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Hurco VMX30Ui Repeatability problems. Anchoring?

Tony2046

Plastic
Joined
Jun 30, 2020
Having a tolerance parallelism problem with our VMX30Ui (Hurco 5 axis). For example, when we cut a 5 sided cube the X cuts will be .002 undersized. Called Hurco but they said they will not guarantee any results unless the machine is bolted to the floor.

Questions:

1. How important is it to bolt a VMC to the floor? I understand vibration issues but undersized cuts?
2. Have any of you experienced something similar?

Thanks in advance.


Some of the details from the test cuts we ran:


Having trouble holding tight tolerance parallelism with A-axis
Randomly lost x postion by .002”

Test parts:

1st test block (no indexing)
Part length and width undersize
Hole positions on ends were almost .002” too far in towards center on both left and right side holes

2nd test block (with indexing and then moved back to zero)
Part length and width undersize
Hole positions on ends were almost .002” too far in towards center on both left and right side holes
Counter bores above test holes concentricity became worse

3rd test block (hole position test)
Part overall length and width undersize
Tst holes got progressively worse from center to edge of part on one side, other side not as bad but did have some error
 
People need to realize that a 5 Axis machine is NOT simply a VMC. All 5 axis machines "should" be bolted down. Doosan recommends it but only requires it for the larger machines. The machine could be level but not square to the table, z column or the ways could have twist. You should not level a 5 axis off of the C Axis table but from the ways. TCP and TWP both use the kinematics parameters to keep the tool where it should be but if your machine is not square or the table or trunnion is out of alignment, all bets are off. You will be chasing your tail not knowing where the error is coming from.
 
Thanks for the reply. I'm new to the company and new to the CNC maintenance world. So appreciate the feedback.
 
We have the same machine and was installed by the Hurco reseller. It is not bolted to the floor but it was leveled. The machine is extremely accurate and we have not had any issues as you note. We are in MA also.
 
Hermle is one of the few builders in some instances that prefers the machine to NOT be bolted to the floor as it's an epoxy granite composite/aggregate "Mineral" casting.

In the case of the Hurco VMX 30Ui it's a C frame 30" machine that weighs 11,600 lbs with a nearly 10" platter / dedicated trunnion.

Like what Locknut is saying ~ Basically the foundation and the way it's bolted to the floor is an integral functional component of the machine. It won't distort as much as a "Universal" with six feet and a bearing at the far end of the knuckle-trunnion.

So C frame with Trunion (no table) ... ; Like what @Kinematic said ~ Is the machine level ? (Also).



@Tony2046 can you describe the actual cuts you are taking and perhaps tools used etc. ?

Are these mainly facing type cuts with the end of the tool / end mill ?

So would Z position of the spindle and tool offsets come into play* ?

IS this a new machine or an old machine / second hand ?

What are the machine options ? Scales , spindle rpm and interface, spindle chiller etc. ?




________________________________________________________________________________________

* Curious feature of HAAS verticals is they don't "Violate" the geometry of the part (in other words you would have to sneak in onto a final surface rather than have a part be undersized at least from Z.).
 
Good to know. Thanks

It has been an interesting few weeks here. Being new to the CNC Maintenance world has given me some unique experiences.

"What?? Your VMX isn't bolted to the floor??"

"Hey Tony this is a couple of tenths off" "Great. What's a tenth?"

Anyway I do like Hurco and we have quite a few of them and we run the hell out of them with good results. Parts are expensive but their service support is excellent.

Our dilemma is that even if the problem has nothing to do with the machine being bolted to the floor or not Hurco won't guarantee any repair results.
 
Here you go.

So C frame with Trunion (no table) ... ; Like what @Kinematic said ~ Is the machine level ? (Also).

Machine was leveled while it was unbolted, have not done any testing since anchoring.


@Tony2046 can you describe the actual cuts you are taking and perhaps tools used etc. ? ½” yg alupower 3 flute, schunk tendo e compact hydraulic holder

Are these mainly facing type cuts with the end of the tool / end mill ? Face cut (Top), side mill profiles (where widths and lengths are coming in undersize @0 comp programmed to size)
interpolate holes for position testing


So would Z position of the spindle and tool offsets come into play* ? No

IS this a new machine or an old machine / second hand ? Not entirely sure, I think it was a floor model / demo machine and when we bought it

What are the machine options ? Scales , spindle rpm and interface, spindle chiller etc. ? 12k big plus spindle w/ chiller. Unsure of scales
 
Have you used a DTI (tenths indicator) from the spindle to sweep the table or test plate / test precision angle plate (like a Starret precision angle plate.).

Wondering if the A axis has a zero return that may be off by 20 arc minutes or something ? I.e. there's a constant tilt angle (tilted upwards) that is "Added" 'cuz the spindle is not trammed square to the trunnion. + square to the XY plane and movements in X and Y of the Trunnion unit being translated ?

It's possible in such a case the part has zero taper on one set of opposing faces but still remains parallel without taper but the two parallel sides measure smaller than they should.

If there is a misalignment of the trunnion / systematic additional tilt error and systematic fixed rotational error in XY plane (as well) you can get a taper on the fifth face and be undersize on the 4 other faces (yet parallel and even one pair of faces could be 90.003 degrees perpendicular to the other undersized parallel faces i.e. 90 degree C axis rotation is pretty sound in spite of all that.).

If the machine sustained a big crash or repeated bumps your head stock and rotary may be out of alignment with each other. Kinematic "restitution" won't necessarily fix that.

Maybe check that the trunnion is bolted down to its saddle/ whatever - properly etc. ?

Check the Spindle is square to the table and vice versa (if you get what I mean lol). ~ I.e. the spindle is not "drooping" downwards essentially rotated in the ZY plane. It's possible if the machine was bolted down elsewhere for a long time the bed could spring upwards / curl upwards (when unbolted) so the trunnion and spindle curl in onto each-other by a few thousandths.

That's one of the "Theoretical" advantages of a mono-block type construction on three legs/feet. (in such a case you are not fighting various twists in a frame and dependent on excellent foundation.).
 
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Thank you.

We've now anchored the machine and are bringing the Herco service rep on monday to relevel etc..


I will let you know how it turns out.
 
It's a 2017 model so relatively new.

Brooks Machinery is our Hurco rep. On the surface they're slightly expensive but their service guys do a good clean job.
 
ours VMX30Ui is a 2020 and we luv it. brooks treats us very right and their tech joe is the best. good luck and keeps us posted.
 
Sorry for the late update.

In short Anchoring the VMX30Ui made a huge difference.

1. After anchoring the machine we had Brooks come in, relevel it and a couple of days later run another kinematics test. The difference between the pre anchoring and post anchoring kinematic results were significant.

2. After anchoring and leveling they did a couple sweeps with a tenths indicator across the X and Y axis. Initially the Y axis sweep indicated a 5 tenths dip towards the center of the axis. They decided to allow the machine set for a couple of days to allow the frame to settle. Two days later the dip had reduced to 2 tenths which I found amazing and probably wouldn't have believed it if I had not seen it myself.


Anyway thanks for all the responses and help.
 
This is not a bash on anyone. Anyone buying a 5 axis machine for the first time should educate themselves a little BEFORE talking to any sales rep. Being naive on such a crucial purchase is not a good idea. Talk to friends, research on the interwebs, find info anywhere you can besides a sales rep. Be at least a little informed, not about any specific machine but about the kinematics of 5 axis machining. How the center of rotation plays into the math going on inside a control. Volumetric accuracy, what happens when you are 10 inches from the center of rotation and your parameters are off by .0002". I say this because I can't count on both hands how many customers I have had to educate after the sale and they are surprised about the added maintenance involved and how quickly things can go south. I really like teaching people but not during an emergency.

Paul
 
Paul, is there a resource you'd particularly recommend to learn about that sort of stuff? I'll likely pull the trigger on a 5ax machine in 2021 and would absolutely devour any "fundamentals of 5 axis machine tools" resource but most of what I've found are relative fluff/sales pieces from MTBs (no offense to MTBs...). At the moment I primarily learn from discussions here or through YouTube, but that's not always the best way to gain a comprehensive understanding of things.
 
Paul, is there a resource you'd particularly recommend to learn about that sort of stuff? I'll likely pull the trigger on a 5ax machine in 2021 and would absolutely devour any "fundamentals of 5 axis machine tools" resource but most of what I've found are relative fluff/sales pieces from MTBs (no offense to MTBs...). At the moment I primarily learn from discussions here or through YouTube, but that's not always the best way to gain a comprehensive understanding of things.

Hello Mutiny,
Since we can't post PDF's, you can email me at paul.anderson@doosanmt.com and I can send you a couple of PDF's that would get you started.

Paul
 
Just to clarify, our company has numerous CNC milling machines. In this particular case, from what I gather, the old management interfered with the installation and didn't want the 5 axis anchored because they were going to move it to a different location which you knew and now I know was a mistake. Many of our machinists knew it was a mistake as well.

My questions here were in regards to if the problems we were seeing on our VMX were related to anchoring. I'm new to the CNC world and needed solid reasoning to spend X amount of dollars to have the machine anchored, releveled and basically reinstalled. The responses to this thread were very helpful.

You are correct that being informed before you purchase any equipment is a must. Thanks for the reply.
 
Not being a machinists or someone with extensive experience in the CNC world I will just tell you that my experience with Hurco has been excellent from a maintenance perspective. I know they provide training and any information etc that you may need.

I've heard good things from our machinists and programmers about other CNC OEMs as well.

I agree with Paul. Doing the research and reaching out to various OEMs is a must when purchasing any equipment.
 








 
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