Tuesday, July 18, 2017

Building a new 3D Printer update 7/20/17

While I am waiting on the boards for the SNA 2.8 I decided I want to build a larger 3D printer.  When I designed the case for the new SNA, I was limited by the size of my 3D printer.  As I mentioned in one of my earlier posts, the main problem with getting a 3D printer, is that I now have another new hobby.  The largest things I can build with my printer is abut 6" x 6", and I would like to go up another coupe inches.  I looked around and found a clone of the Prusa I3 called the Anet A8 that would be the right size.  There are several kits on EBay that can be bought for under $175 including shipping.  I checked several of the user groups on Google and Facebook to see what users thought of these kits.  It looks like they are  basic machines, but with some  work and modifications they can perform quite well.  One of the 3D printing sites I frequent is Tom3d.org, he recently did several You Tube videos on building a I3 clone from scratch.  After watching them I decided to build my own instead of getting a kit.  Looking at some of these kits and mods, I found a mod called the AM8. This uses many of the Anet A8 parts, but replaces the acrylic frame with one made from 4020 aluminum extrusion.  I have many of the parts, and some 2020 extrusion that should work.  I was able to download the  files for all printed parts and several mods from thingiverse.com , now to print the parts.

Some of the parts can be printed in PLA, but most need to withstand more heat and need to be printed in ABS or PTEG.  My printer works well with PLA but I have had problems working with ABS.  Originally this printer only used cartridges, but a recent software hack of the firmware enables the use of bulk filament.  I modified several used cartridges to feed filament directly from bulk reels, and tried several things I had found on-line to help when printing ABS.  My printer does not have a heated bed, and that was the main limiting factor for using ABS.  I added a thin PEI sheet to the build plate, and found that if I put several heavy coats of hair spray on the bed I could get the print to stick.  
I also designed some simple 20 x 1 mm. discs that when added near the corners of the object being printed, helped hold the part down to the bed.   

Without the heated bed, there was still some curling of the part when it cools.  From what I found on-line it looks like it might help to increase the temperature in the build area.  I found that by simply placing a plastic trash bag over the printer, the temperature was increased enough to prevent most of the curling, and also seems to help with layer adhesion.

Now that the printer is working better, I am in the process of printing the parts I need for a  printer based onthe Anet A8 and several mods I want to incorporate in my design. 
I have finished some of the larger pieces, and find very little curling, and what is there is not on any of the mounting surfaces. The pieces are very solid, and show no signs of layer separation. Wonders what a trash bag can do.

Update 7/20/17

Looking at the instructions for the modified printer now being called the AM8, the aluminum extrusion being used is 20 x 40 size. I have some 20 x 20 extrusion so will be using that instead. I do not want to have to re-design all of the parts, so I will mount two pieces together to get the profile I need.  I do not have enough aluminum extrusion, so I looked on thingiverse.com and found some files for printing some of the desired  profile.  My printer only has a print height of 150 mm. so I have to print in sections.  I printed several sections along with some extension support  pieces, and Acetone welded them together.  The resulting piece was stronger than I had thought it would be.  I guess now I just have to print up a few more batches and put them together.  Then I can cut them to length and mount to the Aluminum extrusion.

Friday, July 14, 2017

Lets call it SNA Jr version 2.8 for now

I have been trying to get a 3.2" TFT 8 bit parallel interface display working with the STM-32 board, but have had several problems.  So I decided to temporarily go with the Nano version, and a 2.8"  display with a SPI interface.  I had much of this working previously, so that part should go along quickly.  The previous board had a lot of additional circuitry on board that had been giving me problems.  I did a simple layout with just the Nano , display with simple voltage divider level translation, Ad8307 log detector, and a Adafruit SI351 board.  I usually make my own boards, but saw an offer from a Chinese board house that I wanted to try.  The board layout was under the 10 x 10 cm. size they had on special, 10 boards for $5 plus about $14 for postage.  At less than $2 per board, I decided to place the order.   Generated a set of Gerber files, uploaded them to their web site and placed the order.  Three days later I got an e-mail notifying me that the boards had been completed and were being mailed that day.  It has been about a week now, so expect them to show up some time late this week.  

While waiting on them, I decided to work on the packaging I wanted to use.  I had designed several 2 piece clam-shell type boxes that 3D printed quite well.  I changed the overall size ,and added cutouts for the display and joystick.  I was also able to design in mounting posts for these components, and added a bezel for the display.  It took a couple minor design changes and test prints to get everything exactly as I wanted it. 

It is still a lot easier than making a design on paper, transferring to  a box, then drilling and cutting out all the holes. Then you hope you have everything right, or you might have to start over with another box.  

I like being able to just do the design, send over to the printer, and in a few hours grab it off the printer sitting next to my desk.  The wife also likes the fact that I do not have metal filings all over the place anymore.