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jhinkle

How to square axis in assembly - solved

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Posted · How to square axis in assembly - solved

It is kind of passing the buck, but it is a wiki, so anyone could choose to fix it.

 

In other words, maybe JHinkle should do this.

 

 

I would have thought UM would have updated their assembly instructions on line about the new tool they provide.

 

UM is open source - people can download the plans and make it and UM gets zero money. This is a nice thing to the community. In return the community (me?) helps out and contributes in return. Some of the designs basically came from the community and not UM (for example the current extruder design on UM Original).

Makerbot on the other hand is just out to make money (just my opinion of course) and so I would expect it's harder to get people to help out for free.

Because UM is so nice, and because you will be helping other people - maybe you could post it on their wiki?

 

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Posted · How to square axis in assembly - solved

I just read it. Nice. Although people can make 2 perpendicular lines using a square.

Anyway - thanks for doing this!

 

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Posted · How to square axis in assembly - solved

My UM can print 210 mm x 210 mm, but I was never able to quite achieve full. symmetrical, and square factory-published UM-spec travel after using any of the measurement and alignment tools.

The large 8 mm "axes" rods are fixed. There's nothing you can reasonably do to adjust their alignment. If they are not nearly square in the frame, you have a problem that I've not experienced and I will not address it here.

Therefore, one can only twist and load the small rods, using the pulleys and belts, to maximize the travel of the head at the machine's mechanical and switch limits. FWIW (your mileage may vary), this is roughly how I adjust the alignment of my small diameter rods. I use an iterative process and, now that I have a feel for what's required, I can adjust the rods in about 10 minutes after replacing all the belts.

First, the goals.

Goal #1: Adjust the pulley positions along the small rods such that the long belts remain parallel to the large 8 mm rods as the print head moves throughout its travel range.

Goal #2: Adjust the limit switches to produce their "click" just as the print head reaches its mechanical limit.

Goal#3: Adjust the pulley positions such that the above switch limits are reached at both ends of the print head's complementary positions. For example when adjusting the x=max limit switch, the switch's audible click should occur just as the head reaches its maximum x-travel, regardless of whether the head is maintained near either the y=min or y=max positions.

Once you achieve the above goals, your UM is optimally adjusted. The process requires trial and error iterations using the following techniques:

1. While moving the print head though its full travel in X or Y and holding the other axis steady, watch the moving long belts. As the head approaches its travel limit, the distance from the block to a pulley will decrease and tend to visibly pull the belt to the side, if the pulley is not correctly aligned along the length of the large 8mm rod. Move the head back and forth between its limits while sighting a moving long belt against its nearby parallel large 8mm rod or the edge of the top "window" in the frame. Adjust the pulley positions until the belts run parallel. Once you achieve Goal #1, you will probably not need to do this step again, unless the position of a pulley along its rod is disturbed in the next step...

 

2. With one set of long belt pulleys (four pulleys) slightly loose, apply a twisting force to the small rod (push in opposite directions on each end of the rod) and tighten the pulleys. (It helps to be an octopus but you can use clamps or jam blocks, if you only have two hands.) Changing the angular position of the pulleys on the large rods, in this manner, will "bias" the belt tension and change position of the end of the small rod and its mating bearing block. Using this technique, you can eventually realize Goal #2. Alternately, it is sometimes best to just adjust one side at a time (only loosen two pulleys at a time) or one side only.

The process is much easier to demonstrate than describe. I will try to find time to take a video of the procedure after I install my "direct stepper drive" parts and ditch my short belts. I've had the parts for a long time but never seem to find the spare time to install them.

 

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Posted · How to square axis in assembly - solved

While reading this post i felt like I have a missing twin in Florida. All this is exactly what i was thinking. How are you supposed to set up an fixed system how can u change the direction of something that is fixed build in. I'm currently not in reach for my printer to try your solution but it will be the first thing I´ll do as soon as i get home :DDD

I realy hope this will get the job done. ;DDD

 

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Posted · How to square axis in assembly - solved

THANK YOU JHINKLE FOR THIS!

I've been printing for 8 months with a VERY hard to move head. I was 100% sure that my printhead wasn't making my small rods exactly 90 degrees (because I was unable to get my large rods truly perpendicular), but everyone said it was unlikely that the printhead would cause that.

I will try again now!

Thank you...

 

It squared nicely once I got the rods in the print head to be 90 degrees.

I loosened the print head's clamping screws and the adjoining bolts. The print head was still a very solid and no flexing anywhere was perceived.

Using my drawing of perpendicular lines and the rods as lever arms, I attempted to get to 90 degrees.

I felt nothing move at all. but after a couple of times on the rods applying force in the correct direction, the rods measured 90 degrees. I felt no movement -- but it moved.

With the print head rods now at 90 degrees I inserted the print head into the printer.

Set belt tension and placed the alignment squaring tools.

Perfect square!!!

It only took 8 hours of pain and anguish figuring out root-cause and addressing it.

Now that everything is square WITHOUT having side forces applied to the bushing in the sliding blocks -- the head moves smoothly.

I hope this helps anyone else with a squaring issue. Be careful NOT to just force square by forcing and setting the pulley (as UM suggests) or you will not run smooth and your stepper motor will run hotter than required.

Joe

 

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Posted · How to square axis in assembly - solved

Actually something other you could try that you won't believe:

Sewing machine oil. Few drops on all silver rods(8, including two in the Z stage).

I had a very tough to move head too, squared it, didn't make a difference... Then I bought some oil for 4 euro's. Best buy ever :D

 

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