Tolerance of CTP plate's dimension

[ngocdung93]

Dear All,

Hope some of you that currently have faced this problem can share some ideas for this thread.

Are there any tolerances of plate's dimension for Kodak & Fuji?

I know that some brand plates have tolerance, ex: plate 800x1030x0.3, but reality I measured 799.5x1029.7 or 799.6x1029.3

Is it acceptable for platesetter or printing machine?

Do Kodak and Fuji issue the Technical sheet with note of dimension tolerance?

 

[Hans-Juergen Zehms]

Dear Cindy,

the tolerances you are looking for are written down in the ISO standard 12635-2.
For sheetfed offset the length and width tolerances are +-1mm for plates up to 1500mm and +-1.5mm for plates larger than 1500mm.

Regards,
Hans-Jürgen

 

[ngocdung93]

Dear Hans,

Thanks for your guide!

Could you pls instruct where I can download this ISO standard 12635-2 form?

 

[Al Ferrari]

ISO standard 12635-2 - Google Search

 

[ngocdung93]

Dear Al Ferrari / Hans,

I find ISO 12635:2008, Graphic technology-Plates for offset printing-Dimensions, price 73$ for online buying.

Where can I choose to order for this kind of ISO that is trustly?

Could I download it for free?

I'm newcomer, really appreciated your kind support.

Thanks,

 

[Hans-Juergen Zehms]

Cindy,

the ISO organization is driving and administrating thousands of standardization projects year by year. That's why you do not get their standards for free.

A trustworthy source for their documents is their own online store.

ISO - ISO Store

Regards
Hans-Jürgen

 

[ngocdung93]

Dear All,

Thanks for instruction!

I'll contact them for online buying.

 

[ljgoldberg]

CTP plate geometry

CTP plate geometry

While the overall dimensions of the plate are critical to the proper operation of the CTP hardware the tolerances of the plate IMAGE are much tighter and critical to the printed job.

The physical plate can be measured relatively easily with a caliper, or for the accuracies quoted, a good quality ruler will suffice. The image, on the other hand has no convenient physical edge to hook the caliper over, and if high quality commercial tolerances are to be held, much smaller dimensions are being dealt with. For a 150 line/inch screen, a half row of dots is about 0.085 millimeters or 85 microns. Better printing at 175 lines per inch leaves only 72 microns. These register errors are beyond what can easily be measured with the unaided eye.

Upon initial installation many CTP engines require geometric calibration; is a 750mm horizontal line equal to a 750mm vertical line? Is the left side equal in size to the right side? The top to the bottom? If not adequately addressed, these small geometric errors will plague the pressman in numerous ways.

A non-contact, video-enhanced measuring system makes measurements of this type easier, faster, and more accurate than any amount of squinting through a magnifier and a glass scale. Once a video subsystem is employed image capture and color-separation contrast enhancement is readily accomplished.

The Beta Video Ruler offers all of these features in sizes up to 2000mm (80 inches). More convenient units of 24, 30, and 40 inches are also available.

Details can be seen here:

video ruler

Contact Beta or your local dealer for information or to schedule an in-plant evaluation.

Best regards,

Larry Goldberg
Technical Director
Beta Industries
[email protected]
Color Densitometers, CTP Calibration Systems for Print Quality

 

[ngocdung93]

Dear All,

I have just contacted the representative office in Vietnam of ISO and buy the copy book with cheaper price.

Video Ruler is efficient, but I want know the acceptable standard of tolerance.

How can we avoid the plate tolerance from Production stage, while the Al material's tolerance is +/-0.5mm (from some Al suppliers)?

 

[gordo]

Don't forget that aluminum plates expand and contract with changes in temperature by the same amount as film. It's therefore possible to be in plate size specification at one temperature but out at another.

Some vendor CtP systems, in addition to geometric correction, employ thermal compensation to adjust the image size based on ambient temperature so that image size (and therefore registration) remains the same despite variations in plate size due to changes in temperature.

best, gordon p

 

[KevinC@EFI]

Don't forget that aluminum plates expand and contract with changes in temperature by the same amount as film. It's therefore possible to be in plate size specification at one temperature but out at another.

Some vendor CtP systems, in addition to geometric correction, employ thermal compensation to adjust the image size based on ambient temperature so that image size (and therefore registration) remains the same despite variations in plate size due to changes in temperature.

best, gordon p

Good point Gordo - the expansion for aluminum plates is about 0.5mm across a 1m plate (typical 8-page size) for every 5C temperature change (9F). I'm sure you know that our Kodak CTP's do automatic temperature correction, but does anyone else?

Kevin.

 

[ngocdung93]

Dear Gordo,

Great suggested idea!

Right after production, I measured plate size & no much tolerance, it's acceptable. However, after 3~4 months, I found this tolerance bigger, and plates are stored below 25 degree of temperature.

With Al material's initial tolerance, we have plan to add more units (ex, 0.2~0.3mm) for finished-plate before production.

 

[marktonk]

Hi Kevin,

Glad to say the the Heidelberg Prosetter (only violet CtP with it) and Suprasetter both have temperature compensation.

Prosetter enlarges/reduces the images via algorithms based on the measurement of the temperature of the exposure drum to meet the size of a "digital master". I believe you use sw to change the size too.

On the Suprasetter, we use the chiller for the laser to also control the temperature of the exposing drum so it is always a constant temperature. If the temperature of the drum is always the same, when a plate is wrapped around the drum, it adopts the temperature of the drum and therefore is always the same size. I guess we figured if we chill rollers on a press, why not do the same to a CtP exposure drum. Simple yet very effective!

By the way, this also allows for a wider environmental operating range. Many CtP without Temperature Compensation have a narrow operating range.

Regards,

Mark

Good point Gordo - the expansion for aluminum plates is about 0.5mm across a 1m plate (typical 8-page size) for every 5C temperature change (9F). I'm sure you know that our Kodak CTP's do automatic temperature correction, but does anyone else?

Kevin.

 

[KevinC@EFI]

Hi Kevin,

Glad to say the the Heidelberg Prosetter (only violet CtP with it) and Suprasetter both have temperature compensation.
<snip>
Mark

Thanks Mark - good to know! It's certainly a feature that's more valuable than people may think... until they remake a plate on a hot afternoon and it doesn't register with the rest of the set on press any more.

Kodak CTP's also measure the temperature of/in the CTP and use software to compensate. Between that and our machine-to-machine geometric matching (standard on all Quantum machines), you can mix/match plates between devices at will and still have guaranteed fit and registration - one less thing to worry about on press.

Kevin.

 

[arci]

happy to place a comment.

happy to place a comment.

Dear All,

I really learned many things on your blog, let me share my humble experience. Small discrepancy of 0.8mm to the plate lenght due to slitting fault on the plate production will not cause error on the ctp machine like Topsetter. I experienced error of plate size when the plate was 0.9mm bigger or smaller than the material size encoded. ( It is very rare to see more than 0.8mm/sqm horizontal size variation for key players on aluminum plate production ). For Suprasetter, because the machine registration begins at the center, I never had a problem even if the plate is slightly bigger. Regarding plate expansion or shrinking due to change in temparature, aluminum has better heat tolerance than film. In addition, Suprasetter has temperature stabilizer, an internal cooling system which maintain the temperature to 25C even if the ambient temperature outside the machine is 17C or 30C. I never heard of image misregistration issue due to imaging temperature change ( most of the ctps now will abort imaging if the temperature exceeds the tolerance.) I am more afraid of misregistration due to excessive postbaking temperature and time rather than imaging temperature because during postbaking, the aluminum expands at extreme +220C for several minutes. In this case, better to use 1030 alloy made aluminum plates and place the finished plate in flat surface during cooling time to avoid warping which cause problem when installing to press machine. Get the minimum heat as necessary to your running mileage.

best regards
Arci
-tech. application support heidelberg phils.