Cutting thick acrylic sheet

[ppppenguin]

I have recently acquired (via freecycle) some lovely big clear acrylic sheets. I want to use them to build part of an enclosure for my mercury arc rectifier.

The question is: How do I cut big pieces of 7mm and 20mm acrylic sheet accurately and cleanly? I suspect the answer is to make friends with a local sign manufacturer.

Thinking of alternative approaches, at the weekend I saw one of these:
http://www.amazon.co.uk/Fisher-Price...7877169&sr=1-2

being demonstrated inside a nice glass (maybe acrylic) housing (4 sides and top) that would have been about right to house my MAR. It comprised flat sheets slotted into aluminium corner sections.

[PSValves]

When I made the 5mm acrylic lid for my fish tank, I cut the plastic using a jigsaw fitted with a blade designed for non-ferrous metals. With the pendulum action on the jigsaw set to zero, I got a reasonably smooth edge which was easy to finish with some fine sandpaper. I think the trick is to go really slowly, so the blade cuts though the plastic rather than melting its way though. Hope this helps.

[Sean Williams]

Jeffrey,

Use a Jigsaw, and plenty of paraffin wax as a cutting lubricant - take it slowly, and use as coarse a blade as possible - never stop the saw halfway through a cut, or disaster will occur!

[reelguy]

It will be interesting to see how you get on with this. I was going to suggest you clamp the sheets between a couple of sheets of plywwod to avoid splintering it. Might work for 7mm but 20mm is quite thick stuff. How big are the sheets of acrylic ?.
Peter W.........Reelguy

[ppppenguin]

Jigsaw and lubricant seems to be the answer. Sean, when you suggest paraffin wax, do you really mean a wax rather than an oil?

Presumably I need to clamp some wood to the acrylic to act as a straight edge guide. Jigsaws don't like cut straight lines!

[Jack Spark]

You can use general woodworking tools, so a jigsaw will do it.
But as has been mentioned, the danger is that the blade gets hot and melts rather than cuts the acrylic, this can happen quite quickly.

Using a jigsaw will leave saw marks which will need to be sanded out using increasingly finer grades. Wire wool and then Duraglit can be used for the final polished edge. Care must be taken so as not to scratch the surface.
Its a fair amount of work but the end result is worth it.

How big are the sheets and are you likely to have any left over?

Hope thats some help

Regards

Jack

[Mike Phelan]

I, too, use a jigsaw (actually a Hegner fretsaw) for cutting thick acrylic, then finish off with a Surform and glasspaper. Not tried any lubricant before but will do next time.

We'll look forward to the firework display when you fire it up, Jeffrey!

[GMB]

Be very careful about using mineral oils with plastic especially in a situation where stress is involved. It can produce some very unexpected results.

I would be more inclined to use water cooling. You don't need a lubricant as most plastics are somewhat self lubricating but the smallest rise in temperature softens it and it then binds to the cutting tool.

A professional plastic fabricator once told me that all cutting tools for plastic need very different cutting angles compared to steel. He ground his own drills as regular HSS ones are quite wrong for plastic. Sadly I can't remember how he cut heavy sheets. I only remember that he retained any thin off-cuts to be used as welding rods as you need very close chemical compatibility for plastic welding.

[Jack Spark]

According to the PERSPEX a Workshop Handbook, a bandsaw or Circular saw (Carbide tipped) is recommended for anything over 6mm.

Bandsaw
Optimum blade speed 1500m/min
Up to 3mm teeth/cm = 6 - 8
3 - 13mm teeth/cm = 4 - 5
Over 13mm teeth/cm = 1.5 -2
Recommendation: Keep saw guides as close together as possible to prevent blade twisting.

Circular saw
Optimum blade speed 3000m/min
All thicknesses: teeth/cm 0.8 - 1.6

There is also the other although expensive option of laser cutting it, this will give you a polished edge on thicknesses up to 12mm so no need for the time consuming sanding down.
Can't recall where I downloaded the manual from but it may be worth a google search.

Best

Jack

[Sean Williams]

Paraffin Wax is reccomended for turning perspex, or similar materials - water isnt really viable...

1, it conducts electricity, so is not a good thing when using a jigsaw.....

2, it cools too quickly, and has next to no lubricating properties - if the blade jams when water is applied, it will just ruin the piece, as well as the blade (been there done that)

Good old Vaseline works quite well, and does not react with perspex.

My local plastics stockholder uses an extremely fast table saw, with a tungsten carbide tipped blade - the mess it makes is fantastic!

They use no coolant, or lubricant at all - the speed of the cut, combined with the releif on the saw blade makes up for this.

Bear in mind when jointing Perspex, or acrylic sheets that normal adhesives are no good - you need the proper stuff that actually welds the joint together.

Sean

[pmmunro]

This is probably an updated version of the source of Jack's information.

http://www.theplasticshop.co.uk/plas...pex_manual.pdf

PMM.

[joe]

Jeffery,

Following on from Sean's reply the correct adhesive is stuff called Tensol cement. The main problem is getting it in "domestic" quantities ie not 5 gallon drums. RS do some in reasonable sized bottles.

It may also be that there are two slightly different versions depending on whether the Perspex has been cast or rolled in manufacture.

Oh! and don't do glue sniffing - I believe that the solvent is chloroform!

Joe

[GMB]

Isn't the name "Tensol" that of a product range, not a particular adhesive. I was given a pot of Tensol-7 which is a two part adhesive for Perspex. Other Tensol's are quite different.

I think one of them is just methylene dichloride which you can use to solvent bond acrylic and PVC sheet. Methylene dichloride was commonly sold as paint stripper (I expect that's changed).

[mikelect]

Originally Posted by GMB

I think one of them is just methylene dichloride which you can use to solvent bond acrylic and PVC sheet. Methylene dichloride was commonly sold as paint stripper (I expect that's changed).

Another one is Acetone which is good for solvent welds

Mike