Friday, 4 July 2014

Delta 3D Printer Assembled

posted 9 Jan 2014 12:32 by David Taylor

I set myself a target to complete the assembly of my Delta 3D printer before the end of the year (2013). On New Year’s Eve I assembled the final parts, but the point is I reached my target, except for my Bowden extruder, which I requested in August when I decided to start this build, but still have not received… (Let’s not dwell on this)-:
I’ve had a couple of questions asking why I used pressed wood for the base plates after going through all the trouble of using aluminium extrusion. The answer quite simply is that this is still a prototype until I get it working. Perspex is quite expensive and after getting the first version working and finding out exactly where each whole should be drilled, I might rebuild it or simply build version 2 with all the aesthetic consideration required.
Below is a time-lapse video of the physical assembly.

    This brings me to a quick side rant about misleading phone apps: I downloaded “Timelapse Pro” by Max2 on the Windows Phone Store, a free app. After shooting a full days’ worth of time-lapse photos it turns out you have to pay for an upgrade before you can actually get your shots out of the application. I went back and read the text on the store and no mention of this is made anywhere. I promptly gave them a 1 rating, with a good description of my feelings and reported them to Microsoft as a misleading application.
The video above was shot using Time-Lapse Camera 1.0 by Ryan Tremblay on my Nokia 920 and assembled using Windows Movie Maker as helpfully described in the help section of the application.
One motor wouldn’t move
I realised that one of my stepper motors wouldn’t turn after my initial tests. After swopping my stepper drivers around I found that one of them was the problem. I decided I would take it back and get it swopped, but had one last look and found two of the components (capacitors) on pins 2 and 3 had gotten themselves soldered together during reflow. Apparently these boards were tested…sure:
A quick [tiny and very controlled] chopping motion with a Stanley knife sorted that problem out and I soon had all 4 steppers doing what they did well.
Shorted CoolStep Rev. 2.0
Z+ moving in the wrong direction
Things were moving around, but I was a bit puzzled because the Z+ only moved small amounts and in the wrong direction?!? I checked the other movements and they were correct so my motors were not connected in the wrong direction. It turned out that I had swopped my Max and Min end-stops. Also didn’t have the min end-stops installed or disabled. Checking end stop status with M119 reported that all end-stops were triggered all the time. Swopping the end-stops and disabling the min end-stops which are not really required on a Delta anyway, solved that problem. The first time I tried the Home button after that, left me diving for the power button as I wasn’t expecting it to home quite that fast and the fact that I hadn’t attached my end-stops yet, the trucks where trying to climb through the top of my printer. (Luckily nothing broke.)
Magnetic-connectors and hot-glue
I’ve posted a couple of photos of the way I connected the magnets to the trucks. The problem with that is that the heat shrink leaves a nice rounded end which allows the balls to easily move off the end of the magnet without much effort (a bad thing). I tried a drop of hot glue on the balls and then stuck it onto the magnets. After cooling, the balls quite easily pop off leaving a perfectly shaped seat for them to sit in.

Diagonal rods
I opted for aluminium for my diagonal rods. You get a much better selection of these at the local hardware shop in the UK, but I ended up getting 6mm rod which I had to reduce to the 5mm required to fit into the magnetic ends.
I might upgrade these to Carbon fibre tubes at a later stage.
I found the image below on a forum post on seemecnc which had no link to the original source.
Calibration Diagram
This really helped allot. After entering the values and reloading the firmware, my hot-end was coming down about 20mm to far still. I realised that my trucks where moving about 11mm for every time I clicked the 10 move button in Pronterface. I will reduce my 177 DEFAULT_AXIS_STEPS_PER_UNIT to 161 and see if that makes a difference. Sounds about right given 1mm per move over the full Z-axis movement. Calibrating a Delta 3D Printer has been really helpful so far.
I originally requested Stephan to print me an Airtripper extruder for my printer (Back in August… stop, don’t go there). Quentin Hartley mentioned that his extruder stepper motor was heating up allot due to the excessive current required to keep this extruder going. So much so, that the filament was getting soft on the drive wheel which was causing him some problems.
I’m now waiting for Quentin to print me a RepRapPro mini extruder.
Next steps: Get an Extruder and complete calibration…

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