On Sunday 18 February 2018 18:53:59 Chris Albertson wrote: > Question: What would be the preferred timing belt for a new design? > > Here is the application. I'm making a z-axis control for a Harbor > Freight mini mill (Sieg X2). In this design a 5/8 diameter, 0.200 > pitch ball screw is fixed and the nut spins. The nut is driven by a > timing belt "about" 50 teeth and the motor has an about 25 tooth > pulley. I'm thinking a 400 in/oz. NEMA 23 stepper should work. > Assuming the 2:1 reduction each 1.8 degree step lifts the head 0.0005 > inches. By 1/4 stepping I get 0.000125 per pulse. > > When looking for a good design for the mini mill I was looking for a > good place to put the ball screw. This design places it very close to > the dove tail, almost touching it. Maybe 0.1 inch in front of the > dovetail. The ball screw goes right where the current rack it the > original design. I will have to remove the rack to fit the screw. > > So I need to select a belt type and size. My initial guess at this a > the GT2, 3mm pitch and 9mm wide. > > Some one else used a XL type 3/8 wide and 0.2 pitch but I'm reading > that XL is not the best for new designs as GT2 has a much improved > both profile that eliminates backlash. > > I started to calculate torque and load on the belt then thought "Why > bother?" the actual force is going to be whatever the motor can do as > I'll set the acceleration limits until it start skipping steps then > back up by about 30% or so. I might go with a NEMA 34 1100 in/oz > motor if I need to. So I might choose a belt that can handle whatever > the 1100 in/oz motor can do. Just looking to double check GT2, 3mm > pitch and 9mm wide is reasonable. > > So I guess the best way to ask the question is what kind of belts are > working well with motors in the 400 to 1100 in/oz. range. > > If there is any interest I'm modeling this in Fusion 360. and can > share the CAD files
Its been a while since I did my micromill, but ISTR I used the XL belt and its quite tight. Like you, I spin the nuts, doubled nook bronze ones, and my backlash stays below 3 thou. the screw is in front of the post by about 1/2 the distance between the post and the edge of the gearbox cover, which has been turned 90 degrees to get that clearance. the motor is an 8 wire good for a bit over 300 oz/in. Works well. you can see pix of it on my web page in the sig. The counter springing has been reworked a bit but the rest of the pix are still valid. Not a cad artist, so what you see came straight out of my head, quite a few years ago now. I write my own gcode. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
