Sodick A325 Mk25 problem with 2-3 skim cuts

[Kamil19951]

Hi all,

I've finally found justification and got a used wire edm into my toolroom. Its 1998 sodick a325 with Mk25 control. Machine was used in flush only mode for few years due to tank leaking water. Dirty and not maintained very well, but working.
Got machine for scrap, but I was lucky finding the leak to be just clogged drain pipe....

I've systematically cleaned, aligned and calibrated everything I've found I can do in the manual. Machine is threading and cutting all right, but I still have one last problem that need adressing.

Every time I try doing cuts with with more than one skim pass machine stops cutting after between 10-40 mm and just sits unwinding the spool. Vs and As are on the same levels as during cutting. When I halt the program and restart it will sometimes move another few mm and stop again. I've tried raising/ lowering flushing, changing various power settings and even using the same offset as for first skim pass, so there is less material to take off.

One thing that have caught my eye is that during first skim for example cutting 15mm thick square punch I would get 6mm/min on one side and up to 15-16mm in other places...
I use bobcad to program wire and found using reverse skim the best method to use to prevent unnecessary wire threading and movement.

I do not have hands on wire edm experience, only what I've read and seen online and in manuals, so there might be something obvious I'm missing.

Appreciate any help guys.

 

[AGMantz]

Sounds like the problem might actually be your rough cut then. I am by no means an expert let alone have any experience with WEDMs outside of Mitsubishi, but if your wire is moving a little over 2x as fast one side compared to the other during the 1st skim could it be that your rough cut is taking to little off on one side(the 6mm/min side) and too much on the other(the 15-16mm/min side)? When the wire stalls on your first skim is your contact light on it at all?

If that is the problem it'd make sense to me that when your first skim pass goes through and it hits the side with less material on it it'll fly through that because well.. there is less material and vice versa with the opposite side.

Regards,
-AGMantz

(If I am talking out my arse here please someone correct me, but that is the first thing I thought when reading this.)

 

[Kamil19951]

Thanks AGMantz

Rough cut is generally very equal speed. First skim is unequal but never stalls. Second skim stalls. Ive seen some sparks from time to time when it sat stalled.

There is no contact when it stalls.

Perhaps there could be some backlash or worn guides leading to unequal cut depth depending from which side i aproach?

Ill check the backlash with slips tomorrow. I got new upper V guide that i need to fit too.

 

[50BMG DUDE]

I have newer Sodicks, but I had dropped a large slug and it cut some of the power feed wires (a wide flat ribbon cable). Was causing similar porblem, as the machine moved around the work tank the ribbon cable would touch the work support structure and cause a short, and a control stop.

Replaced the lower cable and hasn't happened since. Yours could be loose connections on either the upper or lower cables as well. Also make sure you have indexed your power feed carbides. There is one in both the upper and lower heads.

Cutting speeds can also be affected by flushing, Is your part held flush to the work surface so the lower nozzle is making contact the whole time? Most guys run an indicator over the part in X and Y to make sure it is flat to the table. If the lower nozzle is only making contact you will lose some flushing and it will slow down.

 

[nlancaster]

We see odd behaviour when our lower power feed contact is worn.
Machine will rough cut fine, but will go super slow or even report shorts on skim cuts.
Adjust the power feed contact to a fresh location and issue resolved.

 

[Kamil19951]

Thanks guys. Ill check the cables over, but my machine doesnt have ribbon cables, just shit loads of standard ones. Ill try indexing power contact too, but i have done it about 15 cut hours ago. Would it go bad this quick?

Thanks for all input

 

[50BMG DUDE]

Probably not your power contacts if you just indexed them. Definately check the cables, I'm not familiar with that machine, do the power cables bolt to the power feed carbide housing? Look for corrosion, edm sludge etc. I would still suspect the main power wires due to what happened to my machine. Check your work platform ground. Check your resistance of your water as well.

Sodick is not the most friendly company for tech support, Cost me 1500 to register my first machine with them that I bought used at 2 years old. That was in 2010

 

[Kamil19951]

Cheers.
I've done some more digging into it. indexed contacts, changed upper guide and aligned the wire and done some test cuts.
I have found some evidence of backlash in the machine I think. If you look at picture below it shows die plate i've cut with 1 skim after grinding down tab level. There seems to be difference in measurement on right and left side. section level with surface was aproached in Y+ direction. Section on the left was aproached from Y- and didnt clean up at the same level. There is about 0.015mm difference there... It might be that because I was always using reverse passes there was a diffrence on how the wire was loaded depending on direction. I'll try to measure backlash and compensate for it. see what happens...

Cables on the machine are literally bolted down to the heads. I've cleaned contact points both ends before, but I think I need to disonnect them and check with a meter.

As regards to Sodick I had to pay them 1000 pounds support charge before being able to order from them... They do offer technical support which was great, but with more complex issues and more frequent emails are tending to say there is a lot involved and offer engineer visit.

 

[Kamil19951]

Update here:
I've managed to compensate the backlash as much as I can and it seems to cut with 2 skims fine now. With 3 skims I still managed to get the wire stuck the same way in 90* corner, so there must have been too much material left there for whatever reason.

Other issue I found out now is parts are coming out smaller in Y direction. I've measured most of the work I've done so far and it seems to be about 0.01mm smaller no matter the distance. Ex. 15mm square would measure 15.002mm in X and 14.988-900 in Y.

I'll confirm if I have accurate Y movement with gauge blocks tomorrow, but if I dont I'm not sure what I can do about it.
There is pitch compensation table for axis, but not sure how to go about it.

 

[Kamil19951]

I just thought I'm going to give an update here for anybody with similar issues.

My backlash/ inaccuracy in Y was caused by worn Y axis seals and sleeve around the seal pipe. They caused too much friction resulting in inconsistent Y positioning.

Wire stopping during skim cuts was caused by corrupted software. Reinstalling helped.

Now machine is running perfect.

I got repair engineer to reseal the machine, but would definitely do it on my own next time. Pretty straight forward but involves a lot of cleaning.

If anybody needs help doing this repair let me know