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Choose my upgrade!

Posted by cubeconvict 
Choose my upgrade!
July 02, 2018 06:44PM
I am still working on understanding all of my settings and getting them dialed in, there is plenty of work to do there, but I am looking for some upgrade advice. I have read a lot about individual upgrades and understand the idea for many of them, but I don't often see them compared as to utility/cost/usability. Below is where I am at, and some of the upgrades I am considering. What comes first?

ReprapGuru Prusa i3 V2

Using Octoprint, and have a camera for it on order

Current Specs:

* Microcontroller: Arduino mega 2560 R3 clone
* Print area: 8 x 8 borosilicate glass
* Bearing: LM8UU linear bearings (12, including 2 spares); 623ZZ bearings (2)
* Rod: 8mm stainless steel 204 threaded rod (pre-cut); 8mm linear rod for X, Y, Z (pre-cut); 5mm threaded rod grade hardened steel ( pre-cut)
* Heated bed: Dual power 12V/24V (Pre setup for 12V)
* Extruder: Mk8/9 Direct drive with injection molded parts for 1.75mm filament
* Power supply: 360W 12V 30A
* Stepper motor: 5 NEMA 17 4.8kg/cm
* Belt: GT2 (2M, pre-cut)
* Pulley: 20 tooth pulleys (2)
* Board: RAMPS 1.4
* Stepper driver: A4988 (5, 1 extra)
* Couplings: 5mm to 5mm
* Endstop: Electronic end stop circuits w/ LED (3)
* Belt tensioners: 2
* Adjustment: Threaded bed adjustment knobs (4)
* Bed spring: 4
* Lcd: 2004 Lcd

Possible upgrades:
* E3D V6 Hot End
* Mk2 version heated bed
* BL Touch bed leveling sensor
* Upgrade the stepper motors (currently has NEMA 17 4.8kg/cm)
* Upgrade the bearings
* Extruder: Upgrade or move to bowden?
* Others
Re: Choose my upgrade!
July 03, 2018 01:49AM
I upgraded the LM8UU bearings with IGUS drylin
I placed a 4.5mm steel ball between Z-axis stepper shaft and M5 threaded rod to avoid compression of the coupler.
I replaced the hotend with a Volcano clone. ( I have a full metal MK8 extruder ).
Using Bowden doesn't improve anything, because the weight of the stepper helps the Z-axis to drop.
The bed weight is the weak point of any Prusa style printer.
So I replaced the acrylic 'frog' with a Dibond alu-sandwich. I already had a MK3 heated bed, but didn't bother to use a 3 point levelling setup.

Now it doesn't print much faster, but is quieter and using a 0.8mm nozzle compensates the slow speed someway.
I've built a few different printers in the meantime and they all aim to different usecases. The Prusa is my workhorse for mechanically solid parts or PETG.

Two things, that really improved printing was a better Z-endstop switch ( Inductive probe ) and mounting the Prusa on a solid MDF plate. Since then I never had to relevel the bed. I just home the printer and GO

Edited 1 time(s). Last edit at 07/03/2018 01:54AM by o_lampe.
Re: Choose my upgrade!
July 03, 2018 03:34AM
First tell us what problems you're trying to address, I don't personally see a point in upgrading the hotend/motors/etc. if the current setup works unless you've got a specific issue you want to sort out. Something like the heatbed not hitting the target temp or taking forever to do so, bearings jamming or making more noise than you're comfortable with and so on.
Re: Choose my upgrade!
July 03, 2018 10:30AM
Fair enough, my issue is mostly overall print quality. I think my #1 culprit there is bed leveling. I have been mostly using the paper method there, and have just started printing leveling test prints, but I don't ever seem to get flawless results on those. And it's a pain! The dual z motors seem to get out of sync rather easily too.

I don't get as smooth of extrusion as I'd like.

I don't get good enough bed adhesion. Most of the time I do glass and aquanet, with pretty large brims, but have done painters tape.

I will admit that I probably don't have a good enough grasp on some of the settings, both Marlin and Cura, and have mostly just used the canned stuff that came from RepRapGuru.


Re: Choose my upgrade!
July 03, 2018 11:51PM
A bed level sensor will only perform as good as you set it up and calibrate it, it's not a way to solve bed level issues, it's a convenience item, not a problem solving one. I don't use bed level sensors and my bed level is just fine. I'd suggest getting a flat print bed if yours isn't flat, and using a three point leveling system. Not only does it avoid twisting the bed, I also find it quicker and easier to setup compared to a four point system.

Extrusion issues could be anything, not enough motor torque, incorrect idler pressure, eccentric hobbed gear, not enough grip on the hobbed gear (related to idler pressure), not enough cooling at the heatsink, partially blocked nozzle or heat break. This is one of the most annoying things to troubleshoot I find. Another issue is your filament roll could be tugging on your extruder as it moves farther away. For me that last one showed very visible artifacts on the print.

Bed adhesion really depends on the material and bed surface. For PLA I've never needed more than painters tape, for ABS nothing short of a thick layer of ABS juice would get it to stick (and this was in an enclosed chamber that got quite warm from the heated bed).

The dual z motors getting out of sync is tricky. The foolproof fix is couple the leadscrews with a belt and use one motor. Otherwise I hear the way they're wired if they're running off a single driver can make a difference. I think wiring in series helped keep them in sync but don't quote me on that, I read that second hand and even then I'm not sure I'm remembering correct.
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