Vacuum forming

DJH

I am new to vacuum forming and I am hoping to get some advice before I ruin a few sheets of ABS, I built a 4 x 8 foot vacuum forming machine , it uses 8 oven burners divided into 4 sections with 4 heat controllers. The parts I want to form are approx. 8 to 10 inches tall and I am concerned about the corners not forming correctly, the ABS is 1/8 of an inch thick.

Chris Ellerby

Here's a handy table that may help:

Plastic Processing Temperatures In Degrees F
Material	Specific Gravity		Mold Surface & Demolds		Lower Processing		Orientation		Upper Temp
ABS	1.07		185		260		280		400
Acrylic	1.15		185		300		325		425
Acrylic/PVC	1.15		175		290		310		400
Polycarbonate	1.20		280		335		350		400
Polyethersulfone	1.37		400		525		560		700
Polyethersulfone, glass filled 20%	1.51		410		535		560		720
Polyethelene, high density	0.99		180		260		270		430
Polypropylene	0.92		257		270		280		380
Polypropylene, glass filled	1.05		195		265		280		450
Polysulfone	1.24		325		375		415		575
Polystyrene	1.06		185		260		275		360
Vinyl, rigid	1.47		150		220		245		310
Vinyl, rigid foam	0.70		160		240		260		350

You can learn more here:  http://www.plasticsmag.com/thermoforming.asp?fIssue=Mar/Apr-03

The challenge is determining the core temperature of your plastic based on surface temperature and material thickness.

/Chris

Chris Ellerby

If you are worried about webbing happening on the bottom edges of your parts,  you can elevate them off the platin using small blocks, or design them a bit taller and cut off the bottom portion.

With new parts, there can be a bit of trial and error as you figure out the spacing between parts, if they need to be elevated, and how much to let the plastic sag before dropping and pulling the vacuum.

For taller parts, you'll want the plastic to sag a bit more before dropping it.

/Chris

DJH

Thank you for the reply, I did leave an extra inch on the bottom to accommodate for any deformities, I was worried about the extra material I may get on the corners, kind of like when you are wrapping a gift and you have to fold over the corners. The extra sag makes sense, what is the max temp you can go to with ABS.  

DJH

Thank you this is very helpful