3d printing and SketchUp help please

[T i m]

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! ;-(

[T i m]

Well done for getting a handle on that one Dave. ;-)

Cheers, T i m

[John Rumm]

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.

[T i m]

Right, today I bought 3 of these:

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. ;-)

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: ;-)

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).

[Dave W]

I've found out what's going on with SketchUp - there can be lots of unused component definitions. I went to Tools>Model Info>Statistics, which showed 27 Component Definitions. I clicked the button marked 'Purge Unused', resulting in 0 Component Definitions. My 1MB file is now only 91KB. Maybe this format could be used instead of stl-- Dave W

[Dave W]

I've found out what's going on with SketchUp - there can be lots of unused component definitions. I went to Tools>Model Info>Statistics, which showed 27 Component Definitions. I clicked the button marked 'Purge Unused', resulting in 0 Component Definitions. My 1MB file is now only 91KB. Maybe this format could be used instead of stl-- Dave W

[T i m]

Ah.

Ok, that makes a bit of sense at least.

It can while you are playing with the 3d model but most of the 3d printing software seems to assume / prefer / need .stl Dave.

If you don't already have but want to see the sort of thing I mean, have a look at (free) Repetier_Host:

You basically open your .stl file (often downloaded off the web in that form (see

slice it and then it will print straight from there. Or, you can save the resultant gcode to the SD card and put that straight into the 3D printers electronics (often Arduino Mega + RAMPS board + LCD controller) and print it directly from there (preferred method for all sorts of reasons).

I'm not suggesting this is the only way but just what we are currently using as it gives us easy manual control over the printer (moving the axis about, enabling and clearing the extruder etc) and basic manipulation of the print job (like copying, scaling etc).

It also works on XP (mate uses W7).

I guess the question re 'what format' is more to do witch what you are doing the most. ATM, we are mainly just playing with / testing the printer so are typically just pulling files off the net a printing them. Yesterdays custom switch panel was created by me because we needed one for the printer, couldn't find one on-line and it seems to have printed out ok. ;-)

Cheers, T i m

p.s. If you have something you would like printed, please let me know. ;-)

p.p.s. That said, we are waiting for a replacement to an extra part I requested my mate got from the printer kit supplier so that I could modify it to make it easier / better to use.

This is quite a nice picture of what we are using (x2).

Left to right you see the fan, heatsink, extruder and stepper motor. Underneath going down you see a length of 6mm threaded stainless steel tube joining the extruder to the 'hot end' (ally block). In the hot end is a 12V (typically) cartridge heater and a bead thermister, then the actual print nozzle (typically with a .4mm diameter hole).The hot end is wrapped with some Kapton (heat proof) tape.

The 'problem' with our printer is it has a dual extruders and they are mounted on an ABS 'carrier'. So, you can't tighten the backnut that should secure the ss tube into the bottom of the extruder enough to stop it undoing easily as you say, remove a nozzle to clean it.

So, it is my intention to open the holes out in the bottom of this carrier to say 10 or12mm diameter and turn an ally spacer(s) / washer combo that will just pinch the ABS as it bottoms under the metal extruder. That way we should be able to lock the ss tube solid to the extruder and that should make it easier to change the nozzles without everything moving around (and needing re-calibration).

[Dave W]

Wow, thanks for all that. I followed the links and beyond to find out all about 3D printing. It's all very interesting but not enough for me to pursue.

I see that your interface software only accepts stl, obj and 3ds file formats. I looked these up on Wikipedia, and see that the stl format is entirely triangular facets defined by the xyz coords of their vertices. The other two formats are much more complicated.

When imported into SketchUp, there is nothing that's easily edited, and John Rumm had to generate your modified holes and put them in place of the array of triangles from the stl file, then export the result to an stl file for your 3D printer.

So if an stl file needs modification to suit your requirements, it's a lot easier either to start out with a downloaded skp file, or draw the part from scratch in SketchUp and export it to stl for the printer.

After your extruder picture I couldn't understand your comments without more pictures, but I doubt if I could contribute anything anyway.

Best wishes for your endeavours.

[T i m]

Hey, my pleasure. ;-)

I am, simply because 1) I have access to a 3d printer to make the bits I need and 2) I am aware of loads of extra things that I need that I would like to be able to print, when I wanted. ;-)

Our daughter has offered to treat me to a 3d printer of my choice but I am happily gradually putting together as many of the bits I need from the likes of eBay as I think it will be a bit more fun, more involving and (hopefully) more rewarding if it works. ;-)

Ah, that would explain the effect I have seen when trying to edit an .stl imported into SketchUp and finding everything seems to be made of triangles, Hence, if you try to drag a side you have to drag it in the form of two triangles. I'm not sure yet exactly where and when that happens, just that I have seen it.

So not for me then! ;-)

Understood.

Agreed (assuming sufficient skills to be able to create your own stuff etc).

Sorry about that. It was more about me thinking out-loud re what mods I might make to my mates printer to make it easier to setup / maintain. The direct drive extruder is pretty well a product and in our case it is the mounting of said extruder(s) that are causing the problems. This is mainly down to not being able to lock up a spindle because it's mounted on plastic (ABS in this case).

This is a picture of the mount (upside down):

The bits in the corners are to hold the linear bearings (with a clever printed 'hole' to allow for a cable tie).

The lugs sticking out at the bottom are to retain the two ends of the drive belt.

The small holes along the centre line are to take some small screws that 'just' hold the extruders to the mount.

The larger more inward holes are for the threaded tubes that join the extruder to the hotend and that tube is lined with 4mm OD, 2mm ID PTFE tube (to stop the warm / soft filament sticking to the sides).

You 'lock' that tube against the extruder with a thin locking nut by compressing it against the plastic mount. As soon as everything gets a bit warm, the tension is lost and everything can move about. So, it is my intention to create a 'rigid' path between the underside of the plastic mount and the metal extruder by the use of what is basically a tubular metal spacer the thickness of the plastic with a penny washer on top (x2 as there are dual extruders). This should have the added bonus of keeping the extruder end of the hollow tube (or heat-block I think they call it) cooler (both via the penny washer and the fact that there is greater thermal conductivity to the fan-cooled metal extruder).

Thanks. The good thing about all this is there is no rush, we can do stuff as / when we want and so continue to enjoy the whole experience. ;-)

Cheers, T i m

[John Rumm]

How about?:

[John Rumm]

I think if you are working with sketchup you need to treat the stl file much as you would treat the output of a compiler etc. i.e. you use the model to regenerate it every time you change the model - you don't bother trying to edit the "object code" produced by the STL conversion. Just treat the sketchup phase as CAD, and STL phase and any that follow as the CAM part of the exercise. (much as you would treat creating tool paths for CNC milling / routing etc as a CAM activity rather than a design / modelling one).

[Dave W]

Absolutely!

[T i m]

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. ;-)

Cheers, T i m

[T i m]

Agreed, as_long_as you have the luxury of the source files to begin with.

Now, if you are skilled in CAD packages then you will also have that 'luxury', even if it means re-inventing a particular wheel but for those who aren't, we have the only practical / useable solution and that is to import the .stl's given. ;-(

Now, for minor alterations I still believe it is quicker to maybe work round any issues that arise from using / importing an STL than starting from scratch, and once complete, it seems like the slicing / printing software doesn't care 'how' the final object was made to be able to print it. ;-)

Cheers, T i m

[T i m]

And it looks like this:

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

[John Rumm]

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:

Its quite interesting to see something go from screen to 3D real thing without having a traditional "making it" phase.

[T i m]

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.

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

[Andy Burns]

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 ...

[T i m]

LOL! (really).

Here are some full res pics I just took (only a SGS4 phone camera):

And that is exactly as it was taken off the printer.

As were these:

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):

Cheers, T i m