The wiring took longer than expected but the new printer was all set to go yesterday morning.
The new Azteeg X3 controller was new to me so there were a few wiring issues to be expected and I managed to get all of the motors wrong on the first attempt. Second attempt had them all wired up correctly but half of them were running the wrong way.
The Installation notes for the Azteeg X3 incorrectly said that the limit switches should be wired as normally-open when in fact they are normally-closed so that was the next obstacle, but eventually I had all the motors going the correct direction and all the limit switches working for the home position of each axis.
Next was the task of modifying the Marlin firmware to suit the printer I had built so variables such as the z-axis lead screws, x and y axis belt pitch and all of the motor data had to be entered and the firmware re-complied. The Azteeg controller makes this very easy and you can virtually modify the firmware on the fly so I was able to quickly re-compile it and test it then alter it again without interruption.
I also added in SD card support into the Marlin firmware and this is working well. The test print on the accompanying video was printed directly from the SD card so that all works, but it is not printing from Pronterface at the moment. Test print here: http://youtu.be/ujQlRW4-98s
For the past few days I have been wiring up all the motors, limit switches, thermistors and heaters and connecting it all to the printer control board. The controller I am using is relatively new and is called the Azteeg X3. It is based on the arduino-type control boards and runs Marlin firmware like all the other boards so I am not anticipating any major problems with it once I have selected the correct board type and complied the firmware. One thing I like about this controller when compared to the others is that it has screw terminals for connecting all the motors and so forth. It is also very reasonably priced and compares very well cost-wise to all the open-source electronics out there.
The company that makes this controller also makes their own hot beds or printer bed heaters so I also purchased one of these with the board and it too is easy to install and better than anything else around at the moment.
One of the challenges with wiring a 3D printer is to keep all the wiring neat and tidy and run in places where it won’t get in the way of what you are printing. This is tricky with this aluminium profile when compared to the larger 20/20 stuff used on the Mendel Max but fortunately I managed to find places where it was out of the way. I also had to design end stop holders for the three axes plus the holder for the controller so these are
all now added to the Thingiverse location along with the rest of the printer here: http://www.thingiverse.com/thing:33946
Next up is to modify and upload the firmware then see if it all works. I am expecting some minor glitches to do with the calibration as I have used unfamiliar drive belt types and non-standard pulleys plus it looks like the Azteeg has a different way of controlling the cooling fans so I will have to sort that out too.
It’s hard to keep the project flowing sometimes when you know something isn’t right. I wasn’t happy with the lack of belt tensioner on the y-carriage and although it is easy enough to pre-load the belt to negate the need for a tensioner, I really wanted to make it easy to adjust later on. So a short update today as I also have a day job that pays the bills on my growing list of hobbies.
Of course version 1 had a few minor flaws so the pretty red unit you see here is actually version 2. It uses the reprap favourite, the 608 bearing mounted with a couple of washers and on a short section of 8mm linear rod I salvaged from a photocopier. It is designed with 10mm deep recesses for 9mm diameter springs either side of the bearing shaft. The springs I have used have sufficient tension to not need the machine screws as well but I know a lot of people like to rack their belts up so tight you can play C flat on them so for them it also has provision for 4mm machine screws through the middle of the springs as well.
After the second attempt I got the carriage to work with the belt, motor and frame clearance. Version 1 had the aluminium plate clearing the end bars but once I added the aluminium plate height adjusters they fouled on the frame so I had to sacrifice another 5mm to z-axis build height.
Fortunately the y-carriage design is made up of the four bearing holders and the central frame so at least redesigns only need to replace parts and not the whole. As well as the print bed crashing into the frame the belt connectors were slightly high so needed to be lowered as well so that the belt would clear the frame. I ended up using some GT2-3 belt I had so I had to make the y-axis motor pulley fit this belt profile as well as be large enough to clear the frame cross-beam.
The basic y-carriage design is an aluminium plate suspended on three or four corners (I have opted for four) on springs under compression. The springs provide a bit of give if the hot end accidentally plunges into the print deck plus it makes bed leveling a lot easier. To level the bed there is a thumb wheel adjuster with a captive 3mm nut in the underside so turning this nut raises or lowers the bed for fine adjustment.
The frame is still just tacked together at the moment as there are a lot of machine screws to take out every time you want to make a change. I can’t see any more changes needed but I will still need to add mounts for the electronics as well as wiring clamps and some sort of spool feeder for the filament.
Next up is the assembly of the x-axis carriage so I might get onto that tomorrow, then again we are having a great spring/summer here and I hope to go blokarting (land-yachting) tomorrow so it might have to wait for another day.
Over the last couple of days my main printer has had some serious print quality issues which I eventually tracked down to a clogged hot end. Of course I first tried new gears, new hobbed bolt and changing my usual settings on Slic3r before I realised where the problem was. But it is printing better than ever now and non-stop catching up with my design changes over the same period.
First up as I mentioned in the last post I have reverted to top mounted cross bars as the gain in height by spreading them to allow the x-carriage to pass between them has proved to be of minor gain for the added build complexity and loss of overall rigidity.
I have also added two more rails front and back to take the load of the motor and idler for the y-axis carriage that will be coming soon. The 15mm extrusions are very strong and would take the load but it is less stress on the frame corners to add the extra rail and I had spare extrusion from the 5 metres I have cut up for this printer so no additional cost and a stronger and easier build.
Along with these changes I made some minor changes to the z-axis motor mounts so all in all I have remade every part of the machine this week – no wonder my faithful V2 Prusa had a breakdown.
Spent most of today designing, printing and redesigning this part and version 4 is currently printing so hopefully that will be the final version. The z-axis is the up-down one and controls the layers that are printed. To print in three dimensions you first use a program called a “slicer” to convert the 3D shape into a series of two-dimensional slices which when stacked on top of one another make up the 3D object.
The z-axis height is managed by using a lead-screw driven by two stepper motors – one for each side of the printer. In early printers these were placed on the top of the printer but most newer printers place them on the bottom to improve the stability of the printer frame. My motors hang from the Open Beam side rails and to save extrusion I have opted for only one side rail so I am also using a the z-motor mounts as extra feet. This should make the whole platform more stable and rigid but just in case I am also using heavier 10mm z-axis guide rails which will add to the overall frame strength as well as improving the print quality by reducing z-wobble.
For now I am using existing off-the-shelf type x-axis ends so I have set up my motors, lead screws and guide rails to match common spacings used on other printers but eventually I am planning on redesigning the x-ends as well to better distribute weight as well as make it more compact.