Improvements for 2nd batch

Topics Related to the ORD Bot Printer

Re: Improvements for 2nd batch

Postby Halfdead » Sat Apr 21, 2012 11:23 am

Some flex couplers instead of the current ones would be a good improvement. Currently Z wobble is a bit of a problem(for me at least).
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Re: Improvements for 2nd batch

Postby IPvFletch » Sat Apr 21, 2012 2:35 pm

I began to mount my Z-axis lead screws and noticed the same wobble. The screws are warped from the factory apparently. One is really bad, the other is not so bad. I don't think I can fix it w/out damaging any of the the threads. I know of some other ORD folks already who have swapped in flex couplers. I think I will procure some myself now.. :)
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Re: Improvements for 2nd batch

Postby Halfdead » Sat Apr 21, 2012 3:13 pm

IPvFletch wrote:I began to mount my Z-axis lead screws and noticed the same wobble. The screws are warped from the factory apparently. One is really bad, the other is not so bad. I don't think I can fix it w/out damaging any of the the threads. I know of some other ORD folks already who have swapped in flex couplers. I think I will procure some myself now.. :)



I printed some makeshift ones. But yeah, the leadscrews are kinda boned.
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Re: Improvements for 2nd batch

Postby bdring » Sat Apr 21, 2012 5:50 pm

The original design had flex couplers, but all the experts talked me into solid ones :) Flex couplers are easy to buy off eBay.

Sometimes when using set screws on threaded rod, the rod can tip a little in the coupler. Try rotating the coupler a little and resetting the rod. It may or may not help. Also make sure the motor and threaded rod are not touching too.

The rods came from McMaster, I just cut them to length. They don't have many length options for metric threaded rods.
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Re: Improvements for 2nd batch

Postby Halfdead » Sat Apr 21, 2012 6:52 pm

bdring wrote:The original design had flex couplers, but all the experts talked me into solid ones :) Flex couplers are easy to buy off eBay.

Sometimes when using set screws on threaded rod, the rod can tip a little in the coupler. Try rotating the coupler a little and resetting the rod. It may or may not help. Also make sure the motor and threaded rod are not touching too.

The rods came from McMaster, I just cut them to length. They don't have many length options for metric threaded rods.



Do you know where I could source some flex couplers from within the US? I checked eBay but It's all from china :\
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Re: Improvements for 2nd batch

Postby crispyfry » Sat Apr 21, 2012 11:44 pm

You can probably get your printer working well enough to print a set of these (http://www.thingiverse.com/thing:9622). If you read the instructions and use a piece of soft hose like you're supposed to they work far, far better than you'd expect. It's a very simple print that should still function as intended even with lots of z wobble.
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Re: Improvements for 2nd batch

Postby Digitalmagic » Sun Apr 22, 2012 1:59 pm

bdring wrote:The original design had flex couplers, but all the experts talked me into solid ones :) Flex couplers are easy to buy off eBay.
Sometimes when using set screws on threaded rod, the rod can tip a little in the coupler. Try rotating the coupler a little and resetting the rod. It may or may not help. Also make sure the motor and threaded rod are not touching too.
The rods came from McMaster, I just cut them to length. They don't have many length options for metric threaded rods.

I would avoid using set screws on leadscrews/threaded rod, if possible.
Why not using Fairloc coupling? Available diam should be ok.
Image

Or flexible zero backlash coupler? If size ok.
I think "experts" discarded them, thinking of angular flexibility, generating Z inaccuracy.
Image

These couplings avoid the set screw issue.
Human has 20 nail ... extruders.
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Re: Improvements for 2nd batch

Postby rogue555 » Sun Apr 22, 2012 6:47 pm

There's a solution to the coupled problem of imperfect alignment and accuracy in motion. The direct drive linear axes I've come across always have two plates, one where the motor mounts and another with some combination of a thrust and radial bearing. This allows you to use a flexible coupling between the motor and lead screw and have a "rigid" mounting of the lead screw. I bet such an arrangement could be made, maybe even printed, without losing any z axis range.

The main problem with this that I see is the icrease in cost and complexity.

-Matt
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Re: Improvements for 2nd batch

Postby Halfdead » Sun Apr 22, 2012 9:11 pm

crispyfry wrote:You can probably get your printer working well enough to print a set of these (http://www.thingiverse.com/thing:9622). If you read the instructions and use a piece of soft hose like you're supposed to they work far, far better than you'd expect. It's a very simple print that should still function as intended even with lots of z wobble.



I'm using them but, they don't seem to work.
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Re: Improvements for 2nd batch

Postby WhiteB0rd » Sun Apr 22, 2012 10:08 pm

I view the Z axis issues as yet another "chicken -- egg" problem, like the extruder mount.

Once I have a printer up and running, there are improvements to consider. The Z axis upgrade to thrust bearings, etc., was actually something that came up in a forum discussion some time ago. The beauty of the ORDbot is that the majority of its integrity and precision stem from the makerslide.

I would even go so far as to advocate a "good enuf to print upgrade parts" standard for the the next gen. Among other things, that keeps the initial cost lower.

I expect Bart and the other gen 0 ORD botters to re-engage on this and other topics once the dust from the initial shipment settles, and we have machines working well enough to prototype new parts.

That's the whole point of a rep-rap after all.....



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