Digital speed indicator for Goss HT70 press for RTF rollers

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Zane
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Digital speed indicator for Goss HT70 press for RTF rollers

Post by Zane »

I work for a print company in New Zealand and at our factory we have 3 Goss HT 70 newsprint double width offset printing presses. Each press has five print towers that feed the printed product into a folder. Within the printing process it is required that a tension is maintained upon the web (continuous sheet of paper) throughout the press to maintain the quality of the printed image and to aid moving the webs through the press to the folder. These tensions are created at several points within the process.
A basic explanation of these tension points is as follows. The reel stands that feed the paper into the press maintain tension on the web from the reel stand to the print tower. At the top of each the print tower is an out feed roller that maintains tension on the web from the top of the print tower to the out feed roller. Before the folder are two rollers, upper and lower RTF rollers that create tension from the out feed rollers at the top of the print towers and assist with feeding the paper into the folder. The folder has nip rollers and the pins within the folder which create another back to the RTF rollers. These tension points can interact with each other too. Each tension point in the process is achieved by the next down stream piece of plant running at speed faster than the piece before it.
The RTF rollers have their speeds adjusted via their own PIV (proportionally infinitely variable) gear boxes. On the front of each gear box is a hand wheel to adjust the gear box ratio and a dial is built into the hand wheel to give an indication of the ratio setting. The reading from the dial is the same as a wall clock ie a setting of 8:30.
The problem we had was that the reading from the dials had no meaning in relationship to the process. Also due to the backlash in the gear boxes if the hand wheel was turned in one direction we would get quite a different result if it was turned in the opposite direction and set to the same position.
To get around this problem it was decided that we needed a digital indicator for each gear box. After looking we could not easily find one that was commercially available that would do what we required. We also have a Rockwell control logix control system used to control the press. We looked at integrating this function into the press control system but with the cost of high speed counter modules and modules to drive a display at the gear boxes, this was not cost effective. After this it was decided that making our own was the best solution (time was not a factor).
To measure the process, the press speed was required along with the output speed of the upper and lower RTF rollers. To achieve this the gears on the back of the PIV gear box would be used to determine the speed by counting the teeth as they passed a gear tooth sensor mounted on some brackets I made up to hold them.
To make circuit board I used Express PCB that is a free down load. I made up the circuit board layouts and printed the circuit board layout onto some Press n Peel blue via a laser printer. I found that an old HP worked well. I have found that newer colour printers, some of the toners when ironed and used with the Press n Peel did not work all that well.
Once the circuit board layout was done I got some single sided PCB board. This was rubbed down with a fine scouring pad and soap and water until the surface was clean of all oxidation. The board was then dried completely and the Press and Peel layout was placed face down onto the copper surface making sure both surfaces were free of dust etc. An electric iron had its temperature set to approx 280 oC using a thermocouple. The iron was placed on top of the Press n Peel and PCB and held there for about two and half minutes. During this process the iron was moved partially out of the way and a rag was used to press down on the Press N Peel as I have found this gives a far better result than pressing down using the iron on its own. Another part of the board would be exposed and the pressure applied there using the rag. This was repeated throughout the process. Once the time was up the board was placed in a cold water bath to quench. Once cold, the Press n Peel was gently removed.
Using an etch resistant pen and a x10 magnifying glass the board was checked for defects and a razor blade used to remove any of the etch pen that was where it was not required.
Using a Pyrex baking dish, sodium persulfate etching crystals were mixed with hot water and placed on a portable element to maintain the temperature around 70 oC. The PCB was placed in the solution and a small brush was used to brush the surface to remove any bubbles that formed. Once the unwanted copper surface was removed from the PCB the board was placed in cold water and thoroughly rinsed. The board once again was checked for any defects.
The boards then required drilling. To do this a drill press was used. On the bed of the drill press a board was placed. Counter sunk into is this was an LED array out of a torch. A piece of Perspex was then placed over this. When the PCB was placed on top of this it made seeing the pin holes for the components very easy to see as opposed to shining a Light source onto the PCB.
After this the boards were populated. Using the x10 magnifying glass the board was checked again for any soldering defects. Once completed a flux cleaner was used to remove any flux. The board was then cleaned again with the scouring pad and soap and water. The boards were then thoroughly dried again and then the backs coated with a clear lacquer.
The boards were then mounted in plastic enclosures then mounted on the press with a power supplies and gear the sensor signals wired in.
The system was then commissioned and checked off line and then in production.

Please not that the original file was written in FCV4 but imported into V5
Attachments
PIV Speed Indicator.fcf
(29.2 KiB) Downloaded 444 times
PIV Speed Indicator.doc
(244 KiB) Downloaded 413 times
PIV Drawings PDF.pdf
(127.32 KiB) Downloaded 487 times

Kenrix2
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Re: Digital speed indicator for Goss HT70 press for RTF roll

Post by Kenrix2 »

Nicely done Zane and thanks for the tip on drilling holes with a drill press. My drill press has laser cross hairs shinning down but, sometimes the reflection off the board can be misleading. I will have to rig up your technique and try it. For PCB making I have had great success with PCB Fab-In-A-Box along with a GBC laminator to set the laser print transfer paper to the copper clad fiberglass board. It is rare that I have to touch up with a resist pen. I can get very fine lines so surface mount IC's are no problem. The copper clad boards are thin, .032"(1.25mm), so with a box cutter and straight edge they can be scored several times and then just snap off the excess with pliers.

Zane
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Re: Digital speed indicator for Goss HT70 press for RTF roll

Post by Zane »

Excellent, thanks for the bit on PCB in a box too, i will have to have a look at that. I'm also keen to check out the design spark (free) package and see what it costs to have some boards made instead. The site Alibaba has a lot of different places on there that offer their services. I think from a quick look that most of the places require Gerber files to make the boards. Has anyone else tried this option and have any idea of the service and the cost?

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