The clampless method of sheet work holding on a cnc router
Find out about VACUUM PUMPS for CNC ROUTERS here
We stock 2 types of vacuum pump. Rotary vane and side channel.
Below is a photo of SIDE CHANNEL type vacuum pump. (blower type)
2.2kw single phase £575.
£625 with inlet filter and exhaust silencer
Filter kits and silencers are optional.
5.5kw 3 phase £995 (inlet filter and exhaust silencer included)
7.5kw 3 phase £1195 (inlet filter and exhaust silencer included)
Below is a photo of a ROTARY VANE type vacuum pump.
These pumps are very similar design to Becker vacuum pumps.
Genuine becker pumps can also be supplied. (we always have refurbished becker in stock)
5.5kw 3 phase 160CuM/Hr £1750 (includes inlet filter)
7.5kw 3 phase175CuM/Hr £1995 (includes inlet filter)
Huge flow pumps - Rotary vane.
7.5kw 3 phase 250CuM/Hr £2995
11kw 3 phase 360 CuM/Hr £3195
We always have a good stock of totally refurbished used pumps
below is a sample of a very low hours used genuine Becker vacuum pump
Larger capacity (flow) is required for hold down of smaller parts. This is where you have to compromise if using single phase as you wont have the power (amps) available to run huge capacity pumps.
For example the ideal cuM size pump for an 8 by 4 size table is around 160 to 250 depending on the materials being cut . For larger bed sizes another 2 to 4 quantity of this size vacuum pump should be added to allow enough "loss" while maintaining enough hold down pressure.
Good pumps are an expensive part of your whole system.
In reality, no matter what size pump you use, good machining technique will make or break your cutting process, It will take a good deal of experience to work out how to get small parts off the machine consistently. Large parts like cabinet sides are easy. Smaller items that are 150mm by 300mm or even smaller can be machined consistently without tabs by onion skinning and ensuring the order of cut and the start and end of the toolpaths so that part is still attached to the very last bit of cut. Cutting smaller parts before the larger items gives you the best chance of solid hold down. This will be explained within your training day!
Tabs: small sections where the cutter is raised to allow the work piece to stay held by the main sheet.
Onion skinning: Where the job is cut "almost" all the way through but leaving a very thin "skin" which allows very low tool side pressure cutting to cut through it on the final pass.
How is vacuum used on a cnc router?
Is vacuum invisible magic?
To use vacuum hold down for sheet work on a cnc router we use a spoil board.
What is a spoil board?
A spoil board is a sheet of mdf which covers and protects the vacuum sealed chambers on the machine bed.
its function is to firstly "seal" against the vacuum table chambers.
The magic- MDF is a porous material, which allows air to flow through it.
The vacuum travels through the mdf and "sucks down your job sheet"
You can now machine your parts by cutting through your sheet fully, and very slightly into the spoil board.
Your wood or plastic sheet "job material" is placed on top of the the spoil board to allow machining.
What do i need?
Recommended thickness of spoil board is 18 to 25mm. plain mdf (not mr or high density)
Preparation: The board should have the outside edges sealed. (we use pva glue rubbed into edge and allowed to dry)
Next, use the skim program supplied with your Machine to skim 0.5mm off the lower surface.
this breaks the pressed surface smooth seal face of the mdf.
Turn the spoil board over and skim the top surface. 0.5mm is usually enough.
skimming the top surface of the mdf flattens the board exactly to the machines cutting level.
When your spoil board gets badly marked, Re surface it (hence the name spoil board)
Shown above: re skimming a well used spoil board flat.