Calibration?

[HotRodTractor]

I have recieved my LittleRP Kickstarter printer and have it fully assembled and JUST printed out my first print. YAY!!

Anyway - I printed the calibration target block with the numbers and letters inset into it with the ramp. I measure the length of it and it comes in at 1.108" - if I am right the block is suppose to be 25mm long (1.020") - how do I correct for this? Change the "Build size" in Creation Workshop? I'm searching this forum for a bit more understanding. Thanks!

[HotRodTractor]

Also, any recommendations to help me improve my prints would be very welcome. I assume that since the smaller holes are closed up that means I have bleed through on this resin and I need to drop the cure time a little bit??

[Praesmeodymium]

Yes to both changing the Build area size changes the size of the objects to get the size right

current size / expected size * build area = new build area

My build area in cw started at 102 and my first print measured 29.4mm of the 50 it was supposed to be so 29.4/50 = .588.... Multiply that ratio with the build area .588*102 = 59.976 I then just used the aspect ratio for the other length

There is a line but you are trying to cure as little as possible while maintaining detail. the more you cure in the printer the harder it is to peel, the faster you burn the pdms. So dropping the exposure time a little is likely a good idea, the worst that happens is the print doesn't hold up, and you know you need to raise the exposure up a little.

http://www.littlerp.com/?page_id=55 on this page under "Calibration STL Files" is calibrationgrid.stl the posts should be 50mmx30mm apart when measured with calipers.

I dont want to direct link someone elses dropbox file. thus the gymnastics

[HotRodTractor]

I was just finishing up another test print when I saw your post. I did the math - but like a bonehead I did it backwards. lol Oh well. I used the new print as a basis - did the math on it, double checked it with the first print and my initial settings and it comes out really close. Tomorrow morning I'll run another print and check my new settings. Thanks for the help! I'm new to it (obviously), but I have been reading and think I get the general idea of everything, I just need some experience and perhaps a little guidance.

[goopyplastic]

You are doing great.

Regarding the holes closing up, it is about balance and trying to balance the different features on the calibration piece. A quick an easy way to check your cure time with a known good resin is to focus on the columns. If you are mixing / playing with your own resins you will have control over adjusting the bleed level and this is where the other features are useful.

1 - Hole sizing
Each hole should be visible, due to the base layer being a longer cure the holes may not travel through the entirety of the part.

2 - Groove sizing
How deep do the grooves go? getting the thinnest groove to not fill in will be tough

3 - Text
Text shouldn't be too closed in, nor should it be enlarged

4 - Columns
We want the columns to be fully formed, the thinnest should have enough structure so that it can stand under its own weight without flopping over (this is the quick and dirty way to test cure time)

5 - body
The body of the calibration piece should be complete with a smooth surface, undercurring can leave you with a rough / eroded texture.

[goopyplastic]

There is also a second calibration piece that is 9 posts, ignore the enlarged bases of the posts they are to help with adhering to the build plate. The distance across the cured posts should be 50mm and 30mm, you can adjust the proper x/y build size by seeing how far you are off.