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Robin Hewitt
07-07-2012, 01:22 AM
The manual has been translated from German but patently not by a Brit.

The name of the game is persuading LED b20 to light show the guards are in place and allow the hydraulics to come on.

The manual says, "Magnetic read-contact on safety grid of the safety gate, activated by a magnet mounted to the stationary mould platen".

Do you reckon "read-contact" should be "reed switch"? If so I am good to stick my multimeter up it's yarris.

It is one, or more, of 3 sensors that is kaput.

#2 looks common or garden mechanical.

#3 is built in to a "Rexroth hydraulic interruptor". Sounds a bit Dr Who but has a little Perspex window and I can see what looks like a contactor going up and down. Hoping it isn't that one, too many screws for comfort.

m_c
07-07-2012, 01:36 AM
Reed-switch would fit the context.

However, if you're wanting to be careful, I'd do it with the machine powered up and using a voltmeter to see if it's working or not. That way you're less likely to blow up your multimeter, or any bits on the machine, provided you don't short anything out while probing!

irving2008
07-07-2012, 09:32 AM
Hi Robin,

I agree that sounds like a reed-switch...

#3.. The BOSCH Rexroth website has a handy multi-language media search and a quick browse suggests that a 'hydraulic interruptor' is in fact a float switch - I would guess to check the level of hydraulic fluid - or it could possibly be a pressure switch. They all seem to be conventional contact switches so I doubt you'll do any damage by probing with a multimeter.. I would guess its a series connected 'AND' gate of switches...

Robin Hewitt
07-07-2012, 11:45 AM
I hear what you say about measuring volts rather than resistance, sounds very logical.

The hydraulic interruptor looks like an afterthought because it doesn't wire to the little distribution board which does the rest of the guard switches. According to the hydraulic circuit diagram it diverts any oil sent to the platen closing ram straight back to the reservoir. I presume they used the electrical switch on it simply because it was there. It seems to do exactly the same job as the "read-contactor".

After much reeding of the manual, I have found a reference to an optional, "pneumatic safety gate" which I don't have. I believe it locks the guards shut while the machine cycles but the manual is vague. There is a socket where an "auxiliary control box" plugs in and the manual says, "Jumper plug in b41/b42 if control box is not connected. Without plug in b41/b42: no mould closing". Off the top of my head, I can't remember there being a plug in it, this could be fun to try and recreate without a circuit diagram if it isn't there. OTOH it would be nice to think that wiring and sensors are all present and correct.

Robin Hewitt
07-07-2012, 08:00 PM
There's another idea out the window, I don't have the aux socket, it's blanked off. Everything seems to work fine, except it doesn't.

To understand it I took the guards right off and found 2 more gadgets to stop me cycling it with the guards open. A switch and an interlock that physically blocks the platen if all else fails. This machine is seriously paranoid.

It all comes down to one box of tricks with a 12 wire connection that covers most everything and I will need help to buzz it out, I haven't got enough hands.

With the guards off I went around all the bits and pieces figuring out what they do. It's much easier to fix something if you know how it works and the manual is not friendly. Now I understand it everything looks bleedin' obvious.

I was surprised to find the fixed platten isn't fixed at all, which explained why it has pipes connecting to it, it's got grease lines. If it moves before it should, the machine assumes something didn't eject properly and it would be a bad idea to insist.

Next. disassemble the box of tricks, buzz it out to the controller, make sure the guard switches are connected. It has 8 switches going to 12 wires, how hard can it be?

Robin Hewitt
09-07-2012, 12:52 PM
Still no reason why LED b20, guards closed, doesn't light. I took the control box apart and found a mess of TTL, this thing doesn't have a microprocessor. The control box has an input labelled b20 which lights the LED and does nothing else.

There must be another circuit board to nobble b20 somewhere in the cabinet which is an absolute rats nest of wiring. However, I now know which pin on the monster plug control box plug goes to b20. Armed with that I should be able to find this mystery board and see which of it's inputs is failing to light b20 and enable the hydraulics.

When I plug/inplug the shorting link on the optional core retract guard socket I can hear a relay click, so I am probably looking for a board with relays on it.

I shall keep posting, I know you lot can't help but somehow it makes me feel less alone :very_drunk:

Robin Hewitt
10-07-2012, 01:11 AM
Hmmm!

Found the safety guard circuit relays and they are truly unwell. I'm looking at 6A 3 pole c/o relays and only 2 out of 9 normally closed contacts actually buzz through.

Close up piccy shows they are full of gunge, probably plastic residue.

This isn't arcing causing the problem, most of the nc contacts aren't even used. These 6A relays drive nothing more than other relays or LED's.

Next problem, they are archaic, not listed by RS, Farnell or Rapid. Do I try and clean them or bodge in equivalents???

irving2008
10-07-2012, 01:24 AM
Hmmm!

Found the safety guard circuit relays and they are truly unwell. I'm looking at 6A 3 pole c/o relays and only 2 out of 9 normally closed contacts actually buzz through.

Close up piccy shows they are full of gunge, probably plastic residue.

This isn't arcing causing the problem, most of the nc contacts aren't even used. These 6A relays drive nothing more than other relays or LED's.

Next problem, they are archaic, not listed by RS, Farnell or Rapid. Do I try and clean them or bodge in equivalents???
These are open chassis relays??? Otherwsie how did they get gunged? If the contacts are ok, I'd go for cleaning them. Can you swap to another contact pair? What relays are they?

Robin Hewitt
10-07-2012, 01:45 AM
Not open chassis but still gunged. The second board has 2 similar relays, different make... 2 out of 6 contacts connect on that one.

I wonder if there are any on e-bay? I will have a look tomorrow.

Robin Hewitt
11-07-2012, 12:26 AM
Found the relays on ebay but then I drew out the rest of the circuit.

I've never dissected a commercial guard controller before, curious stuff.

There are 4 switches tripped when you close the guard, they pair up and close 2 relays. When both relays are shut the guard is accepted as shut.

A third relay closes when you open the guard, this relay has to stay closed for normal operation.

As the other two relays close they cut the third relay back to a holding current. If any guard switch opens momentarily relay number 3 lets go. If the switch should close again the holding current isn't enough to reset it.

Basically, lose any guard switch and you have to open and close the guard before you can restart the machine.

The circuit is dependant on the holding current so changing relays seemed like a bad idea. I had to clean the contacts.

If it plays up again I will rework it and drag it in to the 21st century.

While tracing the circuit I noticed one of the solenoids on the hydraulic valves had had it's connection broken off, probably in transit. Bummer. Luckily the wires are still visible so I should be able to patch it.

Robin Hewitt
11-07-2012, 02:37 PM
Put it all back together with clean relays, fixed the broken solenoid connection, checked LED b20 now lit when I closed the guard and it all looked hopeful.

I switched on the motor, pressed "Close mould" and the platen zoomed forwards, I pressed "Open mould" and it zoomed back, I pressed "Advance ejectors" and heard the ram go, couldn't see it because the guards were shut. Didn't dare press anything else because the screw was cold and I haven't checked the interlocks that would prevent me testing the screw shear pin for functionality at the same time.

Jubilation, shouts of "Yeehar etc.

Next I need to put together the water cooling, check for leaks and descale the pipework. The cooling does the oil, the mould and puts a thermal break in the screw which is in hot plastic at one end and connected to a hydralic motor at t'other. Don't want to cook the seals.

For cooling I have a 1/4 hp suds pump, the cheapest new car radiator I could find on e-bay, 10 yards of 3/4" hose, a nice quiet fan and lots of sulphamic acid for the descaling.

irving2008
11-07-2012, 09:36 PM
Sounds fun! But why are you doing this (oh to have so much time on my hands :) )

Robin Hewitt
11-07-2012, 11:45 PM
Sounds fun! But why are you doing this (oh to have so much time on my hands :) )

I have a full order book and no stock. Everytime my supplier puts me in that position I work to remedy the situation. Last time I started making a pick and place machine, the time before I bought this moulder. I continue until stock arrives, eventually I will succeed or die. Simples.

My logic went like this... I can get 2 new moulds made for around 8k, but for the same money I can make around 15 moulds and buy an old injection moulder to boot.

My experience has not been good. It takes time to set up an injection moulder and you pay for it, plus you have to buy lots of parts to justify the setting expense. My original UK supplier made me wait weeks while he sent my parts off to a home for the disabled to be de-sprued, they couldn't be arsed to cut and simply ripped the sprues off. When I suggested I cut the sprues off myself he shrugged and said "No". Eventually a shedload would arrive as a fait accompli and if there was something wrong I had to grin and bear it because the alternative was to send it all back and wait another month or two. Eventually I gave up and sent the moulds to China but they are now having problems.

irving2008
12-07-2012, 01:09 PM
The only way to get quality control is either to have a supplier you can rely on or do it yourself... for the volumes it seems the latter is the better option for you, if you can stand the setup costs and have the time to get it working. Mind you, once you have got it running you have another string to your bow, mould production and low-volume prototype mouldings as a service? :thumsup:

Robin Hewitt
15-07-2012, 12:52 AM
once you have got it running you have another string to your bow, mould production and low-volume prototype mouldings as a service? :thumsup:

I don't know how hard it is to make moulds yet, they come in a sort of kit form, here's a couple of UK suppliers if you are curious...

http://www.dms-diemould.co.uk/

http://www.bergertools.co.uk/ (http://www.bergertools.co.uk/)

I had to make 2 new hose connectors before I could try pumping water into it's cooling system. Nothing would go through the oil cooler, turns out it has a thermostatic valve so I won't know if it leaks until 32 gallons of hydraulic oil get hot.

Nothing came back down the screw cooler return pipe either, but it did a pretty good impersonation of the "Mannequin Pis" so it would seem I have blown a gasket. Don't think that circuit has a thermostat, seems unlikely, probably just gunged up. Hopefully things will become obvious when I split the gasket seal. It's in a bit of a tricky place to get at, but that has never stopped me before.

Robin Hewitt
15-07-2012, 05:08 PM
Opened the leaky gasket and found a sump full of rust gunge. Just waiting for the top to dry out before I remove the last of the old gasket and make with the gasket compound. Type blue I think.

No obvious blockages, no thermostat, the water goes over the top. I can only presume the rust gunge blocked the pipe, it is certainly the gasket eating culprit.

I sat there for 20 minutes stabbing a screwdriver up in to the top cavity until no more great lumps fell out. If it blocks again I should be able to dislodge it with compressed air and let it drop into the sump. Well, it's nice to have a plan :very_drunk:

HOW INJECTION MOULDERS WORK

We are looking below where the raw plastic granules enter the screw. In front of the screw is a pool of molten plastic. To inject you advance the nozzle to touch the mould, drive the screw forwards to nearly fill it and then start spinning the screw. The screw winds new plastic forwards out of the hopper, forcing it up hard against the heated barrel and squeezing the air out. As this new plastic moves forwards and melts, the plastic in the mould is cooling and shrinking. It can't take all the new melt arriving in front of the screw so the screw is driven backwards inside the heated barrel building up a new pool for the next shot. By adjusting the rpm of the screw and it's resistance to moving backwards you try to maintain the mould filling pressure and get the perfect fill. They call this notion "backpressure". The plastic entering the mould cavity is about the consistency of treacle. Where it touches the mould walls it thickens so the main flow is as far away from them as it can get, ie: up the middle. The exception to that are the "gates", narrow constrictions where the flow is fast enough to stay molten. Injection ends when the flow stops and the gates freeze. I haven't figured out how to size gates yet.

I suppose it is vaguely possible that someone might have similar problems and find my pictures useful, so here are some buzz words for the search engines to pick up on... Arburg Allrounder 221 221-55-250

mmattucc68
30-08-2012, 06:14 AM
I hear what you say about measuring volts rather than resistance, sounds very logical.

The hydraulic interruptor looks like an afterthought because it doesn't wire to the little distribution board which does the rest of the guard switches. According to the hydraulic circuit diagram it diverts any oil sent to the platen closing ram straight back to the reservoir. I presume they used the electrical switch on it simply because it was there. It seems to do exactly the same job as the "read-contactor".

After much reeding of the manual, I have found a reference to an optional, "pneumatic safety gate" which I don't have. I believe it locks the guards shut while the machine cycles but the manual is vague. There is a socket where an "auxiliary control box" plugs in and the manual says, "Jumper plug in b41/b42 if control box is not connected. Without plug in b41/b42: no mould closing". Off the top of my head, I can't remember there being a plug in it, this could be fun to try and recreate without a circuit diagram if it isn't there. OTOH it would be nice to think that wiring and sensors are all present and correct.

Mr. Hewitt,
Through a search for a problem (almost exactly what you describe) I found your posts on MYCNCUK...
I have just obtained an Arburg very similar to yours (221-75-350) with what appears to be the same problem. I cannot get the moving platen to move forward. It will move back (if I adjust the stops b44 etc.), but it seems to me that the hydraulic interruptor is not allowing the platen to move forward. I traced my connections, and I have the b20 lit (safety gate switches). I am able to move the ejectors forward and back, but when I press the mold close button, I hear the machine trying to deliver pressure, but no movement. Any suggestions you have would greatly be appreciated.

Robin Hewitt
30-08-2012, 12:46 PM
I am no expert. If it sounds like it's trying then we assume the solenoid valve is okay? That leaves the clamp closing speed knob on the front panel and the hydraulic interruptor. You have checked the knob isn't set to zero?

If b20 lights the interruptor roller must be dropping into the notch on the rod. It has a perspex window in the front, you should be able to see the switch operate when you open and close the guard.

If it was me I'd probably divert the interruptors return to reservoir connection in to a bottle and see if it filled up. If it did, I'd disassemble, look for a blown seal, then consider bypassing the blessed thing if faulty, it looks kind of expensive to replace. Rather depends on your H&S constraints.

Would a movie of it opening and closing help? There might be clues in the sound track.

mmattucc68
30-08-2012, 02:42 PM
First off - Thank you so much for the prompt reply...I do appreciate your time and advise. It is a reassured feeling that one is not alone in their struggles.
I'm actually not sure what this problem could be. Since sending the first post, I disassembled the interruptor valve and looked closely at the switch - nothing seemed damaged or faulty. The switch contactors are doing their job (as I witnessed LED's inside the control cabinet). Since the hydraulic ejectors are the only thing working normally at this point, I decided to take the plug off of Eject Forward side valve and connect it to the Mold Closing side valve (to see if there was any blockage or some other physical problem inside the lines that prevented the platen from moving forward)...The platen moved forward when I pressed the Eject Forward button (only a short distance - but still forward)...I used this opportunity to double check my b44, b25, and b20 switching. I then returned the plugs to their intended homes to try manual movements (the way they were intended)...back to the same problem:thumbdown:. The pump gives me the pressure up "sound" but no movement. Platen can move backward, ejectors move forward and return, but still no platen forward. At this point I'd rather just bypass the thing anyway...I'm just not sure how or if to jump out the switch. I can make up a block similar to what they have to allow the fluid passage un-interrupted...beyond that I'm stuck. Any suggestions are greatly appreciated. I'm also going to try calling Arburg service...

Robin Hewitt
30-08-2012, 07:06 PM
I'm just not sure how or if to jump out the switch. I can make up a block similar to what they have to allow the fluid passage un-interrupted...beyond that I'm stuck. Any suggestions are greatly appreciated. I'm also going to try calling Arburg service...

Isn't the manifold block behind the hydraulic interruptor only there for the interruptor? If so you don't need a new block, all you need to do is connect the ram line to the solenoid line. Blanking off the reservoir pipe could be a good idea because it is shared by the screw speed control on the diagram, might leak. If the electrical switch is working why not just leave it in?

mmattucc68
30-08-2012, 11:45 PM
Well, after spending the better part of today, and trying a host of other possibilities quoted from the Arburg service technician (who, by the way was very helpful), I found that the issue with the valve was not mechanical, electrical, or hydraulic...it was my failing vision.
When the machine arrived the control cabinet had been dismantled and instead of unplugging the individual connectors from the valve grouping in the rear, all of the wires were disconnected inside the cabinet - (not sure why they chose this method as it is far more time consuming and leaves far more chance for error on the next assembly). In any event, I was the reason there was no voltage going to that particular side of the valve - I placed wire 27 where 37 needed to be. :stupid: The printing on the wires was worn and very difficult to see. The wires are all in their correct positions and success. Thanks again for your replies and advice - it really did help me get on the right path. I'll post some pictures and/or video once I learn how...
Thank you.

Robin Hewitt
31-08-2012, 11:29 AM
Well done, bravo.

My controller box has two big fat sockets on the side, one is the solenoid valves, the other goes to the temperature control box. Then there are about 6 cables coming in the bottom of the controller which are not unpluggable. First thing I did was add a piece of angle iron to the back of the box so I could hitch it slightly off the floor on the moulder table, that way I could pick the whole thing up and move it with a pallet truck.
Have you got a mould to put in it? I only ask because I don't and if you are going to set it up before I do then you can warn me about the pit falls :beer:

As far as I can tell my barrel has ABS in it which may be wet and rusty. I'm hoping the screw hasn't seized. I may disconnect it at the shear pin and try turning it by hand before I try turning it with the hydraulics.

Robin

mmattucc68
01-09-2012, 02:21 PM
Well done, bravo.

My controller box has two big fat sockets on the side, one is the solenoid valves, the other goes to the temperature control box. Then there are about 6 cables coming in the bottom of the controller which are not unpluggable. First thing I did was add a piece of angle iron to the back of the box so I could hitch it slightly off the floor on the moulder table, that way I could pick the whole thing up and move it with a pallet truck.
Have you got a mould to put in it? I only ask because I don't and if you are going to set it up before I do then you can warn me about the pit falls :beer:

As far as I can tell my barrel has ABS in it which may be wet and rusty. I'm hoping the screw hasn't seized. I may disconnect it at the shear pin and try turning it by hand before I try turning it with the hydraulics.

Robin

That is an excellent idea. I think I will try the same thing. I do have a mold to set up in it, and I have set these machines up in the past although not for a few years, but I would be happy to help in any way I can with the pit falls. So far the mold is set up, the mold protection switch is set, and the opening size and damper are set. Now it's on to the barrel and heaters - the rear of mine is a mess, and I will spend a day or so putting things in order. I need to learn how to post pictures to send you a few...
Thanks