Glass doesn't conduct heat so you'll end up with a lot of hot/cool spots. There are some circular pieces of tooling plate about 400+ mm dia that are pretty cheap on ebay.by the_digital_dentist - Mechanics
A little bigger than you need:by the_digital_dentist - Mechanics
The difference between your printer and the thing you used to test the motor is the cable from the controller board to the extruder motor in the printer. When you tested the motor you didn't use THAT cable. Steppers don't turn if there's an open connection, a shorted connection, or a couple swapped wires. Check the cable.by the_digital_dentist - Mechanics
You will need to get aluminum "tooling plate". Extruded plate is always curved. Tooling plate is cast, and milled to guaranteed flatness. Extruded plate will tend to warp when heated, cast plate expands but doesn't seem to warp as much (probably due to more amorphous structure). I use 1/4" x 12" x 12.5" tooling plate in my printer and can print edge to edge. I don't know if you can get 20"x2by the_digital_dentist - Mechanics
I'm no expert, but I use Designspark Mechanical a lot and like it. My training on it is strictly as needed- when I want to do something I haven't done before and I go to the web to find out how to do it. I used to use sketchup but kept running into the limitations- curves/circles are never actually curves/circles which causes numerous mysterious problems with STL files. A lot of things thaby the_digital_dentist - 3D Design tools
I have steel reinforced 9mm wide 5mm pitch belts (don't know the exact designation- they came out of a piece of industrial scrap) on the X and Y axes of my printer. The Y axis span is about 700mm. It used to bounce a lot as the printbed moved and I considered putting a piece of soft sponge or something against it to control the bouncing but never got around to trying it. I did put a 1/2 twistby the_digital_dentist - Mechanics
I have used toothed belts on smooth pullies. In my printer Y axis the motor is about 700mm from the pulley. When the toothed belt rode the smooth pulley I found two things: the print has tiny bumps in the surface that I attributed to cogging of the Y axis as the bums on the belt met the pulley (this causes small changes in Y axis speed that result in modulation of the thickness of the line of pby the_digital_dentist - Mechanics
Are you asking about using a toothed belt with a smooth, untoothed pulley?by the_digital_dentist - Mechanics
Check the motor current settings on the driver board(s).by the_digital_dentist - Mechanics
Putting the electronics under the printbed sounds like a good way to keep the printer small, but you might want to reconsider. You are making a pretty big printbed, so I assume you are going to want to make big prints. If you try to make big prints with ABS and you don't enclose the printer your big prints are going to delaminate even as they are printing. I suggest that you enclose the printeby the_digital_dentist - Mechanics
A mechanical relay on the printbed heater circuit will drive you nuts with all the clicking, and probably won't last long because of the large current being switched. You don't need to use a relay at all if you have a 12V heater, as long as the current is less than about 10A. The MOSFET on the RAMPS board will switch the full 10A for you without complaint. I have moved away from switching poby the_digital_dentist - Mechanics
The RAMPS board allows you to power the printer from two different supplies. They don't have to be the same voltage. One supply, typically 12V, drives the board, electronics, and motors. The other is just for the printbed heater. The printbed heater side has a MOSFET switch and a thermal cutout (a varistor?) that will shut down power to the printbed if you try to drive too much current for thby the_digital_dentist - Mechanics
I have a 12"x12.5" bed with a 24V, 450 Watt heater. There is no effect on the controller- a standard, unmodified RAMPS board. I power the heater from a 24V transformer and switch power into the transformer using an SSR connected directly to the RAMPS board. The SSR doesn't even get warm, and the bed heats to 105C in about 7 minutes. I used to use a switching power supply but burned it up in sby the_digital_dentist - Mechanics
Good!by the_digital_dentist - Mechanics
Check the filament where it is pinched between the gear on the motor and the bearing. Is there a round divot cut into the filament? If so it indicates that the hot-end is jamming. Play with the temperature setting of the hot-end- don't trust the electronics to read the correct temperature unless you can verify it for yourself with a reliable thermometer- either a thermocouple or RTD. If you cby the_digital_dentist - Mechanics
The bed leveling serves only one purpose: to get the first layer of your print to stick to the bed. The bed has to be level relative to the extruder nozzle at all points on the bed so that when the nozzle visits those places it will "press" the plastic onto the bed with equal pressure everywhere. That means you must move the extruder nozzle around the bed in order to check and level the bed. Aby the_digital_dentist - Mechanics
I started out thinking of a design that used a single nut, then realized it would try to twist the filament, so then I thought about how to stop filament rotation (square filament?). I considered pizza cutter type wheels to dig into the filament and stop rotation, then came up with the idea of using a second nut turning in the opposite direction, then realized I'd need left hand threads, then, aby the_digital_dentist - Mechanics
I think the retraction will be fast enough, but right now the problem is that uneven torque on the filament, caused by one nut hanging on tighter than the other, is causing the filament to rotate with the lower nut when the thing tries to retract. That prevents the molten filament from being sucked back into the nozzle and causes blebs in the surface of the print where the retracts are supposedby the_digital_dentist - Mechanics
Unless you want to print very slowly, and with very large prints that is going to take a loooong time, I'd suggest building the machine with architecture similar to the Makerbot machines. Moving a large, heavy print bed in the Z-axis is easier than moving it in the Y axis, though the mechanics are more complicated. My machine has a 12"x12.5" printbed and besides being large, the bed is heavy (1by the_digital_dentist - Mechanics
Status update: further development is delayed by a nasty cold and even nastier income tax season. Those of you not living in the US should count yourselves lucky that you don't have the sort of crap we have to go through every year- there is no greater waste of time, effort, money, and most importantly, human intellect, than the US income tax preparation industry.by the_digital_dentist - Mechanics
I did some thinking about what might be causing the loop blebs. I think it is occurring during retracts- i.e. the retraction isn't working as it should. I have clipped a spring clamp onto the filament entering the extruder to check rotation of the filament. What I have noticed is that the filament twists back and forth a few degrees as the machine prints, primarily due to misalignment of the nby the_digital_dentist - Mechanics
I have been out of town for the last couple weeks, but I'm back and ready to start again... Quotecozmicray If one were to use a solid shaft (Brass, Al, Steel) with a hole drilled in it, What length of threads should be tapped into the shaft. Are the 3 or four threads of a nut optimum? I have no idea what is optimum. I started with off-the-shelf stuff to see if it would work at all. If you getby the_digital_dentist - Mechanics
QuoteBill Clark those loops on the surface are strange. I'm wondering if the (scanned?) surface is just "dirty". The object was made by extracting soft tissue data from a CT scan. I have printed it before with no issues. The loops are definitely a problem related to the SnakeBiter or firmware settings or both.by the_digital_dentist - Mechanics
The specs are all in the instructions page at thingiverse. These are the gears I used:by the_digital_dentist - Mechanics
I spent most of yesterday experimenting with firmware and slicer settings to get good quality prints from the SnakeBite extruder. I'm getting closer- video of latest print here: This print took about 11 hours to complete. There are numerous small blebs in the surface, many of which were carried there from the support material, but some others that are loops that I don't know how to explain.by the_digital_dentist - Mechanics
Compact and lighter will come later. I do have a slightly more compact version that uses 20 tooth gears on the nuts with a 30 tooth gear on the motor, and smaller bearings. That reduces size and should increase speed by about 50%. I'll be testing that later. Right now I have to figure out the firmware and slicing tweaks to get quality out of this one and test its speed limits.by the_digital_dentist - Mechanics
I think it can be made to work. Even if mechanical losses are high, you can use a bigger motor and more current to drive it. If you had to you could mount a set of bearings in the gear to reduce sliding friction along the square rod. It may not be necessary to make the square hole in the gear all that close fitting on the square rod. The whole carriage is going to be moving smoothly on the guby the_digital_dentist - Mechanics
I've been testing a new extruder design that uses counter-rotating nuts to drive 3mm filament into a Budaschnozzle clone hot-end. I was originally posting under this topic: "new light extruder concept". Summary: A simple differential gear arrangement drives two, 6-32 nuts in opposite directions. One nut is left hand threaded and the other is right hand threaded. The reason for using two nutsby the_digital_dentist - Mechanics
I'm going to start a new thread on this topic and stop posting in this one. Look for "SnakeBite Extruder" as the new thread topic.by the_digital_dentist - Mechanics
I dialed the acceleration and jerk settings back and ran the same print again without reslicing, video here: Retraction is working properly, and the blobbing is gone, but it doesn't seem to be laying down enough plastic. There are gaps between lines in the bottom and top layer infills- this was true in the first test parts, too. I will recheck my steps/mm calibration for the extrusion and setby the_digital_dentist - Mechanics