pneumatic fitting

[Andy Noyes]

I think somebody (Richard?) said there was a box of pneumatic parts in storage.

I'm looking for an 8mm push-fit to 1/4" female threaded connector, or some combination of fittings to achieve the same result.

What I'd like to do is connect a pressure gauge to the 911 thermoforming machine to measure the air pressure it delivers to the injection cylinder. From this I can calculate the pressure at which it injects the plastic, the cylinder gives about a 6:1 multiplication ratio. Industrial machines use tens of 1000's of PSI. The 911 obviously uses far less, but it would be useful/interesting to know exactly how much. I have various gauges and 6mm and 12mm fittings but no 8mm. Also if there are any 3/2 solenoid valves I'm on the lookout for a couple of these.

Another way of doing it would be to measure the force exerted by the piston rod. It could be done crudely by measuring the compression of a big spring (would need to be safely secured). I don't think it would be easy to find a scale that would both fit in the space and be capable of measuring the force (possibly 1000's N).

[Ian Petrie]

There is a box of odd pneumatic fittings on the bench next to the pillar drill.

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[Richard Ibbotson]

When are you down ?
I am sure we can find some parts to suit.
Have an 8mm 1/4 male in front of me if you have 1/4 female to female

[Andy Noyes]

Probably down one evening next week. I might be able to find a 1/4" F-F if there's not one next to the pillar drill.

[Tom Allen]

Can highly recommend these guys just down the road
http://www.psibar-compressors.co.uk

I take odd fittings in there many times and they always have something to fit it in stock and happy to build things up with you on the counter.

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[Richard Ibbotson]

I left an 8mm 1/4BSP inside the door of the 911 . Also a 1/4 tee from the box of Ian near pillar drill
Can drop of another 8mm/1/4 tomorrow, and we have some 8mm hose at space, so probably most simple if you have a 1/4 male gauge.

[Andy Noyes]

I actually managed to cobble together a gauge with some bits from the box yesterday afternoon/evening, though it was slightly leaky and I found even a small leak affected the pressure so it might be worth doing again.

For anybody who's interested, the max. pressure I measured when the ram is activated was 75psi. The cylinder is 80mm bore and the piston inside the injection crucible is 32mm diameter, this gives a multiplication of 6.25:1 meaning that the plastic is injected at very approximately 500psi/34bar. That sounds like quite a reasonable pressure, however the system is driven directly from a pump with no reservoir, so it takes a few seconds for that pressure to build, this probably explains why you get good results with a heated mould, but when cold, the plastic solidifies and plugs the mould before it gets very far.

[Stuart Livings]

Sounds like it might be worth creating a reservoir and release valve?  The reservoir could be pumped up to slightly higher than 75psi (to account for the expansion) and 'quick released' using a manual or solenoid valve...?

Stuart

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[Andy Noyes]

Yes, it would probably be an improvement, but I'm not suggesting modifying the machine at all, it's designed to work in a certain way. I'm just trying to get a clear idea of how it operates.

[Richard Ibbotson]

No problem, let me know if you want to experiment further. Also let me know more about the valves you need.

 

What is the maximum shot volume of the injection moulder? I guess the screwed construction of the mould also limits the ease of use and maximum size of mould due to pressure.

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[Ryan .]

What about wrapping some heat tape around the reservoir?

[Andy Noyes]

I'd estimate the maximum shot capacity is around 50cc, but you'd have to have the plastic very well packed in the crucible to achieve that.

The strength of the mould should be a consideration, a 60mm diameter cavity could have a force of up to a tonne trying to burst it open.

I'm looking for a pair of 3/2 solenoid valves, or maybe a single 5/3 valve, port size and coil voltage doesn't really matter, I'd prefer low voltage DC but could always change the coils. If they already have fittings/hoses of whatever size attached that would be great. This is to control a cylinder of similar size to the one on the 911 (for a similar injection moulder I plan on building).