How to hack the speed
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Thanks for sharing such an incredible project with us. I was able to go from print to assembly and testing in about 3 days. It worked flawlesly.
Now, I would like to change the drawing speed. I know it may affect the drawing quality, but I want to test the limit of the machine. I am setting the speed in Makelangelo in the pen section but it does not seem to make a difference. Is this something that has to be changed in the firmware? Is it a hardware limitation? I am using an Arduino Uno with Adafruit Motor Shield V2.3.
The speed is already pretty close to maximum.
See, the AMS1 uses a shift register and two L293D chips. What that means is if you want to make a single step you have to digitalWrite() at least 16 times, plus if() tests. FOR ONE STEP.
The AMS2 uses i2c, which is arguably worse for single steps. A whole library of code has to run to package a message and deliver it to the right shield address, which is then unpacked and processed by the AMS2 board.
Now you might be asking “why not step more than once?” Great question. First, it makes no difference for the AMS1. Second, IF the AMS2 shield could guarantee that both motors finish their moves at the same time THEN that would work. In testing they do NOT make this guarantee and I have found no way to make it happen in the code. So multi-stepping will not make straight lines on the AMS2.
Long story short the AMS1 and AMS2 are already at their maximum. That’s why the Makelangelo 3 & 5 uses a much faster board that can drive many motors – when you get all that you can out of the project you can recycle the board to make a 3D printer, meaning less parts go to waste. A bit more expensive at the start but it saves you money and helps the planet in the long run, I hope. If you get a MEGA + RAMPS board it will cost you the same as our RUMBA board.
Does that help?
Our RUMBA boards work great and they’re fully supported. Don’t forget to buy two a4988 drivers – motors won’t move without them.
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