Let's Make a Robot End Effector!

hello Internet my name is Quinn and this

is blondie axe see the other day I got a

message from David over at dragonfly

engineering and he said hey Quinn I

wonder if I can send you something so he

did let's see what it is

hi Quinn it's a Dave from dragonfly

engineering on YouTube yeah I was

wondering if you could help machine a

couple of new robot end effectors orange

here she's got the original end effector

that I made when I first got her and

it's just a cube of metal without even a

standoff and it's gotten beat up and and

it doesn't have a magnetic kinematic

release plates so she can kind of jam

herself up so we can look at some of the

up-close problems of the current old end

effector which is a universal mounting

cube with a bunch of different hole

patterns on it that I that I machined

like I don't know seven years ago but

yeah so here's the general mounting

patterns but what happens is since I

don't have an extension on the end of

that cube - from the end of the robot

when I rotate the axis or when it's

traveling the corner of the cube can

actually hit the the wrist of the robot

you can see some damage chipped paint

and stuff where that has happened the

other thing I'd like to do is mount all

these grippers and end effector tools on

a breakaway magnet base from thorlabs

that way if the robot crashes into

something then this this gripper will

just break off from the magnet mount

instead of crashing in and jamming up

and getting stuck so I was wondering if

you could make a new one or let's let's

see if Orange wants one do you want one

all right well it looks like you've got

a customer here oh and it also looks

like blue wants one as well this is the

kinematic magnet mount that I was

talking about and blues is a little

funky too so maybe you can make one for

blue as well they'd appreciate it all

right well I look forward to seeing what

you come up with so thanks a lot let's

do an extra good job on these parts

because I have a feeling you don't want

to see orange and blue when they get

angry so here's one of those thorlabs

mounting plates that David was talking

about there and these things are really

cool they have these powerful neodymium

magnets in them and then they have these

cylinders here that are ground that rest

against the spherical magnets and so

there's two in one orientation one on

the other orientation and so in addition

to being a quick-release and a safety

mechanism these guys are also self

aligning and very very repeatable it's a

pretty cool mechanism here's the first

part that we'll be making and those

magnetic blocks attached to this guy

it's basically a fancy cube with some

fancy holes drilled in it for various

purposes mounting different types of end

effectors on the robot and you may

notice that the drawing is in metric

because while it's 2020 so yeah buckle

up friends we're going metric here's

what we're gonna use to make this cube

it's three by three inch aluminum

extrusion and so we're gonna mark out

our piece there and the horizontal

bandsaw we'll make a quick work of

cutting this guy to length

I'm leaving about a hundredth out extra

there on the length to allow me to

square things up and a little wd-40 to

use the process here this saw cuts very

square so I only need to leave myself

between 50 and hundred thousandths to

machine away

yes now one interesting aspect of this

job is that the nominal outer dimensions

of this cube are seventy six point two

millimeters which is three inches and

that's already the OD of the extrusion

so it isn't actually possible to square

up this stock and to stay within the

tolerance on that dimension but I

double-checked with the customer and

this is going to be fine so I'm just

gonna try to take off as little as

possible and to do that I put an

indicator on the top surface here and

mapped out the surface to see what the

lowest spot is so I can try to take the

absolute minimum cut on each side now

the other interesting aspect of this

compared to squaring up normal stock is

that this is a hollow extrusion and we

want the wall thickness to end up within

a tolerance on all four sides so in

addition to machining as little as

possible off of each side I also need to

have each side come out the same

thickness within the tolerance of let's

say a couple of thousands so that's an

extra little wrinkle here I'm using my

two inch tin flew shell mill to do this

facing I had originally wanted to fly

cut this for best possible finish and to

make it one nice clean pass but if you

watched my video on mill alignment then

you know that I was having some trouble

with my fly cutter so I opted to go back

to the show mill which I know I can have

success with sometimes it's best to go

back to what you know is reliable when

you know the clock is tickin and the

other thing of note here is that instead

of using the traditional parallel on one

side and round bar or ball bearing on

the other side to eliminate the

influence of jaw lift on a nun machined

surface you'll note that I'm actually

just using a piece of paper in there I

found that when using a piece of round

bar like I normally would against the

movable jaw it was actually causing a

very strange out of squaring effect on

the part the part was leaning 15,000 the

vise when clamped with the traditional

setup I did a whole video about figuring

all of this out but suffice it to say it

for this video that this piece of paper

on the movable jaw was enough and the

parts came out very square doing it this


though with those four sides squared up

and to the same thickness all the way

around on that extrusion we can now

switch out to a half inch end mill and

I'm going to use a small end mill to

face off the ends of the part the open

square ends of the extrusion and you

could of course just do this the same

way with the shell mill but I'm not sure

why I did it this way I just thought it

would be fun I kissed and I'm setting it

up on the fixed jaw with a parallel

laying flat just to have a little bit of

space there in case that bottom angle is

a little bit greater than 90 degrees but

I know that cut is very square so I'm

not very worried about it and I want to

keep the part as low down in the vise as

possible for the most possible grip with

the jaws to make sure that part stays

square and then I'm getting it roughly

squared up vertically with a stare at

precision square on top that guy in and

then I want these parts to be very very

square so I'm also putting an indicator

on there and just running that up and

down and I tapped it in a little bit to

get those sides nice and vertical and

after a couple of minutes of fiddling

were within a tenth of vertical over

three inches which I'm very happy about

and now we can start milling around the

outside so I started by trying to

eyeball what the high spot is seem to be

this back corner so I started there with

a light pass and worked my way all the

way around and then once I had a clean

up pass all the way around then I know I

can flip it over and bring it down to

dimension we've got about 50,000 to

clean this guy up do a nice finishing

pass and then flip it over okay that's

looking very very nice so we can prepare

to flip this guy over now we're gonna

have to deburr it of course so that

it'll sit flat on that side and because

it's a hollow extrusion we have twice as

many edges to deeper and then we put

that machine side down and I'm not using

the parallel or the paper or any other

methods now because five of the sides of

this cube are now machined square and

shouldn't need anything like that and

I'm just sanity checking everything with

the square if you watched my mill oh I'm

at video you know at this point I'm not

trusting anything on the setup of this

unusual part now I'm gonna be using the

depth micrometer here and if you've

never seen this process I thought I'd

show it to you this is how you

the range of it you can pull out one of

the bars so it's zero to one normally

and you can put in a one to two inch or

three to four-inch etcetera different

lengths of bar give you different ranges

of measurement on this tool so you just

pull one bar out slide the new one in

and then the end cap screws back on it's

a very quick process just make sure to

keep all the bars clean and so on so you

don't get chips inside the mic and I'm

using the depth mic to check the length

of the part and is to mention because I

know that the part is again machined on

the three sides touching the vise and

it's seated firmly down so this is a

valid way to check the length of the

part without having to disrupt myself

and so then I just work my way around

once again again cleaning things up and

then bringing it down to final dimension

now we can start adding features to our

part we've got features on all four of

the solid sides so I'm going to set up

any old side to be our top and I'm also

going to set up an end stop here because

the part is a cube it means I can index

this cube around and add features to all

the different faces and not have to re

in reset up my zero on every single

operation and as it happens I haven't

mentioned this yet I need two of these

cubes so it's also going to save me a

lot of set-up time on the second cube

going back to our drawing here for a

second you'll notice that all the

features are referenced from a datum in

the center and you can see that the

center point of the face has a tolerance

marked on it and then all features are

referenced from that point that's

actually a really great way to design

your own parts using a single origin in

the center so I can easily set up the

part with an edge finder edge finding on

both sides and using the half trick on

the Dro find that origin in the middle

and now it's very easy to navigate in

the four quadrants of our Cartesian

plane on the top surface of this part

and add features as we go and it's

doubly useful on a part like this where

the center axis of it is what's

important that's going to be aligned

with a joint on the robot arm and you

want the attachments that are attached

to this cube to be moving relative to

that Center axis and so by referencing

all the features from that Center axis

we push all of the error that we might

have with edge finding and so forth to

the outsides of the part where it won't

matter and then everything in the center

and referenced from that Center will be

precisely located

and now that we have our origin I'm

gonna put a little center mark here that

we're not going to use yet but it'll be

helpful if we need to change our setup

or move the part for any reason to have

a reference that we can go back to so

we're going to start by making this bolt

circle here around the large hole in the

center I'm going to do the bolt circle

first so that there's lots of material

there to support all of the drilling

that we're going to be doing and to do

this I'm going to use the bolt circle

function on my Dro

it's lots of different ways to make bolt

circles but if you have a dro this is a

very easy way to do it so it's done with

this button here which is either bolt

circles or possibly something to do with

navigating ships or when frozen it might

move the island I'm not sure but I know

when you push it it asks for the PCD

which is the cord and a plane that you

want your bolt circle to be in and we

want the XY plane and then it asks for

the center position where you want your

bolt circle to be we want it to be at

the origin I'm just going to re-enter

these numbers just so you can see the

exercise here but if the number you want

is already there you don't have to do

this step we hit enter on each parameter

and then we hit the up arrow to go to

the next question in this case it wants

diameter so we choose 31.5 millimeters

which is the diameter of our bolt circle

and then it asks for the starting angle

which you can pretty much always put

zero for this and then it asks for the

ending angle which is an interesting

parameter if you remember from your high

school math this is a counterclockwise

angle so it's the angle between your

first hole and your last hole going

counterclockwise an easy way to

calculate this is to just take the angle

between any two of your holes and

subtract that from 360 and that's going

to be the angle of your final hole and

then it asks is how many holes we want

and we want eight so we push that and

now it's telling us the two coordinates

of the first hole hole number one so all

we do is we move the slides to zero out

those numbers and you can see here that

we are the radius of our bolt circle to

the right of our origin and you can see

that the other holes will be wrapping

around the origin as we go and the first

time you use this feature in your Dro

it's a really good idea to do a dry run

and just move through the holes

following the Dro without

drilling anything to make sure it's

ending up where you expect so after

we're done the first hole then we push

the up arrow to get to the next hole and

it gives us two more numbers CIN it once

again we move the slides to zero out

those numbers and you can see that we're

now lined up for the second hole which

is in this case 45 degrees

counterclockwise of the first hole and

then we just proceed with that sequence

Center drilling each of the eight holes

pressing the up arrow after we're done

each one and zeroing out the axes as we

go and there's our last hole right there

looking good so far so we've got all of

our holes Center drilled you can see the

bolt pattern emerging there and now when

you get to the end you push up arrow and

you get an over sign game over man and

the cool thing is you push up by row

again it goes back to hole number one

and so now we can iterate through our

holes again with the next tool so in

this case we're going to drill and you

know you might remit or you might

countersink so there's a good chance

you're going to want to go around your

bolt circle a bunch of times and so the

Dro makes it very easy to do that as

well so you don't have to change tools

four times between every hole now in my

case we want to eventually ream these

holes to five millimeters so I'm

drilling them all out to four and a half

millimeter half a millimeter under the

final size and then we will dimension

them out with a five millimeter reamer

and speaking of that reamer the five

millimeter reamer that I have is too

long to go in my Jacob's Chuck and still

fit within the headspace that I have

here on this little mill so I'm

switching to a five millimeter collet

and I'm gonna hold the reamer in that

this is a nice way to hold Reimers

anyway because gives you that extra

precision and then we're just gonna go

in and ream each of the eight holes and

I'm going a little slower spindle speed

I was drilling about 800 rpm and I'm

reaming these guys about 500 and

clearing chips much more often with a

reamer because these are straight fluted

dreamers they don't have the ability to

clear their own chips so you want to do

lots and lots of up-and-down motion and

clearing the chips as you go okay our

bolt circles looking good now we're

gonna work on that large center hole and

we're gonna need to bore this guy

eventually but I want to do most of the

heavy lifting with drills so we're going

to drill it out in a few stages and get

as large as we can drills are vastly

more efficient than other types of hole

making operations so you want to get as

close to your final dimension as you can

with drills so I started with that

quarter inch and then I'm going up to

3/8 and then a half inch and then I dug

through my drawers and I found a forty

seven sixty fourths which is the largest

drill I could find that was not larger

than the final hole that I need this is

a pretty big drill for this little mill

but it managed it just fine and then to

bring this hole to final dimension we're

gonna use the boring head now I have

previously described boring heads as

though someone described a lathe to an

alien over the phone and then the alien

went off and tried to make that machine

and I stand by that description takes

all the best parts of the lathe it spins

them around in the mill for some reason

so this guy holds boring bars and then

it has a dovetail of its own on it with

a precision adjustment here that allows

us to offset that boring bar from the

spindle such that when it spins it will

create a hole so it's a single point

cutter that you can mount in your mill

so we start by touching this guy off

just like you would on the lathe you can

just turn it by hand to tell when it's

touched off and then we pull it up out

of the hole dial in some depth of cut

and then work our way down the boring

head on the middle

is used for the same reasons that you

would do a boring operation on the lathe

which is that when you need a very

precise hole single point cutting is the

way to go and also if you need a hole of

an unusual size or in this case if I

need a hole that is larger than the

largest drill I have or in this case

largest reamer because we want a

precision hole here so you'd have to

dimension that with a reamer but even

the best Reimers boring bar is still

going to do a better job okay we should

be getting close here so I'm gonna go in

there with my telescoping bore gauges

and space is awfully tight here so it's

a little tricky to get a good angle to

use this guy but I do manage to get in

there they go ahead on the mill is all

the way up and I've still got just

enough room to work in here with the

boring head and this three inch part

sitting on the vise yeah zedd space is

always at a premium on any mill but

especially on these small mills for

hobbyists and we've got a little ways to

go so I'll dial in some more depth here

and do one more pass and then I think

we'll be ready for the finishing pass

and here you can see the technique I'm

using to feed with the boring head I am

feeding with the fine feed on the quill

and you use them kind of a two-handed

technique like you would with the

compound on your lathe I find that works

better on this mill than trying to feed

down with the column on a boring head

and this should be our finishing pass so

we'll check that guy and we need six and

a half foul so here's a way to get a

precise advance on this guy's just put

an indicator on it and adjust it using

the indicator you can see here that

we're six ticks and halfway between two

ticks more or less but the little scale

on the boring heads not precise enough

to really get down into the tenth so you

just put an indicator on there and get

your job done

now when it's time to pull this guy out

you back it away from the cut just like

you would a boring bar on the lathe pull

it out we'll do a final check on our

dimension we're aiming for twenty two

point four nine millimeters which is

eight hundred eighty-five thousandths

and we line it on eight hundred eighty

four and five tenths so we're going to

take that because we're within the

tolerance there on the drawing the

drawing calls for a generous chamfer on

this hole so I'm going to use what's

sometimes called a zero flute chamfering

tool this is a very cool type of tool

that instead of using a traditional

flute to cut it has kind of a circular

hole through the middle that has sharp

edges on it

and the advantage of this guy's the tool

pressure is very very low so it's

basically guaranteed not to chatter the

disadvantage of it is that spherical

opening has a very limited cutting range

and so you need a whole bunch of sizes

of this tool for different sizes of

holes that's looking good so now we can

flip this guy over and add our features

to the other side the other side is

quite similar there's a fairly large

hole in the middle and a bolt circle

around it in this case a simple four

hole pattern now I'm going to use the

bolt circle calculator again for this

four hole pattern but the the pattern is

axis aligned so there's really no need I

mean it's just plus or minus the same

two values on X&Y but sometimes I use

this circle tool anyway just because it

helps me prevent mistakes and keeps me

from losing track of where I am with my

operations these holes are going to be

threaded m61 so I'm drilling them out

five and millimeter and then I'm gonna

come around with the bolt circle tool

again at the end and just use it to

guide my tap follower to tap the holes

and there's another hole pattern around

the outside for tiny little three

millimeter dowel pins and so these guys

are drilled and reamed and what's

interesting about this is that two of

the holes are blind and two of them are

through they all can be through but

because the holes are right at the edge

on the front and back they line up with

the vertical part of the extrusion so it

wasn't specified on the drawing but what

I opted to do here is make them the same

depth as the thickness of the extrusion

so that if the pin was inserted the same

depth on all four holes they would line

up in the same place sometimes you have

to make a little judgement call like

this one dimension isn't specified on

the drawing so I just try to think about

how the part might be used and do what's

best for that and to drill out the

center hole I'm once again working my

way up with drills and I'm showing you

this angle because I don't think I

mentioned earlier that these larger

drills are all being held in colics and

not in a Jacob's Chuck the reason being

that on my small little mill there isn't

enough vertical real estate for at all

part like this and a Jacob's check and

large drills so if you're new to

machining it might seem unusual to see a

drill being held in anything other than

a Jacob's Chuck and so I wanted to show

you this just that you know that drills

are just a cutting tool like any other

and you can hold them in lots of

different ways including kaulitz now

downside to this is that drills come in

many many sizes and so you can only use

drills that you have a collet that's the

right size for and that's where Jacob's

Chuck's really shine because they can

hold a round thing of any size so if you

can limit yourself to call it sized

drills you can hold your drills in a

call it and get a lot more vertical real

estate on a small mill and then you saw

me cruise through boring out the hole

and chamfering as well just like we did


animals drilling and tapping a nine hole

pattern on the other two sides of the

cube I won't show that in a lot of

detail because it's a very

straightforward set of operations

okay now we have lots of deburring to do

so for the tops of the holes it's pretty

easy I'm using a small nova tool here to

deeper these guys and then a slightly

larger one for the larger holes and this

is all great job done right looking good

oh my goodness yeah look at that mess in

there how are we gonna do all of that

stuff I can't get in there with a

traditional Noga tool so that's some

really trick deburring tools that I'm

gonna show you here for this job the

first is this guy it's a deburring blade

with a sharp angle on it so you can get

into the back of a large hole or an

inside edge like that and that works

great now that blade however is too big

to go through these all these small

holes that we have to deeper so here's

what I'm getting use for that this is a

really trick tool from Noga for

deburring the insides of holes it's a

small to fluted deburring blade and the

blade flips around and there's a button

on the end of the tool that you can push

to collapse the blade if you will into a

vertical position so what this allows

you to do is collapse the blade insert

the tool through the hole and then

expand the blade behind the hole pull

upwards and do your deburring and then

when you're done you can collapse the

blade again and pull it back out of the

hole and these little tools only work on

a very narrow range of whole sizes so

there's three different sizes of this

tool that you can buy and I'll link to

these guys in the show notes below and

the little blades on them are also

replaceable but this is a very slick

little tool you can see what a nice job

it does and for a deep burning job like

this this might be just about the only

way to do it and after a lot of quality

time with the deburring tools our cube

is looking mighty fine

so I think we are just about done with

this portion and now let's grab that

magnetic base again and just see how

that might interface together so it's

got an alignment pin on one end that

looks like it goes into various holes

that we've produced here and you can see

that the threaded hole in the center

lines up with the threaded holes on our

cube and it looks like this plate can be

mounted in various orientations all

around this cube so once again I'm not

sure exactly how this thing is going to

be used but you can see that it's got a

lot of flexibility and oh did I mention

we need two of these yeah I made two of

them so

plenty of work was done here but there's

more parts to be made for this project

we'll get to those next time thank you

very much for watching please do

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watching and we'll see you next time