Russian SU76M

[wibblywobbly]

This is starting to drive me nuts, there is something about the design of the hull that is causing it to contract unevenly when it cools, and that is causing it to warp so badly that it is not only pulling the print through a brim, but also pulls additional adhesion cylinders off the bed and its causing me huge headaches. I am 50%/4hrs of the way through 8hrs printing just the rear sides, and its not looking good. I have spent 'hours' trying to get these done using all sorts of trickery.

I found a way to print track links 16 at a time, in an hour, by stacking them all vertically in 4 columns of 4 each.

[wibblywobbly]

Pulled the plug on the print...will have another go tomorrow.... Shame as the spring mounts are ok, it all lines up as it should with the suspension arms. I can only think that the new filament that I bought is dodgy (it was the cheapest I could find), as the last reel printed perfectly and stuck to the bed every time.

[wibblywobbly]

I think I found the track solution, print the upper and lower seperately, so two smooth joining surfaces, and detail on the upper surfaces. Glue them together, pin drill to clean up the track pin holes. I found that common dressmaking pins are perfect, they don't bend and they have a rivet type head on them.

I printed three, and then discovered why my Delta printer has been a pain these last couple of months, all three of the brackets at the top that hold all of the extrusions together in a perfect triangle are split. This allows them to move up and down, and this sets of a chain reaction that wrecks any hopes of reliable printing. Now waiting to see if the manufacturers will replace them FOC, though the only proper solution is to buy alloy ones.

That printer will be out of commission until its fixed, though I am amazed that it printed the tracks as well as at did, when there is no reason on this planet why it should have done so.

[c.rainford73]

I think I found the track solution, print the upper and lower seperately, so two smooth joining surfaces, and detail on the upper surfaces. Glue them together, pin drill to clean up the track pin holes. I found that common dressmaking pins are perfect, they don't bend and they have a rivet type head on them.

I printed three, and then discovered why my Delta printer has been a pain these last couple of months, all three of the brackets at the top that hold all of the extrusions together in a perfect triangle are split. This allows them to move up and down, and this sets of a chain reaction that wrecks any hopes of reliable printing. Now waiting to see if the manufacturers will replace them FOC, though the only proper solution is to buy alloy ones.

That printer will be out of commission until its fixed, though I am amazed that it printed the tracks as well as at did, when there is no reason on this planet why it should have done so.

Wibbly these tracks look excellent

[wibblywobbly]

Thank you sir. They look better from a few feet away, the close up shots reveal rough surfaces that are pretty much invisible to the naked eye.

[wibblywobbly]

The track links are a long haul, I decided to abandon the idea of printing complete links in a tower format for two reasons. Firstly although a fast way of printing, the tracks took a lot of post printing cleaning, and secondly the printer best suited to printing them has managed to develop cracks in the plastic parts of the frame so I can't use it until I have printed or obtained replacements, though I am researching RepRap printers that I could build with the parts from it.

The downside of printing the links in two parts is that I now have around 160+ links to glue together and manually pin drill, the upside is that I have nice clean links with cleat detail on the top and bottom.

The lower hull will be completed once I have received some 3mm styrene sheet that is on order. I'll print the sides and rear with all of the holes, suspension mounts and door detail, and use the styrene for the base/front.

[wibblywobbly]

I could print one in minutes, it would be very simple to do, just create a solid block in CAD, insert the track file into the middle of it, and remove the shape. Then print the hollow block in two halves to clamp around a link.

However, I only have a Dremel drill stand, and that spins way to fast to drill plastic, it melts it in about a second which ruins the hole. I could fit a dimmer lightswitch into the power supply to give me adjustable voltage, which should slow it down, but my guess is that there will be too much run out on the tiny drill bit to get an accurate hole.

[wibblywobbly]

I know what you mean about seeing things around the house, if I am throwing anything out, especially electrical items, I pull them apart and strip the cabling and anything else that might be useful from them. Old pc's have ATX power supplies, which can be used for 3D printers, along with sockets and plugs etc.

[wibblywobbly]

After a few marathon days of printing I have finally managed to 3D print the lower hull. It was done in four quarters. The next task was to join them to each other, so threw caution to the wind and went the plastic welding route. PLA melts at 160 degrees, so all I had to do was use lengths of filament as a welding road and push the soldering iron against it into the gap. It cools solid in seconds, and the whole structure is rock solid. The weld lines can simply be sanded down and smoothed with filler.

I gave up on sticking two halves of tracks together and drilling the pin holes, there are waaaaaaay too many of them for me level of patience, so I now have a container full of hundreds of track halves. When the new printer arrives I will just print the links in one piece. I have done some on the existing printer and they aren't too bad. I just need to be able to print a lot more at a time, which the new one will do.

[c.rainford73]

After a few marathon days of printing I have finally managed to 3D print the lower hull. It was done in four quarters. The next task was to join them to each other, so threw caution to the wind and went the plastic welding route. PLA melts at 160 degrees, so all I had to do was use lengths of filament as a welding road and push the soldering iron against it into the gap. It cools solid in seconds, and the whole structure is rock solid. The weld lines can simply be sanded down and smoothed with filler.

I gave up on sticking two halves of tracks together and drilling the pin holes, there are waaaaaaay too many of them for me level of patience, so I now have a container full of hundreds of track halves. When the new printer arrives I will just print the links in one piece. I have done some on the existing printer and they aren't too bad. I just need to be able to print a lot more at a time, which the new one will do.

Wibbly you are quite the engineer your work inspires me with my builds and is so impressive. I cant believe how nice and solid the sections look as a result of your A-Team welding job! Most importantly you have taken on a challenge head on and have done it