250-20 E/P Clamp Close Issue

[ChrisGross]

Hello all!
So I have posted before about a clamp issue that we remedied by replacing an output card for the Prefill Close Valve. Today I ask for guidance with another issue. I've already replaced all cards involved with Clamp Close with new ones to rule out an electrical issue and I've also tested via amp draw that my valves are doing work electrically. To be thorough I've also removed every cover to a Logic Valve to verify that poppets aren't stuck, springs aren't broken and that orifices are present and in the correct positions. I've also removed every valve located on the Clamp Manifold to verify proper working order, orifices present and in the correct location. Now we get to the problem at hand.

I came into work and found a work order for this press stating that it had a Clogged Filter Alarm(which we remedied) and that the clamp would not close. After I've done all the work above I'm still stuck with a clamp that won't close. However, if I remove my Clamp Traverse Valve (which with my little knowledge of learning on the job I have deduced is responsible for sending a pressure signal to my pump to give me more or less flow) I can get the clamp to close up to the Slow Down Point. If I take my Slow Down setpoint to mold touch then I can get the clamp to close.

Before all the work I could bump my Clamp Close button on the controller and get it to move about a .25 of an inch every time all the way up to mold touch and then hold the button to build tonnage. Also, I noticed that in a previous topic posters had tried to help another person with a similar issue and they found it to be a hydraulic safety issue. Now I don't know a whole lot but I assumed the hydraulic safety was the Gate Valve located under the operator side door so I removed it also and verified that the spring was not broken, that my spool could move freely and that the lever was functioning.


Other information you may want to know. It HAD a CAMAC countroller but was "retro-fitted" to be more "up to date". It now has an X20 PLC by B&R inside it.

I've attached 2 photos, one of the schematic and one of the schematic with how I think the flow moves to tank with my lines for flow following the path as if the Clamp were trying to close.

I appreciate everyone willing to help a newcomer to the field to learn something. Thanks in advance.

[ijchan223]

what does pump pressure look like on the pump that drives that?

We had a similar problem. sounds like a clogged orifices to begin with. But that vv pump may have gernaded.

Milacron tech support may be able to help, but it is hit or miss usually

[ChrisGross]

Appreciate the reply.

So I'm checking pressure of the the pump @ TP9 which has a gauge installed. It's one of several rails that will be fed by the V.V. pump according to the schematics and my limited knowledge. At idle I see a pressure of 400 psi. When I probe the Clamp Traverse valve I'll see the pressure climb quickly to 2000psi.

[ijchan223]

first of all the print isn't readable to me maybe take it in sections or upload it in 2 portions maybe too big and getting compressed.

if the pump ramps psi on command it seems fine.

What operator station is on the machine?

Just to make sure it isn't something silly, not sure on the retrofitted machines, but factory Milacron's have a help screen that comes in handy.

a lot of the time it is looking for an input that you aren't thinking about. like a door switch or a contractor before it allows a clamp movement.

also there are some faults that requires powercycling the controller to clear.

[ChrisGross]

So we ended up having to call in some technicians and they believe that the High Volume, fixed displacement pump went bad. We ordered the cartridges and installed them. I'll reply to this message when the new couplings come in-in about 2 weeks. In the event someone else has this issue. I've seen at the least 2 posts dealing with these antiques.

Thanks for the replies. I've learned a little bit more and finding people willing to share their knowledge is getting to be harder than figuring this new career out.

[ChrisGross]

So I wanted to leave the fix here in the event someone else runs into this issue.
The technicians thought it was the pump (so I finally got the chance to pull a pump and rebuild one, super easy as the 50GPM and 8GPM were vane cartridges. The only issue was figuring out how to invert the rotation which was easy enough with Google) and this did not fix issue. Our 250-20 didn't have the old HVD cards replaced with newer technology. During a stay at this press earlier this week the other tech and myself were working furiously to figure it out and he happened to notice that an LED on one of these cards was not lit. Looking through the schematics I was able to deduce that the card without the light was for the Clamp Pressure Transducer. Which makes absolute sense. Since we have 2, I swapped the cards and it also moved the issue to the injection unit. Instead of the clamp just not working we would build our 250 tons and as soon as the Injection Unit moved we lost all pressure. Well now I know that the card is bad. We ordered a new card (119 USD from ebay) and I tuned it (you just need to turn both the Ramp 1 and Ramp 2 pots Counter-Clockwise until they bottom out) and the press dry cycled all day.

I'm new to the job still, a tad green around the ears but I understand why places want someone that can read Hyd and Elec schematics. The answer was there the whole time. I appreciate all that stopped by and offered help. Hope this can help someone else down the road.

[ijchan223]

The best way to learn is experience, you have to manually poke valves and not trust the 30 year old wires/ electronics