Solved Robo 3D R1 Z-Axis home is way off

Hello and thanks for any help. I work at an elementary school. Their 3D printer had been working for a few years. Lately the extruder had been clogged and before I could come to fix it one of the teachers had unclogged it. since then we have had trouble printing with it. At first the alignment of the bed seemed to be off as it printed further back than expected. It also had trouble about 10 min. into a print where the plastic wouldn't stick anymore and it would turn into a big ball of wirey plastic. By the time I was looking at it, parts of the first layer of the print wouldn't stick to the bed which led to problems. After a night I was trying to work on it today and now the Z-axis seems way off. It says it's at 0 when it's about 3 inches off the bed. I'm not sure how to reset the 0, but playing around with the settings I was able to set different points as the 0. However when I start to print and it looks like it's doing a calibration where it touches the bed in 9 spots it raises the extruder each time, and when it starts to try to print it's 3 inches off the bed which of course doesn't work. I'm thinking if I can tell the machine where the 0 point really is it might fix the problem but I'll take any help and suggestions I can get. Thank you!

 

Thank you for the advice. I don't know what the z switches are so I will watch the tutorial Mark provided and post my results.

 

I just had to sort this out myself recently. The video is super helpful; definitely watch it. This attached picture shows one of my z-switches (little yellow tab) not engaging at all because the black piece above it isn't seated over the nut.

 

Here is an update:

I did find the little Z-Switch was off and by twisting the bar it was on I got it leveled out and working.