Had some strange prints today…
The powder cars came out… okay… but had some delamination on the flat interior surfaces of the shelf area. I decided to reinforce with Bondic, grind it off and leave it be. They were be hard to visualize and not worth the extra time to fix the drawings… yes… the delamination was a drawing problem with some inner layers causing discontinuities, nor worth the extra resin to reprint.
And i had the same kind of delamination on the projectile flat T2. Again, I decided to try a fix instead of spending a half hour to re-draw and then reprint. I know where the drawing defects are and it would have required starting over from scratch to create the object without the interior layers causing the problem.
Here’s what the damaged area looked like.
In these kinds of errors, the resin peels off like Phyllo pastery. Instead of attempting to fill all of this with something and sand it flat, I decided to build a false floor out of styrene. I also wanted to close those rectangular openings for the powder trunks. I’m installing the trunks on each deck instead of feeding them through the decks.
I made paper templates to fill the space on both the deck and the ceiling below.
I measured the diameter with a dividers and then measured that distance with my digital caliper, divided it in half and used the same divider to cut the paper circle. I have two dividers with one point each sharpened to a chisel edge perpendicular to the diameter. I use these for cutting all kinds of circles. It too three tries to get the diameter just right. I’m using 0.040" stock which is a tad thick, but this, like the powder cars, is going to be very difficult to visualize so the extra thickness won’t cause any trouble.
I also had to cut out holes for some of the printed appliances and that too was a bit trial and error.
Notice in the above that one of the air cylinders is cut off. That too delaminated badly. I eventually ground it flat to the floor and will print a cylinder and install it separately.
Underneath I made paper patterns too. For these I used the rubbing method to transfer the shape below to the paper by rubbing a pencil over the edges under the paper. I cut them a bit large and trimmed to the fit.
I used the same modified dividers to repeatedly scribe the circle into the styrene and then snipped around the edges so I could break the styrene on the scribed lines. You have to take special care to break out pieces that on a curve to avoid breaking the styrene in places you don’t want to.
I hand sanded the edges to round it all out. And then tried the fit. It was good. I needed to make the openings for the hatch, tank and the motor sticking up through the floor. I used a special chisel I got from MicroMark years ago which cut perfect 90 degree corners. i mount it in the drill press and use solid blocking underneath so when I crank the press down hard it doesn’t force the table down too. I got the chisel specifically to cut window openings in model structures.
With all the cuts made the false floor fit very nicely. I did the same for the bottom pieces. I may glue these all in with 3M transfer tape adhesive. It’s a very powerful adhesive and leaves no mess. Otherwisie I may use epoxy. CA can sometimes cause styrene to decompose. Here are the paper patterns being fitted.
And here’s the styrene piece in place (not glued) with the center hole fitted to the central column.
I also started working on the patterns for the shells, the first of which is the pan deck walls. My print out was the wrong developed length. I don’t know where the errors crept in as there were many places to do so. I wrapped and taped it around the actual pan deck base and got an accurate fit. This way I will be able to split the wall on the backside where I wanted to have it. I will translate this too into styrene and as i noted yesterday, I will probably put a backing plate at the junction to hold the ends together. I’m a little anxious about the upper unsupported edge. It’s not going to hold a circular shape. I may cut an upper ring… not to wide… to form and hold the upper edge. The lower outer shells will have circular decks attached to them to serve this purpose.
I was going to print the upper traverse parts and just started the machine. I noticed that the base was forming only on some parts of the job and were just little dots elsewhere. Those little dots were the bottom ends of supports that were starting to print on the plate without the raft. I knew immediately what was happening and killed the job after only one or two base layers were laid down. The slicer has a quirt. When you use the heavy supports the base is at level X, when you switch to light supports, the base level raises .5mm. If you’re using all light supports, the slicer knows to put the base at the plate level, but when you mix supports like I do, I have to watch where the raft is sitting. When the raft is on the plate, when viewed from below, the color is bright green. Like this:
When you raise the part just .5mm this is what it looks like. That lifted part will fail. The raft will be attached to nothing and won’t even start to form.
If I know that the raft is no longer on the plate, I can adjust the z-height in the slicer and bring it back down, but in this case i missed it. I went back and fixed the job in the slicer and will reprint later. In 3D printing like a lot of other things, the details will kill you.
if I may be so bold[;)]
…Sigh.
