Problem with y axis assembly

[steve]

finaly found the time to assemble my prt96 however i have hit a slight snag with the y axis side plates,the angle irons are not 90 degrees and so when i place the stepper motor on the side the teeth on the pinion gear are not sitting flat on the rack they are pitched at a slight angle.my question is should i just shim/pack the top on one side until the side plate is at 90 degees with the rest of the machine? or should I ignore it and leave it at an angle?
thanks for your help

[Mayo]

Make sure you have the roller bearings seated on the rails and not to either side of them. The steel of the Y rails should ride in the center groove of the roller bearing wheel. It's possible you may have adjusted your hold down bearings to the point where they have moved the Y rail bearings off or away from the rails. This would make it appear that the angle iron was not square.

I think it would be pretty unusual for the angle iron steel not to be square. Not impossible, but unusual.

[steve]

thanks for reply mayo, when i used an engineers sqaure on the 3" angle irons they were a full 2mm out of square. Made some 2mm spacers and placed under one end so it pitched the side with motor on to 90 degrees to the table, gears now meshing together nicely.
Hey I am a shopbotter at last!

[edwardmc]

I got the SB. and most is going well. But I have had one thing happen that has me qustining my progress. While assimbling the Y axis carriage the hold-down bearings keep turning sideways when I give them the final tightning. I have redone them several times with the same ending. Is this normal or is it some thing I doing wrong?
All the bearings line up and the carriage moves free with just a littel tension

[kilian@mail.direcpc.com]

I hate to say this but i got mine tight then i taped with a hammer to get them square?

[tim]

I have adjusted many Y cars and the holddowns are a challange. I find that if the chanel nut sets it self in one position it will try to go back to the same place, taking the hold down with it. The hole in the hold down bracket is slightly over sized so if you can slide a finger inside the strut chanel and move the chanel nut so it can grab another position. I have used a C clamp to hold the bracket in place while tighting,but I can hold most of them with my fingers.I must say that a dead-blow hammer is a handy tool when making fine adjustments to hold downs. Good Luck with the rest of your assembly.