[dalworth]

I have a Brand New Hurco VM1 and have had nothing but problems with Thermal Expansion.... I run an 18 min warm up program and when this is completed I am still getting .002 to .003 expansion in the X and Y-axis for the next couple of hours. I have come to figure out that the expansion is in the Head and not in the table. I can run just the spindle at 8,000 rpm with the table stationary and get the same expansion I get with the table moving. If anyone is having this problem or similar problems I could sure use the help....

[jackson]

If it was me i would be on phone getting people out there ASAP brand new machine yeah they would get sick of me real quick

[HuFlungDung]

Does the head of the Hurco have coolant circulation ability around the spindle cartridge? My Haas does However, if I want to machine dry, I still set up some hoses to allow coolant to circulate through the head casting, to control thermal growth. Not that I would say I have ever noticed thermal shift of position, but it seems reasonable to try to keep the temp stable.

[ImanCarrot]

Stick a thermometer on it and see the temperature change and find the length of the spindle and tool holder.

For your information: A 100mm (4") iron rod will change in length by 0.012mm (0.00047") at a temperature change of 10 deg C. (Source Mitutoyo Engineers Reference Book).

0.002 seems a lot though, unless you have a 12" spindle+ tool holder and a 15 deg C temperature change.. but I suppose you could have...

Hope this helps!

[dalworth]

The machine/Head Temp at startup is 74/75 deg and after the warm-up it reads 78/80 deg. The thermal expansion is not in the Z-axis depth, the Z-axis seems to be very close +.0003 to +.0005. This Z expansion is something I could live with or work around. The headstock is actually growing outwards and to the side from the machine in the X and Y-axis.

[jetski]

I use to do a lot of close work for Hurco at one time (3yrs). They do not have a thermal expansion compensation program. They do not have liquid cool heads, ball screws, tables or guides. Every time you change speeds and feeds it is going to change due to the heat. It was probably ordered without glass scales this would help some of the problem. The head is putting off most of the problem and at 8000 rpm you are at the top of the problem. Who was the sales man and what teritory are you in. Maybe I can help if you were sold more that you got.

[RON MEYER]

the heat in the head is generated by the spindle belt. i would check the belt tension. too tight is not good---excess heat and load on the upper spindle bearings. yes .002 is not unheard of. consider this, there are machines on the market that have all kinds of thermal comp. and, they cost 200-500 thousand dollars. some manufacturers do provide coolant systems passing through the head and/or spindle nose to help this situation. hurco has this feature on there vmx line. they also have a spindle chiller available on many models. the vm-1 is an excellent performer for the price. remember a chevy and a mercedes are both good cars, but there is a distinct difference in price, ride, and COST. however, they will both get you there at the posted speed limit. the industry these days, because of competition is promising all kinds of .0001 this and that specs. those kind of tolerances are in reality for jig grinders and jig borers or those half million dollar machines. sometimes we expect too much from our technology. back to the issue at hand. sounds like you need a vmx-24 with chiller and 10k or 15k spindle to run all day at 8k. they'll do it. remember the difference is MONEY. right? the vm-1 is an excellent machine and has been very successful. be sure when buying a new machine that those you talk to about the purchase understand it's application and use. you are on the right track to warm up the head first. it will help.

[cnc-king]

I have a Brand New Hurco VM1 and have had nothing but problems with Thermal Expansion.... I run an 18 min warm up program and when this is completed I am still getting .002 to .003 expansion in the X and Y-axis for the next couple of hours. I have come to figure out that the expansion is in the Head and not in the table. I can run just the spindle at 8,000 rpm with the table stationary and get the same expansion I get with the table moving. If anyone is having this problem or similar problems I could sure use the help....

i have to agree with you. our hurco loses it's position if you shut the main power off. the control in the ISNC mode is the most cumbersome one i have ever used

[jetski]

This is a common error among encoder machines. If it is a big problem you needed to order the glass scales. Even with glass scales on a 180,000.00 machine at a power drop I found I was more secure doing a re indication of zero. Just because I am a anal retentive tool maker. Just so nobody could say you dumb-#$%ss you didn't reindicate it after the power went out. Kinda like the guy who goes to the manual mill with a vise clamped down and assumes it to be square. I always run an indicator across a vise and always rezero after a power out just good tool makin. Saves time and embarasment of trying to track down an inocent rookie. He was probably only trying to get the top and bottom flat...no need to indicate.

[dalworth]

I do understand that you are very knowledgeable with power outages but the problem I am having is with THERMAL EXPANSION while the machine is running.
Thanks for your help.

[jetski]

As far as thermal expansion. When you are running in the upper rpm range on similar machines (cost wise). They all have this problem. If they tell you they dont watch for their nose to grow. The only thing that will minimize it is less temp or no temp change. If they can prove it with a Renishaw laser or a ball bar. The closest machines I have seen have liquid cooled spindles, ball screws, and in some cases castings. I would run the machine and find the hot spots like the spindle motor, axis drive motors, ball screws. Run the thing at there recomened top rpm at the recomended rapid rates in a helical path for 8 hours and bring the sales man/ sales engineer in and ask him if he agrees heat causes thermal expansion. If he is dumb enough to say no, or to say their machine stays cool and stable. Touch his bare nether reigons to the spindle or ball screw and see if he now understands heat transfer. The problem is they are going to tell you to warm it up. In the time it takes to load the program and/ or zero the z axis. Your machine has changed. I have seen some shops run a complete 2 hour program empty to get the machine settled in and then run the real part. Oh I forgot to mention, when you change spindle speed the temp will change too. The heat the spindle puts off changes from 1000 rpm to 8000. If they sold you this and you spicificaly asked about thermal expansion. Some sales man or application engineer is in deep do do. and you have a leg to stand on. Or I have seen literatue state thing that are tighter than they can do also. Sorry for the early confusion.

[dalworth]

Jetski

I do appreciate the help.

[Zbuilder]

We had a thermal expansion of .002" also on our Leadwells vertical CNC. after all kinds of money spent with techs coming to check it, we found the solution ourselves. The machine was in front of a large window. During sunning mornings, the machine would heat up. Afternoon, nights & cloudy days, there was no problem.

[underthetire]

This is a common error among encoder machines. If it is a big problem you needed to order the glass scales. Even with glass scales on a 180,000.00 machine at a power drop I found I was more secure doing a re indication of zero. Just because I am a anal retentive tool maker. Just so nobody could say you dumb-#$%ss you didn't reindicate it after the power went out. Kinda like the guy who goes to the manual mill with a vise clamped down and assumes it to be square. I always run an indicator across a vise and always rezero after a power out just good tool makin. Saves time and embarasment of trying to track down an inocent rookie. He was probably only trying to get the top and bottom flat...no need to indicate.

Not all encoder machines have this problem. We have Hurcos and some top quality machines as well. All of them have spindle coolers on them, while the Hurco's we have are no where near as good as the others, we don't ever see that kind of growth. I have seen people mess with the coolers in the past, thinking colder must be better. I could put an indicator on the spindle, power up the cooler and watch the head move from being too cold. Sounds to me like it was a pre-sales issue, or I don't want to pay for that issue. Coolers should never be an "option" on any machine above 6K, especially a belt drive head, should just be a standard. I don't know if Hurco stretches the ballscrews, or even is a double support on that model, but all the builders I worked for would stretch the screws to compensate for growth.

[bloke]

I'll be sure to give 2007 a call and inform them of your findings....

[underthetire]

Ha, your right. Didn't see someone dreged this up from the past. At least I sorta stuck up for Hurco on this one !

[Zbuilder]

Not sure if ball screws are compressed or stretched. hmmm. anyone?

[underthetire]

Again-2007. Ballscrews are never compressed BTW.

[bloke]

Stretched - so thermal expansion relaxes the tension rather than changing the length.

[Rich Carlstedt]

To get .002" growth, you need a 20 inch arm and raise its "Total" temp 20 deg F.
( Actually 400 units ie 1 inch times 400 degrees, 4 inches times 100 degrees or 25 times 16 ect)

I therefore have to assume the spindle head housing is warming up that much to push the spindle away from the column ?
OR
it could be that the table and knee/cross-slide are being cooled by coolant sufficiently to produce that result.
It could be a combination of both.
Do you have refrigerated coolant ?
I would compare the two of them for differential in temps both before and after warm up.
knowing the thermal conductivity of Cast Iron and the twenty degree difference would be incredible

The comment about the belt was excellent. Some old KM3's had to have a fan placed on the head drives to prevent the plastic bushings from premature failure.

Now, after writting the above, I went back to your original posting and reread it.
I now have to add this. I think your assumption about the spindle and head is wrong
Thermal growth of the head does not move X.
The only way it could, and still be in the head is if you have a turret head ?
and only one cap screw of the spider was locked down.

How are you measuring the drift ? what procedures ?