Pre-Newbie Stepper Motor Question; (More-Nit-Picking, lol)

Hello & Good day to you all,

I am very soon to buy a Longboat Prusa from The Reprap Kit Store and it only uses Nema 17 Stepper motors. Now i will want extreme accuracy from my printer (eventually) so i will be buying a Nema 23 or even a Nema 34 to be used for the extruder, but my question is;

Would the upgraded Nema stepper motor be automatically recognized by the electronics hardware so that it will know the motor will be capable of 400/1000 steps per revolution ?

How difficult would it be to upgrade the extruder stepper motor ?

Many thanks in advance for your help !



Also would i have to change all the motors to Nema 23/34 to obtain higher accuracy ?

Speed will be sacrificed of course - which i am not bothered about but would i need to chance all the stepper motors to get higher quality prints ?!!?

Edited 1 time(s). Last edit at 01/21/2012 05:16AM by offtherails2010.

What makes you think bigger motors are more accurate? 400 step NEMA17's are available and I have never heard of 1000 step motors.

I don't think changing any of the motors to larger ones will make much difference to the print quality and they won't fit any of the motor brackets or the extruder. You would need to make those printed parts bigger.

The firmware has no knowledge of the motors connected, you have set the steps per mm and recompile it.

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[www.hydraraptor.blogspot.com]

Ahh i see ! Thanks for the heads-up!

i had assumed that more steps per rotation would yield a more accurate print ?

also i was just browsing for nema motors and stumbled upon this website;

Nema 34

i may have read it wrong but in the data sheet quoted 1000 counts/revolution resolution for a nema 34, but im glad you have corrected my assumptions before i'd gone out and bought anything!

Also i think i'll just be happy with what i receive when i buy the 3d printer, lol, i just cant keep anything standard, always modifying something!, but as i know nothing about 3d printers im glad im asking questions in the right place!

i have been studying your website (hydraraptor.blogspot) and found your work there most-comprehensive and with a wealth of experience under your belt i can rest assured that this is where the experts live !

I am most grateful for the advice!

& Thanks again !

Those are 1.8 degree motors, i.e. 200 steps per rev. The 1000 counts / rev refers to a shaft encoder option.

Most Reprap electronics give 16x microstepping, i.e. 3200 steps per rev with standard NEMA17 1.8 degree motors. You could use 0.9 degree NEMA17 for more accuracy but I doubt you would notice the difference with microstepping.

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[www.hydraraptor.blogspot.com]

... i have motors with corresponding drivers from Precitec (Berger-Lahr) with 3 coils, that i can configure to either 200, 400, 500, 800 or 1000 steps per revolution in normal operating mode (or fullstep mode).

With activating the intermal 10x microstepping of the drivers this modes will change to 2000, ... 10000 steps per rev. accordingly.

But this types of motors+drivers are really pricey, so not so common for DIY ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Again, most-appreciated for the low-down & tech specs @ nophead, i assume that its more the nozzle-size that will be determining the accuracy factor & speed of print, i've alot to learn!

I really want to (ideally, lol) get me printer then make another but double the size and learning from your trials and experience with heated beds hopefully build a larger scale printer !

with the learning into the world of CNC i would like to build a decent laser cutter down the line so all your help is extremely invaluable @ VDX & nophead, so i'll be learning with the 1st 3d printer (as a stepping-stone to knowing what to expect in all the aspects of cnc, from soldering to sourcing the parts & bill of materials etc!)

Once again i humbly thank you both for enlightening me further !

The nozzle size sets the minimum feature size and also the minimum corner radius. Accuracy is determined by calibration, filament diameter variations, build speed, inertia, backlash, friction, etc. I.e. all the things that stop the axes stopping exactly where they should be and laying down filament exactly the right width.

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[www.hydraraptor.blogspot.com]

... it's difficult to compare 3D-printing, CNC-milling and lasercutting.

Every of the applications has other optimal parameters, that are suboptimal for the others - for milling you'll really need high rigidity and torque (what makes the machine heavier), for lasercutting high speed (maybe with optical galvo-scanning) and high accuracy ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

@ nophead, Hmmm, yes the backlash & what ive been reading about the z-axes wobble has me a little worried about when i want to make a double-the-size reprap (from the longboat prusa) but i suppose i'll have to wait till i get my teeth cut on my 1st 3d printer, through which i'll (hopefully!) learn about the concepts behind the engineering of these printers !

just gathering as much info as possible whilst im saving, lol !

also i want to try to get ABS to the UK and try to sell it as cheap as i can, minus my costs of bringing it over but ive almost exhausted virtually all the reprap stores from the USA, its the shipping thats the real killer and im a bit upset that its still quite expensive!

Trying to search Europe now, lol

Anyhoo, many thanks again for all your help, support & advice so far @ nophead & VDX, its most-appreciated !

offtherails2010 Wrote:
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> also i want to try to get ABS to the UK and try to
> [... snip ...]
> the shipping thats the real killer and im a bit
> upset that its still quite expensive!

Have you looked at Faberdashery. Prices seem reasonable, works out around 4 pence per cc if you are happy to use PLA instead of ABS.

I haven't used them yet (but noted the longboat kit included a length of faberdashery PLA), but prices are the best I've seen for the UK and they have a good selection of colours.

Hello & Good Day to you NigeO,

Many many thanks for the point in the good direction, i am most-grateful for your help!

Any and all help received is very much so appreciated as the UK seems to LOVE ripping us all off when it comes to new technologies and their peripherals... (Very Upset with this.... Tut Tut....)

Anyhoo, yes, Just checked Faberdashery's shipping costs, a very reasonable £5.80 to ship to my location in London, the quote details are below for 100m of PLA (approx 200grams under a kg)


Product Qty Price (£)
Robot Silver - 3mm PLA 100m coil 1 31.00
Shipping: 5.80
1 item 36.80 Including P&P

Very happy with their postage costs and for once its not extortionate!

I's still saving up for my 1st reprap but extensively checking sources for when the time comes for me to start buying PLA or ABS filament, i want to know that i'll have a decent price to pay per kg...

Again, many thanks for your input & i am extremely grateful !

Nema23 or Nema34 motor for the extruder will put a lot more mass on the x-axis carriage. This will cause two important problems that can reduce your print quality:

1) due to more weight the x-axis sag [of the 8mm smooth bars] will be more noticeable.

2) more weight also means you'll have to reduce the maximum acceleration on x-axis [and if not careful the axis will skip steps]

Of course with a motor like this you'll have plenty of torque for direct drive extruding at insanely high speeds (which unfortunately you won't be able to use due to 2).

misan

Hello & Good Evening misan,

Many many thanks for your input, its greatly appreciated !

In anticipation of owning my 1st Reprap im nit-picking all i can whilst saving up and i'm extremely grateful for all you Reprap-Jedi's helping me better understand the pitfalls & advantages of what my little brain is working over-drive on!

Um, as the extra weight of the Nema 23 motor would add undesirable stress on the x-axis, just asking, but would it be frustratingly difficult to modify a reprap mendel or prusa mendel so that the Print Bed moves instead of the actual print-head so that i would be able to achieve extremely fast prints without sacrificing speed & still have excellent print quality ?!!?

Again i am humbled by all your most-excellent advice in my preliminary quest to try to obtain a reprap for my very picky (& probably unrealistic, lol) needs!

Many thanks in advance once again !!

Oneil

Hi Oneil,

HAving the extruder static and moving the bed is what Makerbot design does. It would effectively remove the two problems I mentioned, but none of the popular RepRap models is doing this, and I guess that for a good reason. Maybe other can elaborate on that.

My advice is that you try to start with one of the reference designs to later evolve your ideas from it.

Cheers,

misan

offtherails2010 Wrote:
-------------------------------------------------------
> Um, as the extra weight of the Nema 23 motor would
> add undesirable stress on the x-axis, just asking,
> but would it be frustratingly difficult to modify
> a reprap mendel or prusa mendel so that the Print
> Bed moves instead of the actual print-head so that
> i would be able to achieve extremely fast prints
> without sacrificing speed & still have excellent
> print quality ?!!?

As Misan says, there is no reason why you can't keep your extruder still and only move the print-bed - and there are 3D printers that do exactly this, but I don't think the primary design reason is to resolve the moving mass / dynamics / vibration issues. You now have the mass of the whole print-bed to move around (I haven't weighed mine, but with PCB heat-bed etc installed, it is pretty comparable to the mass of the X-Carriage and Extruder Assembly), and you have to do it in two directions, not just one.

I agree with Misan - build one of the latest-generation "standard" machines first (e.g. Prusa Mendel, possibly with LM8UU bearings), and get that working as well as you can, so you get a first-hand appreciation of what really governs the quality and speed of 3D printing. You will probably see some things that you want to improve straight away, and you can start downloading and printing upgrades that others have posted.

You probably also want some hands-on experience to decide what is really most important to you: print speed, or print quality, because the two tend to be contrary goals. Higher print speed means more power / torque required, which tends to mean bigger, heavier motors. Higher speed increases the significance of vibration and dynamic effects, which will lead you to look for a stiffer frame while reducing the mass of the moving components. (But your motors may have to be bigger to run at higher speeds.) Higher print quality means thinner layers and smaller diameter extruded filament, all of which means slower printing. It's all a trade-off ...

After all that, you can decide how to best apply your energy into improving the design further. (Remember to share your innovations with the RepRap community!)

it isn't easy to design and build a machine of this complexity "from scratch" and end up first time with a better result than what has "evolved" from the collaborative efforts of many, many individuals.For example, modifying a Prusa to have a two-way moving print-bed would mean the whole X-Axis motion (stepper, pulleys, belts, etc) would have to move on the Y-axis carriage (or vice-versa). On the standard configuration, the X-axis stepper motor only moves in the Z-direction, which is very slow and intermittent, so dynamic effects due to the mass of the X-axis stepper motor don't really come into play. In addiation, the two steppers whcih power the Z-axis don't move at all. It's the little things like this which may not be obvious to "newbies" who are keen to design their own improved machines (and may not even have been obvious to the original designers - look at how far the Prusa has evolved from its not-so-distant ancestor, the Darwin!)

Cheers - and good luck!

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Follow my Mendel Prusa build here: [julianh72.blogspot.com]

Hi folks!

Thank you both for your most appreciated & awesome insight & advice !

I will endeavor to get my 1st Reprap Prusa Mendel, possibly with the LM8UU bearings as this sounds like a sound design concept even though i do not own a 3D Printer yet...

I'm afraid, as with mostly everything i do, i'm trying to run & sprint way-before i can walk ! the best advice is often the most simplest, and to do what i plan to achieve, i will 1st need to 'cut my teeth' on a standard built Reprap before trying to implement such radical changes! I just cant help myself!

Also i'm a very strong believer in sharing designs and not hoarding/copyrighting them otherwise we all wouldn't have had the latest designs in Repraps that are currently out there now, so rest assured if/when i do make any changes i will endeavor to post them here and on thingyverse so everyone can benefit from them/improve upon them !

Once again, i am extremely grateful for all your advice @ julianh72 & misan as i find it very satisfying to know quite ahead of the hurdles what i'm getting myself into, especially a concept as massive as putting a mini factory on one's desktop!

Your folks are truly legendary!