forum.cncdrive.com

Hi guys, back with a new problem. I have run into a strange problem in that I am getting incorrect dimensions after milling. I've added a couple of pictures to show. the boxes should be 50mm outer width and 40mm leaving a 5mm pocketed area and clearly they are not. The circle and ring should be 10mm and 15mm diameter but they are 14mm and 21mm. Pocketed area on the ring should be 5mm, it's about 3mm. Depth is also out, the ring should be 2mm deep but it is 3mm. The circle should be 4mm but is 6mm. The strange thing is I also did a contour cut with tabs (not pictured) and the tab height is actually correct. The other strange thing is I had recently changed back to windows 7 and reinstalled all associated software but before this I had no problem with dimensions. The problem is consistent though as I cut 4 rectangle pieces and they are all exactly the same, wrong size as per drawing but no discrepancy between them. The alloy ring pictured was cut prior to the reinstall and is accurate per drawing. I noticed the Z dimension when cutting was correct, which could indicate a tool length error input from me but the fact that I was using the same tool from the library from previous successful cuts rules this out. I have absolutely no idea what is going on nor where to start to fix. Any help is greatly appreciated. Posted on the stepcraft and autodesk forums as well to broaden my chances of getting this solved.

Links to pics
http://forums.autodesk.com/autodesk/att ... G_2181.JPG
http://forums.autodesk.com/autodesk/att ... G_2185.JPG
http://forums.autodesk.com/autodesk/att ... G_2189.JPG
http://forums.autodesk.com/autodesk/att ... G_2189.JPG
http://forums.autodesk.com/autodesk/att ... G_2190.JPG
http://forums.autodesk.com/autodesk/att ... G_2187.JPG

posts

Pocketed area on the ring should be 5mm, it's about 3mm. Depth is also out, the ring should be 2mm deep but it is 3mm. The circle should be 4mm but is 6mm.

Since you're using a 2mm tool, this would lead me to believe that this is an issue with your g-code. I can't check to be sure until later tonight, though.

In my opinion the issue is probably wrong steps per units value setting for the axis.

On your picture you measured the circle and the pocket I've noticed that both are about 1.5 times large 75mm vs. 50mm and 6mm vs. 4mm.
If everything is larger with the same ratio then your steps per units are setup incorrectly. For example if you cut a 50mm pocket and it gets 75mm and if you can a 100mm pocket and it gets 150mm.

I advice you to verify the steps per units settings with simple movements.
Move your axes to a known point, e.g. where you can mark the axis position.
Zero the axis and then move the axis to a known distance, e.g. 50mm with commanding a G0 X50.
Measure the distance between the start point and the end point on the X axis in this example.
And it should be 50mm with this example, but ofcourse you can program any distances to measure, so you can get an idea if it is a dimensions ratio and therefor steps per units settings problem.

If it is not a problem with the dimensions ratio as described above then it will be CAM related and then create some simple objects in your CAM software,
e.g. a line, a simple rectange. Place them to a known point, e.g. to 0,0 and check if the generated g-code shows the correct distances or not.

Hey guys thanks for the replies, Gerry yes I wondered about the code but while I can understand some of it I'm still learning so unsure exactly how to diagnose it, I use that 2 mm cutter the most and it is what I used to cut the alloy ring and had no problems with that, which was prior to me reinstalling everything so not sure what has happened, as the same settings I used in that CAM setup I used on the mdf. I will try the your suggestion cncdrive with the axes measurement tomorrow and report back.

Ohh, I almost forgot that there is also an automatic calibration of the axis steps per value, you can use that also to verify and tune the steps per units.
It basicly runs the same function as I described in my previous post. You type in a distance to move and the axis moves that distance,
then you can measure the moved distance, type it back to the calibration screen and the UCCNC calculates the proper steps per unit based on the measured value.

You can run the calibration with the pressing the Calibrate button on the Configuration/Axis step and on the axis page.

cncdrive wrote:Ohh, I almost forgot that there is also an automatic calibration of the axis steps per value, you can use that also to verify and tune the steps per units.
It basically runs the same function as I described in my previous post. You type in a distance to move and the axis moves that distance,
then you can measure the moved distance, type it back to the calibration screen and the UCCNC calculates the proper steps per unit based on the measured value.

You can run the calibration with the pressing the Calibrate button on the Configuration/Axis step and on the axis page.

Just saw this post now thanks cncdrive although I had already done the measurement test before checking here and haven't tried the calibration yet, but the results show that something isn't right, while moving 30mm in uccnc actual movement on the machine was 45mm, so its obvious its not right. I will try the calibration tomorrow but I know the steps per unit were set at 200 so I figure I need to change this setting.

Ok problem sorted, after running the calibration as suggested the issue was with the steps and it was at 200 and it should be 133.33. After digging deeper it seems the earlier version 1 stepcraft machines were at 200 steps and I suspect my stepcraft profile for uccnc was for the older version and when I was given a replacement stepcraft profile from cncdrive it was for the older stepcraft v1 machines. Everything is machining accurate now apart from a possible alignment issue but I will deal with that another day, so all is well that ends well. Thanks again cncdrive for the support and a happy new year to all.

Good to hear you sorted it out, but I did not give any profiles, what I gave you was the latest screenset installer for the Stepcraft machines and that contains the profiles for both the V1 and V2 machines, there are profiles in the installer for all of their machines. You can select which profile you want to install, probably you selected the wrong profile...

cncdrive wrote:Good to hear you sorted it out, but I did not give any profiles, what I gave you was the latest screenset installer for the Stepcraft machines and that contains the profiles for both the V1 and V2 machines, there are profiles in the installer for all of their machines. You can select which profile you want to install, probably you selected the wrong profile...

I see now, I didn't realise it had both profiles, and yes your exactly right I would have installed the wrong profile, probably should have opened my eyes lol! Thanks again cncdrive, really appreciate it.