welding steel base or just getting aluminium extrusion

This is how i was thinking until Dean mentioned that its all good in a cad program but in real world it does not work that way. i was making my machine as tight and solid as possible in solidworks and had in mind that i will order these parts the same dimensions as solidworks and all will be ok, kjn have a tolerance of +/- 0.5mm now my gantry will have 2x 80x160mm in a l shape but how much of a problem will i have if one of those extrusions was - 0.5mm and the other was + 0.5mm.

edit.. more then likely i am way overthinking lol but thats my mind being ocd and following how lovely and neat my cad drawing is :)

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Originally Posted by reefy86

Don't want to be insulting to anyone regarding price but personally i think this is disgusting but then i am no expert on whats worth what when it comes to stuff like this. i have been quoted just under £2k just for 4 pieces and 2 of those pieces are only small plates for the rails

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I feel I have said this before, but Reefy, there may be two factors at work here :-
1. The company has enough on their order books to put them in a position where they can issue F**k Off quotes to one off machining.
2. They are cynically set up to cream off the desparate.

The price per unit if you were ordering 1000 off each would be a lot lot lower.

I would advise you to keep looking:nightmare:

Edit: Having looked at their website, I go for option 2.

True but me personally would not be issuing F**k Off quotes when that person would potentially spread the work and bring me more custom regardless if i have mass companies ordering from me, I would just simply say to them i can but its months waiting list because obviously bigger orders are a priority in business :)

What F**ks me off the most though is they buy materials in bulk and have the machine to make these parts as if they are butter so more then likely it cost them hardly nothing for the material due to bulk buy and charge me almost £2k and thats not even half of the plates i need doing. on their behalf i bet its a good thing but for poor old me it bloody aint lol

They won't save that much in material by buying bulk.

People think that just because it's a flat bit plate, that it's easy to machine, but it's rarely the case. Taking your end plates for example, how would you hold them down?
On a router table, you could just screw the plate to the bed, or rely on a vacuum table, but I'd doubt they'd be using a router to machine them.
On a mill, you could clamp to the bed, but then you have to work around the clamps. You could use some form of low profile vice fixture, but you're still looking at two setups. Other option is to make a fixture plate, but that's additional cost and machine time.
Even your small plates, if you've specified tight tolerances around the full perimeter, instead of just using a bit suitably wide bar in a vice, milling both ends flat, maybe surfacing the top face, and drilling/tapping the holes, you now need to have two setups so all edges can be machined. Every time you have to do a setup, is time that has to be paid for by someone.

Plus you've specified a blasted finish, so that's more cost.

The quotes do seem high, but when you actually breakdown the time involved, they're probably not that high for a professional machine shop doing a one off job.

Could be wrong but i think you will find the +/- .5mm will be on cut length,so all you have to do is group your sections together with all of one end flush lightly clamp them together, call the longest your master rail and measure the difference of the others (shims/vernier) if you recess your end plates these can be done to the same depth and on assembly put appropriate packing into the end plate(simples)

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Originally Posted by reefy86

This is how i was thinking until Dean mentioned that its all good in a cad program but in real world it does not work that way. i was making my machine as tight and solid as possible in solidworks and had in mind that i will order these parts the same dimensions as solidworks and all will be ok, kjn have a tolerance of +/- 0.5mm now my gantry will have 2x 80x160mm in a l shape but how much of a problem will i have if one of those extrusions was - 0.5mm and the other was + 0.5mm.

edit.. more then likely i am way overthinking lol but thats my mind being ocd and following how lovely and neat my cad drawing is :)

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This is very important! If using KJN aluminium to cut your extrusions you must have the pieces cut on the same day at the same time. They can offer a very high degree of repeatability but not if they have to reset the machine.

How accurate are KJN cuts I just had cut my MDF bed cut to 135.1cm *100cm based on my cad models and it dropped into place perfectly so I'd say at least for me there cuts were very accurate. I also had them cnc drill holes in my frame so I could assemble it with m12's instead of corners.

I did say to myself i would stay away from this thread.

That said, I do not like to see people getting quotes like you have for your plates. I have not read all the new posts ive only glanced over them. Plus i have no looked at those quotes in detail but its not right. I know roughly what you require as i have made parts for several forum members router builds in the past.

As mentioned they simply do not want to do the job or your drawings are asking for a lot and thats reflected in the price. Small jobs like this are agro for most company's and they charge you for that agro. Your drawing and the details on them will have a large bearing influencing the price. Some of the comments people have raised, i have said and others have said before and they are totally valid. I think its something most new people do not appreciate and it only sinks in with experience.

As the guys have said, you can do your plates long hand and of course has worked for many on here, in the same breath many choose to get them done outside.

I do this kind of works for people at a fair rate because i know the problem you can encounter with pricing. I like to see people doing these projects because it keeps Engineering alive and the knowledge base alive, if you guys cant do these projects, it dies.

If you want me to look at your plates please send me the drawings in either basic 2d dxf or dwg of if 3d in stp/step format. Be prepared to have your drawings scrutinised and alterations asked to be made. But please remember Anything i have said in this thread to you is for your benefit, even though you may see it as criticism, thats probably true for many other that have made comments also. Just to be clear I do not need the work, I have more work than i know what to do with at the moment, so work like this is done when my normal workload is reduced, so you have to wait until i have the time, but this means you get a professional job by someone who has been in the engineering sector (hand on) for over 35 years.

The offer is there. I'm not an ogre and i do not bite, but realise Engineering is a very straight talking trade. It has to be or we would never get anything done.

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Originally Posted by spluppit

I did say to myself i would stay away from this thread.

That said, I do not like to see people getting quotes like you have for your plates. I have not read all the new posts ive only glanced over them. Plus i have no looked at those quotes in detail but its not right. I know roughly what you require as i have made parts for several forum members router builds in the past.

As mentioned they simply do not want to do the job or your drawings are asking for a lot and thats reflected in the price. Small jobs like this are agro for most company's and they charge you for that agro. Your drawing and the details on them will have a large bearing influencing the price. Some of the comments people have raised, i have said and others have said before and they are totally valid. I think its something most new people do not appreciate and it only sinks in with experience.

As the guys have said, you can do your plates long hand and of course has worked for many on here, in the same breath many choose to get them done outside.

I do this kind of works for people at a fair rate because i know the problem you can encounter with pricing. I like to see people doing these projects because it keeps Engineering alive and the knowledge base alive, if you guys cant do these projects, it dies.

If you want me to look at your plates please send me the drawings in either basic 2d dxf or dwg of if 3d in stp/step format. Be prepared to have your drawings scrutinised and alterations asked to be made. But please remember Anything i have said in this thread to you is for your benefit, even though you may see it as criticism, thats probably true for many other that have made comments also. Just to be clear I do not need the work, I have more work than i know what to do with at the moment, so work like this is done when my normal workload is reduced, so you have to wait until i have the time, but this means you get a professional job by someone who has been in the engineering sector (hand on) for over 35 years.

The offer is there. I'm not an ogre and i do not bite, but realise Engineering is a very straight talking trade. It has to be or we would never get anything done.

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Thats kind of you mate and you were never in the wrong in the first place or did i ever discourage any of your advice i was just simply trying to avoid welding and go with aluminium but that soon changed lol. I have a few alterations of my own yet so ill sort those out and send you the files if thats ok with you.

Been thinking about how i am going to square the gantry up and thought of an idea using the method used below (watch from 2:20)

i know that method won't work on mild steel box section but what if i used epoxy resin on the side and wait for that to fully cure which will then give the side of the steel box section a really flat surface and then do the method in the video? i would need to do this before welding the top rail beam to the frame off course.

what do you think is it over the top?

https://www.youtube.com/watch?v=YOVHtjXi07Q

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Been thinking about how i am going to square the gantry up and thought of an idea using the method used below (watch from 2:20)

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The way I see it is that all he is doing is aligning the rail to the same as the ali profile so if the ali is bent so is his rail:confusion: