Bulding a larger machine

[nkjh97]

Base trial fit and glueup.

The wood parts were fairly straight forward. i am having a little trouble cutting the threads in the delrin nuts. has anyone tried to use brass and a real tap?

[joecnc2006]

Originally Posted by nkjh97 joe, i learned a lot from your thread. i do have a question. what kind of adjustment or alignment mechanism do you have for your lead screw mounts/drive nuts? thank for looking. Jim

Not sure i know what your question is? the lead screws have no adjustments they are fixed, and held in place with lock nots on both sides of the leadscrew bearing suports. Maybe if you can provide a picture from one of mine and circle it and post or email it to me..

joe@lumenlab.com

[nkjh97]

the ends of the lead screw are fixed and parallel to the gas pipes (hopefully).

when i attach the nut /backlash nut assembly to the gantry, if its too high or low or off to one side, it will put lateral pressure on the lead screw when the nut gets close to the bearing support.

i was wondering if it was necessary to put an adjustment to the nut/backlash nut assembly similar to the 4-point gaspipe support assemblies or just eyeball it until its lined up before mounting. i'll try to find a good picture.

[spalm]

I think you are right to worry about the alignment of the screws. You mentioned that you are using 1/2 inch screw and bearings on both sides, and then coupling the motors. This is very wise. I am dealing with really bad whipping with my unsupported 3/8 rods. I can not imagine the problems others have with 1/4 inch screws.

I believe you can adjust your delrin nuts by over drilling the attachment holes for left to right alignment, and then add shims for vertical alignment. You probably don't need more adjustment than that. To test the fit, slide the carriage back and forth with the screw attached before coupling to the motors and make sure that they line up perfectly with opposite bearing and the motor shaft.

As others said, I'm sitll worried about flex on your free flying pipes.

I'll keep watching,
Steve

[joecnc2006]

Originally Posted by nkjh97 the ends of the lead screw are fixed and parallel to the gas pipes (hopefully). when i attach the nut /backlash nut assembly to the gantry, if its too high or low or off to one side, it will put lateral pressure on the lead screw when the nut gets close to the bearing support. i was wondering if it was necessary to put an adjustment to the nut/backlash nut assembly similar to the 4-point gaspipe support assemblies or just eyeball it until its lined up before mounting. i'll try to find a good picture.

No i have no problem at all with alignment, remember i have mine in solid works so i know the exact alignment placement of the lead screw, and i cut with mach2 at 30ipm with no whipping at all.

[chuckknigh]

I found it was easiest to place the gantry at one extreme end of the machine, and position that end of the leadscrew. Then, turn the leadscrew (I used a cordless drill) till the gantry is at the other end, and position the other end of the leadscrew. This makes sure that there is no binding at either end, due to "tolerances" or anything else.

Just make sure your gantry has no lateral play, before doing this.

-- Chuck Knight

[nkjh97]

Chuck,

thanks i'll try that.

[nkjh97]

adjustment blocks

the partially finished gantry on the base and 1" gas pipe has little flex. i won't see how much until i have the top built and installed. if it does flex, i think sliding a 3/4" gas pipe inside the 1" pipe for extra support will do the trick.

[nkjh97]

gantry nut support stiffened gantry significantly. trial fit couplers.

[mvaughn]

I just purcahsed the same LoveJoy couplers shown in you photos. They should arrive tomorrow, hopefully. Can you tell how much slop there is in them...how do you think they will handle backlash?

[nkjh97]

The literature says the Lovejoy couplers have a 1 degree play. the set screws hold my stepper motor and lead screws pretty tight. the rubber star connector absorbs vibration, but has some play.

i'm using a 10 turn per inch lead screw and sleeve bearings. I'll lose more accuracy in the lead screw bearings and skate bearing assemblies than the couplers.