Member postings for John Munroe

Yes, I'd prefer it to have non-rusting properties as it may be exposed to some moisture.

Indeed. But I'm trying to make the whole lid magnetic whilst keeping the front and back a complete brushed finish.

Hi all,

I'm trying to make around 100 metal lids (50mm x 50mm) that are magnetic and have brushed finishes. It's a shame that aluminium isn't magnetic. Is stainless steel my only alternative? I try to keep it cheap and simple.

Any thought appreciated.

I'm hoping to achieve a tolerance of 0.05mm. Is it too tight?

No, the units are in millimetres.

Hi

I'm trying to have about 2000 pieces of this nylon part made:

It's a small rectangular piece with 2 holes in it. Does anyone know of a cheap way for manufacturing? How about laser cutting?

Thanks

Edited By John Munroe on 29/03/2017 07:14:24

@Pete Right. In that case, how does the staking machine position itself with such high precision so that it hits almost precisely above the recesses? Is there meant to be a separate die for staking in place?

@Muzzer, I've now cut another piece off to hopefully get a better understanding:

The features highlighted by red arrows don't seem to be regular shapes. The corners of the deformations in the upper component seem to have very small radii, but the "staked out" parts in the lower component look quite rough. Could this mean that the dents in the upper part were part of the cast and not deformations created by staking into the lower part?

@Muzzer,

Yeah, appreciate that! The lower component is actually 2mm thick, but the top component gets a perfect rectangular cut:

Does staking through a piece zinc that thick still produce a nice rectangular cut though?

Thanks

Sorry about that. Let me try clearing it up a bit.

The bit I'm holding in the 3rd pic actually fits in here:

So it's the right hand part of the top component. My guess is that the rectangular dents are what holds the top component down.

Hopefully I've explained the component a bit better this time.

OK, I've cut off a bit of it now:

Here's a section view of the top part:

It's quite clear that the features circled in red also exist in the top part. Are these stake impressions? Could stake create such a clean, squarish finish even the second layer?

Thanks

Edited By John Munroe on 04/08/2016 19:27:49

@Sam The round rod is actually a shackle. The flat rod is like a lever and is spring-loaded. It clicks onto the shackle to lock it.

@Jeff Could the depressions (circled in red) be results of some stake operations?

Also, those two round marks (circled in blue), are they ejector marks or some kind of intended design? Ejector marks shouldn't be so visible - right?

@Muzzer Unfortunately they're out of stock and this is probably the last one.

There actually seems to be a groove inside, but I can't imagine how any feature in there could be used to lock the parts together.

Lower down inside the enclosure, there seems to be a stud of some sort:

However, nothing protrudes out the other side (top of the box).

Edited By John Munroe on 30/07/2016 12:23:56

Hi

I have a small, cheap metal (zinc) key box looking like this:

which I *think* is made up of two parts.

However, I can't find any bolt or welding joint. Here are some other pics with coincident faces highlighted:

There seem to be complex undercuts inside, so I think these are two separate parts:

Does anyone know how the two parts might be joined? I'm guessing it wouldn't be epoxy since it's meant to be a secure key box. I got it new for just £10, so I'd guess there's no fancy work involved.

Any thought would be appreciated.

Edited By John Munroe on 30/07/2016 11:58:37

@Jeff It's just out of curiosity, because I always thought plastic parts use ISO tolerances but didn't know the actual values. Those values just seem a bit tight to me.

@Murray Is it actually the responsibility of the part designer (customer) or the mould maker to ensure that the plastic flows right? Or should the mould maker study the flow of the given part prior to giving a quote (so that the flow analysis work will be accounted for)?

@Jeff But do mould makers typically use this ISO tolerance class system though? Don't they usually just specify the machining tolerances and the resin tolerances?

Hi

Usually, do mould factories use ISO tolerance classes like fine, medium, coarse, etc.? Like those here.

If I'm reading that correctly, with class "medium", a 1000mm long piece will only have max +/-0.8mm, which is 0.08%. Doesn't the resin alone shrink by 0.5%?

Any thought appreciated.

John

Edited By John Munroe on 27/04/2016 11:19:47

@KWIL Doesn't the patent cover any method that uses software to design and fabricate a mould? Does using CAD to load up the design and using CAM to generate the tool path fall under it? Don't most people here use CAM?