On Tuesday 07 July 2009, Peter Cauchy wrote: >Thanks for the replies, > >Part of the issue is I do not have the mill completely square, and it >was cutting without stuttering, but I was tightening the tolerances and >started losing steps due to friction.
That is often something that can be helped with the right lube, and its been recommended to use a Mobil product called Vectron (IIRC) for that. Unforch it only comes in 5 gallon pails, which would be several of my remaining lifetimes worth, so I have not obtained any of it, yet. >Gene, > >my driver is a CMD-50c which can handle 15-40v, and 3.5 amps, but I do >not have access to anything above the 19v I currently have. A fairly common surplus (from M.P.Jones maybe?) 25.2 volt transformer feeding a full wave bridge should give around 35 volts assuming a sufficient sized filter capacitor. How much current do the motors say they need? Multiply that by the number of motors to get the total current you need. Then you know how big a transformer you need (they can be paralleled for more amperage) and how much current the FW bridge needs to be rated at or above. Generally speaking, these drivers won't be happy when running on a regulated supply, because the stepper motors can also send power back to the supply, and regulated ones don't absorb this back current at all well & may even shut down. So its best to just have a large (2200 uf or more) capacitor as the filter that can absorb these surges without actually running the voltage above the drivers ratings even for a microsecond. I built mine from the remains of an old 2" video recorder, one of the half ton models and it had a pair of 75,000 uf caps, but that is extreme overkill. If you have a 30" x table, that is going to need the biggest Nema 23 motors, Jeff at xylotex has some nice ones that can make 400 oz or more, or even a Nema 34. I have a Nema 23 rated at 425 oz on my Z axis, 10 tpi acme screw, with a 17/42 gilmer belt type stepdown rigging between motor and screw, and at 2.5 amps, I can put 155 pounds of down force on a drill bit to drill a hole. My X/Y motors are smaller 225 oz versions, direct coupled to the micromills 20 tpi acme screws, and they can break a 1/4" solid carbide mill in a heartbeat if the spindle stalls, so that should give you an idea of what it takes to at least get started. >Thanks for everything, it looks like I will be looking for other motors. >The z-axis is 4 in and works alright, but the y-axis at 14 inches is >underpowered, and the x-axis at 30 inches hardly moves without stuttering. I can see why, although those motors could probably move it at 3 or 4 ipm at that voltage, they may stall when actually cutting. The z probably doesn't have what it takes to drill a hole in ferrous material. >Chris, > >I did change the step output to be inverted as you suggested, and no >noticeable change in speed. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> Be careful how you get yourself involved with persons or situations that can't bear inspection. ------------------------------------------------------------------------------ Enter the BlackBerry Developer Challenge This is your chance to win up to $100,000 in prizes! For a limited time, vendors submitting new applications to BlackBerry App World(TM) will have the opportunity to enter the BlackBerry Developer Challenge. See full prize details at: http://p.sf.net/sfu/Challenge _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
