Overall I'm really pleased with this big slab of front end, it's the most accurate and well defined engineering shape I've produced to date.
There is a high chance I won't end up going down this route and opt for a complete etched brass footplate and then fit the 3D prints on top, I may still keep the 3D coupler pocket and small section of frame behind the steps as a bolt on piece though.
The current plan in play right now is to have a brass bed under the 3D chassis, it'll cover all of the base and wrap around the enlarged centre profile, there are also slots in the side cills that will grip the edges of the brass sheet, aiding alignment and reinforcing that fragile area.
Under that will come the big pure metal rolling chassis with thick flanges and risers, a drawing would explain it better and I'll do a colored in one later.
The latest rendition popped out of the printer today, it ran all night and has, for me, my first Form known issue failure. This if nothing else is why you model sub parts, if this had been a big detailed print it'd have been in the bin now, luckily it is salvageable.
Right across the whole piece is a ridge roughly mid centre of the nose access opening, on this side it's a slight trough, on the backside it's a ridge.
By my calculations this happened around 05:30 this morning so I didn't witness what happened, however it's more as likely to be the Form3 stupid inability to calculate resin levels, I'll explain.
When the Form first initialise a run it'll fill the tank so the float switch sensor makes, it's a binary switch so not clever enough to calculate the exact level, also being binary it has hysteresis, such that you might just be 5% above the refill level. This means that at some point during the print the float switch will make and Form will want to top up, it's not smart enough to do it on the fly so it stops the print, raises the part out of the vat and then goes through it's fill cycle. In my case my tank is empty so it will have tried to fill the tank for at least 20 minutes before giving up and carrying on.
The problem now is that the tank is still 35°c and the print is much cooler and the last few layers have hardened off, thus the next few layers are not rendered at the same density as that which has cooled and you get a ridge in the print.
There are ways around this and if I think about it, and remember the tank is empty, will top up manually from a back up bottle, more than enough to do the full print, so the ridge is partially down to my forgetfulness.
However the bit that really ticks of Form users is the companies inability to sort the issue out, it's not hard math, if the tank switch is made then you know you have more than 400ml of resin in the vat...the vats on the Form are huge and hungry and take a lot of resin to fill first time around.
Form also knows exactly how much resin the print is going to take, it tells you this in the slicer so you can bill your clients, it's reasonably accurate to two decimal places, so the part above might be 178.34 ml with 2000 layers at the start of the print.
Now imagine the float switch trips after the first 500 layers, it should be able to calculate it's used 44.58 ml and it knows that if the switch was on and then switched off the level will logically be 400 ml, simple math will tell it that the remaining layers will consume 133.75 ml so why stop, just keep going.
One argument (long and twisty on the feedback forums) even goes one further, when you start you know you have >400 ml, you know the part volume before you start, if it's <400 ml then just bloody print it, you could add a margin of safety in, say 200 ml but the net result is that it's all calculable so why isn't form doing it.
You can get away with stopping a print for a few minutes, much more and you'll get visible lines, if you're quick you can open the door (stops machine) and gloop in 1-200 ml real fast, do it in one corner so it spreads into the tank and warms as it goes, it'll soon get mixed when the next few layers print.
Still, it is what it was so no need to get hissy with it, just work with/around it in future.
The revised tread pattern came out well, it actually looks bigger in the images than it does by eye, I already knew the tread repetition from my handy trips to the real deal.
This is an ATSF FP45 which has the same tread plate as all Gen 2 engines, it also has the same sub base doors and many other common parts, handy as one of these may well be in the build pile though I'm focusing on SP models only right now.
At a rough guess the tread repetition is 45 mm but the best I can manage on the print is 84 mm, so roughly 50% density.
It's a compromise but one that I'm happy to live with right now, I might be able to get to 75% density if I drop to 25 microns, but then a piece like this would take near 30 hours and whilst it's doing that, it can't do anything else more productive.