Vacuforming Production level parts trimming

Jonathan Bowen · Nov 7, 2014

So I own a laser cutter and have an opportunity to buy a vacuform machine for cheap. I don't have room in the shop but I'm thinking about trying to make it work. The issue is this would be used for production level work. Made to create custom box inserts for board games or trays for holding gaming components during play. I'm already over worked dealing with another production issue that is taking all my time now that volume kicked in. I'm stuck at a junction were I can't afford the machines to make it or to outsource it without massive numbers that are a bit out of reach. So I tend to plan things out a lot before I leap now a days.

Are there techniques for quickly cutting out vacformed pieces with precision? This will be a production setup so it will be timed rather tight and I'll be doing several parts per pull. The bed on the machine is 2' by 4' so I figure I'll have several parts in each pull that will need to be removed. Either that or I'll build an adapter plate to shrink the size to something manageable when needed. I've considered transferring it to the laser cut I don't have a good enough fence in the other machine to justify it. I'll never get it to line up with correct tolerances.

Anyone have experience with this? I'm hoping to keep trimming time to less then 1 min per sheet with about 4 items on it.

cavx · Nov 7, 2014

Just my $0.02 worth is that vacuum forming is a great way to make short run parts. It is cheap and even fun to do but can be a bit hit and miss, especially if you are rushing it. To get good pulls, you need correct heat and a good suction. Different plastics heat at different rates, so you need to work out what works for each material type you will be using.

How precise are you hoping to be with the trimming? Again, might take more time based on material and with multiple parts, you may get webbing.

Jonathan Bowen · Nov 9, 2014

I can work out all the numbers and make the pulls consistent. I do it all the time with my laser cutter. Once I lock in each material then it's logged and used every time.

I really want to make something that is akin to what is commercially done for game boxes and other products now. It will just be done for games after they have been punched not for shipping. This is often the case with board games. I'd also like to make cleaver stuff that pops out and stuff. It's done in production environments all the time and I just need to figure out a way to emulate that process for my smaller scale. The timing is key because if I can't cut these out quickly then it's going to raise the price and I was hopping to keep it really low. Right now I'm thinking about adding a groove to the mold design that will guide a knife through the cut.

asalaw · Nov 9, 2014

I think that's sound, or a jig that will hold your knife while you move the part under it or along it. Your design will have to dictate that. The thinner your plastic, the easier it will be to cut and therefore the faster you can get through it, but you already know that. I think you sound like you have it under control.

Jonathan Bowen · Nov 9, 2014

I did some research and I might have to do something interesting like creating a lip under all the parts that is a standard thickness and make some jig that a dremel will fit in. The right bit and it might work. I might have to drop it into a secondary jig to do the cutting depending on the thickness of the plastic. I could easily cut a customer mount to the dremel that fits into the part at the right spot and angle to cut it.

I might pull the trigger on it. I need to measure some stuff at the house. I've also run into something called pressure forming that looks interesting and I might try to experiment with for another application.

Darth Lars · Nov 9, 2014

Styrene or ABS (ABS is a blend with styrene) is not suitable for laser-cutting, unfortunately.

The quickest way to cut styrene by hand is to use the "score-and-snap" method, with a proper "scoring knife" for plastics.
You get the best straight cuts with the knife against a metal ruler.
However, is it not that easy to cut anything but across the entire sheet, so I suppose that you would have to plan the layout of the parts
on the vacuuforming table for a certain cutting order.
Maybe you could come up with a jig that would make it easier to get fast perfect cuts for your runs.

Jonathan Bowen · Nov 9, 2014

I laser styrene all day long. It's tricky.... and annoying at times. I do wear gloves if I handle a lot of it. It produces a slight irritant when cut. I tend to not stay near the machine when it's running but most of the stuff is exhausted outside anyway, I had considered some sort of transfer to the laser bed but it was full of issues.

If I go with the scoring knife method then I'll probably create grooves on a base plate for all the parts (most will be squares or rectangles). Then I can hit that groove and score the entire part quickly. I need to work on my knife skills because I suck at cutting straight lines even with a ruler.

msleeper · Nov 10, 2014

Darth Lars said:
Styrene or ABS (ABS is a blend with styrene) is not suitable for laser-cutting, unfortunately.

To clarify this statement, you can laser cut Styrene and ABS, but they curl and melt and it's generally a mess. If you have a CNC mill it's better to mill it, but still not perfect as the material will still heat up and melt and stick to your cutting bit.

Philly · Nov 10, 2014

msleeper said:
To clarify this statement, you can laser cut Styrene and ABS, but they curl and melt and it's generally a mess. If you have a CNC mill it's better to mill it, but still not perfect as the material will still heat up and melt and stick to your cutting bit.

It's all down to the speeds, power and air assist, I've cut styrene a few times before with a good edge. Same with the CNC, get you feedrates/cutter wrong and it will melt, get it right and it's no different to any other material

Darth Lars · Nov 10, 2014

Jonathan Bowen said:
I need to work on my knife skills because I suck at cutting straight lines even with a ruler.

The thing with a scoring knife is that the blade is shaped like a hook, so you don't cut like you would with a normal knife but in a pulling motion.

Philly said:
It's all down to the speeds, power and air assist, I've cut styrene a few times before with a good edge.

I have not done CNC, but I have dremelled styrene many times. You need to do it at a slow speed. When I only had a knock-off dremel-like tool without proper speed control, I sometimes got the bit encased in melted plastic and it was not always that I could even remove it from the bit.

msleeper · Nov 10, 2014

Philly said:
It's all down to the speeds, power and air assist, I've cut styrene a few times before with a good edge. Same with the CNC, get you feedrates/cutter wrong and it will melt, get it right and it's no different to any other material

Thankfully we have air assist on the cutter I use, but it's a static pressure I can't adjust. What speed (mm/min) and power (mA) do you use?

Philly · Nov 10, 2014

msleeper said:
Thankfully we have air assist on the cutter I use, but it's a static pressure I can't adjust. What speed (mm/min) and power (mA) do you use?

I'll dig out the settings, but for the air assist put an air release valve in the line that vents to atmosphere(adjustable type) and it will adjust the air coming out the end of the assist. Too high a pressure makes just as much mess as too little

Also, I'm glad to see someone use mm/min, starting to get sick of translating 3/32inch etc :lol

Jonathan Bowen · Nov 10, 2014

Our machine is tricky. It starts really slow and ramps up so its a balance act with power. I could have adjusted the power ramp settings but I made it work without having to do that. Acrylic doesn't care because its such a slow start but cutting at speeds of about 40mm/s the ramp is noticeable. I also have to dial in the settings any time something changes. We cut 20mil but I've done 40 mil without trouble for my R2 build. I also vector etch it a lot to get details. It's even more of a pain to get those settings correct. I just spend a bit cutting scraps over and over till I get the settings locked in and then write them down.

If you do need to adjust your air assist then try putting a valve in line. That is what I use. We have a 2 HP 10 gallon compressor that feeds ours. It runs about 20% duty cycle. If I didn't restrict it then I'd never get a straight cut. That is banking on the hoses not blowing off their connectors. I started with a level valve but upgraded to one with a big round handle (gate valve?) so I can tweak it a bit when needed. The lever was a bit touchy.

msleeper · Nov 10, 2014

Philly said:
Also, I'm glad to see someone use mm/min, starting to get sick of translating 3/32inch etc :lol

Metric makes more sense when you are working with tiny parts. What really sucks is the mills are all in inches and I just can't visualize 3/32nd like I can 3mm.

What is the worst is people who use the Full Spectrum lasers and use "speed 3" and "power 1". What do those values mean! How can you use a tool and not know what it is doing!

Vacuforming Production level parts trimming

Jonathan Bowen

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cavx

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asalaw

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