How to Make Things

How to make things! Robin  Coope   Props  to  Dan  Gelbart,  Jon  Nakane,  Bernhard   Zender,  Juga  Kitanovic,  Charles  Guan,   Alexander  Slocum  and  Google  Image  Search  

I am an Engineer! Why Should I Personally Know How to Make Stuff?!

You should know how to make stuff because! •  You will get your prototype parts much faster! •  You will be able to iterate your designs much faster! •  Your designs will become much more efficient as you understand the cost of each process. !

Whatʼs the big deal about waterjets?! •  It is by far the easiest and safest computerized machine tool available.! –  Students can actually use it!!

•  It can cut a very wide range of materials! •  Itʼs much faster to waterjet small part runs than any other machining method.!

A  Prototype  Medical  Tool  

All  parts  except  for  the  turned  parts  were  done  by  waterjet  cuJng,  bending   and  spot  welding.  Total  fabricaLon  Lme  ~  8  hours.              Dan  Gelbart  

The  GSC  Size  SelecLon  Robot  

All  

All  non  OEM  parts  except  acrylic  plates  are  water  jet.  

CT  Test  Jig.  90%  Waterjet     All  carbon  fiber  cross  secLon  for  CT  scanning  

Seth  Gilchrest   UBC  Centre  for  Hip  Health  

CT  Test  Jig.  90%  Waterjet    

Re-­‐designed  to  maximize  water  jet-­‐only   fabricaLon  with  only  a  few  threaded  holes   added  aZer  

A  Dryer  for  a  600  ppm  Inkjet  

All  parts  of  both  dryer  and  control  are  WJ,  bent  and  welded.  No  other  machining   Dryer  is  doubled  walled  with  dual  air  bearing  heat  transfer.            Dan  Gelbart    

Waterjet  FAQ  

What  is  a  Waterjet?  

A  waterjet  is  a  “floppy  grinding  tool”  not  a  cuJng  tool.   Sand  and  water  in  a  1”  Aluminum.   Use  it  to  your  advantage  

Juga  Kitanovic  

Jared  Slobodan  BCGSC  

Causes  of  Bad  CuJng   WATERJET

YOU’RE DOING IT WRONG

Andrew  Porrit,  UBC  Mech  

•  Poor  sand  feed  –  check   for  parLal  blockages   •  Bad  Nozzle  –  should  last   >50  hours.   •  Part  vibraLon  –  bejer   clamping  or  tabs   needed  

The  Good  and  The  Chipped   Note  opposite  facing  waterjet  marks  on  two  halves  

Maj  

Maj  Lam  UBC  Physics  

Thickness  

Maj  

•  Speed  drops  as   thickness1.15.     •  The  pracLcal  limit  for   Aluminum  is  ~2”   •  It  can  be  faster  to  stack   thin  parts  to  ½”.   •  Advantage  vs.  milling   greater  with  hard  and   tough  materials.  

Working  with  Sheet  

Metal  and  PlasLcs  Come  in  Several   Forms   •  •  •  • 

Plate  (1/8”  and  thicker  )   Bar  and  tube  (round,  square)   Extrusions  (complex  shapes)   Sheet  (thinner  than  1/8”)  

Sheet  Materials   •  Typical  sizes    

–  12ga  (2.5mm),  -­‐  structural  elements   –  16  ga  (1.5mm)    -­‐  Structural,  motor  mounts   –  20  ga  1mm,    -­‐  Enclosures   –  24ga  .7mm  .025”  –  253  Robots!  

•  CR  means  cold  rolled  mild  steel.    Stainless  is  5x   more  expensive   •  Shim  stock  (301  Half  Hard)  is  a  hard  spring  steel.   •  In  Al,  can  get  6061  T-­‐6  and  5052.    Only  5052  can   be  bent.    Gauge  sizes  are  slightly  different   between  aluminum  and  steel.  

Comparison  of  bent  and  mulLpart   components  

Maj  

2  different  pieces  of  plate  must  be  cut  out   Drilling  and  tapping  on  the  mill  is  required  

One  piece  of  12  ga  cold  rolled  steel  or   5052  aluminum   Harder  to  get  the  90  angle  just  right   Not  as  sLff  

Comparison  of  bent  and  mulLpart   components  

Maj  

Machined  aluminum  dishwasher  rack  at  leZ  was  >4x  the  cost  of  the  WJ  stainless   version,  and  harder  to  use  and  prone  to  corrosion.  

Bending  

Guides  from  CNC  back  gauge  

Top  die   Maj  

Bojom  Die  

Maj  

There  are  two  lower  dies,  .75”  and  .375”.    The  smaller  die  is  bejer  for  24  to   18ga.  The  gauge  fingers  can  get  in  close  enough  to  bend  ~  8mm  flanges  with   the  small  die,  14mm  with  the  large.   A12  ton  press  brake  can  bend  >  120cm  @  1mm  and  ~  30cm  @   2.5mm  for  steel  

Maj  

Dies  are  cut  into  different  lengths  to  allow  complex  bends  

Maj  

Maj  

Sheet  Metal  Rules  

Dan  Gelbart  

Complementary Errors! •  The  posiLonal   uncertainty  in  these   bends  cancel  each  other   out  as  everything  is   bent  at  the  same  Lme   with  the  same   equipment  

Box  Aspect  RaLo   •  For  most  bends  the   height  of  the  flanges   must  be  less  than  the   width  of  the  box   •  PHAS  has  a  “dog  leg   bender  which  allows   higher  flanges  on   smaller  ¼”  and   Lghtened  into  nuts.    

Machine  screws:  Lower  grade   than  cap-­‐screws,  cheaper,   driven  by  screwdrivers   Stud:  Welded  onto  or  through   a  surface.    Requires  a  nut.  

Other  Fasteners  

Shoulder  screw:  Has  a    bearing  shaZ   Lag  Screw  for  wood.  >1/4”  

Self  tapping  screw   for  thin  sheet  metal   0.005”! •  Bearings need +0.001”, -0.000”. Use a reamer to make very accurate holes! •  For bearing systems use shaft rod and not drill rod! –  “Drill rod” is ± 0.0005, “Shaft” will be +0, -0.0005”. ! –  Drill rod and some shaft is also hardened and canʼt be machined. !

Transmissions   •   ShaZ  posiLons  should  be  laid  out   according  to  theoreLcal  gear   diameters   • ShaZs  should  only  be  supported  at   2  points  –  use  flexible  couplings  as   needed  –  eg  servo  potenLometer   •   SupporLng  either  side  of  gears  is   much  easier.   • ShaZ  clamps  should  be  used  to   prevent  axial  translaLon  

Plate  and  Standoff  

Make  the  transmission  on  the   waterjet  except…  

Source:  Charles  Guan,  MIT  

Bearings ! Plain  Bearings   (bushings)   Ball  Bearing  

Flanged  Ball   Bearing  

•  Ball  bearings  are  low   fricLon  but  more  expensive   and  tricky  to  install     •  For  the  climber  bots,  plain   bearings  will  probably  be   fine.   •  Steel  on  steel  is  OK  but  may   bind  under  higher  loads.  Al-­‐ on-­‐al  =  bad!     •  Polyethylene  (poor  man’s   Teflon)  is  a  good  material   for  homemade  plain   bearings.  

Linear Motion! •   This  drawing  shows   the  key  features  which   any  linear  moLon  must   reproduce  in  whole  or   in  part.   •   The  hardest  thing  to   make  cheaply  is  are  the   linear  guides  and   followers  themselves.   •   Following  are  some   low  cost  ideas      

Linear Motion! •  “Ready Rod” threaded rod is available from 4-40 to ¼-20 in stores! •  “Chase” with a threading die to clean! •  The follower can be made from solid teflon. Make thread length 2 to 3x diameter!

Linear  MoLon   •  Drawer  slides  are  one   cheap  but  heavy  source   of  linear  moLon.   •  For  253,  solid  plasLc   sliders  on  metal  tubes  will   work  if  fits  are  loose  and   loads  are  low.   •  For  bearings,  couple  shaZ   directly  and  only  use  one   bearing  at  the  far  end  of   the  lead  screw.  

Clamping  to  ShaZs   Splines.    Great  torque  resistance.  Can  be  end-­‐bolted  if   the  spline  is  tapered  or  split  bolted  (e.g.  Futaba  servo   output).    A  loose  fit  will  “nag”  the  splines  and  wreck  the   shaZ.    Can  also  be  used  for  longditudinal  sliding  torque   transfer.   Woodruff  keys:  A  single  slot  for  a  steel  shaZ  and   hub.    Material  of  the  key  (e.g.  brass)  is  chosen  so  it   can  break  under  a  specified  load,  as  a  safety   mechanism.   A  waterjejed  crank  and   counterweight  with   woodruff  slot    

Clamping  to  ShaZs   ShaZ  collar  

Set  Screws  and  collars   PosiLves:  Easy  to  make,  can  use  on  any   shaZ.   NegaLves:  Can  mar  the  shaZ,  not  much   torque  resistance,    easy  to  strip  small  set   screws,  need  to  use  shaZ  flats  for  bejer   grip  larger  shaZs.   Best  used  with  small  shaZs  –  eg   Physics  253  robots!    

Coupler  with  two  different  shaZ  diameters.    8-­‐32   set  screws  are  much  stronger  than  4-­‐40’s  

The  best  shaZ  and  bearing   connecLons   Step  1.  Waterjet  with  main  holes   undersized  by  about  .025”.    Powdercoat  at   this  point  too.  

The  best  shaZ  and  bearing   connecLons   A  Reamer  

Final  Size  .375”  

Final  Size  .875”   Step  2.  Ream  holes  to  exact  size  

The  best  shaZ  and  bearing   connecLons  

Clear  hole  

Tapped  hole  

Step  3.  Drill  Clear  holes.  Drill  and  tap  lower  holes.      

The  best  shaZ  and  bearing   connecLons  

Step  4.  Remove  tabs  with  a  hacksaw  

Assembled  Crank  Arm   ShaZ    

Bearings  

Resistance  to  torque  at  the  shaZ  and  axial  load  at  the  shaZ   and  bearings  will  be  very  good.  

Gears  

• OMAX  layout  is  great  for  gears   • Teeth/Pitch  =  Diameter   • Use  a  pitch  >  24  for  waterjet   • Run  gears  back  to  back  to  match  tapers   • Can  drill  set  screws  through  the  gear  body  

Flexure   •  Can  be  made  from  solid   stock  (aluminum,  niLnol   plasLc)  or  welded  together.   •  Best  flexure  material  is    301   half   Maj   hard  stainless  ~0.005”   •  For  fast  moving  parts,   flaring  the  sLffening  plates   is  criLcal  to  prevent  faLgue   failure.  

Flexure  Examples  

High  Density  Polyethylene   Or  Delrin  

Maj  

A  mounLng  system  for  two  Wiring  boards  which  allow  the  boards  to  be   removed  without  tools  

Powder  CoaLng  

Maj  

The  Adiabatmobile,  Physics  253  2010  

Post  Paint  Machining  

Maj  

These  aluminum  hard  drive  bodies  were  die  cast,  painted,  then  machined  in   key  spots.    This  is  the  way  to  rapidly  make  precise  parts.  

A  Lesson  From  Professor  Alldrij   Unlike  code  or  electronics,   mechanical  parts  are  visible.    By  just   looking,  you  can  appreciate  the   genius,  or  folly,  the  craZsmanship  or   sloppiness  of  manufactured  items   everywhere.    Pay  ajenLon  to  how   things  are  made;  you  will  be  a  bejer   designer.