Rob, I have a machine with 2 motors on the y axis. This is how I home both motors together... I have a positive adjustable stop on both ends. This is a bolt with lock nuts. When both ends of the axis are on these stops the machine is aligned and in what I refer to as the "Hard y zero". To get the motors coordinated I either crash the motors into the stops at slow jogging speed until both motors stall then do a normal home (I have a home switch on one end). Or, I manually turn the screws until they are on the stops with the power to the motors off then back off and and home with the motors on. My machine's motors are not strong enough to hurt the machine when they run into the stops so I usually just crash the axis then home... Oh ya, stepper motors...
This method is brutal but effective. Clint B Quote from Emc-users Digest,Vol23,Issue 38: Message: 3 Date: Thu, 13 Mar 2008 07:51:11 +0100 From: Rob Jansen <[EMAIL PROTECTED]> Subject: Re: [Emc-users] Homing using 2 motors per axis To: "Enhanced Machine Controller (EMC)" <[email protected]> Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="utf-8" Rayh, the whole gauntry acts as a swivel :-} It's all made of aluminium sheet 15 mm thick, 30 cm wide and 70 cm height with two 80x80 beams of 122 cm long. If I remove one of the ball screws I can move that side a few centimeters without applying too much force. I thought of adding a timing belt like Dennis mentioned but was afraid there is too much elasticity in such a long belt (when using two motors). When switching on the power supply to the motors both stepper motors will switch to a full step so one motor may move clockwise while the other goes ccw, one full step means 5 mm (pitch of ball screw) / 200 (steps/rev) = 0.025 mm difference. This does not seem too much so maybe I should not worry too much about this and just measure the difference between both sides from time to time. There never is a problem during operation of the machine - at least not after setting up the stepper timing correctly. Meanwhile I decided to leave it as it is, there are enough tother things I have to do before the machine is 'finished' - unless of course someone has a complete canned solution that I could use. My next machine will most likely use just one motor with a belt drive to two ball screws but I have to look at the specs for the timing belts first to see if this will give me the accuracy wanted. Regards, Rob [EMAIL PROTECTED] wrote: > > > > Hi Rob > > > > I've been curious about these dual drive axes for quite a while now. > > There are several possible mechanical lashups with something like > > this. It seems to me that in order to allow separate homing of each > > drive, there would have to be a swivel on one side or the other of the > > mechanical slide. Is that the case with your machine? > > > > Rayh > > > > - ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
