Bad news is we aren't ready for a file release at #MRRF2018. Good news is we will be at #MRRF2018 with two working HELIOS printers.
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GUS is all strapped in for the road trip to #MRRF2018
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Got the 200step/rev steppers installed and doubled the pulley size for the transmission belts. Tons of torque and very little heat. Have not printed anything yet but seems way more rigid and the math says the resolution should be fine.

Hate the top plate design. I have a great idea on how to make it look sweet but it will have to wait for the first child because it won't be a functional change.

We are now going to dive into using an accelerometer for impact probing. This is a big unknown for us. In theory, we can use it for homing and bed leveling but this has never been done before so there is that.

Once that is done...
-hardcore calibration
-design review
-model refactoring
-child printing
-child assembly
-child verification
-file release @ MRRF (fingers crossed)
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On the good news side...it only takes 1 hour to disassemble HELIOS.
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My student Johnathon Cato won 1st in the Mechanical Engineering category at our science fair. He was also 1 of 6 considered for the overall award. It is hard to compete with a computational chemistry project that actually came up with new novel drugs without wasting money in the lab or another project that developed a water testing battery that used no chemicals/only bio-indicators.

We are already...
*printing new pulleys for a bigger transmission belt to reduce effector compliance
*Putting on some 200step/rev steppers to test their print quality and fix the stepper heat problem.
*Redesign the top plate to look cooler.
*Redesign the bottom plate to get just a few more square millimeters of build area.
*Integrating the acceleratometer/arduino for the impact probing and homing.

Once we get this list taken care of we will...
*Livestream HELIOS printing a HELIOS and the subsequent build
*Document the crap out of everything.
*Take tons of pictures of step by step assembly during the build.

Cato is travelling with me to the Midwest RepRap Festival. It is our sincere hope that we can do a proper release of all the files at the festival. (I also have the kids that are working on the rolling tablebot coming with me to. We should have it printing by then.)
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I purchased 8 of these unipolar stepper for HELIOS prototypes. My criteria was that they needed to be about 34mm and 400 steps/rev. There wasn't much fitting those specs so I bought this one even though it was unipolar. I assumed that I could just ignore the center taps and all would be good.

The problem we have is they get hot. Hot enough that I don't want to keep my finger in contact for more than a few seconds. I have adjusted the current to below half of what the spec sheet says. I feel they should be ice cold at this point. I can verify that the current is in fact low because there is very very little holding torque. I wouldn't trust it not to have a layer shift on an overnight print right now and the steppers still get way too hot.

Do any of you have any sage advice for how I can get these steppers working or if these steppers are the problem...what else should we buy?

Information you might need to help me...
*24V PSU
*TMC2208 drivers
*Drivers in Stealtchop2 mode (I think)


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I was trying really hard to get a closed form solution for the center to center distance of arbitrary pulleys for a given belt length. I occurred to me that this has to be a known problem. The first couple of sites gave me a pretty easy formula. I plugged it in and it was always off by .03% which is admittedly small but I was sure that floating point error would add up that much. After more research I figured out that it was just an approximate formula. It turns out that it is impossible to get a closed form solutions. (I think.) It is crazy that such a simple problem can't be solved without numerical methods.

Question?
Right now...I have a python script that poops out center to center distances and then I port them into Fusion. That won't cut it so I was trying to roll it all into Fusion. I know that Fusion uses numerical methods for constraint solving. I am just having some issues getting Fusion to solve for this. Ideas?
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Can't have a heating element on HELIOS for science fair but we found a way to keep the printer occupied for a long time while the judges are walking around.
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Tons of edits left but thought you would want to see the world population of HELIOS printers in action.
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Assembly is simple. Everything is perfectly tensioned. Motion is buttery smooth. Wiring tomorrow.
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2/16/18
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