Jump to content

3D printed PLA plugs for vac-forming


leccyflyer
 Share

Recommended Posts

Last night I made the final vacform pulls of the canopies for the Dornier DO17 which my pal Jim is building. The 3D printed plugs were just a shade too big to print in one go, so needed to be done in two halves. Then they are just a touch too wide for my home made A4 vac-former -they fit, but there isn't room enough to get the soft floppy PETG down to the baseplate and get the vacuum pulling it all tight.

That necessitated making an A3 vac-former, but the pull is nowhere near as strong on such a large box.  That worked much better. The front canopy isn't quite perfect, as it has a bit of a crease on one pane, but it's close enough for jazz and Jim should be able to blend it in. The nose glazing pulled a perfect canopy first go, which was nice. On offering up the mouldings to the fuselage at the field this morning I was delighted -and a little surprised - to see that they fitted.

 

Most importantly the PLA plugs have stood up to several pulls, without melting, which is excellent news. For slightly narrower canopies I'd expect perfect results from A4 PETG sheets. That was my main worry, as I had visions of the plugs melting into a congealed mass the instant the hot and floppy PETG hit them and the vacuum started to suck. My back-up was to make a papier mache carapace on the plug, fill that with Plaster of Paris and use that instead, as I know that works well. It was a pleasant surprise to find the PLA is tough enough to survive the contact with hot PETG and further heating to aid the shrink.

Also printed the three visible crew members- the fourth member is buried deep in the fuselage - and five machine guns -all to 1/12th scale to fit the cockpit.

IMG_0423.thumb.jpg.a2a7c3c6c77df1af612aee0af7e721b5.jpg

IMG_0418.thumb.jpg.c0d310530cf4552c26cb3e000632ffe9.jpg

The first pull, pictured above went really manky on the side, but the final one was only slightly manky. I reckon that for slightly narrower canopies, I wouldn't have that issue, which I believe is caused by there just being just not quite enough space between the plu and the hinged frame on the smaller vac-former.

Thanks to Ron Gray for his advice when I was struggling to get the first plug to print at all, I'd have been stuck without his words of wisdom.

  • Like 4
  • Thanks 1
Link to comment
Share on other sites

Sure.

 

The A4 vacformer was cobbled together by making a simple box from 2x1" PAR timber, which was then faced with 1/8th ply, in which a regular grid of holes had been drilled. There is a hole in one of the end pieces of the box to take a vacuum cleaner hose. The PETG or ABS sheet is held on a hinged frame, which was a charity shop cookery book stand, with the cross member removed. My first attempts secured the plastic sheet with aluminium tape, but I've since resorted to using a staple gun for the job.

 

vacformerclosed.jpg.a9571e3d5c8b1ae33527cfb51c389fb3.jpg

vacformeropen.jpg.a5cee35422b9f7f5740edaf73eb1c2d1.jpg

 

vacformerbed.jpg.a75eb6920c591e5b436903f2e8bd94f6.jpg

In practice the male plug is placed on the bed, the plastic sheet secured on the frame, the vacuum switched on and a hot air stripper gun is played on the plastic until it goes all saggy, at which point the hinged frame is flipped over, the vacuum grabs and pulls the plastic down tight against the bed. I've used 0.5mm and 0.4mm clear PETG sheet this time, but have previously used ABS white.

beaupilotonvacformer.jpg.6cb225d69b930de44d9d3da586d678a9.jpg

1509434896_beaucanopyvacform(1).jpg.23dba388b44e258a3a343b8d32d7b3cc.jpg

 

As the A4 example was just a wee bit too small for the Dornier canopies, I made up a larger box from 8mm ply - slightly larger than A3 size to take the larger sheets. I made a simple frame out of 1/2" square timber, cut from some skirting board, to hold the PETG sheet but I haven't yet hinged that. It's a bit more fiddly to use without the hinging, so I'll change that for next time. The larger volume of the A3 box also means the vacuum isn't as fierce as the wee one-which makes a brilliant squealing noise in use. 

 

 

I need to think up a better means of retaining the sheet than staples, as they damage the frame getting them out, ~I'd thought a series of bolts through the frame. with a thumbscrew on the upper surface, then using a hole punch on the plastic sheet might work better. The thing with daft little home made tools like this is that you can always improve them and that's part of the fun. ?

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...