Scratch building an automated induction heat treat station

Hi!

BLUF: We’re trying to automate the process of loading, heating, quenching, and unloading an induction heat treat station, and I’m wondering how you would do it.

Long story: I inherited a semi-auto induction braze station at one point where it was a simple pneumatic actuator and quick change fixtures, everything else was by hand. The automation team helped me develop an automated braze station, but the project was overkill at $150k or so. I’m on a different team now: we heat treat steel tools and water or oil quench them. Parts vary from 3 oz to 20# but are typically 3# or less and use the same coil.

I’m looking to automate the whole process: tray of parts in, three-axis material handling, coil loading and offloading, quench loading and offloading, and fraying into an annealing basket for secondary heat treat. In my head, I’m picturing Chinese junk servo driven linear rails with repeatability of .030” if that; one 6’ long for moving the pick arm, one 1’ long for the actual picking, and two on the onload/offload trays for segmenting parts. It would need a PLC of some sort, but the operation is simple enough I could run it off of Mach 3 and g-code program it. The PLC route is probably easier, just not something I’ve done before.

Anyways, would be good to get your thoughts.

A rotary transfer system will have fewer parts and be less expensive to maintain compared to your linear transfer design
The system would include the following:

A 2 foot long (for example) swing arm with a load station at 0 deg. , induction heat at 90 deg, quench at 180 deg, and unload at 270 deg. The pick up and drop off actuation can either be done with a pneumatic actuator at each station or with a rise and fall motion at the rotary arm pivot. The end of the arm has a pneumatic clamp that would be specific for each part. You will find that this type of mechanism is capable of faster transfer speeds. The load and unload stations will need their own indexing mechanism to advance the next part to the swing arm clamp position. The mechanism could be either a linear or rotary transfer depending on the design of the parts storage cassette.

The unload station at 270 deg.may be eliminated from the design by placing the quenched part back into the load station cassette.

Something to think on. I’ve worked on several dial based assembly stations before, but usually the application called for very little variation in SKU; all the same diameter, same features for workholding, etc. On most, the onload and offload were essentially 2-axis or even 3-axis transfer systems, but as you said we could accomplish this with some sort of cassette and transfer.

To me this sounds like a job for a SCARA. Even with the cheapest Chinese rails and bodged together controllers, if your time is worth anything a $15k robot you can just drop in and have your motion platform running accurately and reliably is likely to come out ahead. If a 6'x1' work area is sufficient, then an 800mm or 1000mm robot with a rated 10kg payload would probably suffice.

A SCARA is cheaper than a 6 axis robot and moves straight up and down in the Z axis rather than doing some complicated coordinated moves that may or may not play well with your induction coil, which would simplify and lighten your gripper design a lot.

Something like this.

There is one other important consideration in the transfer mechanism design. A design with a single transfer arm has a part processing time equal to the sum of the processing times for each station. For example, if the load is 1 second, the heat is 10 seconds, the quench is 8 seconds, and the unload is 1 second the part process time is 20 seconds. In this instance the induction heat station is only operating 50% of the time. If this is unacceptable the design needs to be modified to a full rotary transfer mechanism.

A full rotary transfer design would have four arms each with its own part gripper corresponding to the four work stations.
With this design the part processing time is the process time of the slowest work station. In the example this would be 10 seconds rather than 20 seconds.

A fast robot arm with a dual part grip mechanism has an advantage over the rotary transfer design. The arm can be working on any of the other three stations while the part is in the induction heating coil. The dual grip allows the arm to hold both the incoming and outgoing part of each station simultaneously. VMC tool transfer arms use a similar design.

Fortunately/unfortunately, cycle times are from 66 to 198 seconds at the induction coil. Volume is low enough that while this automated system replaces four benches, those four benches are rarely run at the same time. FTE reduction is 0.7 at best, but often times we’re short operators, so 0.7 is a big deal.

I think I could sell the boss on a SCARA. Axis New England mentioned the same model you linked to, and it was surprising how cheap it was. There’s other models a bit lower too. I’ll probably price out all three, but leaning towards SCARA or linear rails. The rotary transfer is great for 2.5 second cycle times that we just don’t need.

There’s a good bit of value to offloading into the same tray we onloaded from. These parts go on to annealing in a furnace. There’s no reason we couldn’t, so we probably should.

I agree on scara. Pick up the part, place it in the coil, drop it in a tank. A conveyer can pick things out from the bottom of the tank and drop them in a basket for heat treat.
Or everything sits in a basket in the oil and is picked up with a forklift and moved to annealing.