3D Printing (Part 13)

Part 123456789101112, 13, 14

Many PLA rolls were fused in my Welleman k8400. So far, it has been a good servant in spite of few breakdowns, mainly due to clogged nozzle or improper adjustments. Careful cleaning and fine tuning solved all  these problems except one which is my fault. As I was taking apart the fusing module, I damaged the thread on the alumina plate that I add to replace. I also noticed few cracks on the body parts which occurred months after assembling my printer and which are probably due to over-tight bolts…

Except these minor problems, I have no particular complain and lots of enjoyment with this printer. Although PLA is very, very easy to print in most cases, it lacks to mechanical properties of ABS… And printing ABS on a non-heating bed is almost impossible. As I had to print a small ABS part in a hurry, I used an air dryer flushing hot air beneath the printing bed but this was some sort of desperate option although it proved to work fine. Months ago I ordered a heating plate and a spare DC power supply but I failed to find time to install the option and had no more particular reason to do it. Under the pressure of some Christmas presents that require some printed parts, I proceeded with the modification that I will now describe.

Removing the printing bed is plain easy. Some drilling in the metal plate is necessary and a drill press might be very useful for achieving a clean result. Draw carefully the center of the drilling locations (3.5 mm) using the heated plate as a template. Also, use a special conical cutting tool for removing enough metal from the heated bed so that the heads from the flat screws (M3x15) do not exceeds the surface (opposite to the heating layer).

Cut the original support plate to leave space for the electrical connections.

Cut the insulation rock wool sheet with a simple cutter.

Solder the 100 kOhm thermistor on the heater plate so that the little bulb sits in the dedicated hole. Put some thermal compound in this hole in order to improve the thermal joint.

Take special care to the connecting wires: they must not touch each other and must not touch the metal plate either.

Assemble the parts; use tooth lock washers and gently tighten the nuts. Solder the wires on the plate after checking the required configuration depending on the power supply used (12 or 24 V) and reinstall the whole assembly. Next is an illustration of the retaining springs that I used in the past: I reused the design for making larger springs as the printing bed got thicker.

Then you will need to move the Z axis stop sensor 8 mm downward. You have no other choice than to drill 2 new holes in the back panel of the printer. Adjust the stop position using the standard procedure.

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