hello everyone!
on this summer we were working on a design of a 3d printed shooter for the 2017 STEAMWORKS game.
Some specs of the design:
2X775 pro motors with 1:4 versaplanetary gearbox
4" HiGrip flywheel
total turning angle of 90deg (45 to each side from the center)
shooting angles of 20 and 30 degrees
mounted on 12" lazy suzan
ball compression of 8mm (~0.3")
From our tests we got some conclusions:
As we didnt see a lot of use of 3d printing for making a completely mechanism, we wanted to check if it is possible to design one that will be durable for a FRC competition. Surprisingly, it looks like the 3d printed shooter is very robustic and reliable.
On our tests it looks like shooting with HiGrip wheel isnt powerful and accurate enough, therefor we consider the using of a 4" colsons.
Our shooting angle of 20deg seems to be to high for shooting close to the boiler, so we need to decrease it a bit.
for any questions you can contact us on facebook or instagram!
hi, the compression is about 8mm (~0.3in)
we will realease the cad, but we still do some tests to optimize it, so when it will be finished we will uplaod it
First off, I invite you to take a look at how to keep image sizes a bit more manageable when you post them inside a message.
The design and execution looks good! I will say, it looks very beefy. How long did it take to print all of the components?
I agree with your thoughts about switching wheels. Hi-grips, while convenient, don’t really have any performance advantages when it comes to shooting.
Do you have any way to vary your compression without changing other variables? It might be worth considering; just changing wheel type may not solve everything.
How are you connecting the output shaft of the VP to the shaft the wheels are on? I think I can see the edge of what’s connecting them, but I can’t tell what it is.
I love to see 3D printing used in FRC! Keep using it and strive to learn ways to make your parts stronger, lighter and more effective. You’re starting in a good spot.
It looks to me like two hex hubs with a bearing pilot in the middle to hold them together and space them out. Smart idea if you can’t get a hex coupler easily.
I like this, looks like a pretty solid design. Part of me would like to see it printed in once piece but you’d have to have a massive printer to get away with that.
My only complaint is the use of the servo, but I might just be a bit jaded from a few bad experiences with them in the past that lost my team a few matches.
What kind of angle variability do you get with this? Is the “hood” all or nothing (I imagine the servo might have a hard time resisting the force of a ball being pushed against it)?
Amazing design, absolutely amazing. Really good use of 3D printing and as far as I can see you’re not compromising stiffness anywhere.
I’ve had poor luck with the dual inputs wearing out quickly before, but if it wears out for you guys then I’m sure you can print a new one. The use of churro tubing for a shooter shaft is iffy, but hex stock isn’t hard to come by if it fails.
What printer did you use?
how much infill for the 3D printed parts?
do you plan on mounting it on a robot?
also, instead of switching the wheel type try using 2 wheel on the same axle, it might improve your accuracy
We printed in between 20% to 30% infill, and wall thickness of 2mm.
There isnt enough space to put more than one wheel, but we changed the wheel to 4in diamter 2in wide colson. By putting another wheel the ball compression will decrease.
Depending on the arrangement and type of wheels, a gap between the wheels can be utilized for centering the ball as it leaves the shooter (very common in 2016).
Alternatively, multiple wheels with no gap between them (such as AM “compliant” wheels) can also improve accuracy by avoiding grip variation between the sides of the wheel and the ball when under compression, however your centering is then dependent on your backstop in this configuration.
IMO, your results will vary shooter to shooter in either of the above cases. One arrangement might work great for one shooter but not on another. Testing a variety of wheels and wheel arrangements is key.
i noticed this effect during the prototype phase this season, but forgot about it when we had to CAD XD
i think it is happening because every ball is slipping towards the gap between the two wheels, so they all come out in the same angle from the same spot. especially if there isn’t a smooth pattern on the wheels, like in the KOP andymark wheels, or pneumatic wheels.
i can’t see any sensor or encoder in the assembly you pictured, so it might be another reason for the inaccuracy.
so IMO, to improve your accuracy you have a few options:
put a second wheel
choose a different wheel (we had problems with those wheels as well for our shooter this year)
add a feedback sensor and create a PID controller
add inertia wheel (extremly recommended, but you might want to change motors / gear ratios after that)
The use of churro tubing for a shooter shaft is iffy, but hex stock isn’t hard to come by if it fails.