1 Topic by DLM

  • DLM
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Topic: Bridges and tolerances

I have a Solidoodle 2 with a heated bed.  It is fairly calibrated and makes consistent prints.

I downloaded this pretty ingenious heart shaped locket STL from Thingiverse.  It is like the wooden one in the Illusionist.  Thought it would be a great way to showcase my printer to skeptical girlfriends.  In any case, this design was made with Replicators/PLA in mind, so I'm having trouble in two areas: bridging and tolerances.

http://www.thingiverse.com/thing:44579

The ingenious design is that this is a fully functioning mechanical design that prints in one shot.  No separate prints and assembly required.  What makes this ingenious also makes it hard to print.  Tolerances are important for the action to work.  My problems are that my first test run was fused together in the center joint, so I was never able to twist it.  My second issue was the the top layers didn't bridge properly, leaving holes in the top section in random points, and dropping lines of spaghetti inside the print. 

I know this is geared towards PLA and Makerbot Replicators with extruder fans, but short of modding my Solidoodle to include an extruder fan, any suggestions on how I can print this out? 

Should I try to mess with bridge flow/speed?  What should I tweek for the tolerance issue with the joint?  Maybe it fused together because of Slic3r.

2 Reply by IanJohnson

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Re: Bridges and tolerances

For tolerances, make sure your flow rate is correct - http://wiki.solidoodle.com/flow-rate

For bridging I generally turn up speed a little and flow down a little to help the thread get stretched.

3 Reply by Tomek

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Re: Bridges and tolerances

Also, possibly lower your temps a bit (reduce fusing and reduce stringing)

4 Reply by DLM (edited by DLM 2013-08-08 19:46:04)

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Re: Bridges and tolerances

IanJohnson wrote:

For tolerances, make sure your flow rate is correct - http://wiki.solidoodle.com/flow-rate

For bridging I generally turn up speed a little and flow down a little to help the thread get stretched.

Thanks for the suggestions.  I kind of had a guess that bumping up the bridge speed might make a difference, but I noticed that Slic3r already has it default at 75mm/s, which is already noticeably higher than the next highest (solid infill at 60mm/s). Wondering how high I should set it?  I guess I'll do some test runs at 85/95/105.   

As for flow rate, looks like I'd have to invest in one of those precision measuring devices (caliper?).  Not sure how I would come to the conclusion of proper flow rate without it.  I also noticed the flow rate wiki you showed me is assuming .3mm layers.  I've been using .1mm mainly, so I don't know if I'm still targeting .42mm width.

5 Reply by Tomek

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Re: Bridges and tolerances

You can get decent digital calipers for $15, and I'd say they are a decent investment smile. [I love mine!]

That said, I didn't have the cash for a pricier one. The biggest downside of a low cost caliper is that they have worse standby energy usage, and the cheap ones will need a new alkaline (cheap) button cell battery every 6 or so months.  Adafruit has a tutorial on hacking your cheap caliper to use AAA batteries that last much longer smile.

My father's >$50 caliper hasn't needed a replacement battery for over 5 years.   (they all have to stay on even after you turn them "off" so they drain a little tiny bit.)