Mazak tolerance issue in Automation

[ukkie]

I am trying to get my 2002 integrex 100-IISY running fully automatically, while holding a +-.0005"/.02mm tolerance and struggling.

The part we are cutting just now is very short and are being held close to the jaws which are bored to suit the material.

We are auto tool-eyeing the finishing tools every 5 parts but having to adjust the tooleye compensation to keep the parts in tolerance which defeats the point in auto compensation. we are getting around 300 parts before there is any noticeable wear.

The tooleye seems to be perfect size wise, the tools are measuring within a few microns after dozens of parts are cut.

We have had various ideas, is the machine thermally expanding at a different rate from the tooleye for example, In which case our idea of fully automatically machining hundreds of parts without touching or looking at the machine is out the window.

The room the machine is in is free from drafts and air temperature fluctuation is maybe 5 degrees at most and is kept heated all night.

Currently we do not have a warm up cycle as my cnc guy has never used one in his career as a mazak machinist of 17 years. However neither of us have experience of this style of fully automated machining.

 

[wishin4snow]

I would suggest start by just running a bunch of parts without compensation to see if there is a warm-up period and then the machine "settles in". We have a Miyano that runs a pretty tight tolerance part. The first 20 minutes in the morning, you have to adjust the cutter comp a few tenths every few minutes. I notice about .001" between the first part and after that 20 minutes. After that it just sits there all day.
Having worked with Mazaks, I can tell you some of there machines have a thermal compensation algorithm in the control. There are sensors around the casting that adjust the machine ever so slightly as the casting might warm up. However, I have seen where this algorithm actually causes more harm than good. I don't know if you machine has that but it may be worth looking into and turning off. I don't know what that parameter is though. Your mazak distributor should be able to help with that.
Maybe even keep an eye on the coolant temperature. A coolant chiller might help keep things uniform throughout the day.

 

[EmGo]

You need Carblob to come in on this but he's probably sleeping off the effects of a too-adventurous weekend. Maybe he'll show up later.

Basically, you're doing everything wrong. Read up on SPC. You can't inspect quality into a part. The machine will do what it can do. If it can't do what you want then you need a new machine. What you are trying to do does not work in volume.

 

[007Rob]

Is the air temperature fluctuating 5 degrees every day? The thermal growth on a big machine tool can easily add up to .0005" differences in part size with that much variation. The most important thing is consistency, if the temperature is constantly changing the machine will be constantly moving around and you will never hold a consistent size.

For sure try out a warmup cycle, there's a reason why they exist. And try to pay attention to how the part sizes are moving around in relation to the shop and machine temperatures etc.

 

[cnctoolcat]

There is a lot of cast iron on an Integrex to change size with temperature.

And the biggie on the Integrex---and any integral spindle machine, is the spindle itself.

Although the integral spindle housing is liquid-cooled, there's not much you can do with the heat that gets into the rotating spindle/motor shaft.

Every integral machine I've been around changes size a lot more with warmup and temperature variations during the day (idle during lunch...).

The classic belt-driven lathes of yesteryear usually have more thermally stable spindles than the integral spindle lathes of today.

ToolCat

 

[Winterfalke]

We had a new multiaxis lathe brought in (think it was the Tsugami) that had temperature compensation, needed to hold a couple tenths in superalloy on a bolt shank. The machine swung over 20 degrees F during the day, and could never hold size when it did. Had to get their install techs in to fight with it several times before they brought us a coolant chiller to hold the machine at a stable temperature. Hit the tolerance just fine after that. I'm not convinced temperature compensation works well enough to rely on, but warming the machine up and holding it at temperature is pretty reliable.

 

[alko]

if you want to hold tight tolerances on parts and run unlmanned also look at the proces itself. if your roughing tool wears out it can affect the finishing tool. so adding a semi finish pass with a diffrent tool might produce better results. Dont focus on cycle time alone but try to get the most reliable process first and then work your way up to speed it up.