Member postings for David Jupp

1 ltr = 1000 cc = 10cm x10cm x10cm = 100mm x 100mm x100mm.

Answer should be 0.29 ltr or so.

Overlaps (a line wholly or partly on top of another line) are another very common cause of the failure to extrude/revolve that Mark C mentions. These can be quite tricky to spot. The overlapping lines don't cause any problem in 2D, in 3D the software simply doesn't understand them.

Some CAM programs allow you to project text onto the (non-flat / non-uniform) surface of an object, and they will then work out tool-paths.

Wrapping and projecting are different, so this may not be what you want - or it may be close enough...

I was talking about BIG centrifugal pumps (multi kW) where the electrical start up surge can be a major problem to cope with. By starting against a closed (or just cracked open) valve, the pump doesn't do much work so draws little power and motor can accelerate to full speed, without tripping out the supply. Then the valve is opened, flow increases, as does power draw.

A similar idea can be used in mines as an automatic control for sump pumps. A float is linked to the delivery valve, closes to prevent the pump from pumping the sump dry (and then air locking).

Wouldn't momentary action be preferred for control of a machine tool ? Any latching should be arranged via the contactor.

Of course if the machine doesn't present any hazard, then a latching switch may be acceptable.

The simple answer is 'same HP and rpm as as the 3 phase one it comes with'.

Or just put a valve on the outlet and throttle the pump that way - as long as you allow a minimal flow it won't harm a centrifugal pump. It's actually quite efficient way of doing things too, the power draw will roughly follow the flow through the pump.

Large industrial centrifugal pumps are often started against an almost closed outlet valve to limit the surge current at start up, then the valve is opened gradually.

Mostly it's simply that mentioning guns has proven to be an effective way to generate publicity/hype around 3D printing... much easier to get on the TV than most of the serious and technically interesting things it gets used for.

UNF threads are common on high pressure coned fittings (just as an example).

The sealing method may give some clue - if it is a parallel thread then generally there should be provision for a seal of some kind (O ring, copper washer, Dowty seal, coned pipe end or ferrule).

Is the gauge a fairly 'ordinary' pressure range, or something a bit more extreme?

LazyCAM is a 2 or 2.5 D CAM tool, it isn't a full 3D tool, so would not know what to make of 3D files. It works with 2D DXF files.

Yes - 2D DXF files are imported by many 2D and 3D CAD packages (with varying degrees of success), 3D DXF files are only recognised by some systems.

The strange results probably occur when importing system assumes DXF is 2D (all it knows), but it's actually a 3D file.

I had a quick look around - this document from a track pad manufacturer has some detail about profile and dimension which might be useful **LINK**

The profiles probably are not 'spot on', but are more for identification.

As others have mentioned, this would not be difficult to model in 3D - once you have got used to the software.

BTW - further to point raised earlier the Geomagic 30 day trial does do export of a wide range of 3D formats, and 2D - unlike some trial software export, printing, saving are all fully functional with. So you could have a go at modelling this using the trial, then save in formats that CAM might accept.

Easiest to learn... that will depend as much on you as the software. There is a learning curve to all these - so if you have access to help from someone, then whatever package they use might be a good answer.

Otherwise, take a look at some free training videos for various packages..

Do you just want to draw single parts, or do designs involving assemblies?

Do you need to be able to import files from other people or from manufacturers? (import/export may be limited on some systems - you may well need to get your files into your CAM software).

Will you need to produce 2D drawings from your 3D designs? (not all systems offer this).

Prices vary enormously, both for purchase and then for ongoing maintenance subscription (if you want to keep the software up to date or get help if it fails).

Can you afford the time and money for a training course ? (If they are available).

You can get free time limited trials of many products - though without access to training videos or some help from a friend, it might still be an uphill task to learn anything useful during the trial period, you'll need to put quite a bit of effort and time in.

I have a connection to a Geomagic (Alibre) reseller, so my advice may well be biased - I think the points I've made are generally valid though when trying to choose a system.

Green/ Yellow = Earth

Blue= Neutral (often not required unless you need to produce 240V single phase, neither delta nor star connected motors need the neutral connection to run). Modern wiring regs I've heard require the Neutral wire to be included, even if not connected at the appliance end.

Any other colours - I've seen all white, all black, sometimes labelled, sometimes not. will be L1, L2, L3. Generally the 3 L connection are interchangeable - as has already been mentioned if motor turns the wrong way, swap any 2 L connections over.

Very good advice to verify connections at the appliance end - to ensure condition of connections as well as making sure the wires go where expected.

If in doubt, call in an electrician used to working with 3 phase.

As for only a few threads carrying the load, that is very dependent upon how the joint is designed.

In a nut/bolt combination the bolt is in axial tension, with the nut is in axial compression so the threads tend to mismatch a little, first thread takes most load, there is little contribution to strength after the first few threads.

Bolt in a tapped hole is very different - axial stresses in both parts are in tension, so thread pitch gets stretched in both members. There will be less induced pitch mismatch, so stresses are more evenly distributed.

In many ways 3D CAD is easier than 2D.

Constructing a 3D model has a lot in common with machining. Projected 2D views 'drop out afterwards' with little effort. Updating drawings to reflect a design change is really simple because the drawings remain linked to the 3D model and update automatically after changes to the model.

3D vs 2D is a different mindset though, so making that change on top of learning new software does take time.

1. My bold addition to quote above - this may not be quite clear, Cubify Design does not include 2D section generation capability - though with some imagination and thought this can be worked around at the expense of extra time spent. Note also that there is an even more basic version of the software (sold through the Cubify 3d printer people) called Cubify Invent, this one has no 2D drawing or assembly capability - just 3D parts.

2. The software will stop entirely when the trial period expires.

Cubify Design, and Geomagic Design are available with local support in the UK from Mintronics.

Mark is absolutely correct, though the detail might differ in other parametric 3D CAD packages the same basic techniques would apply.

Often the biggest difficulty in modelling a part is 'getting your head around' how to approach the task (splitting it into discrete simple features) - seeing how others have tackled similar items is always useful.

Etching primers are normally used with Aluminium - these 'eat in' to the surface a bit. Ordinary primer is unlikely to stick well to the inevitable oxide layer.

Copper is currently a 'problem material' for 3D printing because of its excellent thermal conductivity - i.e. need to put in a lot of heat to melt the powder. Having said that usable materials are increasing all the time.