routing acrylic?

[flanajb]

Hi,

Trying to route acrylic using both 10mm and 20mm twin flute TCT cutters from Welden Tools, but am getting the occasional chip on the edge of the acrylic. I have turned the speed down on the router to number 3 which is quite slow, but still get the odd ship. I am plunging into the acrylic to a depth of 2mm.

Anyone know the best way of achieving a plunge cut into acrylic, as I cannot have a single edge chip as the product I am trying to manufacture has to be 100% imperfection free.

Anyone have any ideas?


Thanks

 

[SPSlick]

Score the acrylic first?

 

[RobinBHM]

Would a downward spiral bit help?

 

[Phil Pascoe]

I assume your cutters are bottom cutting? If they're not try one with a bottom cutter - if they have a bottom cutter, try one without? A drop of some form of lubricant, maybe?

 

[Spindle]

Hi

Does the edge have to be at 90 degrees? - if not, try scoring the profile with a vee cutting bit, the obtuse angle produced will be less prone to chipping.

Regards Mick

 

[Dutch]

if you have a plunge saw clamp the rail a fraction inside the groove, set the saw to 1mm depth of cut and run it backwards along the rail slowly peforming a climb cut. Ive used this method with excellent results.

 

[TimothyClaypole]

Laser? The bit of mdf is 2mm thick.

 

[marcros]

Could you clamp some thin sacrificial material to it or even a second piece of acrylic and rout though the first into the workpiece?

 

[flanajb]

Thanks for all of the posts. In answer to the questions

1. The hole has to have a 90 degree edge and cannot be chamfered
2. I am using a bottom edge cutting router cutter

I will try clamping a sacrificial board on top of the acrylic to see if that helps yield better results.

A lazer cutter would be the way to go, but not really viable for me to buy one. If anyone has one and fancies a job then do pm me

Thanks

 

[Racers]

How about a first pass at 1mm and a slower speed it might help to stop the chipping on later passes.

Have you tried spiral milling cutters?

Pete

 

[woodbrains]

How about a first pass at 1mm and a slower speed it might help to stop the chipping on later passes.

Have you tried spiral milling cutters?

Pete

+1. A grazing pass at a very small depth and then subsequent ones at greater depths, is the best practice for any brittle material. Low cutter speed means low feed rate too. Practice on a bit of scrap to ascertain the highest spindle speed that does not cause the plastic to melt. It is likely too low a spindle speed will cause chipping in itself.

Mike.

 

[Hemsby]

Acrylic is best cut with a HSS cutter, while carbide seems sharp it does not have the keen edge of HSS also slow speeds are not the best for this type of material.

Try using a HSS slot drill.

Regards

 

[Hemsby]

Forgot to mention when machining Acrylic you need a controlled, steady feed rate, secured material & tooling as it has a tendency to snatch which will increase the possibility of chipping/cracking.

 

[flanajb]

Forgot to mention when machining Acrylic you need a controlled, steady feed rate, secured material & tooling as it has a tendency to snatch which will increase the possibility of chipping/cracking.

I think that might be half the issue. Plunging a 20mm twin flute tct cutter into acrylic using a router is always going to cause a certain amount of judder of the router.

Based on your earlier post, should I order HS cutters instead or should I try and get spiral down cutters first?

Not sure whether I can get a 20mm spiral down cutter.

I know a lot of this is trial and error, but I want to avoid shelling out £ on the off chance it gives me the results I require.

Would be great if tool companies like Welden offered trial cutters.

 

[Higon]

Theres many types of acrylic, cast and extruded being the most common. Cast is what I work with, extruded tends to chip and craze whenever I tried it. now I just avoid it. To tell which type you have burn a small piece, extruded burns silently and will drip molten balls, cast burns with a crackly/smokey flame and won't drip.

YMMV, but for cutting cast I use a single flute cutter, I find larger is better. For cutting out shapes, 6mm at 24000 rpm and about 100ipm is my preferred setup. Maximum depth I would go with a 6mm cutter would be about 2.5mm (or just under half the diameter of the cutter per pass. Certainly no more than twice the diameter of the cutter.)
You want a cool chip up and away from the area before it has a chance to reweld. Airline, vacuum cleaner, dust extractor can all assist but high spindle speed and reasonable chip load will minimise any problems of furring

Holding it down firmly is essential, attaching the acrylic to a piece of MDF (MDF under the Acrylic) is good, double sided carpet tape with clamps and screws are not overkill! lol.

A search of fleabay for "CNC Single Flute" will give you loads of choice. I've used hong kong and mainland china as well as uk suppliers, HAF have always been good and reasonably priced from HK and CN.)

 

[mlee]

How about www.razorlab.co.uk ?

Depending on the size and quantity they could be an easier choice.

 

[Higon]

For the benefit of future searchers who find this thread;

Here's an image of some clear acrylic, routed with a 4mm cutter to a depth of 2mm. The gap between the two circles is 0.3mm