try.  I should have the answer as to whether cord drive is as good as timing belt, at least for small machines.  Even if it is, I am not really advocating the "pink string" as an improvement over timing belt drive as it takes a lot more trouble to get right.