Re: Minimum Thickness for a Reliable Leak Proof Part

From: Crispin Weinberg <crispin_at_biomodel.com>
Date: Thu, 31 Oct 2013 11:44:11 -0400

Ryan Wicker's group at El Paso did a study on sealing parts for fluid
pressure resistance. They used ABS M30 on a Fortus 400mc. You can
search for "Analysis of Sealing Methods for FDM-fabricated Parts" to get
a pdf of their paper.

-- 
*Crispin B. Weinberg*
*Biomedical Modeling Inc.***
167 Corey Road, Suite 111
BostonMA02135
Tel: 617-738-8168 or 1-888-246-6633
Fax: 617-738-8165 or 1-888-232-9246
*www.biomodel.com <http://www.biomodel.com/>*
*crispin_at_biomodel.com <mailto:crispin_at_biomodel.com>*
On 10/31/2013 10:25 AM, Sean Wise wrote:
>
> Since we need to seal FDM parts before we electroplate them we have 
> become quite familiar with how to make things tight and have been 
> surprised at the variables.  I'll just list a few observations about 
> the sealing methods first.
>
> 1. We have been successful on ABS with both the halocarbon solvent 
> mixtures like those contained in Weldon 3 or 4 or polyurethane clear 
> coats (2 part reactive systems).  We have not been able to make things 
> like acetone or MEK work.
>
> 2.Polycarbonate needs an impregnation and epoxy sealers seem to work 
> well or high end epoxy paints.  PC is very sensitive to aromatic 
> hydrocarbons and it's very easy to degrade your part if you choose the 
> wrong system like a polyester or vinyl ester clear coat.
>
> 3.The Ultem can be sealed with a vinyl ester sealer
>
> 4.With both the PC and the Ultem you have to design a sealing strategy 
> that does not let the resin leak back out after you've applied them.  
> We often pre-heat parts before coatings are applied so they penetrate 
> and begin to harden while the part is still hot.  We always apply two 
> coats but the wait times between coats for the epoxies on the PC and 
> vinyl esters on the Ultem are very different.
>
> We have also found the type of machine matters -- a lot.  If you have 
> access to high end machines like the Fortus where you can control the 
> overlap of the roads, the  smaller gaps between resin beads are easier 
> to seal.  If you have a low end system, the machines set the spacing 
> between roads at the factory and they are quite permeable.  Some of 
> these are so coarse that solvent sealing with Weldon becomes risky 
> because the solvent penetrates so deeply into the part and wrecks the 
> part.  We have also worked with parts from a couple of the low end 
> systems like Makerbot and Afinia. Their parts can be sealed using 
> solvent dipping but I was quite surprised at how easy it was to seal 
> the Afinia parts which have only 0.040" walls that have a 
> cross-hatched fill inside.  Apparently, they set their machine 
> parameters to make the walls as tight as possible.  They still need to 
> go through a sealing process but they seal up more reliably and I am 
> more confident running a hollow part built on an Afinia machine than 
> any others.
>
> Sean Wise
>
> RePliForm Inc.
>
> *From:*rp-ml-owner_at_rp-ml.org [mailto:rp-ml-owner_at_rp-ml.org] *On Behalf 
> Of *ChathamRes_at_aol.com
> *Sent:* Wednesday, October 30, 2013 7:24 PM
> *To:* rp-ml_at_rp-ml.org
> *Subject:* [rp-ml] Minimum Thickness for a Reliable Leak Proof Part
>
> We are trying to determine the reliable minimum thickness for an FDM 
> type process for making a vessel to hold water.
>
> Does anybody have experimental experience with this type of process.
>
> Doug
>

Received on Thu Oct 31 2013 - 19:49:51 EET