Parts Washing at the Machine Shop: Thank you but…
As a metal finisher I am well aware that the major cause of rejects and defects is cleaning. Although I have never taken the time to do a statistical analysis of this I would give an educated guess that 90% of all metal finishing problems come back to a cleaning issue. I know a lot of others in the industry that would agree with that number whole-heartedly.
So as a machinist, fabricator, designer or other creator of the metal products that will be sent out for plating, anodizing, painting, powder coating or other coating services, what can you do to help this situation? Hey, I know! YOU can clean them for the finisher! Problem solved. Glad to help.
Well, much like when I clean the house to be helpful at home, what we find out is that my definition of clean is very different than my wife’s definition of clean. And in some cases I may have just made things worse. Done with the best of intentions and while some of what we do might actually be helpful, best be sure to have a discussion and a do a little research before taking the parts over to the degreaser or the steel wool to the bathroom fixtures.
If you are just trying to help and your removing an oil, lubricant or coolant from a part, how can this hurt the finisher? Isn’t less dirt better than more? Not always. Lets go back to the fact that there are many definitions of clean and you and your finisher may not be in agreement.
By taking off a heavy lubricant from a manufactured part you are creating a couple of potential issues for you and the finisher. 1 of all, you may be exposing your part to corrosion until it gets to the finisher. A steel part may begin to rust, a copper alloy may start to turn green or an aluminum part may begin to develop a white powdery substance on the surface. This is all corrosion and the surface under this corrosion will never be the same. When removed there will be pitting and etching that will only be more visible especially after say nickel plating.
The 2 potential problem comes from leaving something on the surface designed to protect the part from corrosion until the finisher can get to it. For all of you who share the Technical Data Sheet with finisher so he knows what it is and how to effectively remove it good for you! For the other 99% of you… Here comes trouble. Many of these anti-corrosion coatings will come off easily but not all. And some may come off with products or processes your finisher would not typically employ. A solvent, acid or alkaline cleaner may work but that may not be the typical 1 step. Now many finishers will spot this trouble and figure it out with little difficulty. But if they don’t and the parts get further down the line, we may have created a problem that in the best case slows things down costing the finisher money and you valuable time. In the worst case we’re headed for the strip tank or an MRB meeting and keep your fingers crossed.
Another potential problem occurs when the manufacturer does a cleaning operation that maybe doesn’t lead to quick corrosion or the leaving of an intentional protective coating of some type on the surface. In this case we have created a new type of mongrel coating, one that can be tenacious and virtually unidentifiable. Where do we turn for help with that coating when we don’t know what it is or how it got there never mind how to get it off?
Issues recently we’ve had to deal with?
The manufacturer using dishwashing liquid and leaving “something” behind on the surface.
Something changing at the screw machine shop and nickel and gold parts blistering like crazy. Now we cant plate them without tumbling them in a special brass cleaner.
Last summer when the “cleaned” parts had no protection and in the humidity rusted badly and were barely passable (Don’t worry, they blamed the plater).
A paraffin based lubricant left on a washed part that no chemical could remove. Only extra heated solutions and frequent dumping of tanks allow the parts to be plated successfully.
If time and space permitted I could go on… And on… Once again, and this is becoming a theme, a little communication can go a long way.
Before you go through extra steps be sure to ask your finisher if they need or even want you to wash the parts 1. They are going to clean the parts no matter what you do. Sometimes a greasy mess you know how to deal with is better than a seemingly clean part you need to experiment with. If you’re having issues at the finisher or thinking about changing coolants or lubricants, take a minute to review the products you are using in house with the finisher. There may be time and money saving questions answered before trouble starts. Most of all, before you do anything different or take on a new job, process or product, make a phone call to the finisher of choice and let them know what you’re thinking.
And of course you or your finisher or both of you together can feel free to contact me. I’m happy to pitch in and help out to avoid trouble and help create an economical and effective process. One that can start at the manufacturer and carry right through to the finisher.
There may be things we can do together to make things better for everyone. We may even find that we’re doing extra steps that truly aren’t helping. Lets lose those and start saving money quickly! I’m happy to help my wife clean the house at any time and I’m sure you’re happy to help your finisher. What we all want though is do the things that help and not cause any aggravation. Words to live by at home and at work!