Print 3D

Edit:10 nov. 2019, Cre:22 août 2015

Fisher Reinforcment

The acrylic panels are not quite stable, they tend to bend and warp.
I had the corners slipping on the rods, as yet on the Fisher Beta the locking system is not done by pinching the rods but only by having the nuts pushed against the rod.
As the support slide on the rods, that compress the panels which buckles.
I had to reset from time to time the panels in place and my nuts were beginning to became loose, so I was in need of a more definitive solution and I reinforced the side panels with wood laths.

The wood laths are pine wood or equivalent 5×30. This is a modest section, but the stiffness added is really significant and the machine is now completely stable.
This is fairly less classy than the polycarbonate reinforcment done by another member (in this forum topic), but it is low cost and simple. The paintjob could be better, also, but that was paint I had at hand.

You shall note something very important to avoid clearance problems, the ‘knots’ of the zip-tie shall be OUTSIDE.

To clear the carriage, I added thick cardboard (~2mm) made of old calendar.

You shall drill all the lath ensemble (the stack is only 30 mm) on a press drill, in order to have good accuracy. Dimensions are better taken from the DXF files than direct measurement.

This reinforcment allow something important: a proper belt tensioning.
good belt tensioning may give better accuracy to your printer, but the most important point is that increase the belt stiffness and improve significantly the calibration. With proper belt tension, the difference in Z-offset between the center and the side of the bed became less than 0.05mm. You shall not overtigthen the belts, as it may creates friction and you can loose steps. Your carriages shall still move freely on the rods.

That aggravates the problem of stability experienced on the idler carriages. Being supported by the bolt head below the load point, the idler carriages tend to flip sideways and the belt rub on the idler carriage. Also, this side displacment tend to aggravate the bending moment and increase the flip. One forum member have installed 4 screws (see this topic, which is a clever solution, but I don’t think he had given the stl file of the modified supports.
What I have done is simply enlarge and increase the height of the idler carriage in order to have a very tight fit in the support and maintain the carriage straight. The height increase is for reinforcment.
Also, due to higher tension, I have broken all the idler carriage, that I recommend to print in PETG or ABS instead of PLA.

Find the STL file, and the somewhat barbarian Openscad module I write to build it (you may modify the scale to fit your own support) is below:

//RepRapPro Fisher larger and higher idler carriage
scale([1,1.07,1]) { // enlarged
  translate ([0,-8.5,0])  {  
    translate ([0,0,1.5]) // stack to increase height
translate ([0,-8.5,1.5]) // re-stack for good idler width 
translate ([0,-8.5,0]) // re-stack for good nut width 
//cube ([2,18.2,2]); // width check
(c) Pierre ROUZEAU
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