new build opinions required

[george uk]

Hi

Though here is what i think of it in my case, may be concerning this build also:

i agree with what your saying here, am thinking i may cog and belt the 2 ballscrews together, to stop any small chance of them going out of alignment. Or, go back to using one motor to drive both ballscrews.

I still don't like that design of yours, but that shouldn't discourage you :-)

Dont worry me, i prefare people to be direct and to the point. and getting something wrong is not failing, its a leaning step on the way to success.

I don't know if i am understanding you wrong. But:RP is far more wear prone than ball screw.

I was thinking aloud, i am going with ballscrew,

You can not bend with steppers a properly constructed machine.

.

I have seen this happen, Nema23 on z, Z bocx mounted forward like you pictured. Z down gave it enough leaver, that when his limit switch failed, put a slight bend in a very well constructed Y gantry, both the mounting rails and ballscrew had a noticable movment when passing the point were it had bent.

He was very ham fisted with his limit switches, hence it failed, but it did bend it, i will have a go at doing the math tonight again,

IMHO the weakest points in order of a DIY machine FYI:
1. Router bit - deflection
2. Z overhang-plate twist
3. Gantry twist and bend ,
4. Gantry sides
5. bearings/assuming you use square
6.Spindle power
7. Balscrew support bearings, spindle bearings
8...etc

Wen i consider the list of week points, i think of it more the order i would want it to break if it does go wrong. I need to put my design is sketchup so you can see it,

am thinking ( but will acsept that am wrong, ), is that No 1 should be the baring mount screws or the baring, I think you will understand when you see my X design.

[Boyan Silyavski]

Hi



.

I have seen this happen, Nema23 on z, Z bocx mounted forward like you pictured. Z down gave it enough leaver, that when his limit switch failed, put a slight bend in a very well constructed Y gantry, both the mounting rails and ballscrew had a noticable movment when passing the point were it had bent.

He was very ham fisted with his limit switches, hence it failed, but it did bend it, i will have a go at doing the math tonight again,

Thats why i insist that only 2 possible models of homing and limit switches should exist, no other variation trade-offs, like the ones popularized by Mach3 in fact:

1. Small hobby machines with weak motors and more or less rigid / like mine current one/ - no limit switches, instead software limits . Mistake, axis go to end , motor stalls and nothing happens. Probably limits only on Z, as there could be a problem with flimsier ones/ like mine :-)/ Its typical situation where the BOB has limited I/O.

2.BOB with a lot of I/O and homing and limit on for each axis on SEPARATE I/O, so a limit switch is a limit switch, nothing else. Thats what i intend to do and advice you for your build, this with my limited knowledge. And if servos, the limit switches directly to the servos, not the BOB, i don't see a reason why the servo should wait for the BOB to tell him to stop. Cause with servo, a lot could happen in a very short time if geared and running fast. It seems most of the servos i looked at support it, so they stop and later they tell the BOB that they are not moving .