Prusa Tips & Tricks: Why Layer Height Matters

After getting my printer fully calibrated and so forth, I began to experiment with the different settings available inside of slic3r to determine how different parameters affect the quality output of my printer. I found that what affected quality the most was layer height, not only would lowering the layer height make the ribbing on a print less prominent, it also created more precise angles within the model.

I decided to create a comparison of a model using layer height as the variable for determining quality. As you can see, I achieved pretty good results using a 0.5mm nozzle. When printing at 0.1mm layer height or lower, any slight errors in calibration are greatly exaggerated, any slight miscalculations in the amount of plastic being extruded can wreak havoc on quality.

Another issue with layer height is the time it takes to print an object. Printing something at 0.1mm takes 4 times longer than at 0.4mm. When printing large objects this has to be taken into consideration when selecting an appropriate layer height.

In conclusion of my makeshift experiment, I found that my Prusa prints optimal quality at 0.2mm layer height, good to know. 

Prusa Tips & Tricks: Y-Axis Bed Mod

While building my Prusa, I found certain areas of the build process to be seriously lacking on the documentation front, specifically the Y-axis and the hot end. From my humble experimentation, I came up with a simple Y-axis carriage that allows unimpeded movement, is light weight and simple to make.

The first step was to cut a 9.5in x 9.5in square of plywood and then cut it into three pieces to form a middle section and two extensions as shown in the picture. I screwed it together with some screws I found laying around and voila:

The first time I tried to mount the square piece I found to my dismay that I only had about 70% mobility on the Y axis form the plywood hitting the frame, significantly lowering my maximum print area. Hence, the reason for the "H" shape of the Y axis bed, giving the extension pieces just enough height  so that it clears the front of the frame. You can see how the wooden extensions clear the frame in the picture.



After some initial printing directly onto the PCB heated bed with Kapton tape, I quickly found that the PCB was not perfectly flat, so I began looking for some flat material that I could print onto. I asked around on the RepRap forum about whether people using glass were using heat treated glass or just normal glass. I found that the majority had found that any type of glass would serve the purpose. I quickly found a glass pane from an old picture frame that fit perfectly across the X axis of the bed. I was initially worried about the extra two inches that stuck off the Y axis (the clear part in the picture), but I soon realized that it was a great way to remove the pane right after printing as it wouldn't heat up as much as the rest of the glass surface. As an added bonus, I could move the glass around without getting oil from my fingers on the actual printing surface. I covered the glass with Kapton tape, clipped it on to the PCB heated bed with butterfly clips and it printed beautifully.

My one problem after getting the pane of glass all rigged up, was that I could barely get the heated bed above 90C with the element constantly on. The underside of the PCB was heating the air and losing precious heat meant for the printing surface.  I had read on a blog about someone using a piece of cardboard as insulation. I decided to try it out as an alternative to the spray on insulation that seems to be the most popular solution. It ended up working extremely well, it took half the time for the bed to get up to 100C than it had before, now it heated up in approximately 5 minutes. In the last picture you can see my most current setup. It has been working great, I can print at 95C for relatively large pieces and have absolutely no warping. I pull the pane of glass off after printing, let it cool on the table for a couple minutes, and the piece breaks off with a little bit of force no problem.

Overall, I am really happy with my Y axis bed design. I hope that for newcomers to RepRap, this post will help to demystify one of the build processes that I found had the least documentation. Good luck!

The Prusa Build: COMPLETE!

It has been a solid six months since I first embarked on building a Prusa RepRap printer, and last week I finally printed my first print! (yes I have been printing non-stop for a week, hence the week delay for this post) The final build stages before my first print were to assemble the hot end from MakerGear, mount the PCB heated bed, and attempt to wire everything up in some sort of cohesive form. The hotend ended up being a very finicky and almost ended in complete disaster; the connection inside the cured heatcore broke, so I ended up making my own MakeDue hot end from salvaged MakerGear parts which has been working very well so far. After I got the hotend working, I mounted the PCB heated bed and went through a series of slightly dodgy upgrades which I will cover in more detail in a following post. The wiring is still a work in progress, I plan on cleaning the wiring up some time in the future.


My first print was the symbolic RepRap shot glass. The print turned out much better than I expected, I was dreading the big blob of goo that most reprap bloggers write about, but was pleasantly surprised when the print actually resembled the desired object. I used Sprinter firmware with Slic3r for gcode and controlled the printer using Pronterface.






I  put kapton tape directly on the PCB heated bed as a quick fix for a piece of glass. There were some uneven areas on the PCB surface, but overall it did not severely effect print quality.

After my surprising success with the shot glass I went about fine tuning slic3r settings. I followed an excellent blog post tutorial for slic3r calibration that can be found on RichRap's blog,
I would highly recommend reading through the post as it clearly outlines how to properly calibrate Slic3r settings. After my calibration was complete, I set about testing the capabilities of my new Prusa. I started with some gears and pulley parts, and then went on to experiment with lower layer height with a Yoda head. I also began to experiment with the effects of extruder retraction while printing a bracelet from thingiverse. I found that changing the amount of retraction even 0.5mm and adding a little bit of Z lift between moves significantly changed the amount of stringing on a print.

I'm really blown away with how straightforward printing has been and the significant leaps and bounds in quality that I have experienced over the last week. Over the next few days I am hoping to post some of the simple improvements I have made as well as a few observational posts regarding the effects of layer height and other slic3r settings on print quality. 

Printed Parts Update II

So I have FINALLY finished collecting all the printed parts for the Prusa! I ended up having a local guy print the rest of the parts I needed, since it was turning into quite the hassle to get all the parts printed from my local hackerspace, hacklab.to. I opted for LM8UU linear bearings from thingfarm for the x and y axis, and A hinged extruder instead of the standard Wade's extruder. The parts were excellent quality, I didn't realize a well tuned reprap could actually print at that quality level! Now I just have to wait for the linear bearings to come in to finish assembly.

Merry Christmas! 

RAMPS Enclosure Project

After assembling the RAMPS board and testing the pololu stepper drivers with a couple of motors, I found that the stepper drivers were heating up almost to hot to touch after only mere minutes of operation. I decided that I would need to build a nice enclosure to protect the RAMPS board, and also to actively cool down the stepper drivers to attain optimal performance.

I found a scrap piece of acrylic in my junk bin and quickly set about building an enclosure. I picked up a pack of 3/16th inch bolts and drilled 5 mil holes in each of the four corners. The bolts self tapped since acrylic is a relatively soft plastic. I drilled out the center hole for the fan with a series of 1/2inch holes and secured the fan with 3M screws. The fan is directly connected into the PC power supply, so soon as the RAMPS has power, the fan begins actively cooling the electronics. I'm curious to see how well the active cooling works in an actual print situation.

 

How To: DIY PC Power Supply for RepRap

Over the last couple of days I have been cannibalizing a PC power supply to work with my (future) RepRap. I spent quite a while reading and rereading the wiki post for the DIY power supply trying to decipher what was the simplest way of putting the power supply together. I found that the wiki didn't really have any clear instructions for a simple +12V power supply, so after getting one working I decided to share how I did it. I figured out a (somewhat) elegant way of wiring that hid most of the unused wires within the power supply box. The following is a brief simplified how-to on assembling a reprap DIY power supply.

TOOLS:

1. Wire Strippers
2. Wire Cutters
3. Soldering Iron
4. Solder 
5. Electrical Tape

POWER SUPPLY: Any computer power supply will work that has a rating of at least 16amps on the +12V line. It should say the amperage on the side of the power supply, more than 16A is fine as the RepRap will only draw as much power as it needs.

STEP ONE: Cut all the connectors off the wires and group them by color, the four wires you are interested in are the black, yellow, green and brown ones.

STEP TWO: Select about five of each of the black (ground) and yellow (+12V) and cut them off about 2 inches outside of the power supply box.

STEP THREE: If your power supply has a brown wire (3.3V sense) solder it to an orange wire (+3.3V) and wrap it with electrical tape as shown in the image:

 

STEP FOUR: The green wire is a power on wire, it must be wired to a ground wire in order for the power supply to turn on. You can either wire them permanently together, similarly to step three, or run them out of the box and connect a switch to them so you can have a power switch right next to your reprap electronics.

STEP FIVE: Solder the five yellow wires together and all the black wires together in two separate groups. Then solder two black wires to the black soldered connection and two red wires to the yellow connection. After the solder connections have cooled, thoroughly wrap them in electrical tape. These wires will feed into your screw connects on your RAMPS (or similar electronic) board. I braided the all the wires including the power on wire together to keep everything clean and tidy.

STEP SIX: Cut all of the rest of the wires down to about an inch and tape them using the electrical tape in groups of similar colors (Example: all the orange together and all the black together)

FINAL TESTING: Put the power supply back together and turn it on, remember to connect the green and black wires together! If your power supply does not turn on, there may be another sense wire for the other voltage rails, look for any wires that are lighter gauge than the rest and wire them to there corresponding colors as done in step three and four.

I hope this helps!

Printed Parts Update

Just an update on the parts that I have printed so far:

Building a RepRap Prusa Mendel 3D Printer

I have been absent from the electronic scene for quite some time now, but my interested has been rekindled after some time researching 3D printers. I have decided to build one for my Grade 12 project!

My first goal was to build the printer for 450 dollars, so I began to research all the available options and their associated costs. I finally settled on a combination of parts, with the majority ordered locally. I will make a basic list of the main components and where I purchased them from:

Electronics - RAMPS board on Arduino Mega 
http://ultimachine.com/
http://www.ebay.ca/Arduino Mega
Motors - Wantai 42BTGHW811 bipolar hybrid stepper motors
http://www.wantmotor.com/
Stepper Drivers - Pololu A4988 stepper Drivers
http://mixshop.com/pololu
Vitamins - Complete structure kit
http://mixshop.com/
Extruder - Complete Wades Extruder kit
http://mixshop.com/

So far I have received the Arduino Mega and the RAMPS board, which I assembled. If you aren't comfortable with SMT soldering, I would suggest going with the SMT already Soldered option.

I went to the open night at the Toronto Hackerspace http://hacklab.to/ and found out that they had a working makerbot which they are generously letting me print my parts off of. So far I have printed 3/4 of the parts over the course of a couple weekends. Hopefully by next week I will have the Mixshop order and all the parts printed and will be able to begin assembly!

Unpopulated RAMPS

 

Finished RAMPS Board