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Folgertech Prusa I3 build cheat sheet

Posted by CraigMoberg 
Folgertech Prusa I3 build cheat sheet
June 24, 2015 04:15PM
This is a cheat sheet I compiled from the build log I kept while following the Folger Technologies Prusa I3 build manual, listing the things I found missing or unclear and the solutions I found to them. I'm not a mechanical or electrical guy, and the instructions often assume you are, and can fill in the blanks yourself.

It also contains a few comments along the way about problems I encountered about the design, build process, and parts. I've redacted all the swear words, I promise winking smiley


The label on the "Frame Hardware Set" bag lists "3x M3 35mm bolts". These are actually 30mm.

It says you need a 14mm open end wrench for all the nuts that hold the bed frame together. Turned out the nuts are actually 1/2 inch (12.75mm).

It says you need a volt meter (or multimeter). If you have one, or get one, make sure it reads millivolts. That's what you need here, and not all do.

It says only that you need a slotted screwdriver, but the screws get smaller and smaller as you get into the electronics, so you'll need 2 or 3 small sizes.

It says you need a phillips screwdriver, but there are no phillips screws involved.

Some people crack the acrylic frame by tightening screws too much. As the instructions say, "snug is enough." This isn't metal, so go easy.

Specific steps:

Step 7: Assemble X carriage bearings into carriage

The recesses in the carriage for the bearings could use a tiny bit more length. One I was able to pop in with some force, but I had to trim some plastic for the other 2.

Step 9: Assemble left side Z axis carriage idler bearing

The nut trap for the M3 nyloc nut in the carriage is too big. It looks intended to hold the nut in place, but it lets it turn so I had to use pliers to hold it while I tightened the screw, which was awkward since it's recessed.

Step 12: Attach couplers to motors

"You can use the small wedge shaped acrylic piece as a spacer."
The wedge shaped acrylic pieces have been replaced with round pieces. (These are for holding the Z-axis smooth rods in place at a later step.)

Step 14: Attach vertical mounts to acrylic frame

What it doesn't say here is that each mount has different holes drilled -- one mount is for the power supply and one for the electronics. The power supply mount should go on the right side (looking at the frame from the back) and the electronics mount on the left. I attached them reversed and had a code brown moment later, when it came to attaching the components. I thought I'd have to rip it all apart again, but it just meant running some wiring to the opposite side.

Step 15: Build X assembly

Shows using an acrylic part (the mysterious wedge-shaped piece) to "space the pulley from the end of the motor shaft." From the picture, it looks like the pulley should be a couple mm up the shaft. But the pulleys I got look a couple mm longer than in the picture, so using the spacer puts the bottom of the pulley in contact with the motor housing. I just left a small gap between the pulley and motor.

At the beginning of this step it says "2 medium length smooth rods" in the illustration of parts used. But a couple pages down it says "Insert the long smooth rods as shown." It should say "medium."

"Don’t tighten the zip ties until we mount this to the acrylic frame."
Whoops. I already tightened them, and cut the ends off. Because in the picture right above this, which says "You should have an assembly that looks like this," it shows them this way. Maybe I take things too literally.

Step 16: Build the X endstop

Shows only one 12mm screw connecting the endstop to the holder. It needs 2 like the rest.

Pins from the connector protrude from the back of the board and keep it from sitting flush on the holder. Shouldn't the holder have a recess those could go into?

The picture here almost looks like you're supposed to put the 18mm screw through the holder and into the nut at this point. Not till the next step do you see that it has to go over the smooth rod first. This could be made clearer.

Step 20: Mount X assembly with Z rods to motors and frame

"Slide the smooth rods into the holes on the motor mount.."
Which smooth rods? I have medium and long ones at this point. Had to scroll down to step 25 to deduce that I should use the medium ones.

"You may need to adjust the width by compressing the X assembly.."
This is a pain to do at this step, but there's an easier way. Before inserting the threaded rods in step 19, set the X assembly upside down on the motor couplers, and adjust the assembly until the holes line up. Then the threaded rods will slide right through when the time comes. Or just measure it -- it's 333mm center-to-center between the holes for the threaded rods in the 2 plastic parts.

Step 20a: Mount Z axis end stop

"Assemble the Z axis end stop with 2x M3 12mm screws and nuts.."
This means normal nuts (and washers), not Nyloc.

It seems like this step might be done before step 20. It would be a whole lot easier then. And you will be adjusting the exact position later, so don't worry about it now.

Step 21: Mount top acrylic rod keeper

The M3 nuts won't fit into their notches on the main part of the frame. The height of the notch is only ~2mm. This is shorter than similar notches elsewhere, and shorter than the thickness of the nut. I had to file them out.

Step 23: Assembling Y threaded rods (front end cross rods)

The rod labeled "Bottom rod" in the picture should go in the bottom 2 holes of the plastic parts, and the threaded rod with the pulley on it goes in the top holes. It took me awhile to figure this out, because a step is missing here and "Bottom rod" seemed to vanish from the pictures, until I realized that in the top-down perspective, it was already in place and hidden by the top rod.

Step 25: Assembling Y smooth rods

"Shorten the distance between the front and the back from the back side of the frame.."
In other words make the threaded rods flush with the nut at the front, and protruding at the back.

Step 28: Mount Y axis motor to mount on Y axis frame

(use 2 M3 16mm screws)
This is a mistake -- use 12mm screws here, not 16mm. Also, the screw holes in the motor mount were about a half mm too narrow and I had to ream them out. Then I found that the threads in the motor only go 5 mm deep, leaving the head of the screw several mm above the mount, when it should be recessed.

And it might be easier to attach the motor to the mount before this, in step 24, THEN put the whole thing on the threaded rods. It would have been easier to do then anyway, and easier to deal with these glitches.

Step 31: Mount Y axis end stop

"The switch should contact the bearing holder."
Bearing holders have been removed in the Rev B model. It tells you that above, but they forgot to update this section. The recommended place for this endstop is now on the protruding end of the threaded rod on the back left side. You'll also need to adjust your firmware settings for this change.

Step 32: Mount Y assembly to acrylic frame

"Insert the Y assembly into the acrylic frame from the back. Put 2 large washers on to the longer threaded rods."
Oh by the way -- you'll need nuts on these too winking smiley

Step 34: Mount extruder assembly to X carriage

Step 15 said, "Don’t tighten the zip ties [on the X carriage] until we mount this to the acrylic frame". Here it shows all the ties already tightened and trimmed, and then you mount the extruder and you're done. I thought this warning meant it was important not to tighten them until instructed, to make sure everything lined up and rode smoothly, or something like that. But that instruction never came, so I guess now is the time to tighten them.

Again, the screw holes in the plastic part were too tight and had to be reamed out. Then I found that the holes in the mount are a couple mm too close together and didn't line up with the holes in the motor. More reaming.

Step 35: Solder wires to heated bed

It doesn't give instructions here on how to attach the thermistor to the bed. You have to insert the glass bead at the end through the hole in the middle of the bed, from the bottom of the bed, so that the top of the bead is flush with the top of the bed. Then bend the wires over, with the other ends running toward the back of the bed, and use Kapton tape to keep the bead in the hole and the wires secure.

Step 36: Mount heated bed to Y carriage

"Use 4 M3 16mm screws"
I used 18mm. With 16mm screws, the spring is so tight, with the screw barely into the nut, that you don't have much room to adjust.

Step 37: Build Arduino Electronics with RAMPS board and Stepper Drivers

The stepper drivers are pretty tight next to each other, and take some massaging to get them in. It's probably better to wait to put the heat sinks on until after the drivers are all in. I kept popping the heat sinks off.

Step 38: Mount Electronics to acrylic frame

"The right side" here means "the right side looking at it from the front -- but on the back."
In other words, "the left side, looking at it from the back."

When the board is mounted as shown, the USB connector coming out of the bottom doesn't have enough room and jams against the table. The back of the acrylic support doesn't fully contact the table, and this will damage the cable over time. I ended up mounting the board the other way around so the USB is on top.

Step 40: Wire 110V power cord to power supply

Seems like it be A LOT easier to do this before mounting it to the frame. You can't easily get to the bottom of the machine at this point. I thought engineers were all about finding easier ways to do things. winking smiley

"Ground is the green wire, Neutral is the blue wire and Live is the brown wire."
The cable I received had 2 black wires and a blue wire. Nice.

Step 42: Connect fan, hot end and heated bed wires to RAMPS board

"connect the Fan wires to the blue screw terminals.."
The ends of the fan wires are in a connector. You have to cut this off.

"Finally, connect the heated bed wires to the RAMPS board."
The wires from the heated bed seemed too thick to go in at first, but if you back the screws out good and pry the little clamps apart, there's room.

Step 43: Connect hot end and heated bed thermistors to RAMPS board

Reminder: polarity doesn't matter here.

At this point, I took a look at the whole rig from the top and noticed that the Y platform is out of square with the the X smooth rods and the support frame. You may have to adjust some nuts to bring it into square.

Step 44: Connect end stop wires to RAMPS board

according to this , manual has X and Y end stops installed in the MAX locations, but plugged into the RAMPS board as MIN end stops. Also shows some Configuration.h changes necessary. The firmware doesn't come configured correctly, so some fiddling will be needed.

Step 45: Connect stepper motor wires to RAMPS board

This says only to connect the X/Y/Z motors, and forgets to mention the extruder motor. Whoops. The picture only shows an "E" with a partially obscured connector in the general vicinity.

Step 51: Install acrylic rod keepers to top of acrylic frame

This is what the mysterious wedge-shaped pieces used to be for, and are now round pieces. The smooth bars protrude a few mm above the acrylic, so it's a bit tight. Don't torque it down too much or you'll crack the acrylic.

Step 52: Set stepper drivers to correct Vref

As mentioned at the top, the list of required tools should specify a voltmeter/multimeter which can read down to mV, since not all do, and you don't want to get to that step and find out that yours doesn't.

Remember I said I'm not an electrical guy? You want to measure DC voltage, not AC. I had to phone a friend to figure out why I was getting whacky readings all over the place. (I know, I know, go ahead...) A lot of printers are now being sold to people like me who aren't hardcore mechanical/electrical/electronics hobbyists, so I thought I'd mention it.



Step 4: Connect printer to PC

"Your computer should recognize the board and install the drivers automatically."
I believe this statement is wrong for first-time installations. At the very least, you can't rely on this and just go on to the next step. According to the Arduino site, the automatic driver install WILL fail, as it did for me. This is common and not a problem - Microsoft just doesn't have the Arduino driver in its database. The driver needs to be downloaded, and Windows has to be pointed to it in Device Manager. Instructions for this should be included here.

(If you have previously installed the driver, and plug the printer into a different port, Windows insists on "installing" it again. I consider this a bug in USB, but it looks like it will never be corrected. I believe this is the only case when you'll see Windows "install" the driver automatically, because it already knows where to find it. For first-time installations, I believe it will always fail and you'll have to install and specify it manually.)

".. If your computer does not see the Arduino board, you may have some wiring wrong."
This is a bit misleading and unnecessarily alarming, by suggesting that if the driver isn't automatically installed, "your computer does not see the Arduino board." Not true. If Windows attempts to install the driver, it's seeing the board. You just may have to help it install it.

If nothing at all happens when you plug it in, and you don't see the board or "unknown device" in Device Manager, then it may be a wiring problem, or a bad board.

Step 7: Upload the Arduino Sketch to the board [Marlin_RAMPS_EPCOS_i38.ino]

This sketch gave verification error on reading, after uploading ("avrdude: verification error" etc.) The latest firmware downloaded from Marlin loaded successfully. But later, maybe after a reboot, the Folgertech Marlin_RAMPS_EPCOS_i38 loaded fine. So I don't know. I still get this verification error from time to time, but everything works fine anyway.

Step 11: Home Z axis

"This will bring the entire X carriage down so the hot end just about contacts the bed."
Step 47 in the build manual (Set Z axis end stop to starting height) said "Set the starting distance at 50mm, this is higher than it needs to be..." So if you followed that instruction, homing it here will not make it contact the bed; it will stop well above it. You have to move the endstop down little by little, homing every time, to get it close to the bed.

"..if you can it helps to make a cardboard spacer for the next step."
I never figured out what they're talking about with this cardboard spacer.
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