Help with Rostock parts

Hello RepRappers

Around the beginning of the year, I started work on my first 3d printer, a Rostock, but put it on hold until now. I decided to start working on it again but still need a few more parts/pieces. I already have built the frame and sourced most of the essential electronics such as the Arduino, stepper drivers, lcd screen, heated bed, hotend (Budaschnozzle-style -- Lets hope it works), and end stops. All of these parts seem quality, but there are some parts I still need for my Rostock printer. This is where my questions start to rise.

The parts still needed are a Power Supply and Nema 17 Stepper Motors.

The main question concerning the power supply, is which one? I have seen a bunch of discussion between ATX, brick, and server power supplies, but it always seems like the "Switching Power Supply" (If that's what it's called) comes out on top. I have decided to go with one of these but not sure of the Volts, Ampage, or Wattage. I have seen people recommend several different combinations such as 12vDC 20A 240W, 24vDC 15A 360W, and 12vDC 30A 360W, what would be the right combination to power a Rostock without a shortage of power?

On that note, is this brand any good? [www.amazon.com]

As for the Nema 17 motors, would something like these do fine?
[www.ebay.com] and if so, what'd be the difference from these [www.ebay.com] , besides the price and quantity?


Although those are my two main questions, I have a few other not so important questions,

Is there a real difference in using belts compared to using spectra line?

Is there a recommended type of spring to use for the heated bed and extruder? Or will any old spring work fine?


If you have any recommendations for a certain brand, part, or listing, let me know!


Sorry for all the questions, I've read around and have only made myself more confused, my first printer, and have wasted enough money just trying things, would like to make sure I get things right!

Edited 1 time(s). Last edit at 07/19/2014 03:29AM by ikentron.

Since you claim to be buying quality parts, why are you scrounging eBay for junk steppers? Three NAME BRAND stepper motors with the correct 4 wire plugs (and not the 6-wire ones on eBay) and a published spec sheet are $49.95 at TriDPrinting:

http://www.tridprinting.com/Electronics/

They also have a decent price on bulk GT2 belts, sprockets, and several different carbon fiber rod options if you don't have those yet.....

At least some of those aren't junk steppers and Ebay isn't always junk.

The first set are Minebea steppers, and are actually quite good (it was a joint venture with Panasonic up until last year). However, those are short bodies with dampers, the dampeners are awesome for noise, but the short body means you only get 46 or 49oz. in of torque. Which is PLENTY for a printer such as a Rostock or Mini Kossel. I ran those motors on my 1000mm tall Griffin for a short time and a long time on my mini, so yes, they can handle it. I can't say about the second set of steppers, I have no knowledge of them. However, the price difference really isn't as big of a deal as it was even a year ago and for about $15 more, you can get brand new Kysans from Tridprinting and other places. These are new, and 76oz.in. of torque.

Regardless, I would HIGHLY encourage you to get a good, high torque motor for you extruder. In fact, I would even recommend you step up to a geared stepper motor and matching extruder. Something like the Mini Kossel extruder or Griffin Extruder will work with those. The Griffin extruder will work with both motor types. The alternative is to use a geared extruder. I always recommend gear reduction on nozzles .4mm and smaller.


For your power supply, in theory a 20 amp *should* work, however the Chinese use a form of new math that doesn't conform to reality*. So if you want a power supply like that for a heated bed, get a 30 amp. *Always assume it puts out about 75% of what they rate it at and you still want some to spare.


The Buda head works fine.
If you take the time and follow directions on how to assemble it, it can do some good prints. If there is a problem though, they can be a bear to work on. It's overly complex, can become hard to disassemble... There are simpler ways to do things.

Belts vs spectra... BELTS.
Belts, you can get a smaller pulley, and you get a known number to use for calibration.

Spectra is trickier than people think, this is because you have to be able to spool as much filament as your printer is tall. Because of this, Spectra will give you larger diameter pulleys, which means less fine detail, and a harder time calibrating, since you need an exact pulley diameter to calibrate steps per mm. Your printer size means you would need Cerberus size pulleys for your Rostock, not Mini Kossel pulleys if you want Spectra. It's also much harder to install.

Edited 3 time(s). Last edit at 07/20/2014 07:10PM by sheepdog43.

If you did not buy belts yet, get ones with carbon fibre or steal core. Kevlar may be ok if you can get the better one (there seem to be more variants). Avoid glass core belts. They are too stretchy. It is good to get precisely matching pulleys for your belts.

Do not bother with the original arms ending with u-joints. Get ball joints (e.g. MP-Jet is good; other people use Traxxas so maybe there are good too). Magnetic joints are too heavy and may rattle at high speeds.

Just get geared extruder from the beginning (even when you use 0.5 mm nozzle). A good ratio seems to be in the rage 1:2 - 1:3. You do not want to gear it down too much since your retrace speeds will get too slow and there will be blobs of plastic at the retrace (retrace reverse) locations.

Go directly with 24V power source. You need also 24V heat bed for it. You can get hotend for 24V power supply or just limit the duty cycle for 12V hotend somewhere to the range of 1/4 to 1/2.

If you want to print high speed you will need to stiffen the frame more than the original two vertical plywood plates.

If I would build it again I would go with 12 mm smooth rods too.

No need for springs on heat bed. Mount it firmly.

If you intend to run at low acceleration limits of about 1g and low jerk (at most few tens mm/s) and speeds up to 30 cm/s then you can assume the belt stretch just below 0.1 mm. That is if you use steel core T2.5 belts. If you use glass core GT2 belts then the maximum error is about 3 times worse (i.e. 0.3mm). Add play between the belts and their pulleys to that (this will be worse for T2.5 belts). The 8mm rod bend error will be around 0.1 mm.

I have the [www.ebay.com] motors. They have been of decent quality. They are certainly not junk. The added bonus to those is they come with the dampeners. The 6 wire stepper is not bad either as two of the wires do not get used. They do need connectors however. If you look the dampeners if you intend on using them cost about 5 bux a pop. So the price is fairly resonable. I however have not used the dampeners so its a wash with the steppers costing about 10 bux a piece. I can say they have plenty of torque for my direct drive extruder. As for belt, I went kevlar with 20 tooth gt2 pulleys, I mention the pulley teeth as you will need to change the firmware to the correct teeth count.

As for psu's, All the ones you mentioned are switching power supplies. However be weary of cheap PSU's, you need to modify the ramps board and figure out the 5v feed for the arduino if you feed more than 15v into it. Even 15v is pushing the limits of the regular for it. I would stay away from ATX as well. Either find a quality switching PSU that wont have issues drooping if mains power sags or spikes, or a server psu. Although the XBOX psu should be a fairly good psu for the job. Find the highest wattage one and get the proper connector and wire it properly.

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