BenJackson wrote:You can always "join" them by connecting loops by a shaft with two pulleys. You could connect the two sides front-to-back and the two back rails to each other and the motor, for example.
Yes, when I started on this project, that was one of the options - in fact, I have about three A3 sheets with various flavours of this idea
It's probably one of the better ideas as it cuts down on long belt lengths, but trying to get four belts tight without putting idlers on them becomes painful - not to mention all the mounts/brackets/pulleys
I also have some ideas with counterbalances to hold the table up (using shafts) and then just pull the table down.
I spent the best part of this morning again looking at the chain problem. I tested a piece of chain on its own in 'vertical mode' - it was just garbage - either the sprockets are badly sized or the 6mm 04B chain is - the chain would jump as the sprocket teeth entered the space between. I've decided to give up on the chain - I'll punt it to some fighting robot guy
It's not as if the chain and sprockets were cheap either !
Moving on from this, I double checked the 'friction' on each of the four Z leadscrews - they are all very easy to rotate, so a good belt would definitely work.
I made a concerted attempt to look at different belt styles and options but couldn't get anything at 2980mm. However, I actually found a UK company that can supply joined PU belting ...
http://www.beltingonline.com/polyuretha ... elting-38/Surprisingly, the belt is CHEAPER than the flipping chain !!!! Why didn't I see this before
It does say that the strength of the belt is approx half of a contiguous belt 'though. Swapping out a set of sprockets for a set of pulleys and swapping the chain for a belt is an easy out for now - it might even work
I don't suppose anyone has any experience of 'joined' belts ?
BenJackson wrote:There's no burn problem on the bottom because once you go through the focus lens the beam converges at the focal distance and then diverges after. Before the final lens you can burn things with the laser from quite a ways away. I measure about 3 focal lengths below the focal point on the 2.x laser, so the beam has 3x the diameter of the original beam or 1/9th the power density of the original beam.
I do think you want a cleanable surface on the bottom: I cut some plywood with terrible smelling glue and the smell lingered until I wiped down the bottom skin.
Had it been my turn for the family brain cell that day, it might have occurred to me that the beam power density would be appreciably smaller at the distance of my bottom sheet
- thanks for that - seems that brain cell volume is inversely proportional to age
I have some 7.5mm laminated plywood - called 'waterboard' I think (has a real formica skin on each side) - they use it for shower cubicles etc - I think that will be ideal - easy wipe etc.
Cheers
Neil