Tips on Evaluating a Used Machine
By my definition, “the value of any machine new or used is based in its capabilities to produce product that meets the buyers/printers expectations of format, print quality, speed and performance with reliability equal to that of what is reasonable for the purchase price”. Therefore buying a used machine requires knowing the specifications of the machine as it was advertised “new” then comparing this data to the current condition. A starting place is to research this information via the original manufacturers brochures/advertising claims, machine manuals, sales reps, technicians and other owners. Expecting more from a used machine than it was capable of when it was new is a exercise in futility. For example, if a machine did not register well when it was first built it will not improve over time. Yet trusting all advertising claims even when they are found in a magazine ad or literature sheet can also lead to trouble. More than once I have found machine claims to fall short of reality. While some machine specs/claims may be hard to confirm such as “set up speeds” some are more straight forward such as print size or print area, frame size minimums and maximums, press diameters, press speeds, and power/air requirements. I suggest confirming these specifications as much as possible if one or more are critical to you. Relying on manufacturers literature sheets may prove to be costly if your machine is found to take up more room than you have or does not accept the screen library or image placement that you already own.
Since there are many considerations to this topic I will assume for now that you have determined what you are looking for as far as make and model but are now going to consider a specific machine in its current condition and location. With very few exceptions an inspection of your purchase is crucial. The reasons are obvious but one worth noting is simply to make certain that the machine you are evaluating is what you expect. Many machines of the same make and models have varied to accomplish a lower cost by leaving off standard elements or meeting particular customer’s custom needs.
Even veterans can be fooled into believing that they know more than they do when this step is skipped and opinions of others is trusted. These “White Elephants” exist and they can trample you.
Before traveling a long distance to inspect a machine try and get any documentation you can on the machine before you arrive so that you know what you are looking at before you get there. Manuals are good but largely are not kept up to date to reflect changes. For this reason pictures are the best. Once you are satisfied that the information you have on the machine represents what you are looking for then the next step can be taken which is to look at the machine for yourself or to have it evaluated by a technician. (Beware that they may have ulterior motives; lack the expertise etc. so ultimately you may be your own best judge)
I suggest starting your evaluation by zooming out and looking at the big picture stuff first. For example, measure the press to confirm its size. If you have space limitations you may find that this rules the machine out eliminating the need for further investigation. I have found machine specifications to be incorrect from literature more than a few times. This may cause a problem when discovered later. Finding this out when you are having your machine installed may put you into a position of having to crawl under the press to get to the other side or preventing you from placing a flash cure in certain positions. Remember to leave room to get your flash and screens in and out of the machine!
Next, look at the “utilities” feeding the machine. Is the machine air or electric or both? If it is electric, what are the power requirements? Remember to check all the parts to the machine requiring power. Is the machine or any of its components such as the flashes 3 phase? Sometimes the previous owner may have picked up a used flash or a second flash that may look the same but have different power requirements. Newer presses can often be switched at a relatively low cost to run off of single or three phase but many flashes cannot.
What are the Voltage requirements? Flashes built for 240 volts running on 208 will work but may not cure as quickly as a flash built for 208. Flashes built for 208 but running on 240 will also work but normally not as long. If one or more of the flashes require 3 phase power you should know this. Many buildings don’t have 3 phase or lack the service into the exact area needed. In these cases, some form of contracted electrical work may be required to bring the 3 phase to the building or location in the building.
If the machine runs off of air then an inspection of the air system feeding the machine is a must. What you are looking for is a well maintained air compressor with properly sized after cooler, refrigerated dryer and inline filters/ and water traps. Without these items in place and properly maintained the machine will be fed water, dirt, and oil. One or more of these contaminates will ruin the machines reliability over time and milk your maintenance budget dry. I suggest looking for a maintenance log for the compressor. If a service contract existed with a local service company then a service history would exist from their service calls. Checking the storage tank for water is a big picture thing. Unless an automatic drain is installed that regularly expels water from the tank the draining of the tank may be forgotten and the tank may be filled with water. Loosen the drain valve to see if water is in the tank and how much. A lot of water (in excess of a glass) per 80-100 gallon tank can be an indication of a poor maintenance schedule. I have seen tanks completely full of water (75 Gallons) such that they have no ability to store air. Next, follow the lines feeding air to the machine and see if traps exist to let water out that accumulates in these lines. Try disconnecting the airline that goes into the press to check to see if you get water indicating that the lines leading to the press have water in them. A water trap is located on the base of most machines that is the manufacturers attempt to rid the press of water that may be coming from a poorly designed or maintained air supply. These devices attempt to catch the water vapor in the air flowing through a clear plastic bowl by a mechanical process. If this bowl is full of water it may be a sign of a faulty discharge or the lack of maintenance that should have been performed to manually drain the bowl by hand.
Some machine manufacturers use the actual machine frame as an air reservoir tank to buffer the demands of air volume at points when the machine demand is high. In these cases a drain valve on the bottom of the machine will exist. Find it and loosen this fitting (if it is a plug, shut off the air and make sure no pressure is in the tank) to see how much water is present in the frame this can indicate how much water made its way past the compressor refrigerator/dryer and machine water trap.
Another air related issue that is both related to air supply and lubrication is the in-line oil lubricator. This device is used to add clean oil back into the dry air being delivered to the press. This device also has a bowl similar to the water trap but is filled with oil. A adjustment knob found on top of this bowl is used to drop oil every so many cycles of the machine. A check of the bowl to see if oil is present is telling. Keep in mind that too much oil is also a problem so sometimes this lubricator may be shut off due to the maintenance person determining that too much oil has entered the system. If you suspect too much water or oil may have entered the machine take a few airlines off of parts on the machine to verify this suspicion. Popular push to connect fittings make this easy to do so long as the air supply to the press is shut off and exhausted when you are disconnecting them.
A next step could be to look at these same utilities as they are found on or as a part of the machine. For an air machine you are looking and listening to air leaks. Small leaks are often found on air machines but the key is to determine if these are simple are more costly. Plastic push to connect fittings often dry out and do not hold the air lines in tight enough over time so their replacement is sometimes needed. Parts and installation is minimal normally 6-8 dollars per fitting and 5 minutes for replacement. The problem is that there can be over a hundred of these. Other apparent leaks may be air that is leaking past the seals in air cylinders and back through the valve that controls them. These leaks that may be coming from a valve may be an indication of a bad air cylinder/seal and or valve. Some cylinders can be repaired with new seals and others may be not. Check air mufflers as this is where air is expelled from the valves. These are often plugged from contaminates that have made there way through the press and indicate the quality of air that has been fed to the machine and or the shear amount of use/cycles the machine has been used for.
Electric connections, fuses, panel lights, touch screens are all electric components that are easy to check and telling of problems. Turning on all the buttons and running each printhead will let you know what works and what doesn’t. Failed lights may be just light itself but confirming this is important. A print head that does not run may be as simple as a blown fuse or as expensive as an input/output module on the PLC that controls the machine. Yes one can burn out while the others work. This part can sometimes be replaced easily but can cost $400-500 dollars and or may no longer be manufactured.
Other tell tale signs of problems is a cabinet full of fuses that are spent. This normally means that something has eluded the trouble shooter and may still be unsolved. Other tips would be to write down the features that do not work so that you can keep track of the total amount of “issues” you are going to deal with later. I recommend checking the brushes of at least some of the electric motors if applicable to see if they are worn. If they have never been checked and are worn too close to the armature motor damage will occur. On some machines a set of brushes cost about 35 dollars but the motor may run $400.00.
Grease and Oil- Check the maintenance manual of the press and see if it appears that lubrication points have been used and grease or oil is present. A chart of when this may have been done is rarely found but comforting if it is.
Mechanical Points of wear. What gets worn or pounded the most?
Shocks-If the machine relies on a shock absorber to slow down and or stop the indexer or printhead then you should check to see that they are working. In general you can count on head shocks to be bad on many heads of a used air machine. These shocks fail easily and cost upwards of $50.oo each and there are two per printhead. Cycling a printhead without a floodbar dragging on the screen is hell on these shocks. A quick check to see if these are failed is to push the plunger in by hand rapidly using your thumb. If you feel resistance at high speed then there is life in the shock. If the resistance does not change it is probably toast. These devises do not offer resistance at slow speeds so check several until you can tell the difference. Essentially oil flows inside these devices through small orifices that close down as the plunger is pressed in. The further the plunger goes in the fewer escape hatches are available for the oil to escape thus resistance is increased. A slow activation allows the oil to pass without the resistance being created.
The coupling of the machine coming in and out of a free wheel mode is a wear point checking these components for slop, excessive wear is important. The pin or clevis that connects the two parts should be inspected for wear as well as bearings that the clevis may grab. When these bearings come loose the hole they are fitted into can wear out of round allowing the bearing to loose its centered position. This can be a sever problem for smooth indexing and very difficult to correct.
Center bearing and bushings. Critical wear issues are at play and whole machines can be determined unusable if the cost to repair these parts exceeds the value of the machine. (see article on Grease is the Word)
The last bit is the most obvious and therefore I dedicate the least amount of advice. The mechanical workings of the machine as it is used by the operator and seen by eye such as the smoothness of indexing, lift of either the indexer or printheads and the accuracy of the micro registration for printing frames. Since these items are the easiest to evaluate a buyer should notice the difficulty or rough movement of these motions. If any seem to be out of order, then knowing why is crucial. If for example the indexer shock is bad and is the reason for rough indexing of the machine a further investigation should be made to find out if any other damage has occurred as a result of this bad part. Replacing it may be affordable but not the other bits that were damaged as a result of leaving the part on the machine too long when its performance was out of tolerance. Loose drive bearings is a by-product of a rough running air machine. If one or more of these bearing become loose the hole it is mounted in will wear out of round. If left loose for too long there will no longer be a defined location hole in which to replace the new bearing into. This will not allow the machine to travel or index the correct amount resulting in a rough running machine from this point on. Drilling this hole out to fit it with a bushing is a possible solution but difficult/costly and only accomplished with specialty tools by an expert. Since each machine design differs there are many points to consider. For a seasoned expert many items are on the checklist to evaluate a machine thoroughly however, in the end all machines can be returned to their original condition, if you are willing to spend the necessary time and money. This can be thought of in the same way an old car can be restored. The problem is that a screen printing press is unlikely to become a collector’s item and increase in value like the 1971 Hemi Cuda I used to own. Instead you have to figure that your time and money is worth something as well as the predictability of the machine working when you need it. If you feel that the value of the machine is likely to be matched to your expectations at a predictable expense than your purchase may set you on your path to the automation you crave.