Rock Ultra HC magwell 3D

[sqlbullet]

Edit 6/5/2018 13:40:55 MDT

Thread Background:

I have split these out into a new topic.  The dialog here is about reducing the magwell on a Rock Island Rock Ultra HC.  The magwell is designed for competition and not really conducive to those of us crazy enough to conceal carry a hi-capacity 1911.

I modified the steel magwell on my Rock, and am very happy with the results.  However, not being a licensed, and more importantly, insured, gunsmith, I am less enthused about taking someone else gun to a bench grinder.  My response to this requests is where this new topic starts.


"[I would] probably not be willing on someone elses gun/part.  Too many places I screwed up and then fixed it to try it on someone else gun."

--Edit:  I wonder if I could 3D print one in ABS, and if it would hold up well?  Off to Blender to begin modeling.

[sqlbullet]

So, I did a first rough draft last night.  I am new to 3D modeling and printing, so don't judge too harshly.

The goals for this prototype version were to produce a mockup that was solid, that had a recess similar to the final product, and was similarly dimensioned so I could evaluate the strength of the object in this material.



This prototype is printed in PLA not ABS.  PLA is an easier to print material that has higher tensile strength than ABS, but also is a bit more brittle.  I succeeded in the design goals for this version of the prototype. 

It is solid, which is harder than you would think.  All the modeling and slicer software is optimized to use as little material as possible, and I can't find an easy button for "just make it solid".  In fact, material slump is often a problem if something is printed solid, and that was a concern here.  I made the product roughly 40% taller than I will actually need just to see if slump would be an issue, and it wasn't.

It is very strong, not flexing at all in my hands.  Tonight I will test to failure in a vice, but I think it is plenty strong for what is needed.

Next step is to refine the model with correct final dimensions, the recess for the mainspring housing and the hole for the tensioning screw and for the mainspring housing pin.  I also need to radius all the corners to eliminate focal points for stress cracks to start.  This will probably take me a couple of evenings, and probably 5-10 test prints that all have some defect I forgot to allow for.  Test prints are a pain in the a$$ because of the time involved.  This print was an hour and fifty-two minutes.  The next ones will be shorter do to less material, but probably still an hour.  And, once I bevel the walls of the mag well I will have to add a removeable raft to the base to ensure good adhesion during print.  Stupid raft adds 10 minutes to the print by itself.  So, I will probably add the bevel to the model very last.

I will post updates as this goes along, but finally a project for the printer other than glow-in-the-dark cats, llamas and penguins for my kids.

[Kenk]

This is great, Thanks for your efforts!

[Bunny]

Pretty cool stuff.

[mt10mm]

Great stuff!  Put me down for one if you ever decide to market them .

[sqlbullet]

Printed out test number three last night.  This is that last test piece that was not concerned with dimensional accuracy.  In this test I was evaluating how the bevel stack would print, and how well the mainspring housing pin would print.  The print came out very good.  No slump on the bevels and the hole was nice and clean.  This print also included a radius on all the corners and a dimensionally accurate gap at the rear for the frame/mainspring housing, which slide nicely onto that part of my frame.

I have a new 3D model about 75% complete that is a first attempt at full dimensional accuracy.  It has been a real pain because all my calipers and mics are in SAE units, but the tool I am using to build the models only does mm.  So, I have to convert everything, and likely will find I made an error in at least one of the conversions.

I will complete that model tonight I think, and print a test.  From there I will probably have 3-4 revisions to correct things.  Depending on time table I might have some dimensionally accurate prototypes in a week, unless I get stupid lucking and the current model is right in every regard, which I really doubt.

This has been a fun challenge to force me to learn some 3D stuff and to learn my printer.

[sqlbullet]

Update.

Short version, not looking great.  All hope is not lost, but the light is dim.

Layer adhesion and general strength are the issue.  Specifically where the mainspring housing pin passes through the part to hold it on the gun.

So, I have printed now four variations of a prototype that is dimensionally accurate.

Version one, as I expected, we pretty far off.  I took my medicine and quit trying to take shortcuts and went all in on version two.

Version two was pretty close, but had a couple of issues.  First, the part was printed in PLA, which is just a bit too brittle for that I need.  Second, the mainspring housing pin hole was not printed quite in the right place, and resulted in a split on the left side as I installed the pin.  And third, the same alignment issue caused the part to break when the pin came through on the right.

Version two.5 was a version 2 model, but re-sliced to gcode for ABS instead of PLA.  Still too weak in the same areas.

Version three was completed yesterday.  I didn't start fresh for this version.  Instead I went back to the original V2 file and altered the back half adding about 25% more material in and around the mainspring housing pin holes.  I also smoothed out that radius, which i had left with too few sides in V2.  The holes still are not right on this version, but are closer.

However, this enlightened me to the ultimate problem.  It is just too fragile for any kind of hard use like carry.  It is gonna snap off the gun anytime it snaps on a draw, etc.  The design works fine on my gun since the part is steel and is crazy strong for what it does.  But to make this work in ABS, not so much.  And the real issue is using the mainspring housing pin as the attachment point.  It focuses a bunch of stress on a couple of thin, stubby ears that are subject to layer delam and general breakage.

I have to thoughts to try next...Well, kinda four.

1.  Incorporate a new mainspring housing as a part of the model.  This would give a much more support to the attachment point, which would still be the mainspring housing pin.  However, it would also put significantly more stress on the part as it would have to contain the mainspring tension.  I would almost certainly need to print this part in carbon-nylon, which my printer does not support.

2.  Add "ears" to the part so it can attach under the grip panels with the lower grip screws on each side.  These ears could be wide, but thin, and would provide additional strength in addition to, or possible in place of, the mainspring housing pin.  But, they may interfere with grip panel fit.

3.  Print the part with replacement grip panels.  Effectively the magwell, left and right grip panels would become one unit.  This should be plenty strong.  But I really like the factory grips.  These would not look as good I don't think.

4.  Export the model and adapt to [n] CNC ops on a mill.  This would result in a part made in stainless steel, carbon steel, or any number of other materials.  No doubt this could be very strong, but I don't have a CNC mill (yet) and don't know what it would take.  I know a guy though, so when I can I will talk to them.

I am gonna try #2 next, and then #3.  I found a partial STL file for a mainspring housing, but I can't import and alter an STL, so I would have to create a new part from scratch, then merge it with my current part.  And even then I don't think PLA or ABS would work, so #1 I probably won't bother with.

After I talk to my friends that have CNC access I may revisit option 4 if it is feasible.

[Kenk]

Nice work, keep us posted!