Giant 20' x 3' x 2' router build

[charlieuk]

It was a m10 flat head bolt. The stainless bolt works fine on the short cable

[JAZZCNC]

Save yourself the grief and fit mechanical switches for limits, you won't have these problems then.

But thats masking any issues not resolving them.! Charlies wire run isn't long, it's just longer than your average CNC machine but for industry 10-12mtr isn't long.
Mechaincal switches are OK for Limits I agree but what does he do then about Home switches.? . . Shouldn't have to put up with lesser accurecy by using mechanical switches.
I'm sure the problem lies with the fact these Cheap chinese switches obviosly don't like the longer wire run and any capacitance thats coming with it.! . . . . . That or he's got some other issue he isn't aware of yet.?

[EddyCurrent]

But thats masking any issues not resolving them.!

No, it's about finding the right product for the job, I know that mechanical switches will be unaffected over the length of cable he's using, plus I'm trying to find a solution that's cheap and easy to implement. If Charlie want's to keep going to resolve the issues that's fine, I don't have a problem with that.

Charlies wire run isn't long, it's just longer than your average CNC machine but for industry 10-12mtr isn't long.

which is why we used these connected via stanadard armoured cable, okay up to 200m according to Schneider.

http://uk.rs-online.com/web/c/automa...004,4294876081

. . .but what does he do then about Home switches.? . . Shouldn't have to put up with lesser accurecy by using mechanical switches.

No, that's why I mentioned in an earlier post about his Home switches being near to the control box, it would make sense to have the Home position at that end.

I'm sure the problem lies with the fact these Cheap chinese switches obviosly don't like the longer wire run and any capacitance thats coming with it.! . . . . . That or he's got some other issue he isn't aware of yet.?

That is the best conclusion now, but with fault finding it's best to start with the easy things first and in the case of DIY, the cheapest too, and I don't like guessing, it's far better to work through logical steps then we all know the 'correct' answer if it comes up again.

[JAZZCNC]

No, it's about finding the right product for the job, I know that mechanical switches will be unaffected over the length of cable he's using, plus I'm trying to find a solution that's cheap and easy to implement. If Charlie want's to keep going to resolve the issues that's fine, I don't have a problem with that.

Don't talk daft Man course it's masking the problem if you haven't found out why.!! Also you can't say proximity switches are the wrong product for the job of sensing it's what they are made to do for gods sake.! Only thing that could be questioned is the quality for intended application.

No, that's why I mentioned in an earlier post about his Home switches being near to the control box, it would make sense to have the Home position at that end.

That's ok for one axis what about the other Two. . ? Still got to accept lesser accurecy just to make it work M-Switch.! . . . Shouldn't and doesn't have to be that way.

That is the best conclusion now, but with fault finding it's best to start with the easy things first and in the case of DIY, the cheapest too, and I don't like guessing, it's far better to work through logical steps then we all know the 'correct' answer if it comes up again.

We started with Logical steps and eliminating obvious potential issues which don't cost money and now it's got to the point where it's time to swap components to see if fault or weak parts are the cause. Swapping out for inferior accurecy components shouldn't be even considered IMO. Esp with home switches.!!

[EddyCurrent]

Don't talk daft Man course it's masking the problem if you haven't found out why.!! Also you can't say proximity switches are the wrong product for the job of sensing it's what they are made to do for gods sake.! Only thing that could be questioned is the quality for intended application.

You keep on about people picking you up wrong but now you're doing it yourself.

My conclusion is that it's capacitance of the cable so using mechanical switches is not masking it but using a product that will work in that situation.
I never said specifically that proximity switches were the wrong product for the job, but maybe 'those' ones are.
I know full well what sensors of all kinds are made to do having been in industry electricals for over 40 years.

I think the home switches will be okay because of the slow approach speed.

All other aspects I think are what is to be expected with DIY.

[JAZZCNC]

You keep on about people picking you up wrong but now you're doing it yourself.

My conclusion is that it's capacitance of the cable so using mechanical switches is not masking it but using a product that will work in that situation.

No not really got it wrong at all.! Have you considered Your Conclusion is wrong.? Swapping for MS is masking the issue has the capacitance is still there and needs dealing with rather than avoiding (masking). Charlie as tried different cable and it's still there, was worse actually, yes could still be capacitance but I don't think so at only 12mtr length and 24Vdc. But my conclusion could be wrong also.?

The home switches are not Ok even at homing speeds this has been tried.! Also how can they be trusted if we haven't conclusively found the cause.?
Your method while yes maybe getting the machine working isn't the correct one IMO. It's still a mask for the real cause and who's to say this cause isn't going affect other aspects of the machine later down the line.? . . . .What if it is a wiring or grounding issue that isn't found now but surfaces at a later date when newness wears off or other attachments get added like probes etc which could suffer from same issue.?

Best resolved now and after all obvious causes have been eliminated then the next logical choice is to replace suspect components for same type or like in this case with same type but being of better quality. Changing to a compleltely diffeant switch type will in this case potentially mask some other cause or fault.!

[charlieuk]

Thanks for all the input guys I went to rs but they didn't have anything suitable in stock and it would be 3-4 weeks the chap was looking at some by omron ? So unfortunately walked away with nothing. Tony has just found two to try from a place near him in Leicester and he is going to bring some micro switches down tomorrow as we'll just for a test per poses, hopefuly a second brain will help find out what's going on so fingers crossed. Many thanks for all the help it's much appreciated having people to bounce ideas around with.

[irving2008]

The solution to the capacitance issue, if that's what it is, is to buffer the switches locally. It's not clear to me where the switches are located but a simple transistor or IC buffer would fix it at very low cost and could handle multiple switches if they are close together.

[Jonathan]

The solution to the capacitance issue, if that's what it is, is to buffer the switches locally. It's not clear to me where the switches are located but a simple transistor or IC buffer would fix it at very low cost and could handle multiple switches if they are close together.

That's far too logical a suggestion for this discussion ;)

If charlie's keen he could put differential signalling ICs (e.g. MAX488) on both ends and may alleviate problems later on. They're low cost and easy to implement since the circuit's in the datasheet...probably excessive though so personally I'd try a transistor first as it'd take 2 mins to test.

[charlieuk]

The switches are all on the gantry on the moving side of each axis, just let me know what I need to do to try your idea and I will give it a shot if I can get the stuff as I don't really understand what you are saying at the moment.