Mad Mare Studio's Medium-Duty Robot Gripper

by Miax, published

Mad Mare Studio's Medium-Duty Robot Gripper by Miax Feb 17, 2013

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This is my Xdroid's Medium-Duty Robotic Gripper, designed for applications where gripping/holding/lifting something is needed. I designed them to support both Standard-Size servo's as well as the HiTec Waterproof servos (slightly larger than standard size).

This gripper is designed with touch-sensitivity in-mind, with a specially-designed hand/paddle model combo that allows you to pancake an Adafruit Industries 1.5" x 1.5" Force Sensitive Resistor inside safely ; http://www.adafruit.com/products/1075 ; The paddle design ensures that the force is sensed regardless of where the paddles grip an object. :)

This model requires two Standard size servos, I have not completed the version in which both paddles are controlled by one servo, and a standard-size servo at regular torque might have problems just actuating the gripper as it is.

I recommend a high-torque metal gear servo for this! Servo City sells a Great waterproof servo (http://www.servocity.com/html/hs-5646wp_servo.html) and I have a servo-plate that fits them included. Or any standard-size servo, like the one's Adafruit sells: http://www.adafruit.com/products/1142

The models in this thing are oriented in the direction that I recommend you print them - with the proper face-down. To make a complete Medium-Duty Gripper, you will need to print some models multiple times while other models you will only need to print once. The instructions will detail this out.

I am modelling a more sophisticated version that will be able to grip much larger and heavier objects! Stay Tuned. :)


Each model in my Medium-Duty Robot Gripper is designed specifically for 3D printing, and have the minimum-possible vertices/pixels. Each model has a specific orientation that you should print it (i.e. a specific bottom-side), so that each model prints right and looks good. :)

I printed this with ABS plastic, but it should be printable in PLA as well. I use a MakerBot Replicator 1-dual for all of my printing, and set my heated platform to 115C (prevents warping, you can set it to whatever works for your printer and plastic combo).


You will need to print the following models to make a complete gripper:

  1. One of DroidGripper-BackPlate

  2. One of DroidGripper-SupportPlate

  3. One of DroidGripper-GearPlate

  4. One of DroidGripper-TopPlate

  5. One of DroidGripper-ServoPlate

  6. One of DroidGripper-LeftArm

  7. One of DroidGripper-RightArm

  8. One of DroidGripper-LeftDriveGear

  9. One of DroidGripper-RightDriveGear

  10. Two of DroidGripper-PressurePlate

  11. Six of DroidGripper-InterfaceLinks

The numbered-images I uploaded in this thing will walk you through a typical installation process for the gripper, and I provide a number of installation tips below to aid you as well.

I'm using an Arduino Mega 2560 an Adafruit 16-Channel Servo Driver ; http://www.adafruit.com/products/815 to control the gripper and sensors, and I plan to add more sensors to the gripper in future releases.

TIP: I include my notes below on how to get the models off of a hot build platform without damaging them:

  1. When each print is done, leave it on the build platform and let it sit there until the platform cools down to ~60C.

  2. Then turn pre-heat ON and wait until the build platform gets back up to > 100C. Your object should pop off the platform with just finger pressure.

This works because at a molecular level the plastic will mold perfectly onto the platform and into every tiny crack, scratch, bump, and it's bonds to the klapton or surface. By first allowing the model to cool, and then re-heating the platform, you cause the platform to shrink and expand by a tiny fraction - it flexes - and this cooling/re-heating again will break that bond and allow the model to come off the surface with very little force. This does tend to bubble the klapton more than pulling a hot model off the build platform the moment it's done, but this method also prevents cooling-induced warping as well.

You'll need some #6 screws,bolts to secure the gripper arms together as shown in the photo's, I tried a number of ABS-plastic options but none could hold any weight or handle Medium-level duty applications. Here is the list of hardware I recommend if you want to make an exact replica of what I made:

  1. Nine 1/4" tall, size #6 aluminum spacers: http://www.servocity.com/html/6-32_aluminum_standoffs__round.html

  2. Eight 1 1/4" (one and one quarter) inch long, size #6 screws: http://www.servocity.com/html/6-32_truss_head_phillip_machin.html

  3. Four 2" inch long, size #6 screws: http://www.servocity.com/html/6-32_truss_head_phillip_machin.html

  4. Eight 5/8" inch long, size #6 screws: http://www.servocity.com/html/6-32_truss_head_phillip_machin.html

  5. Fifteen+ #6-32 nuts: http://www.servocity.com/html/machine_screw_hex_nuts.html

  6. Eight #6 screws: http://www.servocity.com/html/_6_flat_head_phillip_screws.html

That shouldn't cost more than $20-$25 total, and will secure all of the printed components together nicely, and you can get the parts anywhere. :) I'm going to work-up a Viseo diagram that describes how to bolt it all together.

Thanks for reading and printing the Mad Mare Medium-Duty Robot Gripper! =) All feedback is welcome!


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Hi, I was just wondering if you have a video to see the gripper in action. Thank you!

how can you put one of the thingiview files into google sketchup, need to try something for corrupted files, and I don't have the time to draw it.

Does this work under water? Using it for an rov manipulator about 17' under

Left arm bugged out

What motors do you use and where do I get them for cheap? ~ $20

I'm printing right now and all pieces have come out well so far. Made Gear plate, Back plate, and Left Arm. An changes I need to make?

After printing everything and ordering the parts you suggested, I have found several inconsistencies with the instructions and the reality of my printed parts. Heres the run down:

  • The full-size servo from Adafruit does not fit the servo plate. The distance between the plate's top and bottom mounting holes are about 2mm too far apart . I guess the ServoCity full-size servo has a larger body. To resolve this, I adjusted the distance between the top and bottom mount holes. The bottom side (the side with 2 little legs) had it's mount holes and bottom corner of the serve cutout moved upward 2mm. I have not determined if this will cause any movement issues yet.

  • The BOM says 1/4" aluminum spacers. (1/4" == 6.35mm). The Interface Links are 9.6mm tall. The photos show a flush mount between the interface links/spacers and the plates It would seem I'd need a 9.6mm spacer (at minimum) for this to work correctly. Additionally the servos don't allow the plates to touch both sides of a 1/4" spacer.

  • Where's the code? :-) I'd be down for any sort of sample code you have. I know I can go write my own code, but since you used additional sensors, I'd like to see your full vision working.... at least before I hack it up to do my bidding. :-D



First let me apologize for not reading this sooner!! I have been utterly consumed by a big work migration project and I wasn't even getting on the web for several weeks at a time. Now that its done, I'll be watching this again much more frequently.

Let me respond back to your question in-detail tonight when I get home from work.


Aluminum spacers should be .375" (3/8").

How do you attach the arms to the servo?
love the work thanks for posting

I used ServoCity hardware to screw everything together, I'll put together a BOM over the next week and post it up. They have a Great selection of hardware and connectiors: http://www.servocity.com/html/fasteners___hardware1.htmlhttp://www.servocity.com/html/...

Hi Miax,
Have you put together the BOM? It's been a while since you said you would do so, but I don't see any files. I hope to hear back from you soon.

Could you please upload the original file, so a metric configuration or different servo-sizes can be added to the assembly?

Actually the original .STL files are all uploaded with the gripper :) You can import those into any modelling program to change it however you wish!

I plan on making some big updates to this in a month, have some other modelling work I need to wrap up first.

Is anyone else having trouble slicing the BackPlate stl? Im using Slic3r. The others seem to be working fine...

Hmmmm I can't help here as I only use ReplicatorG right now.. Hopefully someone else will jump in!

Did you really mean 215C? Given the max temp for a Rep1 HBP is 120C...

Suspect typo, anyway, GREAT project!

OOPS! Good catch rocketguy, thanks! =) Indeed, at 215C platform temperature, it would be like trying to keep an ice cream cone from melting whilst sitting on a stove. :)

Change "irregardless" to "regardless". Irregardless is a double negative, therefore it is not a real word.

Fixed, thanks! :)

Can it handle a can of soda? (full)

Miax - in reply to TarlSS

Much more than that actually, I'm hoping it can handle at least 10+ lbs, but I havn't done testing at that level yet.

Thank you Thingiverse for featuring my robotic gripper!! I very much appreciate it. =)

this is cool, ive been wanting to build a robotic arm, to manipulate my printer from affar, you know scraping stuff off the build plate and what not, and i have 7 standard servos. this will be perfect, leaving 5 left for the arm.

Miax - in reply to DFarms

Thanks! :) I have discovered a method of getting parts off my build platform without having to man-handle it and without it warping after print that I use with Everything I print now:

  1. When each print is done, leave it on the build platform and let it sit there until the platform gets to ~60C.

  2. Then turn pre-heat on and wait until the build platform gets back up to > 100C, and your object will pop off the platform with just finger pressure. :)

This works because at a molecular level the plastic will mold perfectly onto the platform and into every tiny crack, scratch, bump, and it's this which makes it so hard to get stuff off. By first allowing the model to cool, and then re-heating the platform, you cause the platform to change size a tiny fraction, it flexes, and heating it back up again will break that perfect bond. Try it out. :)

ramai - in reply to Miax

Great idea!

DFarms - in reply to Miax

oh i see, you said 215C, you should change that to 100C, or 215F. we should figure out the gcode to make that automatic at the end of the print.

Miax - in reply to DFarms

Agreed, I havn't figured out how to customize the default gcode so that every model uses it - I have to change some settings every time on my Rep 1.

DFarms - in reply to Miax

i know in slicer and repetier host there is a spot to have it put in code at the end. i believe it would just be

M190 S60
M190 S100

Miax - in reply to DFarms

Thanks for the tip! I havn't looked into that code yet, I need to. Honestly I havn't touched my Replicator in 2 weeks since I burned-out my second MightyBoard (lol). I will be able to order a new one mid-this week, the Rep 2XL is too pricey for this cat.

DFarms - in reply to Miax

ive got a prusa my self, but im designing my own frame out of tube steel that will allow for a larger build area 300x300mm and also more rigidity. also it will use two motors per axis for more speed.