Calibration - Motors (stepper drivers)

As with all calibration steps you should take your time (as long as you need) and try to be as accurate as possible. Calibration will directly affect the quality of your prints.


In order to calibrate the drivers the printer must be powered on, connected to your computer and requires you to be working very closely with the electronic parts. For this reason I highly recommend you take basic electrostatic precautions before doing this (more information in the notes section).

Introduction

Calibrating the stepper motors is very straight forward and requires only a small flat headed screwdriver and a little time (the fastest calibration step).
However if you miss this step or wing it you can are likely to have issues with overheating (of the stepper drivers) and/or missing steps.


Calibration

Ok enough of the disclaimers and introductions.


First get your small flat heated screwdriver (you can use a cross head with official Pololu's, but a flat heat works with both Pololu's and stepsticks) and turn the trim pot (the bit highlighted in the below image) counter clockwise until it reaches home.

Now turn it back 1/4, using PrintRun move the motor attached to the stepper driver you just adjusted.
Slowly turn the trimpot until the stepper motor moves. Once its moving stop PrintRun then turn the stepper driver just less then 1/4 more.

Rinse and repeat with each of the stepper motors/drivers.


Notes

For the Y and Z you need the carriage on and hotend installed, otherwise the motor will be calibrated excluding this weight.

Electrostatic precautions;

• Don't touch the electronics directly (use the screwdriver)
• Don't do the calibration when wearing socks without shoes, especially on carpet
• Do ground yourself before doing the calibration
• Above all don't moon walk on a carpet when wearing wooly socks, trousers and jumper before doing the calibration.

Wiring - crimps, joining and endstops

The mechanical side of the build (frame, extruder and print bed) is fairly straight forward as long as you have the correct tools and parts. As there isn't much too it and its pretty well documented I'll post that later.

I used 0.1inch crimps and connected housings from Hobbytronics, see my Connectors, crimps and wires post (link) for full details.


Crimping

To crimp the connectors I used a small nosed pair of pliers, as opposed to spending £20+ on an official tool.
Nophead outlines the method in this video.

Motor connectors

This are very straight forward, if you brought your stepper motors from Zapp you don't even have to strip the wire.

Crimp the 4 wires then insert them in order (link to wiki page about wire colour) into a 4 way housing. In the case of the SY42STH47-1684A is black, green, blue, red.


Endstops (mechanical)

Firstly you need to solder or connect (using a crimp on the wire) your 2 wires to the switch.

On the above image I've marked which legs of the switch to join the wire to.

I highly recommend you use 2 different colours or styles of wire for this. Keep the left wire one colour or style and the right wire another. In my case I used a network cable for the wire so the left was solid with the right using white striped.

Crimp the other end of the wire then insert into a 2 way housing.


Transistor

This is the trickiest bit of wiring you have to do, its tricky as solder is fairly pointless and its fiddly.

Remove a crimp (0.1 inch) from the reel then cut across the red line marked above.

Now insert one of the transistor legs into the right side (the side with the longer wings). Using the same pliers you used for the standard crimps close the wings tightly around the wire (so it doesn't move).

Do the same with the wire on the left side (this holds easier).

The above image shows roughly what it would look like (well when its not been crimped), the blue wire going to the electronics board and the green wire doing to the transistor.

Slide over some heatshrink tubing and shrink (the air vents on a soldering iron work nicely) to add an extra layer of support (and a little safer).


Thermistor

As its a small single (note I wrapped the rest of the wire in kapton tape) wire I merely soldered it to a multicore wire, added heatshrink tubing and shrank it. I then crimped the other 2 ends and inserted it into a 2 way housing.

I'm not 100% sure this is the correct way to wire and join the thermistor so stay on the side of caution if you choose to copy me on this one.

It lives (RAMPS)

After finally finishing the RAMPS assembly last night I thought I'd give it a test run.

In truth I was expecting it to go pop and not even turn. I did so many things wrong or in a roundabout way it is stupid.
To quote on of my favourite songs, Do as I say not as I do.

I found the easiest way to wire RAMPS up to a computer psu was to use the pin pin 12v yellow and black connector.
Snip the end, strip the wires then attach.
For anyone reading the RAMPS 1.4 wiki entry and wondering what the heck the COM wire is on  diagram explaining how to attach the power its ground.
COM = ground
It stands for common return path.
So using the 4 pin connector wires it goes;
*top near the 6 pin screw connectors*
Yellow
Black
Yellow
Black
*bottom near the reset switch*

A quick way to start an psu is to use a paperclip (I was told this my Corsairs psu technicians) from the power-on lead to any ground.

I powered on the RAMPS board, connected the usb then booted up the Arduino software (link to download page).
Windows 7 picks up the Arduino drivers, however with XP or similar you'll have to point Windows to the drivers folder in the Arduino software folder.
After setting the coms port to com 3 (generally you have two ports com 1 and com x, use com x) and board to 1280 I uploaded the test file (link).
To my utter surprise it worked, well the LED's all flashed.
So I powered down RAMPS and installed one of the stepper drivers (I'm using StepStick) and attached one of my stepper motors.

Before I installed the stepper driver I carefully turned the dial to 25% (all the way counter clockwise then back 25% of the way), however in a complete daze I installed the stepper the wrong way around.
Install the stepper drivers so the dial away from the mosfets.
Bam Windows no longer regonised the usb device and I instantly knew what I had done wrong.

Luckily it only blew the stepper driver and not the whole RAMPS board. Replacing the stepper driver with a new one and installing it correctly resulted in my stepper motor majestically turning left then right.

Of cause this means I'm one stepper driver down, but atleast my RAMPS works.

Stepper motors arrived and a few pictures

The stepper motors I brought from ruben-ikmaak on the #reprap IRC channel arrived today.

I did notice that instead of the €15 shipping I'd paid for he had shipped next day costing €20.
Its a little strange, but I think he might just have forgotten to send them on Wednesday/Thursday then panicked when I checked to make sure everything was OK via IRC on Friday (as its the day the box was marked as being sent).

I'm very, very impressed with Ruben. Not only is he a really nice guy to talk to, but he also did me an amazing deal on the motors. In fact I'm ashamed to say I think I cost Ruben money. As there was a slight issue with Paypal taking a larger cut then he expected and the fact he seemed to have shipped next day.

Ruben if your reading this and ever need anything just let me know and I'll repay the favour. Or if your in the UK and near me, I'll buy you a pint or four.

Anyway onto the photos. As I mentioned before I took some pictures last week but the quality was terrible (as I used my mobile). I did run into a little issue though, half way through taking the photos with my camera the flash seems to have fubar'd one of the sensors so the display and photos have a red tint.
Sort of looks like Riddick's vision on Pitch Black.

Stepper Motors

   

Micro Switches - Endstops

Flux pen

Soldering Tweezers

Soldering braid/wick

Unfortunately as my camera broke I don't have pictures of the plastics, but they do look identical to the ones on the eBay listings.
Its worth noting (I was going to photograph it) that all the pulleys have grub bolts/screws and nuts already in them. Another point for nophead :-p

Roll on tomorrow night. Finger crossed all the parts will have arrived by then.

Stepper motors

Out of all the parts to source the stepper motors have been the biggest head ache.

The beginning

First I looked over the forums for the best UK source and ZappAutomation seemed to have great reviews with the SY42STH47-1684A and SY42STH47-1684B.
For £11 each they looked like a bargin, however at the point of order the shipping cost was added on. £10.
This brought the total to £65, not as cheap as I was expecting.

As I was sourcing my hardware I noticed Thingfarm were selling stepper motors for £13 individaully or £58 for 5. Unlike ZappAutomation the shipping was only £5, perfect a total of £63.
A small saving of £2, but a saving none the less plus it cut down the number of suppliers.

First Issue

If you read my last post you'll know when I came to place my order with Thingfarm the set of 5 steppers where sold out.
Fine I'll spend the extra £2 any by them from ZappAutomation, nope they had sold out too.

I was left with 2 choices by them from Thingfarm for £13 each plus £5 delivery or find another source.

I picked the later option in the hope that Thingfarm would restock the 5 motor sets in the mean time. However every EU stepper motor source seemed to want either €20 (about £18) for each motor and/or a silly delivery cost.

Another Issue

Back to Thingfarm however just before I placed the order I did a quick google search and stumbled upon this blog by IndieFlows.
Who so happened to be the person who created the thread (link) which came to the conclusion of ZappAutomation being the best UK source of stepper motors.
Anyway the post in question which got me thing was this one. This discredits Thingfarm's stepper motors claiming nophead recommended ZappAutomation's steppers instead as Thingfarm's aren't ideal for the job.

Now I must have read the thread in question half a dozen times and I never noticed the conlusion Thingfarm's weren't ideal.
So I decided to pick through the thread one more time. For some reason I had over looked this paragraph from nophead
I was referring to the eBay ones but the Thingfarm ones do seem to be similar. It is almost impossible to get 2A from a Pololu / Stepstick, even with a heatsink. Since the current available is limited, the torque from these high current motors will be be limited to about 1.65/2.5 * 48 / 43 i.e. 74% of the torque you can get from the Zapp ones. I think that would limit the extruder max flow rate and for a given torque the drivers will run a lot hotter.

Now I read that paragraph before as just saying the eBay ones weren't ideal.
So I went back to Thingfarm's stepper motor page (link), which seemed to lack the specifics merely saying see download tab for datasheet.
At the time of writing this there is no download tab.
Not one to give up easy I decided to check there North America site.
On the stepper motor page (link) there is a download tab.

Finally I got the specs Thingfarm's stepper motors.
In short they are
Rated Voltage - 3.1
Rated Current - 2.5
Holding Torgue - 4800g/cm

Now I can see why nophead wouldn't recommend them as they need 0.5 more amps then the stepper drivers can give to achieve the torque rating.

What now?

So back to looking for another source.
In a last ditch attempt at finding a source I decided to post for help on the RepRap forums (link to thread).

Thankfully devijvers (you might notice I've posted his name before, he's becoming a real savour) recommended ruben-ikmaak on the #reprap IRC channel.

So off I went to the IRC channel.
Within a few minutes of sending him a message I got a reply and within a few more minutes he gave me a brillant price and quoted 2 seperate shipping costs.

It turned out the stepper motors he (I think it was a he) was selling where the ZappAutomation stepper motors I was looking at to start with...

Paid via Paypal, information sent and was told the latest it would be shipped would be tomorrow.

Success

I ended up paying a little more then I was expecting, but atleast all my parts should arrive at a similar time.

Cost of Stepper Motors (x5) - €82 = £74.26
Total Cost so far -  £372.55