My turn at a Jgro build

[silentreaper]

I found this site by way of Joe2000 mentioning it at another site. So when I checked it out it became abundantly clear that it was time I built a CNC Router of my own (I had worked in a machine shop with a wide range of CNC mills and lathes (Mori Sieki, Toyoda, Leblod Makino, Okuma, Mazak) as mill setup for 8 years untill...well thats another story), but time and financial constraints prevented me from building anything but the exact Jgro design.

So anyway here are a few pics the first 2 pics are self explanatory, the 3rd is the control board case (top) and the Mach3 pc (bottom), the 4th pic is the 15" touchscreen lcd that I am using with the flash screenset so it will scale to the monitor size.

The control board is a Xylotex 3 axis board with 425oz motors.

The machine was built to the Jgro design almost to a tee that includes the 1/4-20 threaded rod as the lead screws (insufficient funding was available to go with 1/2-8 2 start which will be the first real mod when funding allows), but a few small mods have been done (not even worth mentioning).

But here is the problem I am having (fifth pic), I am trying as my first cut to cut new router brackets, but as you can see I am either losing steps or something else is wrong.

I thought maybe backlash (real bad backlash) but I snugged all the anti-backlash assemblies up and it still does this (shifts on the x .125" and y .125" but not around the whole part as you can see in the pic the angle on the right side shows no real change only the bottom left and top.

Can anyone take a stab in the dark at what is wrong?

Thanks,

Reaper

[tajord]

hey silentreaper,

this one is a puzzler for me, from the looks of it, seems you are consistently losing steps or the mdf you routed wasn't clamped securely, other than that i really don't know, maybe one of the more experienced guys can offer more input than i.

neat looking build though, good luck.

[silentreaper]

Thanks

Yeah I am puzzled too. I can't get very fast feeds or rapids with the 1/4-20's, so I might just have to slow it down some more and find out, but if I do that I am worried about burning up the only bit I have at the moment.


OK I'm not sure yet of exactly what losing steps really is, so is it just your mesurements would be short or what, if I run my velocity up to high it sounds like the it binds up, is that the way steppers should sound, if I go to 1/4 or half step and can run higher velocity before the binding sound but the way I understand it I would lose resolution correct?

Wait a minute I said [QUOTE=silentreaper;301388](shifts on the x .125" and y .125" but not around the whole part as you can see in the pic the angle on the right side shows no real change only the bottom left and top./QUOTE]

I just though of something the right side is also shifting, but because of the X and Y shifting and the right side being a mirror basically of the left and being the edge of the part you don't notice it as bad.

[tajord]

tell me something, under Config/Motor Tuning, do you have the steps per units for all axiis set the same? Don't know if this'll help, just trying to seek out logical options, give it a check, who knows.

[silentreaper]

Originally Posted by tajord tell me something, under Config/Motor Tuning, do you have the steps per units for all axiis set the same? Don't know if this'll help, just trying to seek out logical options, give it a check, who knows.

Yeah there all set the same

[tajord]

ok this might be a little more than i know "for now", come on guys, chip in here

[Jason Marsha]

How fast are you running the machine?


Jason

[silentreaper]

Originally Posted by Jason Marsha How fast are you running the machine? Jason

velocity is set to 10 and in the program I have the feed set to 10

Maybe thats a problem as this is the first time trying a DIY machine, all thers I have worked on were manufactured machines

[Jason Marsha]

What about acceleration?

[silentreaper]

Right now it is set to 4, I am certain I have no idea what this is for but when testing the machine to make sure it moved I know I don't want 0 in there.

[silentreaper]

OK a little more info right here, the g-code was generated from a dxf that I made in autocad 2007, and generated with lazycam. In lazy cam for this part cut depth is set to -.800 and pass depth is set to -.050.

Maybe some of this info will help my situation.

[Jason Marsha]

It could be a combo of flex, lost steps and a dull bit. Check that all the axis runners are tight against the pipes.

Jason