1st Build, Second machine

[JAZZCNC]

Due to problems (flex of Y axis and Z axis dropping up to 1.5mm from a set position)

The Zaxis dropping most likely won't be due to weak design problem but more probably an electrical problem, possibly a weak or under powered motor thou you'll still have the same problem if not changed.

Other than what marks pointed out then there's not much more to see or say.

[m.marino]

Okay but then comes placement of the lead screw, as don't have the funds for a new ballscrew at present. Folks I am really aprreciative of your input it is just that I have a rather large amount of work that I have been finishing that was supposed to go to this convention for clients who are interest and some that are closed sales IF I get the product there.

Again thanks and will try to get some revised drawings up later tonight.

Michael

[blackburn mark]

but then comes placement of the lead screw, as don't have the funds for a new ballscrew at present.

which one Z or Y screw? i thought you already had them??.. they will already be as long as they are :heehee:


there are ways of squeezing them in

[m.marino]

Okay Mark and Jazz,

Here is an idea for the rails on the Y axis


The leadscrew will run down the channel between the two rail supports and the back plate will be bolted to it and the the uprights. At that point I think I will be able to move the spindle closer to centre that way.

I am going to get some sleep and get on this tomorrow. Thanks for all the input folks and will work on things to the best possible.

Michael

[m.marino]

Okay,

Further drawing, as promised. With additional information.

Uprights of gantry are currently looking to be either 20 to 25mm (or 3/4 to1") thick. The rails are bolted down to 25 x 38mm bars that are going to be bolted to the back plate (12mm). The Z base plate is 20 (or 3/4") . I hope the way I had the jpeg done allows folks to see more of what is going on without getting a headache. This is a rough sketch done with ViaCAD 2D/3D and no I don't own any part of the company nor have vested interest in it.


Any and all opinions are please.

Michael

[blackburn mark]

the preportion of flex along the Y axis looks like it will be huge compared to the X and Z

if the aspect ratio on your gantry absolutly has to be that tall id be tempted to go for a fixed gantry (heavily made) with a moving bed

[m.marino]

I agree,

But space is an issue. I am thinking of using an old bridge builders trick and bolts some strengthening rails to the outside to help add rigidity. overall hight is 475mm will have the distances shortly between it and the rails it will run on. still working on it. design gets to be nightmarish after awhile.

Michael

[m_c]

You could always build tall sides for the base, to reduce the distance between the x-axis supports and the y-axis.
It would mean that when you're machining on the base, the cutter would effectively be working below the x-axis supports, but the higher rails should improve ridgidity.

[Jonathan]

It would mean that when you're machining on the base, the cutter would effectively be working below the x-axis supports, but the higher rails should improve ridgidity.

Yes, that combined with a bed which you can adjust the height of is by far the most rigid way to do it. As there are effectively no gantry sides you have eliminated the flex they cause. You can make the rest of the frame as heavy, and therefore strong, as you want as it is now stationary. I changed my router to that configuration and it has made a huge difference:

http://www.mycncuk.com/forums/showth...ll=1#post22767

It is interesting that you seem to have profile rails yet cannot afford ballscrews? Is that because you spend all your money on the rails!

[m.marino]

Have this beautiful drawing sitting down on the shop computer that I swear I had transferred a copy up to the office. Well will post it tomorrow with a good bit of detail on measurments so that things can be relevant to folks when you look at it. I am now starting to get sources for materials together and final costing for the upgrade. It is coming in at an acceptable cost (lesson learned the hard never really are). If I can arrange things with folks for the cutting and milling that needs done I might just have it up and running in new form in time to make enough parts for the convention.

Also have ordered shielded cable (Thanks Jonathan and Jazz for your sources). Hope that will help with the dropping steps enough to get some cutting done while getting the rest of the parts in.

Michael