Thursday, January 28, 2010

Wow Nopheads drive system is the killer App of RepRap extrusion drives!

The RapTruder Experiments could only be continued this evening as I only had time to make a template and two new versions of the RapTruder increasing the gap between the two blocks so I could try the Conrad shaft coupler as a drive gear and add a Skate bearing clamp with some fairly weak springs.

I used two Plastic blocks to join the welding rod works great!

Using The Flat pack Furniture Screw worm gear combined with a Meccano gear really works.

Please note I had to use a much bigger clamp to hold the RapTruder assembly down !!

Having seen this working now and seen the effect of just over a 3.5kg pull Maximum pull seen was 4.08Kg
I do not think Plastic gears would be strong enough to work.
I am seeing the MDF and plastic Blocks flexing as it reaches 2.9kg of pull.

The flexing makes the Furniture screw jump on the Meccano gear. The furniture screw is only a push fit on the stepper drive shaft it and it has not slipped yet.

The design really needs a shorter Worm gear; so that the assembly is not three plastic blocks high.

The optimum height is 2 Blocks only a proper Meccano worm gear will fit this height. I have not calculated the resolution the number of steps taken in the video clip was.

Taking 24464 steps.
Number of steps (-ve goes other way):

You can hear by the thump of the flexing and just how strong the pull is.

Very pleased with the results as it is only a lash up.

This is the BEST grip I have seen so far.
I am using the Conrad coupler as the drive.
This is very much the way to go the difference is so noticeable.

Having the spring adjustable grip and higher resolution are big winners.!!

I'm not sure if I can get this any better until I can stop the flexing.


Buzz said...

I have previously experimented with plastic worm gears (locally available in australia from Jaycar), and found that they were made of a totally inadequate plastic that was unable to deal with the significant load that an extruder generates, so I agree, we should stay away from plastic for these couple of parts.
What's the back-lash like on your extruder when you reverse it? There seems to be a lot of it, which might interfere with the optional firmware feature that reverses the extruder after each extrusion...?

Unknown said...

I've not looked at backlash.

The stepper has to turn 1 revolution to move the extruder drive one gear tooth forwards or backwards.

If I try to turn the gear in either direction I can't feel any movement so Its achiving worm lock.

However if there is any measurable backlash it would be an equal number of steps for each direction change.

Thus a simple task in SW to add any anti backlash adjustment steps; each time an anti ooze direction change is needed.

Note for this lash up I'm using a screw thread. I don't have a proper Meccano worm that anyone can buy for £4.25.

Greg said...

perhaps put some spacers on the right of the mounting board between stepper motor and mounting board? Then you won't need so much spacing to the left of the mounting board...

Unknown said...

Thanks Greg I will give that a try today some when. I was busy yesterday doing this project as the weather was good :-

Cant wait to get this project done as I will have my own space to work on all of my Ideas and projects once this is completed.

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