Thursday, January 27, 2011

A Little Progress

I have spent most of this week working on costuming for my daughter's musical theatre project so I haven't managed to get much done on the Mendel. However, I did manage to make a flowing black robe and a Greek helmet with a silk flame built into the top so she could play Hades in a musical number from Hercules so the week wasn't a total loss. Whenever I am faced with something like this I immediately turn to the Instructables website. I was able to find instructions for a cardboard version of a Roman helmet that worked great. This is one of the best sites on the Net for information on creative projects.

I did manage to find time to add a washer to all of my idler bearings for the belts. This provides just enough extra space so the belts move smoothly. The X and Y carriages both move smoothly now.

I have also roughed out the mounting board for my electronics. I will cut it and drill the holes tomorrow. I am planning on using the printed mountings for the original laser cut mounting boards to mount it so it should be a nice clean job.

A couple of other small jobs that I will get done in the next day or so:
  • make a new set of opto flags. The pop can aluminum I used for the original ones is just too light. They flex in a strong breeze.
  • make a mounting bracket for the 12v power connector. just need to bend and drill a piece of aluminum
  • make some sort of mount for the USB board. No mounting holes in it so I'm not sure what I will do there.
After I wire up the electronics I will finish off the extruder. I started to assemble it a while back but never finished. I stopped at the point where I was going to make the heater coil. When I read the instructions I realized that they wanted me to turn on the heater in order to cure the paste that holds the wire in place so I had to wait until I had the electronics ready.

My new Z-axis belt has been shipped and should be here within the week. Things are looking good!

Monday, January 24, 2011

Some Progress and Some Planning

Well, I pretty much completed the mechanical construction this weekend. I installed the Y-axis bars and the chassis. I had to remove and rebuild all the bearings on the chassis in order to get them to slide smoothly on the bars but I managed it eventually. Only the installation of the bed remains and I may wait until the heater arrives and make an aluminum bed instead of the laser cut acrylic that I have now.

I discovered one more problem with the mechanicals that I will have to fix. The idler bearings for the belts don't have quite enough room for my 1/4" belts. The belts stay on but they rub against the fender washers and the friction will be a problem during operation. I will have to remove all of them and add another washer or two to make a bit more room for the belt. Not difficult, just one more small tuning type task.

I also ordered a new z-axis belt from SDP-SI. I was able to order the same belt that I had before but with an extra two inches of length (39" vs 37").

Next up - the Electronics!

The next step is the installation of the electronics. I have the Gen-3 remix from Techzone and the boards are considerably smaller than the original boards for which the laser cut mounting boards were designed. I discovered a great alternate design on the Techzone Gen-3 Installation Wiki page that mounts on the side of the Mendel and supports all the boards on a single panel:

Single board electronics mount.

Side mounting of the board with zip ties.

This one is made out of a used nylon cutting board but I think that I can find a scrap of something around the garage to use.

Note - there are actually two Wiki pages for installing the Techzone electronics. The one with this nice mount is largely incomplete. I think that they abandoned it and started over. The one that contains the most current and complete information on installation can be found here.

On the Wiki they also discuss the possibility of using an additional stepper driver board for the extruder rather than using the extruder board to drive it. Apparently it results in a more reliable and quiet extruder. I will have to look into this. Perhaps I can find some information on the forums from someone who has tried it.

I admit to being intimidated by the prospect of installing the boards and wiring everything up. When doing the mechanical build I was able to disassemble and fix anything that I messed up. With circuits I may not know until I turn on the power that I have an issue and it may be too late at that point to avoid the smoke and sparks. I will just have to proceed carefully and do any testing with only the minimum number of boards connected in order to limit any damage that might occur. In a worst case I can always buy replacement boards from Techzone but I would like to avoid spending too much more on the machine.

Wednesday, January 19, 2011

Problem Solved! .......... And a new problem arises

I added the stick-on rubber feet to the Mendel and they raised it just high enough for the Z-screws to clear the bench. I also found that using lock washers on each side of the Z-axis bearings solved my problem with the washers contacting the mounting screws. This means that I am good to go for the rest of the build.

Or it would if I hadn't encouontered another problem as soon as I moved on. The Z-axis belt proved to be too short, even with the tensioner in the loosest position (as these pictures show. I obviously messed up my parts order somehow so I will take a look at the bill of sale to see where I went wrong.

This doesn't mean that I am stalled again. I should be able to proceed with everything else while waiting for the new belt to arrive. I now have all the motors installed and I have the x-axis moving smoothly (by hand). I think that the next step is to install the electronics and the build table.

Wednesday, January 12, 2011

X-Carriage Rebuild

A correction of my last post. The part that I broke was not part of the extruder. It was actually the lower X-carriage. See Below:

When the upper and lower parts of the carriage were assembled the 2 sets of 180 bearings did not close on the steel rod. When I tightened the bolts on that side the two parts of the carriage were drawn together and the lower one snapped. You can see the stress marks where it broke.

When I took it apart tonight I found that it had also broken at the belt clamp mount.

I carefully measured everything that I could think of to compare the original parts that I got from Nophead against the new ones but they seem to be identical. I can only assume that I did something incorrectly during the assembly that threw off the fit but I had completely disassembled it by the time I realized this so I will probably never know. At least I can confirm that Nophead's parts were not the cause of the problem. That comes as no surprise since they have been excellent in fit and quality throughout the build while my own skills have proved to be .............. slightly less than excellent, shall we say?

It only took a half hour to take it all apart and reassemble it. It now fits fine, moves smoothly and I can proceed to fixing my problems with the Z-axis.

I picked up some rubber feet for the bottom of the machine today. They should lift it up enough to resolve my problem with the Z screws contacting the bench and also will help with vibrations. I still have to figure out how to assemble it so that the screws move smoothly. currently the bearings are being contacted by something and won't rotate.

Thursday, January 6, 2011

I'm not Dead!

I'm back!

I never expected when I paused for my vacation back in July that I would still be paused at the end of December. Some health problems combined with an extremely busy fall/winter have kept me away from the workshop for far too long. I notice that I am not the only one as the frequency of posts from all the blogs that I follow has fallen off considerably over the last 6 months.

I went downstairs yesterday and tidied up the workbench so I can start working on the Mendel again. Just to recap - I have finished the basic mechanical structure and I am working on the z axis mechanism. I had to get a new set of extruder parts since I clumsily broke the ones that Nophead made for me by overtightening the bolts. The new parts arrived long ago and need to be assembled. This will be the third time since I had to toss the first set of cast parts that I bought due to their poor quality.

My current problem is that the washers that sandwich the bearings for the Z-axis rods are not the right size. They are too large and interfere with the operation of the bearings. I haven't been able to find the correct washers anywhere here so I have used my bench grinder to modify the ones that I have. Hopefully that will take care of things and I can get moving again.

Also, the z-axis rods extend too far below the chassis. I think this is due to the 1/4" nuts being too large. I will have to put some rubber feet on the Mendel to prevent the rods from contacting the bench.

Hopefully, I will have more progress to report later this week.