3d printing and SketchUp help please



Hi John, this is the sort of thing I was originally thinking about:
https://dl.dropboxusercontent.com/u/5772409/Trailer%20back%201.JPG
There are only really two critical dimensions and they are the internal width of the channel (so it will actually fit over the top edge of the trailer) and the diameter of the 'peg' (or socket, so that it is a loose interference fit in / over whatever pole I select).
One of those brackets on either end of a pole sitting across the top of the trailer lengthwise to stop the PVC cover from pooling water. The trailer sits with a reasonable slope to the front so the cover does shed water reasonably well, as long as it doesn't get a chance to sag inwards too much. I may go to two or even three poles to give a better effect.
So, the real work will be being done by the combination of the inside edge of the bracket, the top and the support tube / peg.
As the trailer is only around 1.4m long, the tube doesn't have to be particularly strong but it does need to be reasonably stiff, easy / cheap to buy and ideally non-rusting. Once I find the right material I can decide if the fitment to the 'bracket' will be internal or external. I briefly considered plastic conduit but that would probably sag in the heat.
Maybe a cheap paint roller extension pole or those mock bamboo, green plastic coated steel poles (the latter being very cheap and reasonably stiff)?
Cheers, T i m
p.s. Alternatively, depending on the diameter of the tube, a simple (3d printed) 'fork' on each end of said tube (with one leg above and one below the trailer top edge) with the tube slid in at an angle might achieve the same end?
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On 17/05/2015 22:21, T i m wrote:

I would have thought a "socket" would be better than a peg - lets you use solid or hollow rods.

How about we make it a spigot - so you have an internal and external diameter - then you could say use a dowel in it or conduit over it?

I will do you one to play with and see...
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John.
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On 19/05/2015 09:50, John Rumm wrote:

ok Tim, try that:
http://www.internode.co.uk/temp/TrailerBracket.skp
Outer diameter 17mm to take electrical conduit, and internal just over 1/2" for a dowel. I added a 5 degree incline, so it will introduce a slight bend in the rail.
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On Tue, 19 May 2015 10:22:24 +0100, John Rumm

Cool, thanks. ;-)

Very flexible.

I thought of that but unfortunately, unless the bracket can be clipped into the trailer frame to prevent the bracket rotating on the top frame, I'm not sure it will do what we would like? (The 'U' section could be made strong enough to maintain a tight fit on the frame but 1) the frame itself is quite light and isn't bolted hard to the (plastic) front panel at the top so would probably twist when any torsional load was put on it and 2) The (thin) metal top frame goes up the outside (about 25mm), over the top (our 22mm) but only back down on the inside about 15mm, so not really enough for any bracket to rest on (especially with that length of lever))?
More importantly (re 3d printing), unless you provide a disposable 'raft' under the bracket whilst being printed, I'm not sure it would print with that angle and partly the reason I had the dowel level with the top face of the bracket, thinking it would have to be printed upside down. You could print the angle as long as it was carried though into the top plane of the bracket. That also raises the question of being able to print the socket. You could do that if printing it with a removable support plug or print it with the open end facing upwards as long as the rest of the bracket was designed differently. Bottom line, you can't print big or instant overhangs without including a support raft or leg etc.
Back on the usage ... If we tried to make the poles slightly overlong (thinking plastic conduit here) and if the brackets were designed the other way round (with the open 'U' facing outwards and could be a rounded U and shorter so printable)) and sprung into the trailer, we 'might' be able to maintain a form of 'hump back'.
I think 'flat' or even a very slight dish to any support solution will be ok (and simple) as currently there are just a couple of nylon straps stretched over the top front_to_back under the cover and they allow the water to shed ok.
My idea for having the dowel level with the top edge of the bracket was that if it went inside a tube of some sort, the tube would be raised above the thickness of the bracket (by the wall thickness of the tube) and the tube could be notched over the top of the bracket to remove some of the stress on the dowel itself and stop the brackets rotating with respect to each other (even if only a push fit on the poles). I think the dowels (or socket etc) only need to be long enough to stay on the pole and generate enough support between bracket and pole. Too short and the bracket could fall off easily then being handled (if not attached or an interference fit) and not provide much support and too long would just be a waste of time and plastic. ;-)
Just thinking out loud etc)
Cheers, T i m
p.s. If once I can give you an actual dimension for the dowel (when I get some tube) could you leave the item on the base with the 'U' facing upwards please as you know what trouble I had rotating the last item! ;-(
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On 19/05/2015 11:30, T i m wrote:

ok can soon lose the angle

With hindsight it would probably print easier if rotated 90 an pointing up (although then you may need a fillet to support the hollow section).

Should be easy enough to include extra material that can be cut out after printing I suppose.

Yup give me the spec and I can tweak.
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On Tue, 19 May 2015 15:09:02 +0100, John Rumm

Right, today I bought 3 of these:
<http://www.homebase.co.uk/en/homebaseuk/garden/plant-protection-and-support/growstick-071783
I just cut the end off one and it's a lightly plastic coated steel tube with an internal diameter of ~ 15mm.
Now what might be nice is a longish dowel (say, 50mm?) plus a bit of a 17mm ID tube around that, 3mm thick (wall) and maybe 15mm long? The top could be trimmed off level with the tube so that there isn't a 'lump' to rub on the inside of the cover (and it can be printed upside down and flat etc).
Something like this crude representation. ;-)
https://dl.dropboxusercontent.com/u/5772409/Trailer%20back%202.JPG
If you could put either a chamfer or small radius on the outside top corner (where the bracket would hang over the outside of the trailer) that would help stop the inside of the cover being cut or worn there (please).
Cheers, T i m
p.s. I was using the 3d printer today and remembered we next need to wire up switches to be able to manage the LED working lights and additional cooling fans at the front. We also wanted to either move or add an additional main power switch to the front (rather than round the back where the IEC plug connects. So, I opened SketchUp and whilst mustering all my patience, managed to come up with this: ;-)
https://dl.dropboxusercontent.com/u/5772409/3%20switch%20panel%202.skp
Because one switch carries 'mains' I put a shroud round it to stop accidental contact with the connections (and they will be heat-shrinked in any case).
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On 19/05/2015 22:29, T i m wrote:

How about?:
http://www.internode.co.uk/temp/TimsBracket2.skp
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John.
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On Sat, 23 May 2015 00:39:06 +0100, John Rumm

That looks perfect John. ;-)
I won't be able to find out till Tuesday if the pole fits my dimensions but it looks promising. ;-)
I did use the printer this morning but we had a couple of issues. Firstly a loss of sync on the Y axis (I increased the motor current in the hope it was that) caused a couple of 'joggles' in a bracket I was printing (that could have been part of a printer for me) and then, when trying to print something else, found we had a blockage near hot end. Basically the 20 mm length of PTFE tube that lines the thermal break between extruder and hot end had some softened (or melted and cooled / re-hardened) PLA filament in it, stopping it extruding. I think I'm going to make a longer thermal break to allow a greater temperature differential so the hot end can get and stay hotter whilst the cold end can stay colder (the stiffer filament is easier to push).
I have no idea if it will work / work-better and I'm going to have to drill out a 45mm x 6mm stainless machine screw to find out!
This is a similar concept to the one we are using but has much more emphasis on keeping the cold end cold. ;-)
http://wiki.e3d-online.com/wiki/E3D-v6_Assembly
Cheers, T i m
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<snip> >>How about?:

And it looks like this:
https://dl.dropboxusercontent.com/u/5772409/Trailer%20bracket%201.jpg
The fit of the dowel into the tube is about perfect (a good interference fit) but I think we could reduce the i/d of the shoulder a little to offer a bit more support. I'm not sure how easy it would be to take that i/d down by say 1mm please John?
Btw, I would only request (you) doing so if it would be of interest to you to try.
I will use this piece in any case. ;-)
All the best and thanks very much (again).
Cheers, T i m
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On 26/05/2015 19:52, T i m wrote:

That's kind of spooky ;-)

Select the inside edge of the spigot, use the offset tool to make a copy 1mm in. The draw in the extra bits to join up the edge before pulling it the full depth. Finally clean up some spare edges no longer needed.

Try this one:
http://www.internode.co.uk/temp/TimsBracket3.skp

Its quite interesting to see something go from screen to 3D real thing without having a traditional "making it" phase.
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John.
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On Wed, 27 May 2015 03:47:28 +0100, John Rumm

Isn't it just! ;-)

I'm sure it's easy to do when you know what you are doing ... when grabbing the *wrong* bit is as easy as being the wrong side of a line. ;-(

Brilliant, thanks. I'll see if I can print that one today.

Isn't it just. I have been involved in electronics and 'IT' for over 40 years and I think this whole 3d printing lark (and especially the 'Openness' of much of it) is one of those few 'special' things, well, for me anyway. It's actually no more 'new' or 'innovative' than loads of things out there today but to me it's as fascinating *and* potentially useful as is my first dot-matrix (Epson FX80) then inkjet printer (HPDJ 500c) or even GPS (I had one right at the very beginning with no auto routing etc, Garmin GPS III+).
Yesterday, I picked up a motorcycle seat base I had shot blasted (shot-blaster, another bit of kit I would love but can't really justify) and then popped into my mates at about 3pm. I sorted the Z axis out (he said he had re-calibrated it and had indeed printed something but it was too low) then printed that trailer bracket first go. We had been having some random problems with (mostly) the Y axis loosing sync somewhere and objects coming out with tiny joggles in them. I had raised the drive current to the Y axis motor slightly and that may have done it. ATM, it seems like this printer does need quite a bit of tending / fettling but it's still early days and we are tending to possibly stumble into issues because we aren't constantly reading the manual (not that there is one as such) but actually enjoy the exploration of different solutions (especially when we find them). ;-)
So, when the bracket finished printing (just under 2 hours) I fitted the micro adjustable Z end stop I'd found on the net and he had printed earlier. Basically it provides a means of easily adjusting the Z axis home position as it seems that is something you have to do quite often, typically after you have cleaned / replaced a nozzle etc.
http://www.thingiverse.com/thing:260179
We took the microswitch off the very basic 'U' bracket and replaced it on the one shown above (using the two small holes provided). We set the new bracket at about midway on it's adjustment then physically moved the whole thing up / down the Z axis rail till it was roughly in position. We then sent the Z axis 'Home' command and 'tested' the gap between the nozzle and the bed with a slip of paper. Now we could micro-adjust the Z stop with the little thumbwheel and re-home the Z axis, rather than having to set / adjust all 4 corners of the print-bed, simply to adjust the general over-bed nozzle height.
I think I'll carefully do all 4 corners again the next time I'm there in the hope that we won't have to touch them again for a while. ;-)
Oh, while I was there I also removed the little roller arm from the microswitch as that potentially increased the accuracy. The arm gave maybe a 3:1 increase in travel but the carriage stops nearly instantly when the Z stop is triggered so it wasn't needed.
Cheers, T i m
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T i m wrote:

Looks more precise than I was expecting, the output from some of the early enthusiast-class 3D printers looked like it was piped from an icing bag by someone with an unsteady hand.
I know it would hardly be "the point" but I'd find it hard to resist sanding or planing things to clean them up ...
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On Wed, 27 May 2015 09:30:59 +0100, Andy Burns

LOL! (really).
Here are some full res pics I just took (only a SGS4 phone camera):
https://dl.dropboxusercontent.com/u/5772409/PTB1.jpg
https://dl.dropboxusercontent.com/u/5772409/PTB2.jpg
https://dl.dropboxusercontent.com/u/5772409/PTB3.jpg
And that is exactly as it was taken off the printer.
As were these:
https://dl.dropboxusercontent.com/u/5772409/Small.jpg
When you consider the walls of that little mug were printed from a single pass with a .4mm diameter nozzle and the handle was built up (bridging) in fresh air. ;-)

Agreed, however, the plastic we use (PLA) doesn't really 'work' (sand / drill) well. If you drill it for example you have to do so slowly or you will just end up with a plastic coated drill bit. Had the printed plastic dowel not gone inside the steel tube as well as it did, I'm not sure how well I would have been able to reduce it (or with what)?
I think the idea is that you just reprint it with modified dimensions. ;-)
It seems like most of the RepRap community are content if the printed thing actually works, no matter (within reason) what it looks like ... which is as you say, is 'the point' after all. That said, much of it is very 'fit for purpose', even if you are bothered about how things look (as I am to a degree, especially where it actually bothers me or is important).
This would be a good example of good function whilst being of reasonable finish. (I'll probably make one for my printer):
http://www.thingiverse.com/thing:23880
Cheers, T i m
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On Tue, 12 May 2015 17:45:15 +0100, John Rumm

In case it might help others, here are my experiences with this.
I was interested in finding out the shape being discussed, so I downloaded the stl file. This turned out to be a load of plain text definitions of vectors. I have used SketchUp in the past, and have found it difficult to set dimensions. Not having it on this PC, I downloaded the latest 2015 version, which then told me that it required at least Windows 7, and I'm sticking to XP until forced off.
So I installed the 2014 version. It has a built-in web facility to their Extension Warehouse where I hoped to install the stl import facility. But it just said page not available, without saying what page it was trying for. So I used my FireFox browser to go to the SketchUp website, from where I was able to download the stl facility, then install it from within SketchUp. I learn that stl stands for Stereo Lithography.
Then I imported the stl file being discussed, and found it to be a psychedelic mass of vectors. However I was able to rotate it and found it to be a flat slab with pillars, so I was able to rotate and move it to get it to stand level on the XY plane as John did.
The flat surfaces had many unnecessary edges forming triangles, so I set about deleting every edge on flat surfaces one by one, as I don't know of a way to select many edges at once but not planes.
I could now make sense of the object. Thinking I could post the result here, I exported it back to stl format. However, when I started a new SketchUp session and imported the file, back came all the spurious edges, although now the object was aligned properly.
I tried exporting my 1MB SketchUp file to AutoCad dwg, but that became a 3MB file. I also tried exporting to AutoCad dxf file, but that was 10MB. I tried exporting to xsi format; this gave a file half the size of the stl file, but it was a binary file, and it too recreated the spurious edges when imported.
So I conclude that there is no file format that can define an object like this clearly in a small file.
--
Dave W



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wrote:

Interesting report Dave ... and pretty well sums up my current 'experiences' with such things.
However, say I want to print a vase for my old Mum, I go on Thingiverse, enter 'vase' in the search box, scroll down until I see something I think she would fancy or be able to make use of (even for pencils etc) and download it to our 'Printing' folder. I then open up Repetier-Host, File, Open and browse to my (.stl) file and open it. I then click on the Slicer tab and slice the file, noting how long it predicts it will take to print. If it's too long, I might reduce the size of the model and re-slice (slicing only takes a few seconds).
Now, I can either print directly from the PC or take the SD card out of the RAMPS (printer controller) board, save the G-Code (sliced) file to the card, put it back in the controller and select it from the SD card menu.
So, in 'many cases' (so far anyway), I / we haven't had to open up the file and therefore don't see all you describe above.
In the case mentioned in this thread, I felt it would be 'nice' to be able to move the LCD aperture to better suit my particular version of the controller / display.
http://reprap.org/wiki/RepRapDiscount_Smart_Controller
This was the original box / files.
http://www.thingiverse.com/thing:29161
This is just the front panel, knob and button extension.
http://www.thingiverse.com/download:86039
Does this look to be the same mess of vectors / triangles to you OOI?
In case it makes any difference, this is what I believe to be all the parts in a SketchUp format.
http://www.thingiverse.com/download:86032
I eventually managed to re-size the LCD window in SketchUp and John kindly made the other changes for me.
Cheers, T i m
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Tim,
I can confirm that the screen.stl file shows even more spurious edges when imported than the one you originally posted. Also it is in binary format, not ASCII, so half the filessize but unreadable to humans.
I can also confirm that boitier.skp shows all component parts in SketchUp without spurious edges. It would be possible to select just the screen from the array of parts, and save it to its own SketchUp file, which should then be much easier to modify than an imported stl file.
I've just tried this, and the screen component fitted exactly into the "Makerbot Replicator 2X" template provided in SketchUp. What I can't understand is why boitier.skp is only 317KB despite containing many component models, yet my skp files with just the screen component are over 1MB. I thought the 317KB was due to the fact that the curved surfaces in the models are not composed of many plane triangles as in the stl file, but use simple cylindrical shapes, but this is not the reason as my pasted SketchUp file is still composed of cylinders.
Regards, Dave W
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wrote:

Ok and thanks for checking.

Ok.

Funnily enough, I did just that yesterday with the little pushbutton extension and printed 4 of them at 90% size (in red to stand out against the black of the panel as it's the 'Emergency Stop' button).

Ok.

Strange (but I'm sure you aren't looking to me for any explanation of any of this ... to me it's all witchcraft!).
In case it helps, the button as I isolated it is 57kB. https://dl.dropboxusercontent.com/u/5772409/button.stl

Like I said, witchcraft! ;-)
Cheers, T i m
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Snip

stl files are all small; it's the size of the skp SketchUp files which are puzzling me.
--
Dave W

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wrote:

Yeah, sorry Dave, I realised I'd mentioned the wrong file after posting. ;-(
Does this make more sense at 152kB (well, not more sense but more in line what the strangeness we are seeing)?
https://dl.dropboxusercontent.com/u/5772409/button.skp
Cheers, T i m
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Unfortunately that is a SketchUp15 file, and the latest that works on my XP is SketchUp14.
I did another experiment. Boitier,skp is a SketchUp8 file. Instead of copying and pasting the screen component to a new file, I deleted all components except the screen, and saved the file to a new file as SketchUp8. Boitier.skp is 317KB, and my cut down file is 385KB. Stranger and stranger.
I repeated that, but did not explode the screen group to delete the enclosed gearwheel and part inside the window, and regrouping. The resultant file was now 308KB.
It seems Windows copy and paste is responsible for enlarging the file.
--
Dave W

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