Happy Accidents

Hi All,

I just wanted to write about accidents I’ve had while using EasyMaker.  So far, I’m pretty happy with them, though I was terrified at the time.

Accident 1:  Drove the active mill head straight down into the machine.

This would normally be a terrible accident, that would at least result in a broken bit.  Or damage.  The Emergency Power Off switch would have worked ( there is one wired behind the machine ), but I wasn’t paying attention, as I was twiddling with software.  So, what happened?  I heard a “think” noise, and the machine stopped going down.  The Screw drive for the Z axis is mounted to a nut, and the forces are counter gravity( going down means the Z force is up on the nut. )  The nut is friction locked into a stanchion.  The nut just popped out, and no damage happened to the machine.  I just loosed the stanchion lock screw, push the nut back in, and tightened the screw.  Total repair time — 1 minute.  I was redesigning the nut stanchion to not allow this, because I was thinking more downforce might be nice for some use cases.  But this accident taught me — keep the design as it is.  I’ll release the stronger stanchion as a public design — but I won’t recommend it.  The existing design has worked really well for a very long time, and so far, seems to help keep damage from accidents down.

Accident 2: Drove the mill head along X way too fast/deep for the router.

This should have snapped the bit, and then hit the frame.  Not a good outcome.  But what did happen surprised me.  The router stalled out, then the drive motor started skipping.  The Belt drive puts out just exactly the right amount of torque!  This wasn’t planned — I had no idea the motor and the router were so well mated.  But the result is — goo too deep/fast with too large an end mill, and it seems like nothing bad happens.  Just correct the GCode, lift up, re-home X, and voila.

Accident 3: placed my hand on the hot plate when printing.

This is a common accident.  I should have been burned, but wasn’t.  Turns out Aluminum is too good a heat conductor, and the hot plate can’t go above 61 degrees C.  This is enough to surprise you, but not hurt you.

Accident 4: Code error kept heat-bed turned on all the time.

I had a bug in some of the code modifications I had been making.  The result was that heat control for the heat-bed was broken, and turned the heater on at full all the time.  I should have over-heated, maybe even caused a small fire.  But nothing happened.  Turns out the Power balance between the heater and the Al plate is exactly right to maintain 60C with no control input.  Although I don’t recommend it ( heat transfer is dependent on ambient air temperature ), it looks like the two systems cannot allow harm to happen.  And, yes, ABS sticks fine at this.  Though PLA, which should work great, gives me some trouble.  I’m looking at a glass print surface to help first-layer adhesion.

So a lesson I’ve learned using EasyMaker: Accidents happen.  Whether you’re 3D printing, or CNC milling, or whatnot, accidents happen.  So far, no damage/harm.  That doesn’t mean there’s no danger.  This is a power tool that you program with a CAM tool.  There’s many ways for it to go wrong.  That’s why I wear safety goggles when running this thing, do air-test first ( set Z above the material and run the whole program. ), etc…  You must practice proper shop safety with this robot.  It just that so far, the accidents that have happened in my own use hasn’t caused serious damage to the machine or to me.  But, I’m sure this thing could remove a finger or worse.