I’m not quite ready for the Show-n-Tell section… I’m wondering if I bit off more than I (or the Simple) can chew
@Printrbot 's reply to my initial tweet was “oh my!!” (which loosely translated, I think means “Thanks for playing, but your warranty is now over” )
I have upgraded the bed to 200 x 200 mm. Right now, I’m using a mirror binder clipped to a very thin sheet of plywood.
I am fighting with 4 problems.
Sag. I upgraded the X axis mounts to Jon’s beefier looking ones - http://www.thingiverse.com/thing:257841 but I’m not sure they (or maybe even the 8mm rods) are stiff enough to carry the weight. Trying to level the bed is proving to be a challenge.
X axis momentum / wobble. The bed is so heavy that there is a lot of inertia to overcome starting and stopping.
Y axis bounce. Again, I used one of Jon’s great designs to extend the Y axis - http://www.thingiverse.com/thing:242185 and when I was still printing on the stock ~4x6" aluminum bed, the Y axis was very solid. However, now out at the 200mm limit, when rapidly moving back and forth, there is appreciable bounce in the print head.
I ran out of tape, so even after all this hackineering, I can’t explore the full potential…
So, now to solicit solutions.
Sag - I’m stumped here. I’ve pondered a roller bearing running under the bed, in line with the Y axis to hold it up, however, the bottom of the bed is plywood and may introduce excessive Z axis drift. (Might need that probe upgrade…)
& 3) Inertia. For now, I’m dialing back the acceleration to try and calm things down - that will have a major impact on printing speed. I’m down from 2000 X/Y to 500 X & 1000 Y and still finding a lot of energy throwing the bed/end around.
Inertia - X axis. Thinner glass? Mirrors are pretty flat. But old school ones like this are thick. I’m kicking myself that I threw out a bunch of cheep desktop scanner platens - they would have been lighter…
Interia - Y axis. I should look into a Bowden system and get the extruder and its heavy stepper off the arm.
Be aware that you’re effectively going way beyond what those rods are meant for. They’re only supported at one end, instead of a machine like the Mendel90 where the rods are supported on both ends.
You want to lighten up everything you can, because you’re causing a bunch of deflection in the arms. Bowden is a must at these lengths and honestly for this size, I’d downright redesign the entire machine.
You could effectively utilize the same parts, in a different configuration altogether, for the same build volume without all the troubles you’re going to face attempting to do this.
Thanks, I could’ve sworn you were a fellow I was following who was making balsa flying wings. I apologize for my mistake. Your profile pic and similar name threw me off.
I agree with @ThantiK . At a minimum, you’re going to have to support the Y access at both ends, which would be easier to do by reconfiguring into something more like the Plus. You’ll also need a much larger base to keep the machine stable.
I realize I’m a little late on the conversation (if there’s a follow on thread please just send me the link), but have you considered using a acrylic or polycarbonate sheet instead of that mirror? They’re actually pretty resistant to power tools (I’ve used a skill saw on polycarbonate easily and acrylic carefully without them shattering) and much lighter than the mirror. They also have melting points of 311 and 320 degrees Fahrenheit respectively, putting them safely out of range of the extruder head. I’m currently undergoing the same upgrade that you’ve done, so let me know what solutions you decide(d) on and how they went!
