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Jolt & friends - Team Overkill - NSW
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shakesc



Joined: 14 May 2012
Posts: 62
Location: UK


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Nick, when I stripped my super cheap Chinese linac down I found it had a plastic nut for the actuator. Not sure what yours is like but mine wouldnt take much more power

Post Thu Apr 14, 2016 5:35 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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I took my linac apart today and discovered the same thing Sad. Its not going to take much of a beating, so the linac is more of a test part than something to put in the arena. The new plan is to build a quick test lifter and then move up to a better linac or a ball screw.

I saw that a short length of ball screw and a nut was $55 from Taiwan, cheaper than many large linacs and you can see what you get. I'd have to make my own back plate with thrust bearings, but it would be better than 'most any commercial linac.
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Post Thu Apr 14, 2016 5:58 pm 
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Ellis



Joined: 21 Jul 2012
Posts: 129
Location: Shopshire, England


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Rolled ballscrews are dirt cheap straight from China. Something like a 1204 ballscrew and nut could make the core of a really nice, efficient actuator. Many of them already have the ends machined, such as: http://www.aliexpress.com/item/SFU1204-ballscrew-200mm-set-1-pc-SFU1204-Ball-Screw-L200mm-1-pc-1204-Ball-Screw-Nut/32436795302.html?spm=2114.30010308.3.29.GsWRqo&ws_ab_test=searchweb201556_6,searchweb201602_1_10037_10034_507_10032_508_10020_10017_10005_10006_10021_10022_10018_10019,searchweb201603_9&btsid=84926650-cc3a-485f-8890-fe93324a453d

edit: that's one monster URL!
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Post Thu Apr 14, 2016 9:40 pm 
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shakesc



Joined: 14 May 2012
Posts: 62
Location: UK


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Tempted to grow my own as well
Rory for Richie made his own out of a car jack but a lead screw system and a beefy motor seems a good route

Post Thu Apr 14, 2016 10:14 pm 
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Nick
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Thanks Ellis - that is exactly what I have in mind Smile. They even machine to spec, which is a huge time saver.

Since this going to be a four bar mechanism and its going to be cheap 'n cheerful, I am going to call it 'Fubar'.
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Post Thu Apr 14, 2016 10:30 pm 
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Ellis



Joined: 21 Jul 2012
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Location: Shopshire, England


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Let me know how you get on with a custom ballscrew (if you go that route) Nick. I'm on the cusp of a CNC build and feedback on one of the many sellers would be useful!
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Post Thu Apr 14, 2016 10:58 pm 
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Valen
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Joined: 07 Jul 2004
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Location: Sydney


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We used to use linearmotionbearings2008 on ebay for our ballscrews/nuts

http://www.ebay.com.au/usr/linearmotionbearings2008

but he seems to have gone quiet. I've just sent him a message, we'll see if he replies
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Post Fri Apr 15, 2016 7:35 am 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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UK aftermath:

I am still sick as a dog after the flight home, so nothing much has started in the workshop yet. Here is what's going on:

* Battery capacity
I charged the pack that was used in the almost six minute long Gladiator battle. Amazingly, it only took 2.5AH to fully charge the 4.25AH pack - only 58% of the capacity Shocked. Unless I somehow created a perpetual energy device, there are huge improvements to be had from the weapon system. The first thing to try is a lower gear ratio on the belt drive.

* Wheels
Drawing up some designs to print is easy even when you are sick, so that's well under way. The absolute widest they can be and still fit is 32mm, up from 25mm. I ordered some Ninjaflex and just today I discovered the Flexion print head on Angus's Maker's Muse channel:



Thanks Angus, the timing could not have been better! My Cocoon printer will hardly have any original parts left soon. Laughing

In case the Ninjaflax idea doesn't work out, I also ordered a small roll of soluble PVA filament. The idea is to make printed moulds for casting urethane that would be impossible to separate using a regular mould, while the PVA will just dissolve away in water.

* Weapon belts
After the urethane belt started melting in the Gladiator battle I want to replace it. I found a range of M sized belts that are about the right length so I'm ordering the three closest lengths and will play around with larger motor pulley sizes and positions to find the best solution.
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Post Fri Apr 15, 2016 9:21 am 
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Valen
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http://stores.ebay.com/linearmotionbearings

Weird it was only showing one item in the store before for me but just spoke to Chai and all is well, He's the guy we get our linear motion stuff from.

Send him a message and he will create an auction for what you want
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Post Fri Apr 15, 2016 10:05 am 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Custom Wheels:

Mr Mangle's new new wheels are evolving fast! With Flexion print head and Ninja flex both on the way, I finished a quick render of how the wheels may look:



The hub is virtually the same dimensions as the existing Colson wheel as the recessed area fits around the outside bearing - I can't change that area much. The orange tread is around 15mm thick and features many 'speed holes' to increase the flex in the tread. That area can be modified endlessly until I find a combination that gives enough flex to track uneven floors and still provide plenty of grip.
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Post Sun Apr 17, 2016 8:40 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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3D printer problems:

I had major issues trying to print a test wheel for Mr Mangle - you know there is something wrong when even PLA won't stick to the bed! It turns out the the heated build plate is warped down in the centre by at least .4 mm. That means when the corners are levelled with zero clearance, there is still too much of a gap at the centre for the first layer to stick Mad.

After all the mods I have made to the printer, Aldi / Cocoon are probably no going to replace the bed under warrantee, so I either have to fix it or find a new one. Bending the plate flat again is going to be difficult but since there is nothing to lose, its the first thing to try.
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Post Tue Apr 19, 2016 10:32 am 
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Nick
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Wheel Moulds:

The printer bed is fixed; I had to put all my weight into bending the heater plate flat and even now its slightly bowed. it managed to stick down the test print for the wheel mould, so its good enough for now.



This is a 10mm high test for a urethane wheel mould to check the strength. The little pillars are more than strong enough but the outer wall is going to need more than two layers when it gets to full hight.

The PVA and Ninjaflex filament arrived today - I had no idea it was made by Fenner drives, the same company that makes the urethane V belts that Mr Mangle uses. I'd really like to try it out but there is little chance of it feeding with with the regular hot end on the Cocoon printer; best to wait a week or two for the Flexion hot end to arrive.
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Post Thu Apr 21, 2016 7:07 pm 
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Ellis



Joined: 21 Jul 2012
Posts: 129
Location: Shopshire, England


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Do you think the small ridges between layers will make ejecting the mould a pain? Every little imperfection will want to grab the rubber a bit. Probably not an issue if it's soft enough but harder compounds might be difficult to shift?

Perhaps ABS and a fairly extreme acetone bath is an option if so.
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Post Thu Apr 21, 2016 8:10 pm 
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Nick
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Joined: 16 Jun 2004
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WAAAAY ahead of you! Smile The final mould will be printed in PVA filament, which dissolves in warm water. Part of the testing is to find how flimsy the walls can be and still hold their shape so they dissolve quickly after the urethane is cured.

The Ninjaflex is mainly for testing the hole pattern before I get messy with the urethane and partly as a plan B in case the PVA moulds don't work out.
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Post Thu Apr 21, 2016 8:24 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Upgrades:

Mr Mangle's broken power link retainer is fixed:



I replaced the whole thing with a slightly thicker titanium spring, a high quality UMHW catch and extra screws. The new plastic will bend twice as far as the original HDPE without breaking and the extra screws will hold it in place even if it does crack a little. Short of getting hit by an axe, the power link is going to stay in place for ever Smile
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Post Fri Apr 22, 2016 1:00 pm 
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