SoliForum - 3D Printing Community — How to print mechanical parts

Re: How to print mechanical parts

2015-03-29T19:20:34Z

Plastic will shrink:

Up to 3%, depending upon size and shape and material (the Moderators comment about a noodle is correct but shrink does play a significant role and it's not uniform in all three directions. Also, it's not just the shrink of the actual design features but, also the infill shrink)
Make your part with appropriate dim’s for the size and shape
Reduce the shrink by good adhesion to the glass
Keep the door closed during printing and keep closed until fully cooled
Put a rag over the top handle opening to help keep heat (and fumes) in

For better adhesion to glass, consider:

Seldom removing the previous glue (just let it sort of build up until common sense tells you to clean it)
Instead of glue or tape, mix acetone with some ABS scraps in a jar - shake it up frequently until all is homogeneous (not too thick). Wipe it on the glass

Design Considerations:

Design yourself some test parts with features you’ll use on real parts, print them and evaluate before assuming the problem is “this or that”

Printing Parameters (Simplify3D enables many parameter changes - XYZware does not):

Increase shells (shells also encase the holes, not just the outer/inner surface
Increase nozzle temp (for reduced compression stress on lines going around holes / corners) and better bonding
Increase infill overlap to at least 25%
Increase infill density
Use Concentric inflll (esp with round features)
Print speed and the part - if it’s a large part, previously printed material will cool (esp if well above the glass) and not necessarily bonds well with newly printed lines - Be clever about how you arrange and print the part.

Most Important - It’s plastic and printed - it’s not a molded part wherein the Steel / hardened mold is designed with warp and shrinkage compensation

The printers have inherent Hysteresis (that is the most relevant physical aspect of the machine’s positioning ability /repeatability. And, the hysteresis is not necessarily equal on all axis'). When combined with Shrink and part features, well...
Hope for but, Don’t expect perfect parts!

Re: How to print mechanical parts

2015-03-29T16:56:52Z

I have the same problem on 2 different printer/software :-(

My brother has a Replicator (I don't know the exact type) and I have a Davinci 1.0 (XYZprinting)
They both have the same problem with holes.

the holes are ALWAYS about the diameter of the noozle to small. So it look like holes are sliced with the middle of the noozle on the edge of the hole... So:
I say this is a calculation/slicing fault.

I've sent an email to the XYZprinting-Team... Let's see what they say...

cheers,
Flex

Re: How to print mechanical parts

2015-03-09T14:06:59Z

It is an issue with this kind of 3D printing. It isn't shrinkage, it has more to do with taking a thread of plastic with physical width and wrapping it around a circle. If you take a noodle and bend it in a circle, the inside edge will get compressed while the outside stretches. The nozzle opening can't put more plastic to the outside edge and less to the inside as it goes around, so the plastic on the inside edge gets squished and makes the hole a little smaller.

http://hydraraptor.blogspot.com/2011/02/polyholes.html

Re: How to print mechanical parts

2015-03-09T13:27:41Z

xairflyer wrote:

Please dont shoot the messager :-)
This is what I was told, the holes they have drawn are perfect sizes after printing and it has worked for me, I am drawing using tinkercad and xyz to slice other slicers may be better.
I have been unable to find out a true solution to this, it is like a big secret no one talks about, all I know is if you draw a 10mm hole in autocad and cut it out on my cnc it is 10mm, on my 3d printer it is always undersize.
It looks to be something you just need to experiment with and maybe come up with a percentage figure rather than an actual measurement.
It is a bit of a pain but maybe drawing the item and then scaling it up 5% (6, 7 etc) might be what is needed, I need to try this method myself

:-) i will do some print tests... but remember that, as is in my case, if you scale up all the measures scales. i Need to resize only the holes and not all the object...
for mechanical prints i will focus on xyzware to lower the variables...
for me is absurd that if you use all the stock hardware and software and filament you get so different results from the design...

Re: How to print mechanical parts

2015-03-09T12:03:27Z

Please dont shoot the messager :-)
This is what I was told, the holes they have drawn are perfect sizes after printing and it has worked for me, I am drawing using tinkercad and xyz to slice other slicers may be better.

I have been unable to find out a true solution to this, it is like a big secret no one talks about, all I know is if you draw a 10mm hole in autocad and cut it out on my cnc it is 10mm, on my 3d printer it is always undersize.
It looks to be something you just need to experiment with and maybe come up with a percentage figure rather than an actual measurement.

It is a bit of a pain but maybe drawing the item and then scaling it up 5% (6, 7 etc) might be what is needed, I need to try this method myself

Re: How to print mechanical parts

2015-03-08T20:34:21Z

fabio.mastromauro wrote:

mmm.... i'm sorry but i do not agree...
I agree when you say that different slicing software may lead to different results and that's why i have included the factory file for simplify3d that is what i used for slicing.
but the final measures of the rectangle are ok, the only problem is with holes and with a difference of 1 mm!
So your .4 less rule doesn't fit for me...

The issue is more with the filament. The pigment depending on color and concentration changes the shrinkage factor. Even a spool from the same vendor but different batch could be different. The first thing I do when I load is spool is print a test object I made for the sole purpose. It is a 30 x 30 solid cube with a 15 bore vertical and a 15 bore horizontal. Once printed I then measure it and use the results to modify my drawing dimensions for that spool.

Re: How to print mechanical parts

2015-03-08T19:22:10Z

mmm.... i'm sorry but i do not agree...
I agree when you say that different slicing software may lead to different results and that's why i have included the factory file for simplify3d that is what i used for slicing.
but the final measures of the rectangle are ok, the only problem is with holes and with a difference of 1 mm!
So your .4 less rule doesn't fit for me...

Re: How to print mechanical parts

2015-03-08T15:41:59Z

So do you just add .4 to every dimension in the model regardless of the original size requirements? For instance, if you wanted a 1mm circle would you print at 1.4 and for a 2mm x 5 mm piece, print at 2.4 x 5.4 mm ? I understand for a specific case the actual number may not be exactly .4 and experimentation may be needed. I've been scaling all dimensions by a specific percent change rather than add a set value and that has not been working well for me.

Re: How to print mechanical parts

2015-03-07T12:12:27Z

When you print things shrink, I asked this question on another forum and I also contacted a guy who has done a lot of 3d drawing for printing, he says he always makes everything bigger by .4 so if you want a 9mm hole then you draw it 9.4mm
I have since tried it myself and am getting much more accurate parts now.

Different printers and slicing programs also have an effect, you just need to experiment to see what suits your means.

How to print mechanical parts

2015-03-07T11:09:39Z

I need to print some mechanical parts.
I started with a very easy one.
i have 6 holes: two with a diameter of 39 mm and four of 9mm.
The Davinci makes the holes of 39mm 38.2mm and the ones of 9mm 8mm!!
How is it possible and how i can fix it?!