Monday, September 30, 2013

LCD Panel Mount for Mendel Max 2

I wanted to install an LCD screen on my 3d printer so that I could run it from SD cards without a computer constantly needing to be plugged in. I was inspired a great deal by a panel mount that Ohm Eye developed but I have a reprap discount LCD which will not fit Ohm Eye's configuration. I saw a different case by Wersy where it was designed for the correct LCD/SD card combo I have but it fit on a Prusa Mendel. Through the wonders of 3d modeling I created a mashup that had the best of both worlds.
The front has the LCD, a click wheel and a reset button (white oval below wheel). I also added a power switch to easily flip the power to the power supply on and off. The power comes in from the outlet to a fuse at the back of the printer. The 120 V then hooks up to the switch like this:
I bought the switch from Pololu.

On the side, I put a slot for the SD card. 
The front of the mendel max has 4 holes so I wanted an accompanying 4 holes in the panel mount as well. Unfortunately, since the model is printed layer by layer with that front face on the bed, this created a problem since the panel curves at an angle.
See what I mean? Since it will be printing the upper hole supports last, unless the stripes went all the way up, there would not be a way to support the upper tabs (without the support feature turned on in slic3r). This works great except that with the supports going across there isn't a good way to get the LCD in! To solve this problem, I inserted the LCD while it was printing. I waited until  the print had finished 60% and just dropped it in.
I was lucky because had I mis-engineered the box and needed to print a new one, this wouldn't be the easy to remove without breaking the box. A messed up box wouldn't do me any good anyways so it probably would have been okay to break at that point if I had issues.

Configuring the firmware
I have been primarily using Marlin as my firmware so after installing the LCD I set the following settings and booted it up:

#define MOTHERBOARD 301

Unfortunately, it appears as if there is an incompatibility with the combination of RAMBO, reprap discount smart controller and Marlin because my screen just displayed a series of white boxes:

I at first thought it was a bad solder point or cable installation. Installing a specially modified version of Repetier that was set up by folks over in the Rostock Max forums corrected the issue. I think the click wheel works and that it is just the screen itself but there are enough differences between Marlin and Repetier that I can't figure out what to copy and paste yet. I am still stumped by this problem so let me know if you have any suggestions! 

Download the files at my Github or thingiverse.

Wednesday, September 25, 2013

Testing Layer heights with Owls

Now that I have the printer working well, I wanted to test out how intricate I could make my prints. I found these owl earrings and printed them at 10% and 20% size. My layer height was 0.1mm and the prints took 15 minutes for the small guy and 2 hours for the lager one.

It is truly remarkable how well that they came out. The smaller owl is sitting on a US dime which is 17.9 mm in diameter! These are hard to see in real life and it was not trivial to even get my SLR camera to properly focus on the objects to take a picture.

A key development that made this possible was using hairspray to get the first layer to stick. I have tried many different methods of getting it to stick:

For PLA:
1) Blue painters tape- Does an average job especially without the use of a heated bed.

2) Heated glass- I wasn't able to get this to work on my Mendel Max but I did have luck with my Prusa previously. It could be that the Mendel Max uses a different type of heat resistant glass, similar to pyrex, which requires more playing around with the bed temperature to get it right.

3) Aquanet works really well. I spray it when the bed is cold (important to potentially prevent cracking) and warm the bed up to 70 C. I am sure to check with my extruder height that I can fit 1 piece of paper between the nozzle and the bed. Then, I can just print it and forget it!

In the US the hair spray can looks like this purple one:
The only issue I have now is that the parts almost stick too much so there probably is some fine tuning of the bed temperature that could ease that issue.

Slic3r Settings for a 0.4mm jhead nozzle:
Layer height: 0.1 mm
First layer height: 0.32 mm - Important! I had troubles sticking if this first layer was too short
Fill Density: 0.3 mm
Fill Pattern: rectilinear

Perimeters: 30 mm/s
Small Perimeters: 30 mm/s
External: 100%
Infill: 80 mm/s
Solid Infill: 50 mm/s
Top Solid Infill: 30 mm/s 
Support: 30 mm/s
Bridges: 10 mm/s
Gap Fill: 50 mm/2
Travel: 150 mm/s
First Layer Speed: 25%

Loops: 1
Distance from object: 15 mm
Brim: ~a few mm if needed on a large part

185 C first layer, 180 C after 
Bed: 70 C
Fan: 35 to as high as your ears can take! Disable it for the first layer

Start Gcode:

M301 P21.47 I2.24 D51.36 - set this based on your printer with PID tuning!
G92 E0
G1 E3 F1200
G1 E2 F1200
G92 E0

End Gcode:
G1 X12.0 F4000
G1 Y170 F4000
M104 S0
M140 S0 

Friends don't let friends RUMBA

I know that I have been slow about updating this blog but I ran into several issues with printing that I have just recently been able to solve. I'll detail the problem here and my solution and hopefully it can help someone else.

Problem 1: Randomly crashing X axis
I was getting really bizarre motions where after starting a print that was going well, the X axis would just randomly start moving in much bigger motions than it should. For example, I notice that when printing a circle that instead of printing a 0.5 inch circle suddenly it will start printing a 6" circle. This frequently happened when I would start a print and so when it tries to find the center of the bed it will go off the +X axis and start grinding on the gears. 

Solution 1: Unshielded LCD cables were causing a problem
This seemed like an electronics issue so I replaced my USB cable and switched to printing from a SD card and it did not solve the problem. I was running a new RUMBA board so it was hard to find any support for this issue even in general much less for this specific board. I eventually found that removing the reprapdiscount LCD screen seemed to fix the issue. It is likely that it was interference with the unshielded cables even though mine were <30 cm.

Problem 2: Extruder randomly extruding 4x as much plastic
I thought that I was out of the woods with the X axis problem but then I ran into a new issue that I didn't have before. I would turn my printer on and start a print which would go fine. Often I'd want to tune a slic3r setting so I would stop the print and restart it several times. I noticed that sometimes my extruder would put out way more plastic than it should. At first I thought it was different slic3r settings but after doing some controls where I took the same gcode and printed it several times I discovered that the printer would just apparently squirt out different amounts of plastic with the same gcode. Here is an example where you can see one parameter on the left when it is thick and one parameter on the right which is what it should be doing.

This made me think that it was a steps/mm setting that was getting reset but I noticed that after unplugging the board for an hour or so that I could get the settings to reset and behave normally. This led me to believe that it was a flaw in my Rumba electronics themselves. 

I paid more attention to the extruder motion which gave me a clue. Here is the normal extruder extrusion rate:
After printing for a while I can do the same experiment and see that the extruder is moving 4x the speed as before:

This evidence makes it seems like there is some sort of switch such as on the microsteppers that is defective and is randomly switching between microstepping and normal stepping during the print. The hitch with that hypothesis is that I get the same behavior when I hook up the extruder to a different stepper on the board which has different switches. 

Solution: Purchase non defective RAMBO Electronics
After reburning the bootloader to no avail, and getting no where with reprapdiscount to actually replace the board, I gave up and purchased a set of RAMBO electronics instead. I wanted a way to directly test whether it was the RUMBA board or some other firmware issue that I couldn't think of. Boy was I impressed when I hooked it up. 

After printing a test cube that came out beautifully, check out my second print with the RAMBO electronics, the curve fan holder, with all the stock settings:
There was not a layer or boundary out of place on this print. I am just so impressed with the quality of the Mendel Max Setup now that I have the electronics working properly!