[CNCer__]

Hi Guys,
My Y-axis gibb removed from the new Tormach PCNC 1100 seems to be noticeably bowed on the scraped side only. The other side (not sliding one) is perfectly flat. My table has quite bad slop/play even with the gibbs over-tightened (with backlash out of spec). The issue probably comes from this bowed surface. I just like to confirm with other experienced Tormach users that this curve is not made by a design. I know that there should be a taper on the gibb, but curved surface? Can you please confirm that for me?

[flick]

It's not by design, but it's not designed to be much better. Yours may be worse than average. I was also dissatisfied with my gibs, but ended up having to remediate them myself. It made a big difference.

[MichaelHenry]

I was also dissatisfied with my gibs, but ended up having to remediate them myself. It made a big difference.

How did you do that?

[flick]

How did you do that?

I scraped one side flat with reference to a surface plate. Use Prussian Blue to find the high spots. I'm not sure if Dykem (mentioned above) makes Prussian Blue, I've only seen their layout bluing, which is a much different product.

I scraped the second side to the proper taper with reference to the way itself. For this operation I used whiteboard marker to find the high spots. It was the opposite process as the Prussian Blue - the whiteboard marker is applied to the gib, and it comes off the high spots where the gib makes contact with the dovetail.

Highly labor intensive, but it got the bow out of the gib and improved machine backlash, geometric accuracy, and rigidity immensely. I did both the X and Y.

[Mueller]

I scraped one side flat with reference to a surface plate. Use Prussian Blue to find the high spots. I'm not sure if Dykem (mentioned above) makes Prussian Blue, I've only seen their layout bluing, which is a much different product.

I scraped the second side to the proper taper with reference to the way itself. For this operation I used whiteboard marker to find the high spots. It was the opposite process as the Prussian Blue - the whiteboard marker is applied to the gib, and it comes off the high spots where the gib makes contact with the dovetail.

Highly labor intensive, but it got the bow out of the gib and improved machine backlash, geometric accuracy, and rigidity immensely. I did both the X and Y.

You can get a tube of Prussian Blue made by Permatex for about $5 thru Amazon or your local auto parts store (Autozone or O'Reilly can order it for in store pickup as think most FLAPS can)

[MichaelHenry]

I scraped one side flat with reference to a surface plate. Use Prussian Blue to find the high spots.

Thanks, I was hoping you'd found a quicker and simpler way.

[CNCer__]

Thanks flick for the confirmation. This is hand scraped right? Why manufacturer didn't bother to make it flat. Is there something else behind this poor finish, any explainable reason? It looks like I'll need to scrap the centre of this surface but it's just hard to understand why it's poorly made this way.

[GBru]

Have you sent this picture to Tormach? If you have not then perhaps you should, as it is, like you said a new PCNC1100. The more feedback they get of issues on "New" machines the better. One would hope they communicate this back to China were they would implement stronger Quality Control or is that just wishful thinking........ :roll eyes:

That being said I am sure going by your picture they would send you a replacement one.

G.

[CNCer__]

Have you sent this picture to Tormach? If you have not then perhaps you should, as it is, like you said a new PCNC1100. The more feedback they get of issues on "New" machines the better. One would hope they communicate this back to China were they would implement stronger Quality Control or is that just wishful thinking........ :roll eyes:

That being said I am sure going by your picture they would send you a replacement one.

G.

I'll send them images and some data, to highlight the issue. I'm not expecting a gibb replacement. The gibb has to be made for the particular machine and it's not replaceable part without an additional treatment.

[SCzEngrgGroup]

NEVER start scraping without knowing what the problem really is! If you scrape the gib flat, you will very likely make things worse. If you suspect a problem, you need to get some Dykem, and test to see what the actual contact pattern is. That is the ONLY way to have a clue what, if anything, needs to be done to make it right.

Regards,
Ray L.

[CNCer__]

Sure thing Ray. I'll wait to hear back from Tormach guys. The non-invasive trials with Dykem sound like a good idea in the meantime.

[CadRhino]

Great input, as always, Ray.

NEVER start scraping without knowing what the problem really is! If you scrape the gib flat, you will very likely make things worse. If you suspect a problem, you need to get some Dykem, and test to see what the actual contact pattern is. That is the ONLY way to have a clue what, if anything, needs to be done to make it right.

Regards,
Ray L.

[CNCer__]

LATERAL DISPLACEMENT OF WORK TABLE TEST

As per suggestions I've received from the Tormach support I was tightening the gibb to reduce the table slop. Results you can find below.
It looks really bad to me. It's a new machine, newer ever used. It's probably the gibb with geometry issue. There could be also curved support where this gibb sitting, or maybe the opposite dovetail? Any other suggestions? There is a noticeable improvement when the gibb is tightened but the sacrafice in the backlash is unaceptable. The slop from the X-axis looks pretty good when compared with the slop generated by the Y-axis.

Test Preparation
I was removing the gib for cleaning again, just before the test. It was cleaned with microfiber cleanroom cloths. All the way surfaces were also cleaned to mirror finish, no way there is any deburr or FM. The backlash of Y-axis for loose gibb is .008". The gibb limit screws are not excessively tightened. After reinstalling the gibb I was manually triggering additional way oil cycle. The oil was well distributed by mowing X, Y axes a good few times from 0 to max. Both axes were possitioned in their middle for this test.

Tightening the gibb to max. spec. backlash
Lateral displacement of work table way out of spec, even hard to measure (at the end of table) with my dial indicator.


Gibb tightened with backlash 3x max. allowable error
backlash (center of table):
0.076 mm (0.0030"), max. spec. for allowable error: 0.025 mm

Slop measured at 7.5" from the center of table
Measured for Y-axis only: 0.036 mm
Measured for Y-axis + X-axis: 0.044 mm
Calculated for X-axis: 0.008 mm

Slop measured at the end of table
0.074 mm (max spec. for lateral displacement of work table 0.04mm)

Video:
Lower Quality: https://photos.smugmug.com/photos/i-...GxNXJ9-640.mp4
HD: https://photos.smugmug.com/photos/i-...xNXJ9-1280.mp4


Tightening the gibb to 30perc over spec for backlash

backlash (center of table):
0.033 mm (0.0013"), max. spec. for allowable error 0.025mm

Slop measured at 7.5" from the center of table
Measured for Y-axis only: 0.054 mm
Measured for Y-axis + X-axis: 0.058 mm
Calculated for X-axis: 0.004 mm

Slop measured at the end of table
way above the max. 0.04mm of allowable error

Video:
Lower Quality: https://photos.smugmug.com/photos/i-...Ms3Rrj-640.mp4
HD: https://photos.smugmug.com/photos/i-...s3Rrj-1280.mp4

[keen]

Hi CNCr

Sorry I am too bogged down with work to study all your findings in detail.

If a long gib like the X gib is just a little bent equally on both sides - but was made straight and accurate, then you can (and Tormach do) argue that it will straighten out when installed.

However if your gib is curved on one side and flat or of less of a curve on the other.

There is no adjustment that will fix this. Simply the factory have made a major slip up and you need replacement.

I am surprised that Tormach have not reacted strongly to this serious problem.

I have a background in this type of work - have measured. stripped and reconditioned several machine tools over the years.

Keen

https://www.youtube.com/watch?v=EchELgqGz-c

[TurboStep]

I just viewed your videos for the first time and what I see doesn't immediately suggest an issue with the gib. When your dial gauge starts to move you see a distinct movement for each 0.0001" microstep in both videos. This suggests to me that the gib is not overly tight or causing excessive drag. If you were seeing jumps every 2-3 microsteps this would be an indication that something was resisting movement. Judging from the results you've shown I'd be more inclined to check the angular contact bearings and the ballnut for excessive play. first.
The big problem is that a remote (forum) diagnosis is often difficult - it may indeed be caused by gib - I can't rule that out while sitting on my sofa. Venting frustration on a forum doesn't help anyone, especially when there are lots of people more than willing to help you become dissatisfied with your mill. These discussions should be taking place between yourself and Tormach. They're the ones most likely to help you, and I'm sure they will.
Step

[CNCer__]

I just viewed your videos for the first time and what I see doesn't immediately suggest an issue with the gib. When your dial gauge starts to move you see a distinct movement for each 0.0001" microstep in both videos. This suggests to me that the gib is not overly tight or causing excessive drag. If you were seeing jumps every 2-3 microsteps this would be an indication that something was resisting movement. Judging from the results you've shown I'd be more inclined to check the angular contact bearings and the ballnut for excessive play. first.
The big problem is that a remote (forum) diagnosis is often difficult - it may indeed be caused by gib - I can't rule that out while sitting on my sofa. Venting frustration on a forum doesn't help anyone, especially when there are lots of people more than willing to help you become dissatisfied with your mill. These discussions should be taking place between yourself and Tormach. They're the ones most likely to help you, and I'm sure they will.
Step

Hi TurboStep,
Please note that this thread is more about the table slop potentially caused by the gibb geometry issue. The backlash was just temporarily increased to see the relation: tightening gibb vs table slop. I do not see any issue with ballscrew nut, and angular bearing as the backlash on loose gibb is 0.0008". I'm keeping my frustration our of this board. By posting here I'm trying to share my findings, see others experiences in this matter. I'm expecting to get some corrections on my testing method, diagnosis, etc. I'm also intensively (intensively from my end so do far) discussing this issue and a few more with Tormach support. With no success so far but I still believe in them.

[wjh308]

Count on the Chinese to hand scrape and fit a machine properly??? Haha


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[pickled]

Hi Guys,
My Y-axis gibb removed from the new Tormach PCNC 1100 seems to be noticeably bowed on the scraped side only. The other side (not sliding one) is perfectly flat. My table has quite bad slop/play even with the gibbs over-tightened (with backlash out of spec). The issue probably comes from this bowed surface. I just like to confirm with other experienced Tormach users that this curve is not made by a design. I know that there should be a taper on the gibb, but curved surface? Can you please confirm that for me?

Well you know that scraper can get pretty heavy after one has worked consecutive 80 hour weeks hand scraping in a "state of the art factory" in China-especially so in the summer months. I think that you just need to invest in better precision angle gauges and 1-2-3 blocks that have also been made in China- everything would look good "on average" then :-). I mean come on look at what you are using right now. There is a sticker on the one triangle thingy with some sort of number...why would one ever want their QC tooling serialized? All dripping sarcasm aside I am sure that the folks at Tormach will work with you to understand what went wrong and how to get your machine to specification. Keep us posted.

[chuckorlando]

I dont care what they say, these machine are not hand scraped one machine at a time. I would bet they are not hand scraped at all. But rather they are ground and flaked to look as if they were. Same thing that was done to a lot of old machine that have been "rebuilt". How would you even manage to do that by hand .001 at a time, blue it, .001, blue it. And you certainly would not get that if it was truely mated to that way. As they might like you to think

[wjh308]

Go watch MuellerNick on YouTube, what he does to scrape in a machine. He actually took a brand new Chinese lathe and showed how disgustingly off it was. It's best you learn how to scrape and more importantly, how to measure and check your work, and do it your self.


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