Tag Archives: 3d printer

From paper to plastic

… or more correctly, from CAD to reality, as it is time for 3D printing!

I’ve recently got a new 3D printer in the form of a FlashForge Creator Pro 2017, which means I can start printing some of the structural components for the quadruped now, leaving the decorative pieces for later. In fact, some of them have already been printed, as you can see in the images below.


Chassis parts

All the parts were recently updated from their previous iteration slightly, by adding fillets around the edges, and decreasing nut hole diameters by 0.2 mm in order to provide some material for self-tapping threads. On the other hand, I increased the tolerance of some slots by the same amount, to allow a tolerance for their connection to interlocking plastic tabs.

The rear section has also been modified: the underside aluminium base will have a tab at 90° that connects to the rear, to provide more rigidity to the central connection with the spine servo bracket.

Here are the CAD models of the chassis parts:

Foot base

Front body assembly

Rear body assembly

 


Printing

All parts were printed in PLA plastic.

The first part I started with was the foot base. I printed it with a 20% honeycomb infill. I didn’t add any intermediate solid layers, but might do so in other parts. I have so far printed two out of the four bases.

Each leg will connect to a leg base bracket, which is the same design for all legs. The part was printed “upside-down” because of the orientation of the interlocking tabs. This meant that some support structure was needed for the holes. For the first print attempt I also added supports around the overhang of the filleted edge, along with a brim, but for the subsequent prints I didn’t bother with these, as the fillet overhang held fine without supports, and saved from extra filing/sanding down. These parts also used 20% infill.

For the front and rear “bumpers”, I reduced the infill to 10%.

For the larger part comprising of the central section of the front, the spine front bracket, I also used an infill of 10%. Due to the more complicated design that would have included many overhangs, I found it easier to cut the part lengthwise and print it as two separate pieces. These will be super-glued together after sanding.

Time-lapse GIFs and images of the printing process:

 


The parts so far

In terms of printing times, the foot bases and leg base brackets took about 3 hours each, the bumpers took around 4 hours each, and the two spine front bracket halves took about 7 hours combined, so total printing time is going to be fairly large!

The 0.2 mm clearance seems to work fine for self-threading the plastic with M2 size metal nuts, but was too large for some of the plastic-to-plastic interlocking tabs, possibly since this tolerance is close to the resolution limits of the printer (theoretically a 0.4 mm nozzle and 0.18 mm layer height). However after some filing and sanding down, all the plastic parts fit together nicely.

The resulting 3D prints before and after sanding:


The assembly so far

Finally, here are some images of how the chassis assembly is shaping up, as well as the foot bases shown attached to the foot metal brackets. These fitted snug without any sanding, and all the holes aligned perfectly with the metal brackets, which was reassuring!


The next step is to glue the front bracket halves together, and maybe spray paint all the parts, as they lose all their original shine and end up looking very scratched after sanding.

 

Reprap is live again!

After a long delay, the RepRap has finally been re-assembled and sprung into life to produce some first calibration parts!

Here are a few shots of the completed printer, including an additional protective glass plate over the heating PCB, which also makes cleaning of the printing surface easier.

 The completed Reprap Prusa Mendel.

The curved plastic tubes on top of the printer are actually plastic water pipes with crocodile clips attached to them, which were a perfect fit onto the top threaded M8 rods. They make a great set of spare hands for holding various things in place, such as the plastic filament spool.

Next are some images of the first calibration prints. Up to this point the calibration process has been fairly painless, as it is using the calibration settings of its parent Prusa, however minor tweaks will be needed to improve the print quality.

The set of very test first calibration parts that were printed out.

A further set of calibration parts, trying a new plastic filament.

The print quality actually starts to degrade at the upper levels, which is very likely linked to the fact that the bolts which hold the PTFE barrier in place (see the mod that was done back at the start of the printer build), become very loose as the print progresses. As a result, the shaking of the extruder tip may be causing the loss of precision. Also, the x-axis idler has taken some damage, possibly due to the tension of the x-axis belt, which is causing misalignment, let alone the fear that it might break at any point!

Damage to the x-axis idler.

Until these issues have been solved, here is the first video of printing in action:

Wiring the electronics, testing the motors and heating up the extruder

With the mechanical part of the RepRap largely completed, the next step was to wire up the electronics.

I had underestimated the amount of wiring required for the printer, so I braided the wire before wrapping it around the printer’s frame in an attempt to keep it as neat as possible. The wires have to be kept away from many moving parts, hot points, etc. Keeping them isolated should also minimise any cross-talk noise between the large lengths of cable. However, as the printer is going to have to be disassembled, packed and moved in the near future, I haven’t fixed the wires up with cable-ties yet.

The Danguinololu successfully communicated  motor and temperature signals so everything seems in order, except for the extruder motor which is behaving in an irrational manner and only intermittently accepting movement signals in one direction. Leaving this problem aside, I moved on to testing the heated extruder tip.

The heated tip temperature was incremented in steps up to 210 °C, while manually feeding some PLA plastic into the extruder. The plastic flows out of the tip effortlessly at around 200 °C, so things are looking positive for the extruder assembly! The remaining step is to calibrate a working motor to extrude plastic at the right speed for printing.

As I’m experiencing some issues with one of the motors, unfortunately the long-awaited calibration and test-printing stage has to wait!

Completing the axes and print table

Some further progress on the RepRap build this weekend. The frame is now complete and awaiting electronics (sneak peek in the last picture)!

Main updates have been:

  • The x-carriage plastic parts were reinforced with some Sugru as the vertical columns seemed weak and flexed with little force. The carriage was completed and mounted to the frame. The z-axis motors were attached to the top of the frame and connected to the x-carriage via the new-style couplings.
  • The MDF wood top plate was attached to the bottom plate and can freely tilt via the corner springs. This allows the printing area to move under pressure, ensuring that the frame and extruder will not get damaged if the extruder happens to get lowered too far onto the print area. The heated bed (wired-up previously) was attached to the top wood plate, with all thermistor wiring tucked in-between.
  • The extruder tip was attached to Wade’s extruder. Another strengthening mod here should ensure that the extruder PTFE barrier doesn’t get pushed out of the extruder by the force of incoming molten plastic, something which has happened with printer #1! The complete extruder assembly is now mounted on the x-carriage.

Further progress on extruder and axes

Extruder

First off, the idler block was attached to the extruder. Simple job and the extruder is almost complete! I’ll return to it again later.

The idler block is attached to the extruder at the top with two long (40 mm) M3 bolts. The hinged bottom pivots on another M3 bolt (need to cut the excess thread or use a more suitable size).

Y-axis assembly

Assembly of the y-axis started by attaching the appropriately sized print bottom plate to the bushings which run along the smooth guiding rods. The bushings were glues onto the plate with two-part epoxy.

For all five stepper motors, we chose the NEMA 17  SY42STH47-1684B model, which provides the required torque for all axes as well as extruder.

The y-axis motor was attached to the y-bracket on the RepRap frame. The rapid prototyped (RP) pulley was also attached and secured to the motor shaft with an M3 grub nut and hex bolt.

Print bottom plate. The timing belt is secured onto the plate using two RP belt clamps.

Close-up of y-axis motor, pulley and timing belt. The motor is attached to its bracket with three M3x10 mm hex bolts.

You might notice that the motor is mounted on the side of the y-bracket opposite than that shown in the instructions. This is actually because, due to a small hiccup, my y-bracket was printed as a mirror-image of the original STL part (this is also the case for some of the x-axis parts as you’ll see later). The reason I had to mirror the motor position, is because the side of the y-bracket on which the motor should sit has recesses for the M3 hex bolt heads. The M3x10 mm bolts are too short to secure the motor if it’s mounted on the other side. Later on I will simply have to mirror the y-axis movement direction in the control software.

The final step was to mount the timing belt in place using belt clamps and M3x25 mm bolts with washers. Enough tension is needed so that the belt doesn’t sag and the print bottom belt moves smoothly along the guiding rods.

X-axis assembly

As noted previously, the x-axis end parts are also mirror-prints of the originals, hence the assembly will have to be adjusted accordingly. This however shouldn’t have any impact on the functionality of the printer.

The first step was to attach the smooth rods to the x-end parts. Some filing was in order to get the rods to squeeze in. I believe the x-end parts you see here are the versions which use LM8UU metal linear bearings (similar to the ones here), although I will be using RP plastic bearings instead. These RP parts don’t have long channels travelling all the way through them, so the rods can only slide in up to a point. They attach firmly on each side, without the use of M3 bolts. However, this means that the distance between the x-ends is essentially fixed, so later on the z-motor mounts on the top threaded rods will have to be adjusted accordingly.

Smooth rods attached to the x-end-motor and x-end-idler RP parts.

Close-up of the x-idler bearing over which the x-axis timing belt is mounted.

The x-axis carriage mounted onto its guiding rods.

Attaching the idler bearing to the x-end-idler was a straightforward. The M8x50 mm bolt was used as a suggested alternative in place of a plain threaded bolt.

Next, the x-axis carriage was attached to the guiding rods. The blue carriage you see above is missing its bushings (print hiccup), so they were printed separately and glued on. The timing belt clamps are the same as the ones on the y-axis belt.

Before the x-axis carriage is mounted onto the z-axis vertical smooth rods, the latter have to be inserted into the RepRap frame.

Z-axis assembly

A plumb-line helped to line up the rods with the bottom bar-clamps. The top rod-clamps were attached to the z-motor holders using M3x25 mm bolts and respective washers. The bolts were placed with shafts pointing outwards from the frame, to avoid interference with the motors which will sit next to them later on.

Close-up of Z-axis motor mount and attached vertical smooth rod.

In the next stage, the x-axis carriage and remaining motors will be attached to the RepRap frame!

Wiring up temperature sensors for heated bed

Next on the list was wiring up and soldering the temperature sensors (thermistors) to the heated bed PCB. Since the heated bed covers a fairly large area, I’ve used a combination of 4 to provide a mean value for the temperature across the bed. By wiring up two thermistors pairs in series and then in parallel as shown in the drawing and pictures, the overall resistance, and in effect temperature, provides a form of “averaged” value. If all thermistors register the exact same temperature and have the same resistance, the result  is the same at the output of the  whole circuit.

Layout diagram for the four thermistors wired in series and parallel. The thermistors’ total output resistance results in an averaged temperature reading.

Top view of all four thermistors wired.

Central thermistor. Heat-resistive Kapton tape holds down the thermistors on the heated bed.

Corner thermistor.

I put the thermistors roughly in place first using normal tape, in order to measure wire lengths and solder with ease.  The soldered joints should be fine as the heated bed has to reach around 110°C for ABS plastic and 60°C for PLA plastic, whereas solder melts at around 180°C. The thermistors were finally to the heated bed with heat-resistive Kapton tape.

Next, I should have the remaining parts needed to continue building the frame!

Extruder continued and start of RepRap frame

Continuing from the first post, I made some progress on the extruder while also starting construction on the RepRap frame.

For the extruder idler block, a piece of threaded rod was cut down to size. Based on instructions this should have been smooth rod, but since it simply sits through a bearing there isn’t any issue of friction.

Fitting two hex nuts to the top of the extruder where the idler is attached required some extensive filing which ended up in the plastic splitting at the weakest points and a small part of the plastic breaking off, but the issue was easily fixed with some two-part epoxy. Once the epoxy has set and I get the required M3 bolts, the extruder assembly can be completed.

Extruder idler block, 608 bearing and a threaded bolt piece sawed to the right size (2 cm).

Fitting the M3 nuts into the top of the extruder (drill bits used as rough guides).

Repairs on one of the bolt holes using epoxy glue..

Switching to the frame construction for a change of scenery, the first task is to put together the two “frame vertex triangle”, i.e. the triangular frames which make up two opposing sides of the printer.

The first frame vertex triangle

Both frame vertex triangles completed.

Next, the frame starts taking shape by connecting the two vertex triangles. A few more threaded rods attached and it starts looking like an actual printer!

The frame taking shape

Close-up of one side.

Close-up of side with bracket where y-axis motor will be mounted.

Top view of the frame, with z-motor mounts on either side.

Basic frame connected, before calibrating and tightening.

The frame remains untightened for now, as I need to replace the large washers (M8, 24 mm diam.) on either side of the 608 bearings with even larger ones (M8, 30 mm diam.).

Next step will be to calibrate the frame, start attaching the remianing rods and complete the extruder. Coming up soon!