Member postings for Muzzer

I paid some local guy with a machine to transfer 16 rolls of 8mm colour film to MP4 or similar. Wasn't massively cheap but I have them as files now and can share them so easily, unlike before. Saves faffing about - you can get on with your life while someone who knows what they are doing sorts it out for you quickly.

Murray

Wondering what EDPM rubber is all about, I looked it up on Wikipedia. That did the trick and I was lost almost in the first sentence. Must have been written by a chemist! However, it seems to be used in cars for door seals, hoses etc as Howard mentioned. Seems the service temp range is around -50C ... +150C and it "does not pollute the run-off rainwater" when used for roofing.

**LINK**

Murray

Wikipedia (never wrong!) quotes the following solubility of citric acid in water:

117.43 g/100 mL (10 °C)
147.76 g/100 mL (20 °C)
180.89 g/100 mL (30 °C)
220.19 g/100 mL (40 °C)
382.48 g/100 mL (80 °C)
547.79 g/100 mL (100 °C

Sounds as if lemon juice is about 0.3 mol / litre. The molecular mass is 192g / mol ie so presumably lemon juice for comparison is only about 6g/100mL(?) ie about 4% concentration at room temp. Yes, it's years since I did any chemistry apart from making big fireworks.

Merry

Be wary of the so-called "2 tonne" engine cranes. If you mean one of these fine machines, which are available in almost any colour and brand name under the sun, you can start by halving or thirding that number. I enjoyed great amusement when lifting my Bridgeport clone milling machine (almost exactly 1 tonne) with one of these. With that kind of load, it wobbled around as if it was made of rubber. Luckily I have a proper, sturdy engine crane that was able to pile in and finish the job without me ending up in a box and the machine in a hole in the ground.

I'd love to see somebody lift 2 tonnes with one of these.

Merry

Edited By Muzzer on 12/09/2014 03:16:19

Go bigger rather than smaller - you have to get your tee-slot bolts and clamps around the outside of your workpiece. Also think about whether 3 or 4 slots would be better. May not matter to you but if you are planning on fixing chucks and stuff to it, it could make quite a difference. Ask me how I know.

Vertex are Taiwanese although it sounds from what Ketan said recently that they make some of their products in China these days. At least they have a reasonable reputation and will hopefully try to maintain stds. With generic Chinese stuff you have little idea what you are getting. I have some Soba (Indian) toolholders etc and they are OK but not fantastically well finished. Given a choice between Vertex, Soba and generic Chinese, I'd rank them in that order.

Murray

To answer the OP's question, I'd suggest you use some form of carbon steel that will allow you to harden them once you have made them. The dimensions are given in the drawings but there is no mention of material or hardness. I can copy you the original document if you are interested (PM me).

Apart from needing to set them up carefully and machine them accurately, the basic shapes involved are fairly straightforward. I only made up the mating parts but I imagine a rotary table in the milling machine would be the way to go if you want to make the studs yourself.

I'm sure I've seen these on sale in a few places but not at a particularly appealing price.

Murray

The mass doesn't change with acceleration unless there is some form of warp in the space time continuum! And the addition of a counterweight will increase the total mass but reduce the static force the motor has to overcome to raise the table. That would be an improvement.

Andrew's sums are correct, as would befit a Cambridge Engineering PhD. Rather than trying to get your head around the physics, it's probably best just to get some stuff connected up and try it out!

It's a simple matter to accelerate a stepper motor. You start by sending it a low frequency pulse train (= slow speed) and steadily ramp up the frequency to a higher frequency (= high speed). You really aren't moving the table in sharp jerks - the inertia of the rotor and leadscrew ensures that the speed of rotation is reasonably smooth. The motor applies a force to the mass which results in an acceleration. Or not if there is not enough force to overcome the static and dynamic forces.

Murray

I wouldn't agree with Ian's explanation of stepper motor operation. Like any synchronous machine, the torque generated is proportional to the angular difference between the rotor and the magnetic field. When you step the drive, the field rotates 1/200 of a turn ie 1.8 degrees. If there is no resistance, the rotor will follow the full angle. If there is no movement, the rotor will generate a significant torque, hopefully somewhere close to the alleged "stall torque". Sounds as if you simply don't have enough torque.

Microsteps increase the number of steps but (if driven by a half decent driver) don't significantly decrease (or increase) the torque the motor can generate, despite a lot of misinformation to the contrary.

Although it isn't usually obvious, the speed-torque characteristic of most steppers looks rather like a constant power curve, so changing ratio from direct drive won't necessarily change the maximum speed you could drive the leadscrew at. Indeed, by gearing the motor down by 2 or 3 to 1, you would be able to increase the stall torque at the leadscrew and probably still get the same feed rate under load. As Andrew says, you are probably suffering from static friction (stiction?). This is probably one of the main reasons people change to ballscrews, apart from the backlash improvement.

Anyway, in terms of solutions, 2 come to mind:

• If you are intent on driving the knee up and down, you can reduce the load on the Z leadscrew by fitting one or more gas struts (springs) underneath to offset the weight of the knee assembly. You could get an adjustable gas spring if you wanted to play with the spring rate. This seems to be a common technique. Certainly neater than hanging a massive counterweight out the back of the machine. You probably need to leave a bit of weight on to preload the leadscrew and reduce backlash.
• The other solution would be to drive the quill rather than the knee. That's what I've done on my Bridgeport clone (see my albums under "Z-axis drive" or similar) and is much more commonplace with knee mills. Admittedly it limits the travel to 4-5" or so but if you need more, you can always move the knee up or down during the machining process.

Murray

Edited By Muzzer on 05/09/2014 17:28:25

Looks like a cut above the normal 3D printers which are little more than hobby grade. They are probably worth the extra cost but only for professional use. I'd love to try one....

I'm a little surprised that they are trying the "1 year warranty included" caper. Whoopee. You might expect that from the ignorant youth in Currys who is on commission for pushing the "extended warranty" scam but in the UK the warranty is potentially several years by law - and certainly more than 1 year. Hopefully this is typically Japanese and reliable to start with.

Murray

When I was in my mid teens, I lived in Northern Ireland, in a seaside town called Whitehead which was the home of the Railway Preservation Society of Ireland. They had (and still have) steam engines which they would steam most weekends.

I once observed a steam engine being rerailed, after some of the wheels came off the tracks. The tool used was rather like a double version of this - although considerably larger and stronger obviously. A pair of jacks raised the bogey above the rails, then the whole thing was shifted sideways until the wheels were above the tracks and then lowered again. The load must have been considerable.

Obviously not the same tool but similar idea. Wow - I'm making a steam-themed post, possibly for the first time!

Murray

No idea what Bob was on about when he talked about the EU putting him out of business. I'd love to know how they "cost" so much. There are many British companies making electronics products successfully in the UK and in the EU in general. Interesting that he is now offering products again. I wonder what changed.

If you don't get the volumes up, you can't get the pricing down. If the price is too high, you can't get decent sales volumes to start with, which is a bad place to be if you've spent a lot of time and money getting there. I guess it just wasn't compelling enough and/or competitively priced or marketed. Easy to blame the EU, mind.

Murray

Funny, I was reading about LED replacements that plug straight into legacy fittings just this past week - many of them work with either inductive or switching ballasts. Presumably the starter won't do anything and can be left in place (inductive) and the LED driver is designed to tolerate the HF voltage (switching).

There are direct replacements for strip lights and all the other single ended types as well, in a whole variety of colour temperatures. Of course, there was no discussion about pricing but there must be at least some cost justification otherwise nobody would be interested in using them. LIfetimes of 15-20k hours were mentioned. Hopefully the reliability will on a similar par.

Murray

I love poking about in workshops. The only thing missing from this experience is that special smell you get in proper workshops but I can imagine that easily enough!

Thx for posting.

Murray

My machine is identical to Graham's apart from being the floor standing version which weighs even more. Neither Graham's nor mine have the gearbox, only the 5 speed belt drive.

Used to have a 3-phase motor and VFD on mine until I swapped it for a Christmas cracker quality Chinese 1-phase motor so I could liberate the VFD for my milling machine. It's less useful in this state but its reduced usage is more down to the fact that the milling machine is more versatile for drilling anyway and more accessible. Nice machine though.

The conical recess under the head almost cries out to house a lamp and seems to be designed for it although it doesn't seem to be used for that purpose. I wonder if that was the original intention.

Murray

Here's a page from the local tool emporium (in Canada) which shows 2 models. The bottom one has reversible jaws. They are generally for thin wall pipes etc and seem to be more popular in North Merca.

These own brand chucks are generally Chinese or Indian. I was quite temped to get a 6-jaw or possibly a 4-jaw self-centring chuck at one point but a different kind of sense prevailed in the end.

Murray

Whether or not you use Solidworks (or even use any form of CAD at all), here's an interesting video showing how to construct a gear model. Using parameters, the module size and number of teeth can be dialled in and the rest adjusts appropriately. This approach could be applied to DP (imperial) gears with minor changes.

It takes a little time to build up the model but about 10 mins in, the tooth construction is apparent.

Murray

Wow! One of those ooh er moments!! Well held!

That price will be coming down soon and the LED replacements are improving rapidly If you look at the trade rags and see what is coming through from the suppliers, you can see that what we get will soon be a lot better - or they could be once they've recovered their pound of flesh from the retail market.

Murray

I got sick of replacing the halogen lamps in our study. We have a dozen or so on one of those track things and they only seem to last a thousand hours or so - and cost an arm and ten legs. IKEA now sell LED replacements that are just as bright and use a fraction of the power (= heat and cost). They should also last considerably longer: 50,000h is often specified.

LEDs will soon replace those awful "low energy" CFLs too. There was a big song and dance about phasing out incandescent filament bulbs not so long ago but the CFLs did little more than reduce the cost of the electricity. Some of them take ages to warm up and wear out pretty quickly, like their larger cousins.

I'm looking forward to LED prices coming down. And hopefully we will see dimmable LEDs becoming more readily available soon. Already there are direct replacements for the T5, T8 etc tubes that can be driven by existing reactive and electronic ballasts.

The thermal time constant of a filament bulb is surprisingly short. You can pass music or voice audio from a bulb to a photocell. If you drive a bulb with a PWM voltage, the frequency needs to be in the hundreds of Hz before the lifetime is as good as what you'd get driving it with clean DC. That's because the lifetime of the filament is inversely proportional to something like the 5th or 6th power of the temperature (I forget which). The lifetime mechanism is fundamentally driven by evaporation of the filament, if that's the right word.

Murray

You could look in Maplin if there is one near you. If you order from them online it may be with you next day unless the service had suffered recently. Or try Rapid Electronics, CPC Farnell etc. Those coaxial power connectors used for phones and laptops may be just what you need. There are several different sizes so you'd want to make sure you got a mating pair.

Murray