Passing the Talking Stick & What Would Your Do with This Lathe?

Please see the presentation that introduced the talking stick on our Web site.

Passing the Model Lathe

Sensors

• Probes to measure dimensions
• Laser sensors
• Vision to measure surface finish
• Power and force to measure how much work the tool was doing
• Thermal to measure tool tip conditions
• Thermal to determine if the machine has expanded and changed its shape to allow for correction
• Encoders on all axes and motors
• Detect which tool is mounted
• Measure the part while it is being made
• Measure taper and deflection when turning long parts
• Determine if there is a part in the machine and whether it is mounted properly
• Determine if correct tools are mounted and mounted correctly
• Strain gauges to check power readings on all axis and deformation
• Detect if the operator is in the area. Halt operation if there is a possible threat to the operator to improve safety

Feedback - to the controller, the operator, the cell, and the whole plant

• Error correction (Also see set up)
• Quality control - local as in don't make scrap - higher level as in record dimensions of each part made for history
• Production reporting
• Tool performance and tool life monitoring
• Determine when to change tools
• Compensate for tool wear

Set up

• Assist operator by showing pictures of required tools and where and how they are to be mounted. Detect that tools are properly mounted.
• Have automatic set up sequence when tools are changed. Quality control blanks will be machined at various rates. The machine will measure the result and set up an error correction table which will correct for tool mounting errors and deflection. The controller will use this table to increase accuracy.

Geometry

• Long and short depending on the customers parts
• Variety of sizes. 64% of parts are round. 80% of round parts are less than 2 inches in diameter. So a family of lathes from 4 inches to half an inch should hit a large part of the market.
• Variable number of pairs of ways (1, 2, or 3). First pair would be for tool turret. Second and third pair of ways could be for any of: tailstock, second tool turret, sensors and probes, milling head for simple operations such as set screw hole drilling and tapping

• Three sets of ways would be required if a powered tail stock with special collets which grab the part when one end is finished and backs up so operations could be performed on the other end by a second tool holder. In this way complete parts could be produced in one operation.

• Perhaps these lathes will be so cheap a second simple lathe would be more cost effective and flexible than two tool holders on one lathe

Motors

• All discussion of drive systems seemed to imply electrical with computer controlled digital variable frequency power supplies
• Some inferred linear motors for X and/or Y axis
• The spindle motor might be an Armenian hollow core printed disk motor for direct drive and provision to feed bar stock down the middle. Simplicity is a good rule.

Maintenance

• One chap thought this would be a maintenance night mare because an operator would be expected to monitor a whole fleet of these machines and when one broke down it would hold up the whole plant and the pressure on him to get moving again would be unbearable.
• Another felt we would be able to make them so cheap that we could afford to have a bunch of spares so all maintenance would be off line.
• Another was planning to make them so light and portable that they could be carted off to the maintenance shop where they had the proper tools to fix them
• One chap related his experience where one board indicated it had a problem and they swapped a whole bunch of spares through the machine before deciding the problem was in another board. Another person said this indicated the need for clear interfaces and for each separate digital function to be both self diagnosing and as well check all input and point at the other unit if it was having trouble.
• It should be possible to transmit diagnostic information to anybody on the network including the manufacturer if required.
• Use data from sensors to predict failure
• Comprehensive, precise, English, diagnostics with pictures

Markets

• Many markets were assumed. It would probably take separate sales forces and perhaps assembly departments to address these markets:
  • Schools - education
  • Maintenance shops
  • Hobby
  • High volume lower tolerance parts
  • Low volume, high tolerance, exotic material, exotic cutters, special coolants
  • Part of a machining cell
  • Space station - special chip containment and removal
• Many features - let the customer choose
• Family of chucks
• Family of application specific lathes

Control

• Modular so it can start cheap
• Modular so it can handle new features as they are developed
• Modular so it can work with other machines
• Features to allow it to be connected to a network
• Features to allow it to be operated from the network
  • Robots
  • Chip removal
  • Feeding machines

How fabricated

• One approach was to make a composite vacuum molded shell and fill it with something cheap such as concrete for rigidity and mass to reduce vibrations and then glue the ways and spindle in place. The "Concrete" could be the ordinary stuff or heavy stuff made with iron ore. The concrete could be reinforced with fibers or bars made of iron, glass, kevlar, carbon graphite, ceramic, or other. In a conventional lathe with lots of welding there are annealing cycles to remove distortion followed by scrapping to get it straight. By gluing at low temperature we should be able to avoid distortion, reduce cost and increase speed. The only installation would be a foam rubber mat for vibration isolation. Primary accuracy is from rigidity of construction.  This would be enhanced by the control system which would have tables and feedback for error correction.
• Another approach was to make it a very light fabrication to allow it to be taken where ever it is needed. Take the tool to the work.

Tool changer

• Most assumed a turret
• Separate tool holders for inside and outside operations allows more rigid tools
• Another option is a tool changer, instead of a turret, and a magazine just like a milling machine with the following advantages:
  • Larger possible number of tools
  • Fewer interference problems
  • Increased rigidity of tool holder
  • Simple tool holder - more complex tool changing
  • Service more than one tool holder if the lathe has two tool holders
  • Dull tools could be replaced in the magazine without interrupting operations

Operator interface

• Must be simple
• Voice actuated
• Operator may be controlling as many as 12 of these machines
• Should show production control information - part number and quantity
• Should be able to see production schedule - material needed - tools needed
• Some wanted to display the tool path, tool geometry, part geometry, spindle and machine geometry
• Automatic collision detection at execution (Some thought collision detection at planning or programing time was sufficient)
• Show actual surface feet per minute and ideal surface feet per minute

Chip removal

• Blower
• Vacuum
• Mount vertical so chips fall away from the lathe

Design of lathe

• All assumed a 3d CAD system so that the solution space could be properly investigated.
• CAM integration seemed to be assumed so we could offer many features quickly.
• Kinematic analysis would assist in designing tool changers and integration in machining cells
• Finite element and dynamic analysis would be important to achieve the rigidity necessary to achieve accuracy and avoid resonant frequencies.

Programming

• One chap wanted to feed a fax drawing into one end of the lathe and get parts out the other.
• Several wanted programing at the machine
• Make it easy to program
• Give the system the geometry and let it figure out the tooling and tool path
• Most assumed a direct connection to the CAD system
• Several participants wanted process planning to be at a higher level than the lathe so the correct machine could be used for each required operation. Turning on turning machines and milling on milling machines.
• One suggestion is to allow programming to be done remotely by the customer and then to allow him to watch the progress of his part as it is machined.

New kind of lathe

• Should investigate the feasibility of lasers building up the part by fusing powdered metal to build up the part

Conclusion

Two important areas we did not have time for were cost and customer value. If we were serious about getting into the lathe business we would have to figure out why people will buy our lathe. What value we add. "What we can do easily that was impossible a few years ago." Robert Hope SME Toronto Chapter 26. But that is next months session.