MK2 Alignment Sticks
I'm currently working on making some Prusa i3 MK2 alignment sticks. I bought my printer as a complete build, NOT as a kit. When it came, the Y axis was more of a parallelogram than a square. I had to take apart the rear y-axis stage to change the Y-motor mount so I could add a NEMA damper to quieten the printer a bit. I can never seem to get the proper spacing between the front and rear parts of the Y axis and the Z-frame. These Alignment Sticks are my way of making the process easier. I am still missing one dimension; the distance between the Z-frame and the front corner of the Y-axis from a MK2 that is known to be truely perpendicular and square. I did get most of the dimensions I needed from the Y-axis assembly manual and what my own MK2 has for sizes. You'll see that in the STL models.
I recommend printing out 2 sets on 2 separate print runs. Even if your printer isn't square, it should be dimensionally stable enough so that you can print these to get square. Printing these twice vs printing 2 sets on the same run doesn't guarantee that the parts will be the same. I realize that the Z-axis can cause some variation, but it shouldn't be significant.
I printed these with Simplify3D using the following settings different than the MK2 profile settings: 5 top and bottom layers, 3 perimeter shells, 0.2 layer height, 30% infill using Triangular internal fill pattern, Include a solid diaphram every 20 layers, NO supports. I used PLA because I didn't want to worry about any shrinkage issues.
I printed these out and it 12 hours with the above settings. I did notice that I lost 0.3 % in dimensions. I'll be adjusting my models to try and compensate for that unless anyone has any better ideas.
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
Can you tell me what the center to center distance is supposed to be on the Y-axis bearing rods? I measure 169.3 mm in the model with Inventor but 177.80 mm is printed on the part. Maybe something isn't translating correctly when imported into Inventor?
Re: MK2 Alignment Sticks
The center to center distance is 170mm. The 177.80 (which is now corrected) was actually supposed to be 178.00 from the outer edges of the rods 170mm on center + 8mm rod diameter).
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
Thanks for the quick response. One other question i have. What is the small block with the notch in it for?
Re: MK2 Alignment Sticks
The small block is supposed to be a Z-Frame corner foot. I find that I get some oscillations because of the Z-Frame being suspended in midair. They aren't calibrated correctly for the proper spacing. I'm having difficulty finding what the proper spacing is.
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
Ok, i see. If they are just corner feet, what spacing are you referring to?
Re: MK2 Alignment Sticks
The height they are supposed to raise the Z-Frame up from the desk needs to be adjusted. Otherwise, those Z-Frame feet work just fine.
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
The Z-Frame feet are now perfected. I just printed a couple of them and the printer does not rock, nor does it oscillate like it used to.
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
Thanks for the great work on the alignment tools!
Would you consider them complete now? The Z-frame feet don't affect alignment or twisting of the y-frame?
Re: MK2 Alignment Sticks
The Z-Frame feet prop up the Z-Frame by about 2mm. This is enough to help prevent the machine from oscillating. I've had problems with that causing artifacts in the past.
These adapters are probably 90% complete, but unless someone has any better way to design them, I'm not going to touch them.
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
The Z-Frame feet prop up the Z-Frame by about 2mm. This is enough to help prevent the machine from oscillating. I've had problems with that causing artifacts in the past.
These adapters are probably 90% complete, but unless someone has any better way to design them, I'm not going to touch them.
But even with the lift the Y-corners are still sitting flat?
Re: MK2 Alignment Sticks
These alignment sticks are fantastic. Great job.
I was considering trying to go one step further and make a squaring tool that could be used to square the xy bed during assembly. It would be like a speed square: https://en.wikipedia.org/wiki/Speed_square but with two modifications: one leg is longer than the other for placement along the Y axis, and the inside corner is relieved enough to fit around the legs and nuts/bolts. It would be taller in the shorter leg so as to rest against the double X axis rods.
Thoughts? Is that something you'd like to tackle and make far more elegant than I?
Re: MK2 Alignment Sticks
These alignment sticks are fantastic. Great job.
I was considering trying to go one step further and make a squaring tool that could be used to square the xy bed during assembly....Thoughts? Is that something you'd like to tackle and make far more elegant than I?
The conventional way of making sure a rectangle is true is to measure the distances between the diagonally opposite corners and compare them. If the distances are the same then the thing is square.
This method is as old as time and works well so perhaps there is little to be gained from a creating of purpose built square.
Re: MK2 Alignment Sticks
The conventional way of making sure a rectangle is true is to measure the distances between the diagonally opposite corners and compare them. If the distances are the same then the thing is square.
This method is as old as time and works well so perhaps there is little to be gained from a creating of purpose built square.
Boy -- that should be in the Y-axis instructions somewhere. Would have been a great tool to use to confirm my unit was square. As it turned out, mine was - mainly due to many, many different measurements with my micrometer. It has been decades since high school geometry, and I had forgotten all about that simple way to ensure something is square. 😳
Re: MK2 Alignment Sticks
http://www.thingiverse.com/thing:1850161
I integrated your alignment stick into the Y axis block. Work in progress.
Re: MK2 Alignment Sticks
http://www.thingiverse.com/thing:1850161
I integrated your alignment stick into the Y axis block. Work in progress.
This is definitely a better arrangement. The threaded rods can really skew the alignment, even if the top or bottom small rods are not lined up. You do want to keep in mind that the Y-axis belt has to be skewed a bit to the right as you are facing the printer. Maybe you want to integrate the Idler pulley holder and Y-axis motor holder, and Y-motor brace into this too to possibly remove the threaded rods all together?
and an 8 inch (200mm) or greater caliper is recommended.
Re: MK2 Alignment Sticks
Just a notice. Any type of printed alignment gadget should be printed on perfectly calibrated printer. 😉
Re: MK2 Alignment Sticks
http://www.thingiverse.com/thing:1850161
I integrated your alignment stick into the Y axis block. Work in progress.
This is definitely a better arrangement. The threaded rods can really skew the alignment, even if the top or bottom small rods are not lined up. You do want to keep in mind that the Y-axis belt has to be skewed a bit to the right as you are facing the printer. Maybe you want to integrate the Idler pulley holder and Y-axis motor holder, and Y-motor brace into this too to possibly remove the threaded rods all together?
Noted. about the belt not in center, I will print and do a test mount.
As for removing the threaded rod, I am not sure as the 3d print may not handle the load.
Re: MK2 Alignment Sticks
Hi Ya'll,
Any chance of posting the CAD files? I use Solidworks; would love to chip in.
Thanks,
Madhu.