<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div><span>Sean,</span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1461030467306_3492"><span id="yui_3_16_0_ym19_1_1461030467306_3491">I have to admit,I find the process of mould making quite romantic. I think that is one of the reasons I keep looking at concrete. With concrete you have total freedom of form. I have it all worked out how I would make a perfect sphere. </span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1461030467306_3490"><span><br></span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1461030467306_3263"><span id="yui_3_16_0_ym19_1_1461030467306_3262">I thought you had to over build when you cast parts, does this not mess with your buoyancy. That can be costly- your sub is likely big enough to handle the weight. </span></div><div dir="ltr" id="yui_3_16_0_ym19_1_1461030467306_3261"><span>Hank</span></div> <div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"><font size="2" face="Arial"> On Monday, April 18, 2016 7:18 PM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<br></font></div> <br><br> <div class="y_msg_container"><div id="yiv9018387849"><div><div dir="ltr">Actually, I would think that casting would be a useful process for a hands-on guy like you, Hank. You could probably do your own patterns from plywood and Bondo and then deal with a foundry without having to pay for the pattern making. Just do some research first - you need to accommodate shrinkage, and the draft requirement. Also, you do need to 100% NDT the completed castings. Unlike billets / plates, voids can be quite common in cast parts, and these need to be detected and corrected for our application.</div>
<div dir="ltr">Sean<br clear="none">
</div>
<br clear="none"><br clear="none"><div class="yiv9018387849yqt9548585235" id="yiv9018387849yqtfd75645"><div class="yiv9018387849gmail_quote">On April 18, 2016 7:05:01 PM MDT, "Sean T. Stevenson via Personal_Submersibles" <personal_submersibles@psubs.org> wrote:<blockquote class="yiv9018387849gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<div dir="ltr">There are a few reasons:</div>
<div dir="ltr">1) Economy of process. Creating a casting entails creating a master pattern, usually by a pattern maker at the foundry or associated with them. Once this is done, additional parts can be obtained for the cost of an additional heat / pour. For multiple similar parts (six identical hatches) this is cheaper than machining them all from billets.</div>
<div dir="ltr">2) Economy of waste. Machining from billets obviously is less material efficient, as much of the billet ends up as chips on the machine room floor. With a casting, extraneous material exists in the form of risers, flow channels and flash that must be trimmed, but in many cases these wastes can be cleaned and remelted in the furnace for reuse.</div>
<div dir="ltr">3) Suitability to size. Some parts which would be awkward to handle or difficult to machine without access to suitably large machines can be more readily cast at lesser cost.</div>
<div dir="ltr">4) Efficacy of form. The casting process allows you to readily incorporate large sweeping or compound curvatures and other features to reduce local stress concentrations or improve aesthetics, without necessitating multiple machining operations or tooling change outs to do so. Often, recreating a cast part with machining operations exclusively is prohibitively expensive. The design process is different for each - with machined parts, you need to think about machine envelope, repositioning, cutter clearances and interferences, tooling, avoiding impossible operations, and so forth. With castings, there is greater freedom of form, although you have to avoid thin-walled parts, apply draft to parallel edges to facilitate mold release, and consider material flow into the mold and how the part will cool to avoid warping. Often, combining processes gives you the best of both worlds: casting a blank to get the overall desired shape where surface profile is generally not
critical, and then subsequently machining specific faces or features to establish critical dimensions.</div>
<div dir="ltr">This is the approach I am taking - casting the transition rings from the hull shell thickness to the hatch seat thickness to get that smooth large curvature (and a sexier looking part, IMO), where the contact interface is machined in situ after stress relieving the hull, and then also casting the hatch blanks and machining their critical features (contact interface, O-ring grooves) into the blank.</div>
<div dir="ltr">Sean</div>
<br clear="none"><br clear="none"><div class="yiv9018387849gmail_quote">On April 18, 2016 4:11:09 PM MDT, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="yiv9018387849gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204, 204, 204);padding-left:1ex;">
<div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;"><div id="yiv9018387849yui_3_16_0_ym19_1_1461017365265_2579">Hi Sean,</div><div id="yiv9018387849yui_3_16_0_ym19_1_1461017365265_2579">I am curious why you wouldn't machine your hatch from a heavy disk, it would be one piece and any shape you want.</div><div id="yiv9018387849yui_3_16_0_ym19_1_1461017365265_2579">Hank</div></div><div style="margin-top:2.5em;margin-bottom:1em;border-bottom:1px solid #000;"></div><pre class="yiv9018387849k9mail"></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none">Personal_Submersibles@psubs.org<br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a><br clear="none"></blockquote></div><div style="margin-top:2.5em;margin-bottom:1em;border-bottom:1px solid #000;"></div><pre class="yiv9018387849k9mail"></pre><hr><br clear="none">Personal_Submersibles mailing list<br clear="none">Personal_Submersibles@psubs.!
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