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Re: What is my problem here?

Posted: Mon Sep 09, 2013 5:48 pm
by morrows_end
I added another motor to my Y axis to support my gantry on both sides and fixed up my slipping Z-axis and took all your advice and got something that worked (kinda).

https://dl.dropboxusercontent.com/u/640 ... on_877.png

If you look at the top right pads, you can see an issue there, as well as the bottom right-most trace. They are both 45 degree cuts and for some reason all of my 45degree cuts to the top right are very thin. In my design all the traces are 0.024" so I am not sure why the width varies for horizontal, vertical and 45 degree length traces. The 45 degree cuts going towards the upper left look great so I can't figure where my problem is.

I used autoleveller.co.uk and set my mill up for -0.005906" (about 0.015mm) deep traces. I instantly broke my 30 degree engraver bit (feedrate too high maybe? it was 20in/min with a 6kRPM spindle) so I cut board this with my 60 degree engraver.

I think I will switch to mm for everything though since that's what I am used to. I just got in some 0.5mm endmill bits from china. I'll have to test them later.

Any suggestions about my variable trace widths?

Re: What is my problem here?

Posted: Mon Sep 09, 2013 9:06 pm
by cvoinescu
If that's a single pass, maybe your board has slipped a little and moved. If it's not, it could well be backlash. Check for the obvious things (tight bolts, tight belts, sturdy belt anchors), but one thing that's easy to miss and could cause exactly that effect is the belt pulley not being tight on the shaft.

Re: What is my problem here?

Posted: Thu Sep 12, 2013 12:12 am
by morrows_end
I thought I had posted this update, but I kinda got something working:

I added another motor to my Y axis to support my gantry on both sides and fixed
up my slipping Z-axis and took all your advice and got something that worked
(kinda).

https://dl.dropboxusercontent.com/u/640 ... on_877.png

If you look at the top right pad, you can see an issue there, as well as the
bottom right-most trace. They are both 45 degree cuts and for some reason all
of my 45degree cuts are very thin. In my design all the traces are 0.024" so I
am not sure why the width varies for horizontal, vertical and 45 degree length
traces. The 45 degree cuts going towards the upper left look great so I can't
figure where my problem is.

I used autoleveller.co.uk and set my mill up for -0.005906" (about 0.015mm)
traces I instantly broke my 30 degree engraver bit (feedrate too high maybe? it
was 20in/min with a 6kRPM spindle) so I cut board this with my 60 degree
engraver.

I think I will switch to mm for everything though since that's what I am used
to.


Any ideas why I am getting weird 45 degree errors? A couple of people said I have a backlash problem at the PCB-GCODE forum, but I don't know how I might fix that on my e-like-ShapeOko.

My setup: Nema 23 Z axis, dual Nema 17 Y axis.

Re: What is my problem here?

Posted: Thu Sep 12, 2013 1:33 am
by WillAdams
What is your belt tension like? I had similar difficulties before I replaced my anchors and tightened them more than I could w/ the mending brackets.

Re: What is my problem here?

Posted: Thu Sep 12, 2013 4:10 pm
by morrows_end
My Belts are held in place with 2 zip ties, and are pretty tight. They only deflect about 1cm when I place the weight of my entire hand on them and they are uniformly so. When I put them on, I checked to make sure they weren't too tight. If they are too tight it didn't seem to move at all. This was as tight as I could get without making them too tight.

Both motors on the gantry are the exact same NEMA 17s. I'm driving them form the same output of my stepper drriver (one is reversed) and I've upped the current on that output of my stepper driver by 2xs so it is almost maxed out. I do have an A axis open which I had hoped to use for a 3d Printer extruder, but I can try moving one of my Y axis motors to it and try to figure out how to make linuxCNC drive Y and A together. That will give me up to 3A per motor (which is too much for my motors: Here are my NEMA 17s http://www.pololu.com/catalog/product/1200 which are on my X and Y axes)

My driver board is the HobbyCNCPro, which can output 3A per phase maximum. Right not I have it set so my single NEMA17 on my X outputs 1.0A, and my double NEMA 17s on my Y outputs 2.0A.

My Z axis has a nema23 on it. I may replace my Y with a couple of these, but they require 2.3A per phase and 2 would overload my driver board.
http://www.alltronics.com/cgi-bin/categ ... tem=25M002

Re: What is my problem here?

Posted: Sat Sep 14, 2013 12:04 am
by calica
Having two steppers on one driver splits the current between them. Your driver has enough current capacity to drive both (2 * 1.2A < 3A) but keep it in mind while adjusting the driver. The two stepper won't split the current evenly because of individual variation so be a little conservative.

Having two drivers for one axis is simple on LinuxCNC. In the stepper config wizard, just select the Y step and Y dir for the parallel port pins. It WON'T work when testing the axis in the wizard but will generate the proper .hal files and work in LinuxCNC itself. At least it didn't in my old 2.4 setup. Haven't tried latest 2.5. Or learn how to do HAL config manually. It is worth the effort. Post questions and I can help.