Safety Saw Auto Cut-Off
In recent history, we have had customers bring us some Auto Cut-Off saw applications. The following is an application overview of multiple applications condensed into one. Not all had exactly the same features and needs, but together they are merged and represented below.
This application was a repurposing on old pneumatically controlled circular saw heads into new production cut off saws.
The saw head featured a large diameter blade, pneumatic rapid up, rapid down – until just above the work piece, and then a controlled decent through the work piece by a rate control (think shock absorber). The blade – when raised retracted into a guard and eliminated access to the hazard of the blade teeth.
The machine sequence:
- Operator loaded the part by hand against the back stop through a light curtain protected load window
- Exited the protected space
- Pushed the go button to start the sequence
- Two part clamps closed and locked the part against the back stop
- Saw head rapid retracted (lowered) thru free space
- Saw head made contact with rate control and decelerated into cutting mode
- Saw head reached bottom of stroke and rapid returned up
- When saw up, blade stopped and clamps opened
- Ready for unload / load
For safety, we utilized a CM26 internally monitored safe return valve.
At any time while the saw was in motion, if the light curtain was broken, the CM26 redundant 5/2 safety valve would rapid return the saw blade up – cylinder fully extended to safe position and also drop out the current to the saw motor.
The valve was sized for flow / speed to return the saw head quickly. The light curtains were placed sufficiently far back for the reaction and travel time of the saw head.
For this application, DECI provided:
- CM26 Safe Return Valve
- Air Prep (FRL)
- Rate Control – down slow
- Rate Controls – fast up and fast down
- Saw Micro Mist lube system
- Part Clamp control valve
Customer integrated their own clamps, control PLC, safety relays, light curtain, mechanical build and perimeter guarding.
Contact us today if you have a unique problem that the Donald Engineering can assess and engineer the right solution!
Safe Accumulator Systems for Pressure and Return Flow
One of our customers had a challenging problem: Quickly move a large cylinder and briefly transmit a massive amount of energy in a safe (Cat 3 PLd), fast, and cost effective solution. Cost effective in purchase price and also operating costs.
The cylinder needed to extend 12+ inches and retract in less than a second while delivering tonnage throughout the extension stroke.
Along the process there were secondary issues that we addressed:
- System shock
- Electrical amp draw
- Footprint of power unit
Instead of a massive power unit with a large tank and 150 HP motor – with all its expense in electrical, we designed an accumulator system to store energy between cycles and a second accum system to deal with the extreme return tank surge flow.
Four Main Features:
- Pressure Side Accumulators (see “A”)
- While the machine dwells, getting ready for the next cycle, we use the time to refill the pressure side accumulators.
- We now have a much smaller pump motor and tank that is running continuously versus a larger system being called on intermittently.
- Block and Stop (see “B”)
- Ross Stop and Block valve used to prevent any potential stored energy from going to a cylinder downstream when not desired.
- Lock out tag out procedures.
- Waiting for the accumulator dump valve to dump system
- Accumulator Dump Valve with manual dump and indication for stored energy (see “C”)
- Accumulator dump valve will dump accumulators at a controlled pace as to not create a huge inrush of oil into a tank.
- Dump valve has the following safety features:
- Since the pilot dump valve is not monitored or redundant, this valve cannot be relied on for full safety protecting.
- There is a pressure gauge or pressure transducer plumbed directly to the accumulators for visual indication of trapped stored energy.
- There is also a manual ball valve that can be used to dump the accumulator in case the pilot valve fails.
- Use of an accumulator to absorb a high rush of return line flow (see “D”)
- Accumulators are charged to a low pressure.
- As the inrush of oil comes into this assembly to the two smaller accumulators, the oil is forced up into the accumulator and energy absorbed.
- The oil is trapped from going back out via a check valve.
- The oil inside the accumulator is then discharged automatically through a flow control back to tank. Flow can be set to meet the flow restrictions of the return line filter.
We accepted the customer challenge to provide a safer, faster, and more cost effective solution.
1. We reduced the size of the power unit
2. We reduced the size and amp draw of the electrical system
3. We achieved a Cat. 3 PLd hydraulic safety rating
Our customer now has the ability to deal with massive return surge flow to the tank in a safe way.
Contact us today if you have a unique problem that the Donald Engineering can assess and engineer the right solution!
