The Displacement Exercise (DEX)

DEX is a small materials testing machine that should be capable of running tensile and compressive tests at up to 600N of force. The machine can be manufactured by anyone with access to a laser cutter with at least a 24x12" bed, and nearly any FDM 3D Printer. A bill of materials of purchased parts required to complete the machine is below.

Usage

DEX runs a squidworks controller, which is in development but is pulling data from samples successfully.

Controller TODOs:

• serverside squidworks: machine contained system
• server config for bootstrap entire system ! (/url-to-program-location)
• setup and config-it
• assign meaning to charts and graphs
• save tests as .json objects (optionally) develop program for reading
• save images of tests (genpurp canvas save tool?)

Circuit TODO:

• draw / fab temp and humidity sensor (looks like Bosch BME280 828-1063-1-ND)
• better implementation of load cell amplifier ?

Building a Displacement Exercise

Hardware Documenting TODO

• mcmaster order
• CAD shuffle and export

BOM

Part numbers are from McMaster Carr unless otherwise linked.

Part	Spec	Count	Notes	PN / Link	Cost / Per
Delrin (Acetal) Cast Sheet	24x12", 0.25" Thick	2	Fits on 24x18" w/ no mistakes	8573K35	$50.49 / 1
PLA 'Tough'		~ 300g	Many 3DP Mechanical Bits	Matter Hackers M6E9T65K	$52.00 / 1kg
625ZZ Bearings	5x16x5	24	-	VXB 625ZZ	$24.95 / 20
Bearing Shims	5x10x0.5	37	-	98055A098	$8.62 / 50
Carriage Shoulders	M4x5x6	12	-	92981A146	$2.16 / 1
Reduction Shoulder	M4x5x10	1	-	92981A030	$2.32 / 1
Idler Shoulders	M4x5x20	5	-	92981A042	$2.33 / 1
NEMA 23 Stepper Motor	> 56mm Can Length	1	Spec Shaft with Pinion	Stepper Online	$14.83 / 1
GT2 Pinion	20T	1	Spec Shaft with NEMA 23	Amazon (or) RobotDigg	$9.96 / 5
GT2 Closed Loop Belt	280T, 6mm Wide	1	-	Amazon (or) RobotDigg	$15.88 / 10
GT3 Open Loop Belt	~ 1m, 9mm Wide	1	-	Amazon (or) RobotDigg	$15.00 / 1
6806 Bearing	30x42x7mm	2	x	6806-2RS VXB	$12.95 / 1
M3 Inserts	Tapered, 3.8mm Tall	~ 300	-	94180A331	$12.92 / 100
M4 Inserts	Tapered, 4.7mm Tall	16	-	94180A351	$14.96 / 100
M5 Inserts	Tapered, 6.7mm Tall	4	-	94180A361	$12.00 / 50
M3 Washers	18-8 Standard Flat	300	-	93475A210	$1.62 / 100
SHCS	M3x16	100	Pinning T- to the wall, and pulley endmatter	91292A115	$5.87 / 100
SHCS	M3x20	100	Pinning T- to one another (?)	91292A123	$6.78 / 100
SHCS	M3x25	100	Pinning T- and X-es together	91292A020	$7.23 / 100
SHCS	M3x45	8	Pinning the 'squat' together	91292A025	$12.21 / 50
FHCS	M3x10	30	Pinning blisters to faces	92125A130	$5.81 / 100
FHCS	M3x25	(?)	-	92125A138	$11.50 / 100
Steel Dowel Pins	5x8mm	10	-	91585A506	$8.40 / 25
Feet	M4 Stud, 15x15mm	-	-	93115K881	$1.78 / 1
Approximate Mechanical Total					$446.80
Loadcell(s)	10, 30, or 50kg	1	Choose Range for Sensitivity	Amazon 50kg Amazon 30kg Amazon 10kg	$39.00 / 1
Loadcell Amplifier	HX711	1	-	Sparkfun 13879	$9.95 / 1
Power Supply	350W 24V LRS-350-24	1	-	Amazon	$32.25 / 1
Rough Control Total: Incomplete					81.20
All Up					$528.00

CAD Notes

• fusion / parameters

Tools for Fabrication

• laser, 3dprinter
• soldering iron for inserts
• arbor press is nice, but not necessary

Dependencies

This repo is for the machine itself, it implements / uses / depends on the projects below:

• pdbs
• router
• stepper driver
• loadcell circuit (find amp, make board?)

MFG Notes

I used the trotec w/ 80 watts power, doing two passes per cut at 0.25 speed and 100 power. The colors to setup with are:

Black, Red, Blue, Cyan, Green, Magenta

To export from Fusion, use Rhino for layout, export cut files as DXF, for the trotec the best move is to export as 'R12 Natural'. This will keep segments together.

...

fixturing moves / top to bottom

Testing Notes

Use the D683 ASTM Dogbone - normally Type 5.

Controller Desires

• cyclic loading
• direct upload -> materiom (generic: databases) ... MQTT (and nodered)
• https://cookbook.nodered.org/mqtt/ (and: https://cookbook.nodered.org/)
• add to data: humidity, temperature, location, time ...