Any advice on the Flatness and Allignment of the Mill Table, can I do anything

Thanks again everyone for the great advice. I like the idea of measuring an even amount of points and graphing them. I will try that tomorrow and report back with the results. And that is some great advice SCzEngrgGroup, I will try measuring both of those things tomorrow. I wish I had a micrometer big enough to do it, but I will try with calipers. The description of what could have happened makes sense.

I am new to the CNC thing and often times I mistrust my own measurements or methodology. It seems like there IS an inherent problem with the mill I have and I will definitely contact Tormach for advice and help on this. I just wanted to make sure I wasn't interpreting anything wrong or looking at the situation wrong. Thanks again and I will keep you informed with what I hear back. I will post up the video of the measurements we took tomorrow as well.

thanks again,
~Zach

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Originally Posted by SCzEngrgGroup

I would suggest you contact Tormach, and report what you've found. What you describe seems far outside the normal range of tolerance one would expect from a Tormach. Perhaps they will offer some better resolution.

Regards,
Ray L.

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Originally Posted by EvolveES

. And that is some great advice SCzEngrgGroup,
~Zach

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imho the above quote was the best advice he gave you!

Remove the table and have it ground, maybe this is easy and normal for other brands of mills. I bet tormach would replace your mill before you need to do this. if its new and it has not fallen off the dock or something.
just some observations.
md

Here is a quick video of the measurements we got. We will call Tormach on Monday and see what they say.

www.evolveeng.com/HostedMedia/MillMeasurment.mp4



Thanks again everyone for all of your helpful input.

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Originally Posted by LeeWay

You guys knoow that you can cover the holes with cling wrap quick easy and cheaply. When you change the setup, change the cling wrap. That will keep probably 99% of the chips out of the holes.

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That sounds like a good idea, so long as air from the Fog Buster or blasts from the air gun don't blow it off.

Mike

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Originally Posted by SCzEngrgGroup

That's exactly the problem I've had. I find it easier to leave the holes open, and just push a punch through the clear them. Hence my suggestion to user risers and leave bottoms open. I've had some Allen screws that were a real bear to get out, because chips got so tightly packed into the hex holes it was near impossible to get them out so I could get an Allen wrench in.

Regards,
Ray L.

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Risers would be a good solution so long as they don't reduce Z travel so much as to create a problem. About once every month or two I end with a job that challenges the Z travel of my mill and losing 3/4-in to the fixture plate is bad enough. The ability to blow chips, and especially coolant out of those holes would be very nice, though.

Mike

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Originally Posted by Steve Seebold

I used 1/2 inch long hex set screws. The only problem was, it took over 2 hours to install them all.

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Steve do you have any problems with the hex sockets plugging with chips or coolant seeping between the threads in the hole and on the set screws? I'm wondering if slotted screws might not be easier to clean. Do you use steel or plastic set screws and if the former have you noticed any corrosion in the threads?

Mike

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Originally Posted by EvolveES

Thank you for pointing that out, i have read through that document but i seem to have missed the relevant tests,. when you told me to look at G2 and G12 i can see it now, and i guess my machine is borderline in spec (probably could be measured to pass i would bet) but those are kind of loose specs in my mind.

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In case you didn't realize it, those specs are in mm, not inches. The error in the T-slot over the entire length of travel is 0.002" or less, which seems about the best that can be expected for a machine of this class.

Mike

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Originally Posted by MichaelHenry

Risers would be a good solution so long as they don't reduce Z travel so much as to create a problem. About once every month or two I end with a job that challenges the Z travel of my mill and losing 3/4-in to the fixture plate is bad enough. The ability to blow chips, and especially coolant out of those holes would be very nice, though.

Mike

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It's never been a problem for me. The only time I've ever even been tight on Z space is when drilling 5" deep holes into a part standing on end, or when using a tapping head on a part held in a vertical 3-jaw chuck, with the chuck being held in a 6" vise. Even then, it's been close, but quite doable. The risers only get used when I need to mount low fixtures (typically made from 1" 6061 plate), and need to use small tools (1/8" and under). These are typically parts made from thin material (under 1" thick). For anything else, I never need the risers.

Regards,
Ray L.

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Originally Posted by MichaelHenry

Steve do you have any problems with the hex sockets plugging with chips or coolant seeping between the threads in the hole and on the set screws? I'm wondering if slotted screws might not be easier to clean. Do you use steel or plastic set screws and if the former have you noticed any corrosion in the threads?

Mike

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No problems with the hex plugging up with chips, but I would recommend you use a long air nozzle when you blow them out, otherwise, you're going to be wearing some coolant.

I picked up a 18" x 9.5" x 1" thick tooling plate today to try and make a temporary base plate to get things level.

I measured the distance from the flat underside of the table (where it rides in the saddle) to the surface of the table (on the very edge because i was only using a caliper) and i couldn't get more that 0.0005" deviation, but that is the resolution of the caliper and it could have been me holding it also.

I also tried to put a think piece of 0.001" shimstock in between the flat bottom and the saddle with the table at different positions and i could never get it in, it seems like it is making good contact (or at least the edges are).

I set the Z=0 to the top left corner today and took values in a grid pattern WITHOUT changing the Z height. the results are shown below, it has a definite twist in it.

Attachment 266222

I am really at a loss and will be emailing Tormach tomorrow and i will link them to this thread also. hopefully they can help out. Thanks again everyone

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Originally Posted by EvolveES

I picked up a 18" x 9.5" x 1" thick tooling plate today to try and make a temporary base plate to get things level.

I measured the distance from the flat underside of the table (where it rides in the saddle) to the surface of the table (on the very edge because i was only using a caliper) and i couldn't get more that 0.0005" deviation, but that is the resolution of the caliper and it could have been me holding it also.

I also tried to put a think piece of 0.001" shimstock in between the flat bottom and the saddle with the table at different positions and i could never get it in, it seems like it is making good contact (or at least the edges are).

I set the Z=0 to the top left corner today and took values in a grid pattern WITHOUT changing the Z height. the results are shown below, it has a definite twist in it.

Attachment 266222

I am really at a loss and will be emailing Tormach tomorrow and i will link them to this thread also. hopefully they can help out. Thanks again everyone

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Hi Again. If your thickness measurements are correct then grinding the table will be of no advantage. Have to tried relaxing the base to remove any chance of base twisting? A quick way to do this is via three point contact. IE loosen the base bolts and lift the front up enough eg with a crow bar and lower back down on to a central packer. Leave loose, then redo your Z heights....thats a quick way to check for base twist....don't be surprised if they are different. Keen

My table measures out the other way, I am high in the rear by about .003". What I found is when I left it for a few days after messing around with shimming (had it about .0015) is when I measured again cold it was out .004. I am thinking that temperature has way more effect on these machines, mine anyway, than I could have thought.

It seems that people think that it is a necessary part of setting up the machine that they need adjust alignment by shimming and stressing the base in order to achieve satisfactory performance. Shimming the base, if you actual believe it will help, should be an action of last resort. The mill when inspected in the factory is performed with the mill unrestrained and supported at 3 points only, this is with the express purpose of avoiding stressing the machine in anyway. When you receive and set up your machine you should uniformly support it under each corner and bolt down only finger tight with the sole purpose being to prevent the mill from moving around on the stand. There are multiple alignment surfaces between the base and the table surface, attempting to solve one perceived issue by stressing the base will undoubtedly introduce other issues, which may or may not be apparent at the time. Once you start stressing the base you are in no-mans land.

Phil:)

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Originally Posted by philbur

It seems that people think that it is a necessary part of setting up the machine that they need adjust alignment by shimming and stressing the base in order to achieve satisfactory performance. Shimming the base, if you actual believe it will help, should be an action of last resort. The mill when inspected in the factory is performed with the mill unrestrained and supported at 3 points only, this is with the express purpose of avoiding stressing the machine in anyway. When you receive and set up your machine you should uniformly support it under each corner and bolt down only finger tight with the sole purpose being to prevent the mill from moving around on the stand. There are multiple alignment surfaces between the base and the table surface, attempting to solve one perceived issue by stressing the base will undoubtedly introduce other issues, which may or may not be apparent at the time. Once you start stressing the base you are in no-mans land.

Phil:)

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I agree with that Phil. I suggest resting the base on the back two base pads, and temporarily on a middle centre packer. (I gather that is how the base is held at the factory when the Y slide ways ares machined in the base). Then only shim under the front two mounting surfaces to get even contact on the stand so that when the bolts are tightened, no twisting will occur. The base is heavy enough, and flexible enough that even its own weight if loaded unevenly on the left or right corner, will cause base flex. This can introduce many errors. Twisting the base to fix accuracy issues is most like to result in a trade off elsewhere. keen.

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Originally Posted by philbur

It seems that people think that it is a necessary part of setting up the machine that they need adjust alignment by shimming and stressing the base in order to achieve satisfactory performance. Shimming the base, if you actual believe it will help, should be an action of last resort. The mill when inspected in the factory is performed with the mill unrestrained and supported at 3 points only, this is with the express purpose of avoiding stressing the machine in anyway. When you receive and set up your machine you should uniformly support it under each corner and bolt down only finger tight with the sole purpose being to prevent the mill from moving around on the stand. There are multiple alignment surfaces between the base and the table surface, attempting to solve one perceived issue by stressing the base will undoubtedly introduce other issues, which may or may not be apparent at the time. Once you start stressing the base you are in no-mans land.

Phil:)

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So how to you go about setting up without shims? When you set the base down and adjust the legs there is little to no chance that it is flat. When you set the machine down it is twisted out of the gate and to me that is where adjusting the feet of the base or shimming comes in. I know they are two different things but something is needed to make it flat to begin with. When I set up my machine after I bought it it was out in all of the specs telling me it was twisted already, no shims involved yet.

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Originally Posted by philbur

It seems that people think that it is a necessary part of setting up the machine that they need adjust alignment by shimming and stressing the base in order to achieve satisfactory performance. Shimming the base, if you actual believe it will help, should be an action of last resort.

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Strange that Tormach does not agree with you. This is not a Bridgeport or a rigid bed mill. The base is made out of relatively flimsy sheet metal (compared to those other types of machines), and significant variation in tram can occur if you don't take the time to set it up correctly. Tormach directs shimming between the base and the stand to fix tram issues. From the operators manual, page 19, (section on mounting mill to base):

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Originally Posted by TORMACH MANUAL

Attachment 266330

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When you call them they tell you the same thing but they do seem to make it seem kind of last resort. I am sure it is for the reason that philbur says in that you are in deep. At the same time, you have to have a level base platform to start.

I would consider shimming between column and base more like the last resort. Shimming between the base and the stand just seems like a normal part of setup.

My stand has some significant twist to it. I leveled the stand, and one of the feet is significantly extended vs the rest to keep it from rocking.

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Originally Posted by luv2ride

So how to you go about setting up without shims? When you set the base down and adjust the legs there is little to no chance that it is flat. When you set the machine down it is twisted out of the gate and to me that is where adjusting the feet of the base or shimming comes in. I know they are two different things but something is needed to make it flat to begin with. When I set up my machine after I bought it it was out in all of the specs telling me it was twisted already, no shims involved yet.

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When the base sits down on the stand it is unlikely to contact evenly on the four mounting pads. Let me explain again. Sit the machine down on the back pads but not on the front two - rather a central packer between them - that gives the base 3 point contact and cannot twist it. Now measure via feelers or shims the difference in the gap on the front left and right, make up some shims to account for that and lower the front down on its two pads. Now it is untwisted and can be tightened up, and the Y gib can be adjusted up as the Y slide is straight. Keen

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Originally Posted by luv2ride

So how to you go about setting up without shims? When you set the base down and adjust the legs there is little to no chance that it is flat. When you set the machine down it is twisted out of the gate and to me that is where adjusting the feet of the base or shimming comes in. I know they are two different things but something is needed to make it flat to begin with. When I set up my machine after I bought it it was out in all of the specs telling me it was twisted already, no shims involved yet.

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You guys are not reading what I wrote or understanding what Tormach is trying to achieve.

I wrote:

" people think that it is a necessary part of setting up the machine that they need adjust alignment by shimming and stressing the base in order to achieve satisfactory performance."

and

"you should uniformly support it under each corner" this can be done in a number of ways, including shims.

If you read the Tormach procedure carefully you will see that it is specifically aimed at avoiding and removing the potential for any stress on the base, not using stress to correct alignment. It is attempting to set up the machine to the same condition when it was tested in the factory, i.e. unstressed. It has to be this way because the machine was manufactured and tested without any applied stress on the base.

I stand by what I said.

The one thing that bolting the mill firmly to its stand (without stressing the base) will give you is you add the stiffness of the stand to the mill base, provided the stand is also set up correctly. However I would contend that a thin sheet metal stand is about as stiff as a wet noddle.

Maybe I should have spelt it out more clearly, you should not apply stress to the base to correct an alignment issue.

Phil:)