|
Should I use or at least consider using double acting cylinders?
Double acting cylinders will assure full cylinder retraction on a timely basis even in systems where restrictions such as small orifices or long tubing runs have been introduced. The use of double acting cylinders is especially important if "return" time is critical (as in some CNC controlled systems). We also recommend use of double acting cylinders in systems operating below 800 psi.
If single-acting cylinders must be used: Have I reduced the number of fittings (orifices), length of tubing and restrictions as much as possible? Are all of these properly sized?
Some fittings and hoses which are locally available (not from Vektek) have extremely small orifices which restrict flow. The use of 1/8 or smaller size fittings can have this effect on a system. This restriction is even more pronounced when introduced at a main feed line. This can happen with some fittings and many hoses.
Excessive tubing length can create a "column" of oil, which is very long. Friction created by moving oil through tubing and hose will slow response times because of the inertia of the column of oil and increased backpressure of returning oil. If single acting springs are all that is pushing this oil, it is possible that this backpressure can become sufficient to stall the cylinder.
Proper sizing of fittings for main feed lines and device supply lines will normally be accomplished by using the appropriate VektorFlo® fluid distribution manifold.
Device lines are size -4 (1/4 OD which match to fit SAE #4 ports, and adapt to the occasional use of SAE #2). Main feed lines are -6 (3/8 OD, SAE #6). The use of smaller lines -2 (1/8) for devices or -4 (1/4) for feed lines may cause excessive restrictions.
Normally avoid using an SAE #4 quick disconnect to feed an entire fixture.
Before you order devices, build your fixture or even consider your design complete we suggest you run through this checklist to check for some common problems.
Is my plumbing free of obstructions and contaminants?
Tubing must always be flushed after cutting. Even if not cut in your shop; it was cut before it came to you. Chips, burrs, dirt and other contaminants have collected inside your tubing and drilled passages. These contaminants can cut device seals, damage valve sealing surfaces, cause erratic operation and reduce service life if not cleaned prior to fixture start up.
The use of improper fittings can also cause obstructions and restrictions. Some people have adapted fittings, which they had to use in SAE ports. Yes, the threads are the same on SAE and JIC flare fittings. The body length may be different. In one case the use of JIC fittings in an SAE port made a metal to metal seal at the bottom of the device inlet port. Obviously the "clamps didn't work." Be sure you haven't created obstructions by using non-standard parts.
Is my pump of appropriate size? It is rated for_____gpm, or_____cu. In. per minute. My devices require a total of_____cu. In. of oil to actuate.
For most normal size fixtures, a pump rated in gpm (gallons per minute) is not recommended. If your pump is rated much more than 1 gpm, call us, we'd rather give you sound advice now than have you damage clamps and have to sell you replacements. Be sure that you do not exceed the recommended flow rates for your system. If you aren't sure, ask us.
My pump runs continuously. Is it the right type of pump?
Call us. It can often be made to work. Some modifications will probably be necessary. If you have a VektorFlo® pump, which runs continuously, call us immediately (they are not normally set up to run continuously).
I've been using a dump pump (builds to pressure, shuts off and releases pressure automatically). Is this pump suitable for workholding?
It can be. It will work if the circuitry is properly designed. It may require special circuit modifications or a special pallet decoupler to work properly.
I want to make a cut directly against (into) a clamp. Is this possible?
Yes, it is but it will require special design considerations. We encourage that cutter forces always be directed toward a fixed stop. A fixed stop is designed to prevent part movement. A clamp is designed to position and force a part against a fixed stop. In order to machine into a clamp, the clamp must be sufficiently sized to resist all cutter and machine forces or the part will tend to shift.
When I use a dial indicator on my part, it bends when it is clamped. Why?
Clamps should be positioned directly opposite a fixed locator, hydraulic support or other supporting element. This element may be a part of the fixture, a solid portion of a rigid part or a properly sized floating locator such as a hydraulic work support.
If your clamp is putting force into your part which is not directly transmitted into a solid stop, it may distort the part.
Clamping on draft angles or "mushrooming" the part with excessive force can also cause part distortion. Send us a print of your fixture design, we'll be pleased to evaluate it and make suggestions.
I hold all four corners of my part on solid locators. When unclamped, it seems to "spring" back into a different shape. Why?
First, holding all four locating points in exactly the same plane on your fixture is virtually impossible. (See your favorite text on fixture design for an explanation of 3-2-1 fixturing principles.) Second, your part can't have all four of these points in the same plane which causes it to distort when clamped. Other factors such as stress relief may cause the part to change its "free" shape after machining.
My pump turns on and off approximately every 3-5 seconds. Why?
There could be several causes:
A "spool" valve when used with a demand pump will cause it to turn on and off as its internal leakage bleeds off pressure. Use of spool valves voids warranties on VektorFlo® pumps. We suggest the use of "zero leak" poppet or shear type seal valving. Vektek offers 2 position, 3 port and 3 position, 4 port directional control valves.
Industrial type double acting cylinders (even high quality ones not designed for clamping) have significant leakage across their internal seals. This leakage will not normally be externally visible. Internal leaks from one side of the piston to the other will cause pumps to cycle excessively. Note: These cylinders should be avoided in all palletized applications as they may cause pressure loss or backpressure quick disconnects.
All leaks at fittings seals or other typical leak points will eventually cause a pump to cycle. If your VektorFlo™ pump cycles more often than you feel appropriate (more than once per minute without a valve being shifted) call us. We will gladly offer advice.
I want to limit the pressure into a sequenced hydraulic circuit. Which valve do I install first?
We recommend that you avoid putting one special function valve behind another if possible. If you must, put the pressure limiting valve after the sequence valve. This avoids the limiting valve being shut off before the sequenced circuit is fully actuated.
I want several sequenced operations to happen on my fixture. Can I put three or four sequence valves in a series?
We do not recommend it. Our sequence valves operate better if run directly from the main hydraulic supply line and set at different pressures. (We recommend at least 500 psi differential.)
My company uses lots of brass fittings on our product. Can I use these to connect my hydraulic clamps?
Absolutely not recommended, brass fittings and some aluminum or steel fittings are for low pressures. Be sure that locally sourced fittings are rated for 5000 psi operation. All of our fittings are rated for at least 5000 psi. We do not recommend the use of low pressure fittings. If you have a local source for high pressure O-ring style fittings, by all means feel free to buy these items locally. We want you to know that suitable fittings are available from us.
I need to disconnect my fixture from the pump. I also need double acting clamps. How can I do this?
Our pallet decoupler was designed with a double acting port incorporated. You can add a second quick disconnect (we suggest a female) to this port, connect a second line and appropriate valving.
This is an exclusive feature of the VektorFlo® Pallet Decoupler.
We use anti-freeze, not hydraulic fluid in our plant. Will this effect your clamps?
Yes, our warranty specifically excludes the use of non-standard hydraulic fluids. While there are some good fluids out there, please see our approved fluids. If you must use another fluid and it has good lubricity and corrosion resistance, we can tell you whether it is likely to cause problems or not. Some fluids may provide adequate long-term service; we will offer advice upon request. We do not approve of the use of these fluids but may be able to recommend compatible seals.
We run a fixture for three months, store it for six months, then bring it back on line. How can we keep everything working?
Preventative maintenance. Before you store your fixtures, be sure that they are free of coolants, coolant buildup, clean and dry. A light coating of corrosion protection may help. Be sure to store in a cool, dry, clean environment. We encourage the use of double acting clamps on fixtures which will be stored for extended periods.
Our clamps are used for cast iron grinding. Our coolants also seem to be corrosive (our fixture plates rust). Will your clamps stand up to this?
Better than other brands. Nothing is 100% foolproof. Our extensive use of hard chrome plating, stainless steel and our corrosion resistant BHCTM will give you the best possible resistance to corrosion. Our processes will allow our clamps to run longer with less problems even in this destructive environment.
When I unclamp my single acting clamps, a "squirt" of coolant comes out of the vent port. I am running flood coolant and the clamps are covered during the entire machine cycle. Can I eliminate this problem?
Maybe. We suggest you run a vent line to fresh air to each breather port. This can be done in copper or plastic tubing. If you can't get to fresh air, a trap in the tubing or protected vent inlet area will reduce the amount of coolant entering the cylinders. Keeping the coolant out will reduce the chance of corrosion in the cylinders. It will also keep the cylinders from having to expel the coolant as they return causing sluggish return. Our swing clamps are now available with "bottom" venting to allow them to breathe dry air from protected areas under the fixture.
When I look at my clamps, there are threaded holes in them. What do the labels "P" "ADV" "RET" mean?
These threaded holes are called "ports". They are either SAE 4 or SAE 2 depending on the device (SAE 6 on some manifolds). SAE 4 (7/16-20 straight thread O-ring port) is the most common. Some devices that have space restrictions may use the SAE 2 (5/16-24 straight thread O-ring) ports. The label "P" or "ADV" ports are normally used to clamp the part, "RET" indicates the port normally used to unclamp or retract the clamp.
My local chemical representative has recommended the use of "water-glycol" hydraulic fluid. What are the benefits of this fluid and should I use it?
Water-glycol is a nontraditional hydraulic fluid. This fluid was developed for use where petroleum based fluids is not allowed. They are commonly used in areas requiring "flameproof" fluid. They often cause problems with device seals, valves and pumps. We do not recommend water-glycol fluids. We may in some cases be able to provide devices with seal compounds acceptable for use in this environment. We cannot recommend or warrant their use in any Vektek pump or directional control valve.
What about using seals made of Viton®?
Seals made of Viton® can be a good answer for high heat applications up to 350° F, however, fluid type is also important. It may be acceptable in most fluids at lower pressures, but it is not a universal remedy for all fluid problems. There are other acceptable seal compounds for use in water-glycol and other unusual fluids. Our staff can help direct you to a seal that is best suited to perform in your application Because seals made of viton may work in your application, we offer this as an option on many of our cylinders, call for details.
How hot is too hot to run hydraulic fluid?
Anything above 350° F is considered too warm for most hydraulic fluids and seals. Even seals made of Viton® are not recommended above 350° F. For advice on high heat applications, you may contact Vektek's Engineering Department.
I notice that in your fitting section you have both flareless and 37 degree flare fittings, why?
We do stock both 37 degree and flareless fittings. You may also notice that we do not stock the nuts for 37degree fittings. We recommend that you connect tubing with flareless fittings. They are proven to work well and be somewhat more forgiving than flared tubing. A good flared tubing connection is very reliable. Should you happen to cut it 1/8" short, it is difficult to stretch. A flareless fitting has some built in forgiveness. We suggest that you use 37 degree fittings to attach hoses to devices or feed fluid to your fixtures.
I have my cylinder hooked up to a pump. It extended but won't retract. What have I done wrong?
Is there a directional control valve in the circuit? If not, one is required. Is the cylinder single or double acting? Can you provide a schematic or simple hand sketch for us to troubleshoot from? We are glad to help.
My cylinder is hooked to the air line and it won't hold the 5000 pounds your book listed, why?
Is it an air cylinder? We do not manufacture a 5000 lb. air cylinder. We do manufacture 5000 psi and 5000 lb. Capacity cylinders. If you have a cylinder with an effective piston area of 1 square inch and you are putting 5000 psi into it, your effective clamping force will be 5000 lb. Call us, we would be happy to calculate the force for you. Note: Work supports cannot be adapted to lock up on air pressure.
I want to run my clamps on air. I really don't need much force. Since these cylinders are being used as positioners, is it OK to use air?
Some of our cylinders, (but not work supports) can be run on air, others may be adapted. If air will provide adequate force and you are happy, so are we. In some cases straight line cylinders and work supports have been run successfully using high pressure gas. Swing clamps may not be used on high pressure gas. Please call our factory for information on our pneumatic clamping line, specifically designed for workholding.
I need some type of retractable locator. After my part is loaded, I want it to "disappear." Do you have anything to do this?
Block pull cylinders or any double acting cylinder may be used in this way. If highly precise location is required, please be sure to use a guide bushing to provide more precise location.
When I called in my salesperson referred to a "breather." What is it and what does it do?
A "breather" is a port designed to let captured air vent to atmosphere when a cylinder is actuated or a work support plunger is moved. This lets the trapped air "breathe" into the room. Breathers will sometimes "inhale" coolant and it is often preferable to plumb them to clean, dry air space rather than allow them to suck coolant. Vektek cylinders are all designed with Stainless Steel springs to reduce the possibility of corrosion from this coolant contamination. You may not plug these breathers as doing so may cause the cylinder to malfunction.
How do I read my gauge and what does it mean?
First, release all pressure on the system. Check the gauge for proper operation. Check to be sure the gauge is returning to "zero." Pressurize the system and read the gauge. The current reading from the gauge indicates the pressure your clamping system operates at when clamped unless there is a pressure limited circuit branch. (The entire system equalizes at this pressure; Δ P is negligible under static clamping conditions.)
I need a clamp just like your 15-0109-08 except it needs a 6" long rod. Can you help me?
Maybe. We do entertain specials from time to time. Please ask us. We often find that "special" requests coincide with our ongoing new product development. If you have a special need, it is worth asking. We may decide to do your special as a development project. We may not be able to produce it (actually you may not want it) because of cost. It may be something we have done before and will be relatively easy.
The danger involved in using "specials" is that we do not stock replacements on custom parts. When your machine crashes (when, not if) and you need a rush spare, custom parts have to be made from scratch. You will need to order spares at the time of the original order. The cost of a single replacement on a complicated special can often be 5-10 times the cost paid in the beginning. A little foresight will be very beneficial if you must have a special.
|