Repeat length and number of teeth

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HOLOMEX
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Repeat length and number of teeth

Post by HOLOMEX »

Hi, we just acquired our new flexo and would like to know how to calculate the repeat length if I have the number of teeth and teeth in millimeters?

Also, how do I calculate the deformation needed when we prepare the artwork?

Dan
Frank Burgos
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Re: Repeat length and number of teeth

Post by Frank Burgos »

If the 'teeth in millimeters' is the 'gear pitch', the repeat length is simply number of teeth * teeth in millimeters.

To calculate the 'deformation', which we call 'distortion', let me know what gear pitch and number of teeth and I'll calculate the distortion here.
HOLOMEX
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Re: Repeat length and number of teeth

Post by HOLOMEX »

Hi Frank, thanks for answering, the number of teeth are 96

Hope to hear from you soon
Frank Burgos
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Re: Repeat length and number of teeth

Post by Frank Burgos »

HI Dan. What is the gear pitch? I believe that's what you are calling 'teeth in millimeter'
ESF_PRINTERS
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Re: Repeat length and number of teeth

Post by ESF_PRINTERS »

Hi, I came across this post and kinda disappointed it was left without an answer. This distortion you guys say we call it (K Factor) but I'm not sure that is the correct meaning. That's how it was explained to me back in the late 90's... Both our presses use same gears measurements and the gears are 1/4 pitch. I always said it was simple to figure out because 4 teeth measures 1" but my company acquired another business with a press that uses metric measurements and I tried to use our formula that we use here but of course it doesn't add up correctly.

They use 10 pitch gears so how would the distortion be calculated for a repeat of 28.346 with 72 teeth?
Frank Burgos
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Re: Repeat length and number of teeth

Post by Frank Burgos »

I wanted to use HOLOMEX’s numbers to illustrate, but I’ll do this, instead.

Way back, in the age of troglodytes, I was training some guys on a narrow web press in the swamps of Georgia, USA. The subject came up, so I went up to a white board to teach them about distortion. I would make this video differently, today, but I think it’ll do.

I also wrote an article on distortion: https://flexoexchange.com/calculate-dis ... ctors.html

I also created a calculator for distortion: https://flexoexchange.com/distortion.html

Hope this is helpful

Frank Burgos
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Re: Repeat length and number of teeth

Post by Frank Burgos »

They use 10 pitch gears so how would the distortion be calculated for a repeat of 28.346 with 72 teeth?
Hi ESF_PRINTERS. I also wrote an article on the difference between CP and DP: https://flexoexchange.com/cp-versus-dp.html

Your gears are 10mm CP, or "circular pitch".

To calculate distortion, I'd need the plate thickness.
ESF_PRINTERS
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Re: Repeat length and number of teeth

Post by ESF_PRINTERS »

Frank Burgos wrote: Wed Jun 05, 2024 9:46 am
They use 10 pitch gears so how would the distortion be calculated for a repeat of 28.346 with 72 teeth?
Hi ESF_PRINTERS. I also wrote an article on the difference between CP and DP: https://flexoexchange.com/cp-versus-dp.html

Your gears are 10mm pitch.

To calculate distortion, I'd need the plate thickness.
Plate thickness is .107"
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Re: Repeat length and number of teeth

Post by Frank Burgos »

Makes sense, for a 10mm press. You're printing wide web.

The tape is probably 0.020, but it doesn't matter.

28.3464 / 3.1416 = 9.0229" print diameter
9.0229 - ((0.107 - 0.005) * 2) = 8.8189, the diameter excluding the soft part of the plate

8.8189 / 9.0229 = 0.9774 or 97.74% distortion.
ESF_PRINTERS
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Re: Repeat length and number of teeth

Post by ESF_PRINTERS »

Thanks Frank it's much appreciated. Yeah it's wide web and using .020"

I will definitely try that 97.74% distortion, I will relate this to my graphics designer and test it out. Right now they are just having us add an extra inch to solid plates, when they receive it they mount and mark where it overlaps and cut the plate.
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Re: Repeat length and number of teeth

Post by Frank Burgos »

You're welcome.
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