Frame and mechanical build - Print bed

Before drilling or preparing the print bed check the sizes are correct.

I asked for my mdf to be cut to 225mm x 225mm and 140mm x 225mm at my local B&Q. For some reason they took it the 225's as 275...


Drilling (corners) - page 39

Its pretty straight forward however if you want to be precise there should be a 42.5mm gap on both sides of the 225mm plate (when drilling the 2nd set of holes).


Drilling (belt clamp) - page 49

First follow the alignment steps from pages 41 to 43.
Once its aligned jump to page 49 and follow the steps.

Doing it in this order means you don't have to remove the print bed with the bushings glued on. Otherwise you have to be extremely careful both when drilling the belt clamp holes and when removing and reattaching the bed.
I had to re-glue one of the bushings on eachof my first 2 removals (the 2nd was due to the bed being the wrong size) which is another step and another wait until its set.


Glueing - page 43

Skip if your not using PLA bushings

I found it best to line the bushings up at either the front or back of the frame. This way when you join the bed and the bushings you can use the horizontal bars to ensure the alignment.


Top print bed surface

Before attaching the top print bed you need to apply some form of printing surface. You could print directly onto mdf or glass however you'd have 2 big issues; damage to the surface (160C+ plastic and the mdf or glass aren't the best of friends) and grip.
To solve this most people with either kapton tape or blue scotch tape.
Kapton is slightly better, but costs considerably more for similar width tape.
Blue scotch tape has a surprisingly good tolerance to heat, is cheaper and is more widely available.

When applying it to the top print bed on mdf its best to apply a few layers in criss cross pattern. One layer horizontal, followed by one vertical. About 3 or 4 layers should be enough. This stops the tape peeling the mdf or removing the tape below when removing prints.


Attaching the top print bed - page 101

If your springs are fairly weak its best to have at least 5mm of thread sticking out. Otherwise as the bed sets in there is a good chance it will sink on one or more of the corners.

If you have m3 nylock nuts this is definitely the time to use them. I found standard nuts loosen extremely easily during printing and the bed will need constant levelling between every (even the small ones) print.

An oops and quick update

The oops

For what ever reason my last 2 posts where back to front.
The tools sections should have been released before the frame build tips/tweaks.
When I came to give a quick update I noticed the tools post was marked as draft.

Anyway I apologise if it confused anyone.


Quick update

I've managed to calibrate my Prusa and I'm getting good prints all round (well not round as Sprinter doesn't like circles much :-p).
In light of the halfway decent prints I created a Thingiverse account which can be viewed here.

I still have a lot I want to write up as information from a newbies point of view is still pretty hard to come by.

My current list is;

• Build part 2 - X axis and print bed
• Slicing and Hosting software
• Calibration part 1 - Axis, extruder and levelling print bed
• Calibration part 2 - Printing and troubleshooting

Don't worry I made notes and kept all my failed prints.

Frame and mechanical build - Tools

Personally I found building the frame, extruder and print bed fairly simple. I did however run into a few issues (hence the delay) as well as making a few notes as I went along.

I've broken this down into two sections; the frame and extruder, and the print bed and X axis (plus carriage). The frame and extruder can be build separately and don't rely on any other parts. The print bed and X axis rely heavily on the frame and the X carriage requires the extruder.


Tools - Frame/Extruder

Required tools are the ones you can get by with, recommended makes the build a lot easier.
This is for a Prusa using a standard Wades extruder. 

Required

Hex (allen) keys or Torx keys Note 1
M8 sized spanner
Measuring device (ruler, tape measure, etc)
Plumb (or some fine thread and a nut)
Levelling device (spirit level, phone with an levelling app, etc)

Note 1 the thingfarm prusa kit requires torx. You can use hex to tighten torx however you can't remove them easily and you can't tighten them as much.
Note 2 a bomb style fishing weight attached to some fishing line makes a very cheap and effective plumb. The weights sell for as little as 30p and include a swivel, its a lot cheaper then official plumbs (£2+)



Recommended

Pliers
A second M8 sized spanner
M3 sized spanner (6mm works)
Plastic parts cleaning tools:

• Craft knife
• Files
• 8mm drive bit
• Drill

Tools - Print bed and X axis (plus carriage)

Required

Adhesive (glue)
3mm drill bit
Drill
Hex (allen) keys or Torx keys (see frame/extruder notes)
Measuring device (ruler, tape measure, etc)
Pencil
Levelling device (spirit level, phone with an levelling app, etc)


Recommended

Pliers
M3 sized spanner (5.5mm)
Plastic parts cleaning tools:

• Craft knife - if using a hot glue gun its highly recommended
• Files
• 3mm and 4mm drive bits
• Drill 

General notes

Depending on where you get your printed parts from the cleaning tools may be essential.
Cable ties (zip ties) help a lot with the wire management as well as for a few hacks.

Frame and mechanical build - Frame

At this point you've got the tools mentioned in my previous post and you've got the parts required for the build.

For the build itself I highly recommend you use the visual guide by Gary Hodgson, its a very nice piece of documentation.

The purpose of the build posts is not a how to guide its merely notes or tweaks I made while building as well as tips.


Y axis motor bracket - page 17/19

The visual guide gives you the following image.

The optional section isn't optional, but at the same time doesn't work for every motor.
If you don't use the washer, nut, washer, washer combo the M3 bolt will push against the large washer and cause it to slant.
If you use the combo and have a short shaft on the motor the pulley won't reach over the bearing.

The solution is to attach the motor with pulley to the Y motor bracket then slide it onto the rod. Make sure it lines up correctly then remove the motor.
For reference the motors I used, SY42STH47-1684A, 3 washers seemed to be the sweet spot.


Y axis motor bracket (part II) - page 47

If you followed the above tip you should be able to mount the pulley the opposite way around.
This should prevent the belt slipping (it also helps a lot when you come to tighten the Y axis belt).


Z axis motor mounting - page 73



Don't bolt the motor to the Z motor mount.

If you do you'll have issues with the Z axis wobbling, they need to have some movement so that they can counter any wobble in the Z threads.
Attach them using cable (zip) ties, 2 medium sized ones coupled or 1 long one either side. Remember to leave a few mm gap from the motor shaft.


End stops - 89/91

If your using RAMPS 1.4 and Sprinter the Y endstop is on the wrong side for the default settings.
RAMPS will try to home the opposite direction and it requires some tweaking of the configuration file.


Its much easier to just fit it on the motor side. Although I'll post which lines to edit in a later post just in case you've already made the same mistake as me.

UPDATE the endstop for the Y axis should be on the opposite site to the motor. You need to change the following line (line 74) in configuration.h

const bool INVERT_Y_DIR = false;

to
const bool INVERT_Y_DIR = true;

If you don't all your prints will be mirrored as the Y is going in the wrong direction.

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.

I'm back

Firstly sorry about the massive lack of posts. Christmas was busy this year (when isn't it) and I got dropped with a big project at work when I got back.

Luckily I'm nearly complete with my build.

Its not been pretty and its not been as easy as I'd have liked. While I'm waiting for another stepper driver to arrive (it doesn't seem to hold torque when moving...) and I'll back date my build log and tips/tweaks I've done.