Hello Chris, I would love to have ballscrews but I thought I would need to large of a diameter to avoid them to whip. Remember that I have a 3.8 meters in lenght for the longest joint. I've reading about using anti whip guides that move with the gantry and also aply tension in the screw with a nut to improve the work speed and reduce whip but I don't know wich option is better. Also there's the solution of rotating the nut.
Anyway, for such long ways and screws, I need to see if I don't have too much trouble importing them to my country, because of the size of the package. I'll just have to make a call to DHL here in Argentina! Thank you! El jue., 4 oct. 2018 a las 14:58, Chris Albertson (< albertson.ch...@gmail.com>) escribió: > On Thu, Oct 4, 2018 at 5:49 AM Leonardo Marsaglia <ldmarsag...@gmail.com> > wrote: > > > > > > > About the last question. Is there any disadvantage other than may be a > > little more mechanical complexity with the one motor and shaft approach? > > Because I've seen lots of routers driven with two motors that I almost > > think it's mandatory for some reason. > > > > What are the guide rails made of? precision stainless steel or chromed? > They will need to be very high quality and very expensing if you use a > bronze bushing. I think most people are going with HDPE. The friction > is lower and you never need to use lube. that last part mean the rails are > never coat "dust magnets" You can buy HDPE bearing for not much money. > Typically there bearing are not very thick and are pressed into aluminum > housing > > Also they make rails that lay on the table like rail road tracks the seem > like a good way to go and then use round rails in the second axis. or use > these for both. They are inexpensive and you can mount them to aluminum > extrusions of any size. these would be absolutely rigid and you'd not > have to make anything. Like save money too as they don't cost a lot. > > Here is a smaller set, they make them bigger needed > .ebay.com/itm/2-X-SBR12-1000mm-For-CNC-12MM-Supported-Linear-Rail > < > https://www.ebay.com/itm/2-X-SBR12-1000mm-For-CNC-12MM-Supported-Linear-Rail-Shaft-4-Pcs-SBR12UU-Blocks/202160641942?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D52885%26meid%3Db5963b764d384f598e468b383f921b1c%26pid%3D100005%26rk%3D4%26rkt%3D12%26sd%3D401470856046%26itm%3D202160641942&_trksid=p2047675.c100005.m1851 > > > > I know someone who built a large router and, all I can say is the quality > of the rails REALY matters. That is where all the budget needs to go. > The supported ones are nice because you can place shim shock under them > and use a laser to get perfect alignment. > > About rack and pinion. You will need way-expensive rack and pinion set to > reduce backlash. Butter to use a timing belt (with curves tooth profile) > as these have zero backlash and cost less. The other option is ball > screws. Ball screws will out perform racks and cost a lot less and > again bell screws are zero backlash > > User direct drive or timing belt reduction as gear reductions on the motors > have backlash. > > It is assign how much the cost of zero backlash ball drives have fallen. > They are now the lowest cost option for precision linear drive. These > are made mostly for the Chinese domestic market but some are sold on eBay > The Chinese domestic market is HUGE compared to Europe or USA and we can > take advantage of their economy of scale. > For usr use a 12mm diameter screw would work well. Use them at least of > the shorter axis (certainly the axis) here is an example. I have a set of > these. The bearing are hold in compression so there is zero backlash and > they measure "perfect" at least according to a dial indictor. > > With these ball screws nd a pair of the rial mounted guedes you can mill > mild steel and certainly aluminum and have resolution at better them 0.001 > inch. Use normal stepper motor as the systems nearly frictionless. Cost > is very low. Maybe $200 per axis plus the motor for a one meter square > router. It is almost disappointing to use this as there is"nothing to > build" Just some mounting brackets and you are done. > > ebay.com/itm/CNC-Ball-Screw-12mm-SFU1204-w-Ballnut- > < > https://www.ebay.com/itm/CNC-Ball-Screw-12mm-SFU1204-w-Ballnut-BF-BK10-End-Support-L-250mm-1500mm/173060231282?hash=item284b319072:m:mg4uq51qVvrK8RmcksDoOUg > > > > > > > > > Thanks again! > > > > Leonardo > > > > > > > > > > > > > > > > > > El jue., 4 oct. 2018 a las 0:03, Gregg Eshelman via Emc-users (< > > emc-users@lists.sourceforge.net>) escribió: > > > > > The easiest method is mechanically connect the two sides with a shaft > > > along the gantry and use one motor. Then it *cannot rack* or have any > of > > > the other issues that can happen with driving both sides of a > constrained > > > axis with two motors. > > > If you need more Z height, you can elevate the racks on the sides. Or > run > > > chains or belts from the cross shaft ends down to stub shafts with the > > > pinion gears. > > > > > > On Wednesday, October 3, 2018, 4:03:48 AM MDT, Leonardo Marsaglia < > > > ldmarsag...@gmail.com> wrote: > > > > > > Hello to all! > > > <clip> > > > > > > About how to drive both Y joints as one axis: I've read that there's a > > way > > > of simply adding two Y joints for the Y axis in the 2.8 master branch > > but I > > > don't know if there's documentation available already. > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
