Accuracy of printer

Hello all, I am creating a part. Basically a washer and it came out smaller then designed.

I designed it with an inner diameter of 19.2 mm and it came out 18.2 mm
then I created a new one with a diameter of 20.2 mm and it came out 19.2 mm.

is that what I should expect for accuracy of the printer ?
or could this be something in my print settings that is causing it to be off 1 mm ?

thanks for your help
John

 

Thanks for the help Harry. I think i understand the concept. Where do you edit the Goode ?
Do you do that in the repeater software? Where do you find that value?

Thank you
John

 

You are right i was not off exactly 1 mm on both prints it was close but not exactly the same .
So i did a test box with different x y z lengths and measured them. They were all off 0.98% from the drawing.
Not sure if this is due to shrinkage or not.
Hate to mess with the firmware my prints are coming out great otherwise !!!
Oh I am using PLA.

Thanks
John

 

Have you calibrated your extruder? and or calibrated your extrusion rate multiplier if using slic3er.

editing step per mm only goes so far. If your extruder is extruding 10mm into free air when you tell it to extrude 10mm. Then your steps per mm are correct. (tip: you have to remove the hot end to do this so you can measure how much filament is being feed through)

next step would be to calibrate the extruder and adjust your extrusion rate multiplier. (with the hot end attached and up to printing temp)

 

Why bother printing calibration models ? They take time and filament.
Why cant you just move your axis and measure how far it went ?
Just wondering.

 

How would you measure your axis and determine how far it went? Printing calibration objects tell you lots of things about the printer, not just if you're spot on in size. They can tell you how well your printer is bridging or how badly it strings. It can tell you if you need to adjust your temperature up or down to deal with a specific problem, or give you a hint of where you may have a problem before it happens.

Trying to use a caliper on your printer by measuring the axis movement is difficult. The registration marks you'd use to measure before and after may have slop in it. Measuring a calibration object is significantly easier and filament isn't necessarily an arm and a leg. Calibration objects are typically only pennies to print.

 

Here is how i checked mine.

 

I'd recommend the procedure described here to figure out the right numbers:
http://www.thingiverse.com/thing:53668
You can use these as starting numbers: http://forums.robo3dprinter.com/index.php?threads/upgraded-to-metric-rods.1525/#post-10585
I think it was Leon who figured out that the x and y axis have wrong values in the firmware, and figured that, if you do the math, x and y should be set to 80. As I changed my z-rods to metric, you can start at around 2200 for Z instead of 2500-ish as per my post.

 

hrm. I like it. Though it doesn't give you information on how the print will do.