Building a Prusa i3 3D Printer

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kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 8:07 am

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Even though we have access to a (sometimes working) 3D printer at our local hackspace my friend Kevin and I decided to build our own from scratch vs buying a kit or finished printer. The reasons being we'd get to learn how they work, we can pick the quality of parts and we like to make stuff.

After looking at various designs we decided on a Prusa i3. We hope to document the build from start to finish, initial calibration and our first prints.

For this Instructable we have obviously used information gathered from all over the Internet and that was a part of the learning process. A great place to start is the RepRap wiki, particularly the section on the Prusa i3

We had a lot of great advice from another friend Rob I met through my day job as an IT support person and also members at our local Hackspace - a big thanks to Ashley in particular.

The Prusa i3 is a part of the RepRap 3D printer family. It is a design from Josef Prusa, and the i3 stands for iteration 3.
It uses either a "single frame" or "boxed frame" and there are many derivatives from the original design. His original single frame uses a water jet cut aluminum frame but for our build we used a derivative - a laser cut plywood frame with braces designed by sgraber. It was cheaper to make and we were able to use the laser cutter at our local hackspace. The rest of the parts were sourced from vendors on AliExpress, eBay and local businesses.

We used the "vanilla" printed parts, but did make some small changes along the way.

To build this printer you should be comfortable with "making stuff", Arduino's, know how to use a multi-meter, solder and also know a little about electronics.

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 8:10 am

Step 1: Sourcing the Parts
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Parts list:

Frame - laser cut 6mm Baltic birch plywood. We bought a 5'x5' sheet from Windsor Plywood - a Western Canadian and North Western US supplier of wood products. I used the "frame-6mm-colored-lines.dxf" design as a basis but narrowed the slots a little to make the 6mm ply fit tighter. You will need 6x 6-32 x 1" bolts and 6x 6-32 nuts to match. You could use 3mm or 4mm x 25mm bolts but we found the 6-32 a better fit.

Printed Plastic Parts - You will find them on eBay from various sellers. We had hoped to find someone local to print the parts for us but went with a set from eBay. If you want to get your own printed look under Josef Prusa's GitHub for the Prusa3-vanilla scad or stl files. You can also search Thingiverse for Prusa i3

Threaded Rod, Nuts and Washers - you will need approx 1 meter of M8 threaded rod and 1 meter of M10 threaded rod. Also 26 M8 nuts, 26 M8 washers, 12 M10 nuts, 12 M10 washers. These are for the frame Y-axis. We used zinc plated threaded rod from Fastenal - but you can find it at some hardware stores, AliExpress and eBay. You will also need 2 lengths of M5 threaded rod and 2 M5 nuts for the Z-axis. The minimum length we could buy was 1 meter. We first bought zinc plated 5mm threaded rod for the Z-axis but it wasn't very straight. The supplier told me this was typical of the cheaper zinc plated threaded rod so I looked for stainless threaded rod which was a lot better quality and very straight.

Smooth Rod - The design we used needs M8 smooth rod for the X, Y and Z axis, 2x 370mm, 2x 360mm and 2x 320mm. Quality straight rod is essential for good prints. We sourced them from BST Automation via AliExpress. You will also find sellers on eBay and local hardware stores. My mentor Rob tells me not to cheap out on the smooth rod.

LM8UU Bearings - These are the linear bearings for the bed movement on the Y-axis and the extruder/hot-end movement on the X-axis and the Z-axis. You will need 10 of these. Available from many eBay vendors.

Pulleys, Belts & Idler Bearings - The X and Y-axis travel each use a 20 tooth GT2 pulleys and approx 1 meter of toothed belt. We sourced ours from a local eBay vendor ibi-battery, but you will find them available from a lot of vendors. Also needed are idler bearings. Most i3 designs use either 608zz or 623 bearings. The 623 bearings are tiny and use printed guides which fit over them. You will see what I mean in later pictures.

Stepper Motors - You will need 5 NEMA 17 stepper motors. The NEMA 17 is a stepper motor with a 1.7" x1.7" faceplate. The RepRap wiki has quite a bit of info on them. My mentor Rob suggested this vendor on AliExpress - We had to buy 10 to get the pricing (but you have 5 to sell or use in your next 3D printer project). They are 1.2A which will keep the RAMPS drivers cooler, have approx 47N-m holding, are 1.8° stepping, 5mm shaft. If you are unsure then buy from a 3D printer vendor or check the RepRap wiki.

RAMPS 1.4 Kit - This consists of an Arduino Mega, a RAMPS 1.4 shield and 4 or 5 "drivers" The "drivers" control the NEMA 17 motors as their current requirements are greater than what an Arduino could handle. We sourced ours from SainSmart, but found a cheaper alternative on AliExpress Naturally you can find them on eBay too.

MK2A Heat Bed - As per the RepRap.org wiki article you want to be sure to get a good heated bed. We sourced ours from Botech Eng. There are a lot of other vendors listed on the wiki page. Make sure you get a 214mmx214mm size. You will also need a 3mm thick sheet of glass 8"x8" and blue painters tape or wide kapton tape.

Hot End - The hot end is another place not to cheap out. This blog article explains the difference between the original designs and clones. This RepRap.org wiki article has more info on hot ends. We went with this one from Makerfarm including the install kit.

Power Supply - You can use a PC ATX power supply, but we opted for a slim 12V power supply as it's smaller and I think it looks neater as it only has the necessary wires. Something in the 200W to 350W range should work. Check ebay. Also needed were a 115V plug with wires and some spade terminals.

Extruder - This was included in the printed parts we bought from eBay. It is a "Wades" style

Nuts. Bolts & Washers - You will need different length M3 bolts with washers and regular and nylock nuts. We bought M3 in 10mm, 14mm, 18mm, 25mm lengths. A bag of washers, a bag of regular nuts and a bag of nylocks.

Also M4 bots/nuts to bolt the hot-end to the extruder mount.

Wiring Kit - We bought a generic wiring kit off eBay. You will also need some heavier wire for the 12V connections. We bought a small roll or red and black stranded wire (16awg or 18awg)

Tools you will need:

Allen Keys for the hex bolts

Small sockets for the M3 and M4 nuts

Small adjustable wrenches for the M8 nuts

Screwdrivers

Long Nose Pliers

Crimpers

Wire Strippers

Soldering Iron

Multi Meter

Calipers

Heat Gun or Lighter for shrink tube

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 8:12 am

Step 2: Assemble the Plywood Frame
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The frame design uses T slots in it to hold the nuts.

Assemble the frame but placing the nuts into the T slots and bolt from the front of the plywood frame as per the pictures

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 8:15 am

Step 3: Build the Y frame chassis
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The Y frame holds the bed the printed objects will be built on. The Y-axis runs front to back (when facing the printer)

It is built from 4 printed plastic corner pieces, M10 threaded rod/nuts/washers, M8 threaded rod/nuts/washers.

It holds the Y-motor and Y-belt idler, M8 smooth rod & LM8UU linear bearings for the heated bed to move on.

Cut 2x 380mm lengths of the M10 threaded rod. Slide on 2 washers, then 2 10mm nuts from each end, then a washer from each end, then a y-corner piece and finish with a washer then a nut. The inner nuts and washers are later used to attach the chassis to the plywood frame. The M10 threaded rod will go front to back.

It should look like the picture above.

Next cut 3x 205mm lengths of the M8 threaded rod and 1x 305mm length of the M8 threaded rod. The longer M8 threaded rod is for the rear of the frame where the slots are cut.

The top front threaded rod holds the y-belt idler pulley.

From left to right it goes nut, washer, y-corner, washer, nut, nut, washer, idler, washer, nut, nut, washer, y-corner, washer, nut. The bottom goes nut, washer, y-corner, washer, nut, nut, washer, y-corner, washer, nut.

The back threaded rods hold the y-axis motor.

The back top from left to right goes nut, washer, plywood frame, washer, nut, nut, washer, y-corner, washer, nut, nut, washer, y-motor mount, washer, nut, nut, washer, y-corner, washer, nut, nut, washer, plywood frame, washer, nut.

The back bottom from left to right goes nut, washer, y-corner, washer, nut, nut, washer y-motor mount, washer, nut, nut, washer, y-corner, washer, nut.

Assemble it as per the pictures and bolt it into the frame for a test fit. From the front face of the frame to the end of the front M10 nut should be 215mm.

Cut 2x 360mm M8 smooth rod for the y-carriage. They fit into notches on the top of the y-corners. You will need to undo the M10 nuts to enable the rod to slide into the groves. Before you place them onto the Y-corners slide 1 LM8UU bearing onto the left rod (when looking from the front) and slide 2 LM8UU bearings onto the right side rod. The smooth rods should be 170mm apart measured on the center-line of the rods when placed into the notches.

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:16 am

Step 4: Y-Motor, build frame and belts
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Attach one of the motors to the rear bracket using M3x10mm cap screws. Attach a GT2 pulley to the motor shaft.
The idler in the front uses a 623 bearing which has 2 pieces of plastic on each side of it to make a larger pulley.

Note: some designs use a larger 608zz bearing which doesn't need the plastic pieces. Assemble the idler as per the picture. Attach the Y-belt holder to the build plate with M3x14mm cap screws using washers and nylock nuts. Using zip-ties attach the build plate onto the LM8UU bearings as per the pictures. The last step is to attach the belt. We found it easier by removing the Y-frame from the plywood chassis and flipping it upside down. Start at the Y-belt holder go around the motor, then idler and back to the Y-belt holder. Leave the belt longer than needed at the Y-belt holder and loop it back over itself and zip-tie as per the pictures. Use something like a credit card to press the belt into the notches on the belt holder.

Tip: If you slacken off the front M8 nuts a little before you install the belt, you can tension the belt later by tightening the nuts back out.

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:20 am

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The X-axis hold the extruder and moves left to right when facing the printer. It holds the LM8UU linear bearings that fit onto the Z-axis smooth rod. It also holds the X-axis motor and idler pulley.

Find your X-End-Motor mount and the X-End-Idler. Press 2x LM8UU bearing into each. You may need to cut small tags from the top and bottom of the printed parts and the bearing should press in without too much force.

You also need to press 2x 5mm nuts that will be used by the Z-Axis threaded rod. Ours were a press fit but you may have to heat the nut up a little to get it pressed in - be careful with the heat!

Cut 2x 370mm M8 smooth rod for the X-Axis. Slide on 2x LM8UU bearings on the top one and 1x LM8UU bearing on the bottom one. Fit these into the X-Axis. They are a exact fit and the holes in the X-Axis side may need to be cleaned a little - but don't over do it. Ours was a snug fit.

Install the X-idler pulley c/w a 623 bearing on the right side X-mount. It goes together the same as the Y-Axis idler pulley in the previous step.

The extruder will have to attach to the X-Axis carriage. Out plastic kit came with an adapter we had to trim down a little. It is held onto the carriage with 2x 25mm M3 bolts and nuts. The nuts slide into slots on the adapter and the bolts fit from the back of the X-Axis carriage. There are a few different ways of attaching the extruder so test and check fit everything well. At this stage we just test fit everything with the X-carriage not installed onto the smooth rod. Do all this now as it will be too hard once the X-Axis is assembled into the chassis.

Update: The X-Axis smooth rods are 370mm not 350mm

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:25 am

Step 6: Z-Axis and X-Axis motor/carriage.
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The Z-axis moves the extruder/hot-end up and down. It has 2 motors, M5 threaded rod, M8 smooth rod, top and bottom printed plastic mounts and couplers for attaching the M5 threaded rod to the motor spindles.

Attach the Z-Axis bottom mounts to the frame with 14mm M3 bolts, washers and nylock nuts.
Attach 2x NEMA-17 motors to the Z-Axis mounts with 10mm M3 bolts. Temporary mount a top Z-Axis mount and measure the distance between the bottom to the top. We got 320mm - this will be the length of your Z-Axis smooth rod so measure twice and cut once. You could make it longer if you want.

Cut 2x 320mm lengths of M8 smooth rod for the Z-Axis and fit them into the bottom mounts. They should fit flush against the Z-Axis motors.

Fit the X-Axis frame onto the Z-Axis rods and attach it all in place with the Z-Axis top mounts.

Confused? See the pictures.

Attach the X-Carriage to the 3 LM8UU bearings with zip ties.

Attach a GT2 pulley to one of the NEMA-17's. We found that the toothed part need to sit on the inside so the belt would fit through the slots in the X-Ends. Mount the motor with 3x 18mm M3 bolts. Thread the belt as per the pictures making sure to tension it. Start at the X-carriage and press the belt into the slots the same as you did for the Y-belt. Go around the motor pulley, over to the idler and back to the X-carriage. Use zip ties to hold it in place as per the pictures. It was hard to get good tension on the X belt and we will probably print up this design of tensioner once the printer is up and working.

The Z-Axis moves on 2x 5mm threaded rod. We used stainless steel as the cheaper nickel plated threaded rod I found wasn't straight and the supplier said it was typical of the cheaper nickel plated stock. Cut 2x 310mm lengths.

They attach with 5mm x 5mm flexible couplers.Attach the couplers to the Z-Axis motors, thread/screw the rod through the 5mm nuts you placed in the X-Axis mounts and into the top of the couplers. There should be a gap between the motor shaft and the threaded rods so that the couplers can flex - if they are tight against each other then the coupler will not flex.

Once this is all complete then attach the extruder adapter that was test fit in the previous step.

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:31 am

Step 7: Extruder
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There area few different designs for extruders. Our plastic kit came with a "Greg's Wade" style.

It consists of a "hobbed" bolt, 3x 608zz bearings, small gear for the motor and a large gear which the hobbed bolt fits into, M8 nuts and washers, a 25mm M3 bolt and nut for the idler, a 10mm M3 bolt and nut for the small gear, a 20mm length of M8 smooth rod, 3x 10mm M3 bolts to hold the motor. For the idler tension you will also need 2x 6-32x2" (or longer) bolts and nuts to match. Also 2x tension springs - we used discarded springs that are found on a car brake-line.

Start by cleaning out the holes where the motor will mount and make sure the 608 bearing fits into the main piece of the extruder.

Slide a 20mm length of M8 smooth rod into one of the 608 bearing and press it into the idler. It should snap into place with a little force.

We used a 25mm M3 bolt and nut to attach this to the body of the extruder. The nut fits on the inside of the tag - check the pictures.

The M8 hobbed bolt fits into the big gear and through a 608 bearing fitted into the large extruder piece. You will have to add shim washers between the gear and the 608 bearing to make sure the hobbing lines up with the guide hole for the filament. A second 608 bearing holds the bolt in place. Test fit and shim as necessary. Use an M8 nylock or 2 M8 regular bolts cinched together to hold the hobbed bolt in place.

The small gear fits onto the motor shaft, we had to ream the hole out a little for a good fit. An M3 nut goes into the slot on the side of the small gear and an M3 x10mm bolt screws through this to hold the small gear against the motor shaft. We filed a flat face onto the motor shaft to help hold the small gear to the motor shaft - if your motor shaft does not have a flat face on it you must file one onto it. If you don't then the gear will slip on the shaft and the filament won't extrude properly.

Bolt the motor to the extruder and test fit the gears to make sure they line up - just make sure the hobbed bolt has been test fitted first and that the hobb lines up with the guide hole for the filament, then make sure the small gear will fit and mesh with the larger gear. There are slots on the main body of the extruder where the 6-32 nuts fit into. We had to file quite a bit of material off ours to make them slip into place, see the pictures. Assemble the 2x long 6-32 bolts through washers and the springs. The correct tension will not be known until you test and calibrate the extruder motor.

At this stage the physical build is pretty much done. Next we will move onto mounting the Arduino Mega c/w RAMPs board and start to wire up the electrics

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:33 am

Step 8: Power Supply
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For our Prusa i3 we bought a slim 12V power-supply vs using an old ATX PC power-supply. It's nothing to do with function - it's just a smaller neater power-supply. Kevin laser cut an enclosure for it. The power supply will need to supply approximately 9A for the heat bed and 4A for the hot end. A 350W (29A-30A) is a good choice, though a 20A should work.

Note: If you are not comfortable with working with 115V AC (or 230 depending where you live) get a licensed electrician to do this next step for you.

We started by cutting the end off a computer power cable, we then crimped spade terminals to the 3 leads. Use the ones with small hooks on the end - this will help stop the terminal from sliding off the screw terminal (see the picture). There is a live, neutral and ground connection - make sure they go onto the correct terminals.

Next to the AC input is 2x 12V DC outputs that go to the RAMPS board.

We used 18awg stranded wire for this. Again we used spade terminals with the hooks. There is an adjustment pot next to the 12V output. Use your multimeter to check the output voltage and adjust if necessary. If you don't have a multimeter go get one! They are needed for this build. As with all the wiring for our project we want to make it neat right from the start - so we got the mesh type cable wrap and used that along with heat-shrink tube to make the ends neater

kyogjj
Posts: 219
Joined: Wed Jul 22, 2015 7:56 am

Re: Building a Prusa i3 3D Printer

Postby kyogjj » Thu Aug 13, 2015 9:37 am

Step 9: Arduino, RAMPS and Motor Wiring
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On our laser cut frame are mounting holes for our Arduino Mega. Use plastic stand-offs so the Mega sits off the plywood. The holes lined up perfectly though we found we had to file the heads of a couple of the bolts (slightly) as the mounting holes in the Arduino were right next to header pins.

Mount the Arduino to the frame with the USB connector facing the bottom - leave enough space to plug in the USB cable. The RAMPS board mounts on the Arduino.

Before you mount the RAMPS have a read of Step 14 and what we found with the heat-bed and the MOSFET that controls it. Basically we found the MOSFET got very hot even with a heat-sink on it. After reading a number of reprap forum threads we decided to change the MOSFET to a IRLB8743PBF. It would be easier to do this now rather than later - but you may also find the quality of your RAMPS board is better than ours and the standard MOSFET is OK.

The RAMPS board has places for 5 "drivers" one each for the X, Y and Z motors, one for the extruder and a place for an optional second extruder . We are using 4 of the 5 for this build. If your RAMPS board came with the drivers pre-installed onto the board you should remove them and check the jumpers under them. There should be 3 rows of jumpers and depending on how they are jumpered it will affect the stepper motor. According to this chart we need to jumper all 3 pins to get 1/16th of a turn of the motor per pulse/step. So make sure all 3 pins are jumpered. If you don't have jumpers they are the same kind as found on PC motherboards, SCSI hard drives etc. Make sure you fit the driver back into the board with the correct orientation - if you don't you will blow components. The driver also has a tiny potentiometer on it to adjust the amount of current that you give the motor. This will have to be adjusted later - too little current and the motor will not step, too much and the driver will heat up and go into a thermal shutdown.

Once your drivers are installed we can move onto wiring the X, Y and Z motors. We found a wiring kit on ebay which has a selection of 2, 3 & 4 pin ends that fit onto the RAMPS board jumpers. They are the standard 0.1" spacing.

The NEMA 17 stepper motors we need to use have 4 wires coming from them. They are 2 sets of coils and you will need to use a multi-meter to make sure you have the correct pairs. The RepRap wiki has info on how this is done - basically you meter the pairs in turn. You will find open circuit on non pairs and low or no resistance on a pair. Mark which wires are a pair.

On the 4-pin connector the pairs are next to each other - so it's wire1 of the first pair then wire 2 of the first pair, wire 1 of the second pair, wire 2 of the second pair. When we spliced the wires that run back to the RAMPS we staggered the joins so that if the insulation we used ever broke down the wires wouldn't short. We used small shrink tube on the soldered joins and braided wire sleeves with shrink tube on the ends to make the wiring look neat.

Route the wires where the are out of the way. For the Z and Y motors you can make the length pretty exact as the motors don't move. For the X motor keep in mind that it moves up and down on the Z-Axis. The extruder motor will move both up and down and side to side. At this stage you should be able to wire the X, Y and Z motors. Temporarily mount the extruder c/w motor to figure out how long to make the wires. There will be the hot-end wires and also a fan wire in this "loom" and they should all be routed together - though not necessarily in the same braided sleeve.

Have a look at the RAMPS board, next to the drivers you will see 4 pin connectors for the motors. One each for the X, Y and extruder motors and 2 sets for the Z motors. Plug them in either way around for now (match the orientation for the Z-motors) - we just want to see if the motors move.

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