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Information on the SDM Process

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Materials

UPDATED 3-22-06 MarkCutkosky: Some interesting NewCastableMaterials

Urethane Properties

2-18-04 MarkCutkosky
For some older materials and property information see

Table of Material Properties and Observations
Note: for information on disposal of these materials see: UrethaneWaste

Urethane Color Gel Time (min) Published Demold Time Shore Hardness Tensile Strength (psi) Application Observations Manufacturing observations
IE-10A cream 10 10 hrs 10A 150 Very sticky to the touch, sticks very well to many surfaces. Stickiness decreases as it collects residue. Can be cleaned with water to restore stickiness. Too soft to machine in any way, including planing. Instead, can be "squeegeed" by pouring enough urethane to slightly overflow cavity, and then scraping off any excess with a flat wax bar or other flat object.
IE-35A clear 15-20 24 hrs 35A 400 Somewhat sticky, but not nearly as much as 10A. Much tougher than 10A. Probably too soft for most flexure applications. Can be squeegeed as with IE-10A. Seems to take significantly longer to cure than other urethanes - up to 72 hours!
IE-90A cream 15-20 8 hrs 90A 1800 Commonly used for flexures Can be planed (carefully!) if cutter is cleaned off after each pass.
IE-72DC clear 15-20 4 hrs 80D 10000 Commonly used for structural components. Can be machined after curing
Tap Quik-Cast White 2 10 min 72D 5000 Commonly used for structural components. Have not done any degassing because of fast gel time. Have not had any problem with bubble formation. Can be machined when cured.
RC-77D Amber 1.2 15 min 75D 8500   Did not do any degassing because of fast gel time. Cured part has significant number of small bubbles throughout.
RC-520 Black 1.2 20-30 min 80D 7900   Did not do any degassing because of fast gel time. Cured part appears to have significant number of small bubbles throughout, although opaque color makes it difficult to tell. Significant part shrinkage left exposed gaps around edge of mold. This resulted in the part popping out of the mold during planing operation.
VA-190 White 2   85A 2500   Rapid Vac product, has low viscosity for better results when using vacuum-assisted casting.
VA-285 Semi-clear 4   77D 11718   Rapid Vac product, has low viscosity for better results when using vacuum-assisted casting. Did not do any degassing because of fast gel time. Cured part has significant number of small bubbles throughout.
Note: all polyurethanes listed above are from Innovative Polymers except for Tap Quik-Cast (from Tap Plastics)

To order polymers of the Smooth-On brand (e.g. Vytaflex), you should order from Reynolds Advanced Materials ( http://www.reynoldsam.com/ ) rather than the Smooth-On website ( http://smooth-on.com/ ) because Reynolds has a store in Hollywood and it will come to Stanford really fast rather than having to be shipped across the country. The prices are pretty much the same.

Other supplier worth checking out: http://www.freemansupply.com/
Silicones: http://www.silicones-inc.com/

End Mills

End Mills we currently use (all Carbide)

Here are the tools we currently order:

Order already-extended tools made by Harvey Tool (http://www.harveytool.com):

End Type Diameter Length of Cut Overall Reach Harvey Part# Cost
SQ 0.062" ~= 1/16" 0.5" 1" 13662 $27.80
SQ 0.031" ~= 1/32" 0.155" 0.31" 13631 $28.40

These tools need to be ordered from Coast Tool (http://www.coasttool.com/) or Western Tool (http://www.westtool.com/) or Shop Tools or other places that can be seen if you look at the Distributors part of the Harvey Tool web page. I'm not sure about the Western Tool website but I believe Aaron thought you could get mill bits from them. I also believe you have to call these places, you can't order from the websites.

Coast Tool - 2099 Edison Avenue San Leandro, CA 94577 Phone numbers: 510-569-1945, 800-966-8665. Fax: 510-569-2420
WESTERN TOOL - SANTA CLARA 3195 DE LA CRUZ BLVD SANTA CLARA, CA 95054 USA Phone: 800-743-0818

Source for tiny end mills and drills: http://www.pmtnow.com

Where we used to get tools that are NOT extended-length:

These are all part numbers for GARR tool, and they are NOT extended-length. So, with these tools you have to get them "necked down" by the person mentioned below to make them extended-reach.

End Type Diameter Flute Length Series EDP# Cost
SQ 1/2" 2.0" 620M 41250 $40.92 as of 10/11/04
SQ 1/4" 1.5" 620M 41090 $19.36 as of 10/11/04
SQ 1/8" 1.0" 620M 41030 $14.35 as of 10/11/04
SQ 1/16" 0.25" 220M 11030 $7.26 as of 10/11/04
SQ 0.0312" 0.0938" 220M 11010 $7.84 as of 10/11/04
SQ 0.015" 0.0450" 220M 11600 $12.65
BALL 1/4" 1.5" 720M 43090 $21.60
BALL 1/8" 1.0" 720M 43030 $16.08
BALL 1/16" 0.25" 320M 16030 $8.92
BALL 0.0312" 0.0938" 320M 16010 $9.45

Local vendors:
Shop Tools Inc, 892 Commercial St, Palo Alto, CA 94303, (650) 494-8331, Note: doesn't keep Garr in stock!
To get tools "necked down" for longer reach, call Marcel 964-6188, tell him you work with Tom Hasler.

Cutting Parameters: Feeds and Speeds

(See Machinists Handbook or http://www.endmill.com/pages/training/spdfeed.htm for more info)
Depth of Cut: No greater than 1:1 depth to tool diameter (recommended ratio of 1:2 is safer)
Basic Formula: InchesPerMinute = Chip Load * RPM * #OfFlutes
Tool Dia Chip Load per tooth RPM (spindle speed) Feed Rate for Al, plastic, wood (mm/min) at 6000 rpm
1/16 .0002 -.0005 12000 60-150
1/8 .0002 -.001 6000 60-300
1/4 .0005 -.002 3056-9168 150-600

How to order a new block of wax

Here are some detailed instructions on how to use ORACLE and use a PO to purchase the wax blocks.

WaxBlockPurchasing

 
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