picclock's modified i3 3d printer attempt

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picclock:
Hi All

So having got to the stage where I can print some stuff I thought I would have a go at designing a new X carriage and printing it. It will incorporate a servo for automated bed levelling/calibration, a longer std Lm8Luu for the upper bearing and a std LM8uu for the lower one. I decided to use Designspark Mechanical because it is the right price (free !!) and simple to use - a definite requirement.

As you can see from the pictures I made the rookie mistake of generating an unsupported edge at the bottom which came out straggly. The part shown is still attached to the raft which will break away easily if I decide to use it.

I have also decided to scrap the underperforming heater bed and replace it with an aluminium plate heated with resistors. See next post.

Thanks for your interest

Best Regards

picclock

picclock:
Sadly the above part did not conform to the drawing :scratch:. There appears to be a fixed extrusion error which makes all the parts 0.14mm larger than they should be in the X and Y direction. This is not a scale error, but a fixed addition. So that whether the part is 10 or 30mm long the length will be increased by 0.14mm. This also makes slots or gaps approx 0.28mm smaller. The part was made with ABS, a 0.4mm nozzle (Std E3D V6) and a 0.2mm layer height. I have tried adjusting the extrusion rate (Cura Flow) to 80% but this just seems to create weaker parts, with minimal effect on size change. The positional accuracy of the nozzle is pretty good (X is amazing < 1 thou deviation over 20mm), see attached pdf. So I think its likely that the slicer is not correctly calculating the extrusion bead thickness. I have checked the filament diameter, and its very good, varying between 1.69 and 1.75 mm. I have also checked that the correct amount of filament is being extruded by the firmware, and its spot on.

Any thoughts or ideas or fixes ( :beer:) much appreciated.

Best Regards

picclock

PeterE:
picclock,

I am inclined to go along with the answers in Pete49's thread in that the oversize is due to good accuracy :loco:

What I mean is that your extruder nozzle lays the melt string at the center of the line stated in the program but it flows out a bit on either side then making the part ever so slightly wider than was expected. So like already suggested, try to compensate that by decreasing the important measures according to the overflow to give a detail taht is spot on.

You seem to have very consistent measures so accuracy is really not a problem. It is just necessary to compensate for the true width of the melt string to get items on spot.

One of those parameters to compensate for that was not obvious from the beginning. Oh how much one learns from all these threads.

BR

/Peter

picclock:
Hi PeterE

I'm pretty sure the slicer is supposed to compensate for the extruded bead width. I tried the craftware slicer on one of my test pieces printed with 0.4mm nozzle and 0.2mm layer height as before, and although for some reason it failed to complete the print, when I measured the base it was pretty spot on, 19.99x 20.02 ~ so they clearly got that bit right. It sort of confirms my guess that the slicer is causing the issue.

Think I just need to find the right slicer. Am going to try slice3r, kisslicer, repsnapper, and any others that come to mind, feel free to recommend an alternate.

Best Regards

picclock

PeterE:
I see. I downloaded a copy of Repetier Host as I have heard good things about it, and if I remeber correctly it included the slice3r. A program I also saw mentioned in a copy of 3D make magazine. Supposed to be quite OK to use.

Then about the mis-settings in your current slicer. Could it be that there is a setting possibility to adjust the extruder centerline so it follows the center of the path rather than the outer edge - which is how I get the impression it does from your description. (Odd description but I hope you can follow my thought.)

/Peter

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