Wednesday, June 19, 2013

RepRapPro Mendel (part 7)

The RepRapPro Mendel has been a great printer, but it’s been plagued by a number of issues which arise from prolonged print runs and constant use. This, I believe, is not indicative of an inferior machine, but just the nature of DIY printers in general.

This entry will survey more of the problems I’ve had with the RepRapPro Mendel. Some of these problems must be prevalent with their printers at large since RepRapPro has made some recent design changes to correct them. Most of these problems, I’ve had to solve on my own.

Here are my recent issues:

I’ve had problems with the parts which are exposed to the heat of the bed. This is probably because the parts are made with PLA rather than ABS. PLA has a lower tolerance for heat.

The Y belt clamp has been a continual headache. The heat from the bed softens the clamps and this causes the belt to slip. The screws are instrumental in this problem by conducting too much heat through the clamp. I’ve had to make several adjustments or modifications to keep the belt properly tensioned.




The Y axis motor mount has warped considerably over time and had to be reprinted. RepRapPro now sends this out as a laser cut wood part in their kits. I remade the part in ABS which should hold up fine for my use.



The next problem I’ve had is with the bowden cable attachment at the extruder side. The clip which holds it in place would wiggle its way out and the cable would detach. I lost several long print runs because of this. I fixed it by simply tying the clip in place with a zip tie.




The next problem is with the Melzi controller. I just haven’t had much luck with this board. This time it's with the mini USB connector. It separated from the PC board. Fortunately it wasn’t damaged and I could solder it back in place, but it wasn’t a very easy task to accomplish. The 5 pins are very small and it  required some very steady work and I think some luck to get it in place.






The last problem has been a reoccurring failure of the heat resistor, but RepRapPro has made a component change and now sells a more robust ceramic heat resistor. The replacement part I found as a substitute has been easier to install, but hasn’t provided any longer service than the OEM part. I’ve purchased replacements for all my RepRapPro hot ends with the new ceramic resistor.






Once again, I think the RepRapPro Mendel is a great machine and I would recommend it highly to anyone who is looking to purchase their first printer. It’s a very nice system and it’s continually improved.

There are just inherent weaknesses in the DIY system. I hope that by finding these weaknesses in all of my printers, I’ll be able to perfect the technology for my use in creating sculpture. This has been my underlying rationale for building the printers I have so far.

Addendum Aug. 18, 2013

I can't seem to keep the belts on my XY axes tight. My best solution was to drill holes in the X carriage and run the belts through them and then clamp with nylon ties.

 I did this also for the bed.


I also had a problem with one of the PLA printed pulleys. I replaced both XY pulleys with aluminum T2.5's that I found on eBay. Since the pulley diameter is larger than the OEM versions, I had to re-calibrate the axes.


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