I’ve been doing machine design for about 10 years and I often compare the mechanical design process to a creating a jigsaw puzzle. The most obvious parallel is that there are many pieces for both a machine and puzzle that must fit and work together.
Even simple machines are broken down into multiple subassemblies that need to fit together like puzzle pieces. Each subassembly piece has to fit together in the process and in the context of the overall machine, both in a static and dynamic state. If one piece needs to grow your other pieces may need to shrink. You may have a rough idea of what the final puzzle may look like but you’re figuring out the pieces as you go along.
The puzzle process gets more challenging when you remember you’re dealing with 3D pieces and working collaboratively. The best advice here is to divide the puzzle so you can each work a corner and have someone paint the broad strokes so you know what the completed puzzle will look like.
Machine design is complicated because in many cases you’re fitting together dynamic systems and subassemblies. There are a few constraints or requirements that shape the design from the start but there are many self imposed constraints that arise during the design process. Things like part clearances, working planes, conveyor pitches, and transfer points need to be established. These factors will greatly influence your design along with a common thread that ties everything together.
I stumbled across this album in /r/welding of a pipe laying vessel out in the Gulf of Mexico. It’s always interesting to see specialized equipment for a specific industry. The album covers joint prep, welding, inspection, and laying.
This is the Samsung SM421 surface mount chip placement platform (not to be confused with the SM421 showerhead).
The machine vacuum picks 6 tiny SMD components from cassettes in the front of the machine and moves to place them on a fixtured PCB. The high speed precision and motion is amazing.
This video may not have the best clarity but the camera angles show a lot of the machine mechanics.
The individual axes are ballscrew driven and the flashes of red light are from a vision inspection process to check if each component has been picked correctly. There’s a vision camera on the front of the placement head that appears to be used for PCB fiducial recognition or part inspection.
I’d like to learn more about the placement head because it’s not immediately apparent how the individual chip feeders are vertically actuated. There are some clues that they’re belt driven but it’s still somewhat of a mystery.
How do you assemble a giant machine tool? Very carefully. A lot of thought needs to be put into the machine design early on to accommodate assembly, alignment, shipping, and installation. Simple things like providing lifting points and making sure fasteners are easily accessible can help things go smoothly in the field.
The above video shows a time lapse of the installation of a Waldrich Coburg Powertec gantry style machining center for customer MAN Diesel. There’s a lot going on so I’d like to break down the individual installation steps.
Pouring the Machine Foundation
The installation starts with the machine bed foundation. This is the foundation that will support the X-axis beds and ultimately the entire machine weight. A thick foundation with a lot of reinforcing bar is important to minimize deflection in concrete due to the machine movement and operation. Any deflection or settling in the foundation will ruin the machine precision relative to the workpiece.
Pouring the Workpiece Foundation
The workpiece requires an isolated bed foundation. Similar to the machine bed foundation, stiffness is the key. Any deflection in either of these foundations relative to one another will ruin the machine precision.
Installation of the X beds is an important step and one they appear to skip over in the video. The X beds are anchored to the bed foundation and will ultimately form the X-axis of the machine. The beds support and guide the machine with linear rail. Straightness of this rail is critical to the machine precision and must be adjusted during installation using jacking screws built into the beds. Some of this process is shown in the video. Gear rack for driving the machine must also be adjusted and spaced correctly during this process.
Installation of the workpiece fixturing plates is also shown during this stage.
The X axis way covers are installed to keep chips and debris away from the X rails. Interesting they’re installed this early, they can dent easily.
X Axis Carriages
The X axis carriages are lifted and mounted to the X rail. It depends on the style of rail but the bearing cars are likely already installed onto the rail and carriages are bolted down to the cars.
The gantry legs with integrated Z axis are installed next. They’re flown in via the overhead crane, stood up, positioned and installed onto the X carriages. It appears that all of the necessary fasteners are installed prior to the legs being set into place.
The Y bridge is flown into place and ties the two gantry legs together. This takes some coordination with the crane operator and some time spent in the man-lift. The maintenance platforms and electrical cabinets also appear to be installed behind the gantry during this process.
A tricky part of the installation. It looks like they place the Y-axis on blocks during the installation process. Careful positioning is required to attach the Y-axis to the bearing cars and ball nuts on the tower legs. It’s important to make sure these fasteners are easy to access during the design phase.
The Z-ram is bolted onto the Y-axis without a lot of hassle. The assembly is lifting by red painted installation tooling bolted to the sides of the lower assembly. Note the whole Y axis assembly is still resting on blocks.
A movable operator platform is installed and bolted onto the front of the machine. This makes getting right up to the tool point easy for the operator. I’m speculating that this is for automated tool changing as well.
Axis alignment occurs before all the final way covers and bellows are installed. Important to make sure everything has been installed correctly and running smoothly. Most of the axes are modular but there can be some tricky alignment in the Z-axis due to the tandem configuration.
Minor details such as decking and cell guarding are installed, the machine is bought off in a factory acceptance test, and everyone gets to go home!
This has an impressive envelope for a mill and is used in the manufacturing process of wind turbine blades. I initially guessed this was for composite trimming operations but the manufacturer lists the machine for work with “polystyrene, resins and fibres.” This is possibly used for form or blade core manufacture?
This is a high-rail gantry style mill which can make part loading more difficult due to the mill legs but ultimately decreases the moving mass of the machine. The numbered assembly hanging off the gantry appears to be a tool changer.
Manufacturer link here. No information on tolerances.
This is an interesting video from NASA showing the manufacture of what appear to be different composite spacecraft parts including a fuel tank.
The center piece here is an articulated robot mounted on a “seventh” linear axis with a automated fiber placement end effector. The end effector heats the area and applies strips of resin impregnated composite “tape.” The whole process requires a high level of motion control especially with a rotating work piece.
I’m not an expert on the process but it’s easy to have an appreciation for the new manufacturing processes required by high performance composites.
The pair of blue “post” style machines in the beginning of the video appear to be testing for voids in the finished part.
They were definitely thinking outside the box on this one. Interesting concept but some of the claimed advantages seem dubious. The machining envelope appears limited for the size of the machine and the control enclosure is never shown in frame. The tool changer seems like a bit of a kludge and makes the whole system difficult to guard – everything would need to be isolated and caged as a cell. Work piece access also appears difficult and would require a lot of reaching and bending at the waist.
I’ll give them credit for trying something new and developing the concept as far as they did.