How to get more control over your set-up times
Kent Allen, Preco Industries, Inc., Lenexa, KS, USA
In most cases, the actual speed of the press proves to be less critical to your turnaround time than the effort required to prepare the press to run.
So what constitutes set-up time? Basically, it's any function you have to perform to start a job and keep it running heating up the press, setting up the feeder, locking up the dies, stringing up the foil, registering the job and doing makeready. For each of these tasks, companies have found that a little communication and pre-planning will cut the time it takes to prepare your press for operation.
Heating Up The Press
When you've got a series of short run jobs to produce, it can be agonizing waiting for your press to heat up. Try installing a timer on your heater. The heater can be programmed to come on in advance, so when you're ready to start a job, the press is at the exact temperature you need.
Feeding Sheets
Hand-fed presses can skip this step, but with sheet-fed equipment you can expect anywhere from five minutes to more than an hour. Time can be saved if you have a feeder that is computerized as opposed to manual, however the quality of the sheets and your pre-planning efforts will prove the most valuable.
If the sheets are curled or warped, you're guaranteed extended set-up times. Work with your customers to ensure the sheets are bound and skidded to keep them flat. And always have your customer square your sheets. When possible, have all four sides trimmed, but at a minimum, trim the gripper and guide sides, making sure your customer marks these edges.
Light weight stock also poses its own unique feeding problems. By planning ahead, you can schedule the job on a press that feeds light weight stock well.
Die Lock Up
Adding an extra chase to each press will enable you to lock up your next job while the current job is still running. The extra chase ensures the least amount of downtime during job changeover.
Once you heat up the chase, plan on making die adjustments due to the expansion of the metal. You'll find some presses are easier to adjust than others. Reciprocating platen presses require you to pull the chase out of the press and flip it over to make adjustments. The fundamental design of a clamshell press makes it difficult to adjust dies mounted on the lower portion of the chase. However, one clamshell press manufacturer has developed a time-saving feature that lifts the chase up in order to make die adjustments.
Stringing Up The Foil
There really is no magical solution to decreasing the time it takes to string up foil. Each type of equipment poses distinct challenges. Clamshell presses are generally quick and easy to string up the foil; whereas, reciprocating platen presses can be more challenging to get the foil up and around the head efficiently. One manufacturer of reciprocating platen presses has designed a newer model press to string the foil for you.
Obtaining Register
Communicating with your customer is the best way to decrease set-up times regarding register. Tell them up front what tolerances you can consistently hold and make clear what can and cannot be done on your presses. Give suggestions as to how the job can be designed or laid out to give the quality they want within the tolerances you can offer them. This means educating designers, since fighting to obtain a registration tolerance your press is not designed to meet will only prove to be a costly battle. And remember, a good operator can hold consistent register on most equipment, but having a press that enables an average operator to hold good register is what counts.
Makeready
Consistent pressure is the name of the game. Theoretically, if your press, dies, foil and paper are perfectly and consistently flat and level, you will only need to adjust the overall pressure to achieve a perfect impression. Not a likely scenario.
Two things directly affect consistency of pressure on a press: deflection and levelness. Deflection is the amount the head and platen bend, distort or deviate from their natural, flat condition. The amount of deflection a press has is a direct result of its design and engineering. While you cannot improve upon the amount of deflection your current equipment has, you should inquire about deflection when looking into new equipment. Ask the manufacturers you are considering how they quality assure minimal deflection and what guarantee they offer that it will not exceed a certain amount under full load.
Load cells provide one way to measure the deflection on a press. The cells gauge the pressure in various areas of the press and calculate the amount of deflection at each pressure setting. This is a great way to quality assure minimal deflection. Some equipment manufacturers use this technology. If you're interested, have your current equipment tested by an independent company. Finally, level your press periodically. Preventive maintenance will keep your press in good working order and help in decreasing set-up times.
Materials
The metal that is used to manufacture dies can be sanded down to a reasonably consistent thickness, however dies milled on a CNC machine are the most consistent. The uniformity of thickness should fall in the range of + .003", but check with your die supplier to see how they quality assure the dies they manufacture. With all else being equal, choose the die supplier who offers the best consistency of thickness.
Hot stamping foils are probably the most unwavering variable in this equation, with consistency of thickness at less than one micron. Work closely with your foil supplier to ensure you're ordering the correct foil for the job. Communicate with them on the inks, coatings, paper type, etc. They'll know what questions to ask to supply you with the correct foil product and ensure the job sets up fast and runs smoothly.
Paper consistency will vary from type to type and will depend on what other processes its been put through before you received it. You will undoubtedly have little say in what paper you get from your customer.
The message is clear. Better communication with your suppliers, equipment manufacturers and customers is the winning ingredient to decreased set-up times. Only by having the right materials on the right press with obtainable job requirements will you gain the competitive edge.