thanks for the information, i took a look and the site has some good information my machine is having a moving gantry not a moving table due to if you have a moving table you end up with a machine with twice the foot print compared to a moving gantry machine and as i have said i do not have the room to spare so that was the reason i choose the moving gantry and the reason for using the aluminium profile is due to not having any welding equipment if i had started doing this back when i was still working then i would have built a welded frame and also most likely built a much larger one, in the past i use to go to extremes and either go as large as possible or as small as possible, this machine is as large as i can build with the room i have i think it will end up with a working size of 340X300X150 as the rails i have are 420x420x250 and as i will lose at least 80mm for the bearings plus whatever space i leave between them so on the x axis the bearings are touching so i only lose 80 mm as the bearings are 40x40, on the y axis i am thinking of leaving around 40 mm between them so i will get a 300 mm working length and on the z axis i think i will end up with around 150 mm i accept that using the 20 mm profile that the machine will not be that strong but i only want to play around with some softwood and foam board, as long as i have some fun with it it will have been worth the money.
at the start the machine was only going to be used as a 3D printer but then i thought that i could add a laser cutter/engraver to it and when i came across the low cost spindle i decided to add that to it as well.

again many thanks to everyone who has given me some feedback,
regards Poppy Ann.