build finished but

finished building fisher printed out 2 robots and a few other things when all of a sudden 3 of the laser printed arms decide to snap after 3 days not a happy chappie at all getting to the point at the moment of wanting to put it in a corner and forget it i know its a cottage industry but the arms should not snap after 3 days the only other alternative is to now go and spend extra money on carbon arms this to say the least is not really exceptable with a new item.

dissapointed.

Its quite likely that snapped arms are down to a build issue over tightened arms or catching on something, RRP report that they have built and operated Fishers that operate for a long time without an arm failure.

RRP have made attempts at improving the arm design since the Fisher Beta, but frankly, I'm really not surprised to be hearing reports of snapping arms again.

The thing to remember about the fisher is its designed to be a cheap easy to build kit, and the arms are effectively made from material that would be waste from the manufacture of the side plates, bit it will be a shame if many fishers end up gathering dust because owners get frustrated after the arms break, because once its running well the fisher really is a great little printer.

The other great thing about the Fisher is its easy to work on and easy to improve and the good news is carbon arms are definitely worth the effort and not really all that expensive to build.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

not over tightend or catching have been using ball joint links for 30 years now so I know they were not over tight ensured on first print that nothing was catching. may be it is a cheap easy to build kit but parts shouldnt break within 3 days of being built. carbon rods now bought along with ball end joints so thats another £25 ontop of the purchase price after 3 days cheap it may be to buy but expensive to run and maintain up to now.

Mark.

The problem with having 30 years experience with ball joints is it doesn't really prepare you for the day when someone makes their ball joint assembly out of laser cut acrylic.

There is a common wisdom on this forum that overtightening and catching may cause many breakages, not suggegting you did your up with a 200lbs torque wench, just relaying the common wisdom.

Myself, I broke all the arms, so decided to try and make something better and your welcome to the fruits of my efforts.

Once you get past the acrylic arms problems there are not really many more hidden costs, look on the bright side, it may have cost you gbp25, but if rrp has included the parts in the kits then the kit would probably have been gbp30 higher.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

I feel for you, same happend to me, the just kept on breaking. I even used the scrap around the arms to make new ones by hand and they broke too. I made carbon fibre arms and they have been great, and the make the machine quieter too. The down side is that it adds another £20 or so to the build as you have to buy 20 ends when you only want 12.

Edited 1 time(s). Last edit at 01/02/2016 11:15AM by DADIY.

sorted this now with carbon fibre arm much better prints much quieter as well

Mark

I made some carbon arms for mine, but had printing issues. The first layers weren't sticking together at all. Could this be down to the arms not being exactly the same length? I made a jig using spare acrylic arms, but I still struggled.

Thanks.

When I made mine I got a piece of wood ( 2x4 ) and two 5.5mm drill bits. I marked two dot 160mm apart and drilled each with a 5.5mm drill. Then into each hole I slid the smooth shaft end of the 5.5mm drill bit. I used the mugen track ends.

As I glued each rod with epoxy I slid the arm down the drill bits which held them apart at the right distance. I then layered grease proof paper between each rod in case glue dripped. Each one had a little a little air which inside which tries to push the ends off the rod.

I think it's important that they are all the same length. It may get be worth checking they are all the same hole centres.

Hope that helps.

Hi, Dadiy. I actually did that, after reading your other posts about it. I bought extra arms too, so used those to help. I was really struggling to get the ends on and lined up after drilling them out, so I think one or two are a bit longer. I might try making a few more, I've got plenty of carbon rod. Shame the mugen ends aren't threaded, though I could try tapping them. Obviously threaded rod will be heavier, but easier to get accurate.

The probblem with threaded rods is you can only adjust the length by half the thread pitch, unless you make a turnbuckle style arm which would be heavier, complex, ugly and very likely to come loose....

If you want to try a threaded rod solution look at the printed arms in this forum.

There is also my carbon stiffened printed arm design which is untested but available on thingiverse

Edited 1 time(s). Last edit at 01/06/2016 04:04PM by bgkdavis.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Assuming that you drilled your holes nice and square and left the arms on untill the glue set they should all be the same length. You could use an existing arm to check the jig.

Well, I can't guarantee I drilled them all to exactly the same depth, or cut the rods exactly the same. I've just measured again, and I reckon there's less than 0.5mm difference between the longest and shortest. Unfortunately my caliper only goes to 150mm, so I had to use a ruler.

You need to build a jig to hold them all the same length. Dry assemble the first one and tweak the carbon fibre length until it fits over the jig ok. A little wiggle room is ok as the glue will fix that and the jig holds everything to the same length while it dries. If the rods too long the jig won't allow you to slide the arm over so at least at that point you can tweak it n

I might try redrilling them out a bit wider, I've got a 3.2mm bit, which will should make it a bit easier.

When making up carbon fibre rods for delta printers, I use a jig to assemble just one rod at a time. The epoxy I use sets hard after about 3 hours in the airing cupboard, so I can still make a set of 6 rods in a day.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

For replacement arms, there is still the solution to have arms build with a combination of printed parts and 3mm threaded rods.
The elements are here : [forums.reprap.org] or there [rouzeau.net]
But you need to have an access to a printer to build them, so better to print ends and have them ready just in case.
That may looks low tech compared to carbon fiber arms, but cost is very low and they work well. They even are slightly lighter than the original. If printed in PETG, their wear may be negligible and you can use whatever lubricant you have.
Other have tried with success ends in PLA (beware, this is not the same file for PLA ends as PLA is nearly twice the stiffness compared to PETG, so I modified the design to be more flexible).
M3 threaded rod length 1m is 0.5~0.8 euros.

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Pierre

- Safety [reprap.org]
- Embedded help system for Duet and RepRap Firmware [forums.reprap.org]
- Enclosed delta printers Lily [rouzeau.net] and Lily Big [rouzeau.net]
- OpenScad delta printer simulator [github.com]
- 3D printing on my site [www.rouzeau.net]