HTM Complete
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Files
HTMComplete- 8way 2018-4-28 v3.f3d
HTMComplete – 3way 2017-4-5 v12.f3d
HTMComplete – Pump St 2017-4-5 v2.f3d
HTMComplete – Battery Tray v13.f3d
htm_tray_8way.tap
htm_tray_3way.tap
htm_tray_pumpst.tap
htm_battery_tray_BOTH.tap
htm_battery_tray_LEFT.tap
htm_battery_tray_RIGHT.tap
Hybrid / 8 way 2018-4-28 mounting plate
5mm fillet radiused corners on extruded body.
3 way 2017-4-5
Pump St 2017-4-5
Battery tray
Ritar RT1272 [12V 7.2AH 20HR]
Dimensions: 151mm x 65mm x 94mm (L x W x H). Add 10-20mm for terminals clearance.
Weight: 2.15kg
Design requirements:
– Must be made of plastic, not aluminium, not galv steel.
– Must be strong.
– Detachable part is preferred.
Plastic bookends (HDPE)
We can machine two of these out of a single small cutting board.
To allow for outer bending radius (unwanted stretching of material) and inner bending radius pinching of material, we need a 1.5mm to 2.0mm deep 7.5mm wide “trench” scoring mark to allow for bending radius (K-factor):
Threaded inserts
Do not use threaded inserts. Bolts will pull on the threaded insert and the threaded insert will start to slide out.
Pop rivets
Pop riveting works well. Pop rivet does not pull into the material much when installing. Optionally put a metal washer behind plate to prevent this. Strong fit. Rivets sit flush. Rivets can be drilled out if disassembly is required.
Thermoforming
Strip heating:
– Use heat gun.
– Attach wide strip nozzle
– Low fan speed.
– Maximum heat
– Timer
– (Make rests for plastic to sit on whilst heating.)
Bending:
– Bench vice magnetic mount Kinchrome metal folding dies (cast iron base):
Thermoforming (bending) plastic
Thermoforming is a process of heating a thermoplastic sheet to its softening point.
Step 1. Strip heater
Step 2. Bending jig
Sometimes the heater and bending jig are integrated.
Nichrome wire is safer (12v) but slower / lower wattage. 300W heating element from an infrared heater works best.
For improved accuracy / repeatability:
– use timer.
– draw a line on your material or score line. place line centered directly over heating element.
– heat slowly.
– heat a very small strip area only if possible.
– for thicker materials, turn every 30 seconds.
– use a bending jig and press block.
Materials
Ideally we want (UV stabilised) ABS plastic, but HDPE kitchen cutting board material can be locally sourced relatively easily and cheap. Note that HDPE can be CNC machined well, but not laser cut as it melts.
Reject Shop “Cuisine Selections” high-density polyurethane (HDPE) cutting board 2pk. 350mm x 245mm x 4.8mm (L x W x D). 300mm usable length from edge to hand grip hole. $6 AUD. SKU: 30107930
https://www.rejectshop.com.au/p/plastic-chopping-board-2pk
Kmart 2 pack chopping boards. Small: 23cm (L) x 14cm (W). Large: 36cm (L) x 24cm (W). Material: Polyethylene (PE) and antibacterial material. White. Anti-bacterial. Reversible. BPA free. $5 AUD. SKU : P_43073764
https://www.kmart.com.au/product/2-pack-chopping-boards-43073764/
HDPE is food safe, moisture-repellent, very strong and resistant to chemicals. The black version is UV-resistant due to the addition of soot and is therefore suitable for outdoor use.
Properties of HDPE
– Highly impact-resistant and dimensionally stable
– Temperature range up to 80°C
– Has a moisture absorption of 0.5%
– Has a coefficient of friction of 0.25
– Good price-to-quality ratio
– CNC machining is preferred over laser cutting (melting).
Manufacturing
A first attempt.
This is new.
Avid Pro CNC https://www.avidcnc.com/