Steps/mm  

Re: Steps/mm

nickel test? I have just shown a print I made on my Prusa I3 that had push fitted parts, my BB7.5 shown with pics of prints made. Across I admit now 4 different printers. They pushed together perfectly. The core body was printed on my Prusa I3. I own six different 3D printers, I spread the workload and print quicker with my projects in my small workshop. Only 4 used, the green body inserts on my Fabrikator Large, the grey parts on my Prusa I3 , the caps on my Kossel Mini. The black parts on printer 4, black, loaded of my Fabrikator mini 🙂

Oops printer 5, BB 7.5 head printed on my Ultimaker 2+ Another oops and edit, the common denominator between the printers was Simplify3d

My main requests are from my grandkids and Son in Law, all Star Wars fans.

Re: Steps/mm

Hi Kevin,

To change the steps/mm in the firmware, it will require you to get the source from github and recompile it with the changes. There is a good tutorial on doing that in this thread http://shop.prusa3d.com/forum/software-f13/firmware-compiling-help-what-is-the-exact-process--t861.html Be warned, it's not a job for the beginner as you can damage your printer if things go wrong.

Probably a better alternative is to use the M92 Gcode command to temporarily overwrite the default settings and add it to the "Starting G-Code" section of your printer profile. This G-code will then be inserted at the beginning of every file you slice which is almost as good as having it directly in the firmware. You can see the M92 command is already included in the starting sequence of the Slic3r profile Prusa Research provides.

M201 X1000 Y1000 E600
M109 S[first_layer_temperature]
M92 E161.3
G28
G92 E0.0
G1 X8.0 F2000
G1 Y60.0 E4.0 F1000.0
G1 Y100.0 E8.5 F1000.0
G92 E0.0

They are using it to adjust the extruder rates, and you could simply add an appropriate M92 with X and Y adjustments you need as well.

Here is the description for the M92 G-code command from the RepRap Wiki.

M92: Set axis_steps_per_unit
Parameters
Xnnn Steps per unit for the X drive
Ynnn Steps per unit for the Y drive
Znnn Steps per unit for the Z drive
Ennn Steps per unit for the extruder drive(s)
Examples
M92 X87.489 Y87.489 Z87.489
M92 E420:420
Allows programming of steps per unit (usually mm) for motor drives. These values are reset to firmware defaults on power on, unless saved to EEPROM if available (M500 in Marlin) or in the configuration file (config.g in RepRapFirmware). Very useful for calibration.

Good luck!

Roger

Re: Steps/mm

Oh, one more thing.... You mentioned the nickle test and I have learned that the slicer also can make a difference with how it handles circles and interlocking parts.

I printed a new spool holder for my printer from Thingiverse which had a hub made of two halves that slipped together with interlocking tabs. I was using Slic3r when I printed it the first time and the inner radius of the part ended up a little too small and the outer were a little too big. Needless to say, the parts didn't slide together as they should. There was also a recessed hole for a M5 nut that was about half a mm too small.

I started printing calibration cubes to try and figure out why things didn't fit and found the cubes printed exactly at the proper dimensions. At that point I wasn't sure what to adjust, but knew I didn't really want to go back and have to modify the STL file to compensate only for the circular portions.

I had been thinking about buying Simplify3D based on a bunch of favorable reviews, so I went ahead and did it. I used the same original STL file that I had used previously, and the profile settings found elsewhere here in the forum, and reprinted the hub parts. This time they slipped together as smooth as silk, and that 8mm hex hole for the M5 nut was the perfect size.

It may not necessarily be the steps/mm are off on your printer, but the algorithm the slicer uses to try and deal with circles and arcs.