A beginner has some questions - Jakarta, Indonesia

[kkilst]

Moved from another thread:


. . . . . . Our project is to build 1220x2440mm effective working range, for grinding and polishing the bevel edges of flat glass. Most parts are to be subcontracted.
Firstly, I apologise if asking questions already answered in the other parts of the forum.
1). Cross Member Tube (1020440SA)
Is it possible to stack and spot welded 2 pcs of hollow square (50x50mm),
in order to get the hollow rectangular (50x100mm), without altering the original design.
In this drawing, it is explicitly stated that the length is cut to 2330mm.
So, what is the width of board does this plans suppose to be able to cut?
What does the variable Y refering to (Y+500)? Is it the actual cutting length of the tool?

2). X-Rail and Y-Rail
I have contacted one shop for the machining of /\-profile of the long rail.
Huron CNC with swivel head with 10 meter table.
The rail is clamped in the long table, milling 45 degree edges and drilling holes, can be done in one set-up.
Subsequently, grinding/polishing by hand is done with "rail grinding tool".
But I am not sure the straightness of the stock purchased from local shop.
From your experience, is this method advisable?
Option to use ready-made rail, I have contacted Yitong for their SingleEdge-Rail "YT3" and W-Roller "YTG W3".
What is the word "ALU" in 1010220AA refering to? Is it aluminium material?

3). Looking at the forum, most users are using geared stepper motor.
Does the direct drive DC servomotor could be implemented?

4). X-Rail-Drilled&Tapped (1010246DB)
"Pitch betwen holding screw holes to be 200-300mm"
Is this pitch is determined from the value of X, or any value between this range is ok?
I am still not sure of this X variable.
"Scribe line 46mm from reference edge"
Where is the reference edge located?
Best regards,
Lie S.T.

[Gerald D]

If you are building for 1220x2440 effective working range then
"Y" = 1220mm and
"X" = 2440mm
See The starting points for building your own MechMate - selecting table size, etc.

1.) Yes

2.) ".... I am not sure the straightness of the stock purchased from local shop. From your experience, is this method advisable?" The Huron operator will have to decide. It could work okay.

Yes, alu is abbreviation for aluminium.

3.) Direct drive servo motors can work if you find one that enough continuous holding torque before it burns out. Be careful when reading the supplier specs - they often quote peak torque, which is about 5 times greater than holding torque.

4.) the 200 to 300 mm means you can choose any number in between those values.

See the enlarged view at top right of 1010246D, to see which side of the angle rail is used as the reference for the 46mm dimension.

[kkilst]

Hi Gerald,
Thank you for explanation of the last post.
We want to ask further questions, as work is going to start next week.

1010300WA
I have been searching for the distances of "A" and "B" (Please enclosed see the .dxf file), but could not find it.
As these would subsequently afffect the other parts dimensions in Y.
I want to get confirmation for this CRITICAL distance, before cutting the cross member (1020440SA).
Critical distance = Effective cutting distance + 430 = 1220 + 430 = 1650
Length of cross member = Effective cutting distance + 500 = 1220 + 500 = 1720

1010246DB
"6. Enlarge holes in rails to Dia 12mm"
The mounting bolt of rail to beam is M8, why does this has to be Dia 12mm?

[kkilst]

It seems .dxf file could not be attached.
We try with the .jpg file.

[Gerald D]

Re-name your .dxf file to .txt,
or zip it into a .zip file,
then it will attach.

[Gerald D]

I think the reason for your question is your belief that the dimensions are CRITICAL. They are not critical. You can make 3mm errors (even more) during the cutting welding process and still make a 100% working machine. That is part of my design because I know that 90% of people will make 3mm errors during the cutting & welding.

After the cutting & welding, there are two opportunities to rectify the "mistakes": . . . . .

Originally Posted by kkilst

1010246DB
"6. Enlarge holes in rails to Dia 12mm"
The mounting bolt of rail to beam is M8, why does this has to be Dia 12mm?

. . . . . gives you the chance to move the rails +/- 4mm in total for a coarse adjustment.

And then drawing M1 20 100 A mentions "shim washers" without giving the thickness of those washers. There you select your washers for the fine adjustment of getting the rollers to sit perfectly on the rails.

[kkilst]

I try to the attached file, in .txt and .rar

[Gerald D]

This is what I get when trying to open your .dxf:

DXF read error on line 1042.
Invalid or incomplete DXF input -- drawing discarded.

[domino11]

Gerald,
I could not open the dxf as well. Actually it crashed my free viewer.

[kkilst]

Sorry for the inconvenience of the attached file.
I try again with this .jpg, hope it is ok.
I want to know what is the recommended distances of A and B,
of using rack dimension 20x20 mm cross-section.

[Gerald D]

Still can't read your picture. But if your rack is 20x20 then you can expect some problems. You should reduce the Y+430mm dimension down to Y+424. That solves the x-rail.

But, how will you find the space for the rack on the gantry's y-rail?

Suggest you stick to the drawing dimensions and ask your Huron guy to cut the racks narrower.

[kkilst]

Attached .jpg

[Gerald D]

Theoretically, A=25 and B=21 for the x-axis.

On the y-axis, those figures will only be true if you get 50mm wide tubes, however 2" tubes also common.

I say again, this is only theory, and actually meaningless, because the beams and tubes are not precisely made, nor welded. A lot of people find their B dimensions getting too small at some places.

[Gerald D]

An important correction to your drawing:

Graphic3.JPG

[kkilst]

Thank you very much.
Next week we start works, confirm with the purchase of materials,
and pay a visit to lasercutting-bending company.
We just hope the price of lasercut service is reasonable, and within
our budget of US$7,000 of building this machine.
We design the machine base base, which must accommodate for the
water tank dan pump.

[kkilst]

Gerald,
1). In (10 20 451 PA), the unbent profile and all holes are laser cut together.
Whereas in (10 20 451 BA), there is a "Note that this plate should be drilled after bending and before welding".
I need clarification, forgive me if I overlook something.

2). There is very small discrepancy of dimensions stated in .pdf and .dxf files for laser-cut parts.
Is this ok?

3). Is there any major modifications between the latest plans and a year ago?
I did the download last year January 2008.

Thank you.

[domino11]

1) There is countersinking for two holes on the carrier plates. You do this after the bending and before you weld in the plates to the gantry tubes.

2) I believe this has been mentioned before and is not a problem. Gerald can probably comment better on this one.

3) The last set of plans are from June 30, 2008 as seen on the plans download page here.

http://www.mechmate.com/forums/showthread.php?t=376

This is the set you should be using at this point.

[Gerald D]

1) Heath answered that.

2) I hope it is okay. Please list the discrepancies, but please only refer to the latest published set of drawings.

3) I can't remember what the changes are between January & June last year. If you look at the latest set, the reason for each revision is stated on the drawing.

[kkilst]

Gerald,
We had visited a few sheet metal workshops for the lasercut profile and bending, and would place the job order this week.
I would like to get confirmation that these small discrepancies could be ignored?
For example, "Near Carrier Plate - Profile Cut (1020451PA)",
the outer dimensions in printed .pdf is (264 x 525 mm), whereas in .dxf (263.80x524.90).
Thank you.

[Gerald D]

That small discrepancy can definitely be ignored!

[kkilst]

Gerald,
1). Main Longitudinal Length (10 10 322) is 3000mm, and
we want to to get cutting length 2600mm (To maximise the working range of X).
Two proximity-swicth holes are drilled at 2600+110mm, resulting 145mm left on either side of the
beam. We do not know whether the Y-car would over travelled for this?

2). As for Near Carrier Plate (10 20 451) and Far Carrier Plate (1020 452),
looking from "Front View" of Mechmate, "Near Carrier Plate" is supposed to be located
at the right-hand side?

3). As for Car Carrier Plate (10 30 450), we need to make 2 identical workpiece, just for confirmation.

Our laser-cut parts had just arrived, and we are preparing for the welding.
Thank you and best regards.

[Gerald D]

Mulyadi, I am having some difficulty in understanding your questions . . . .

1. Realise that the gantry wheels are spaced 475mm apart. Therefore if the rail is 3000mm long, the absolute max. theoretical movement is 3000 minus 475 equals 2525 mm, which is shorter than the 2600mm that you are talking about?

2. You mention "Front View" , but on which drawing sheet number do you see that? My definition of "near" is when you stand at the 0,0 reference corner of the table, then y=0 is nearest to you. The far side is the side of the gantry with the x-chain.

3. Yes, you need two identical parts 10 30 450.

[kkilst]

Gerald,
Thank you very much for the explanation.

1). Gantry Frame-Welded (10 20 400)
Yes, I understand now the position of the Near Carrier Plate (10 20 451) and Far Carrier Plate (10 20 452).
Can the position of these 2 plates "interchangable"?
There is no such word "Front View" in your plans,
I am just thinking it is easier to describe it while standing in front of the machine.

2). Referring to,
> #11 Fri 13 March 2009, 16:39
>Gerald D. Just call me: Gerald Fish Hoek (Cape Town), South Africa
>But if your rack is 20x20 then you can expect some problems.
>You should reduce the Y+430mm dimension down to Y+424. That solves the X-rail.

Shorthening the span to (Y+424)mm, the only purpose is to acommodate for uneven surface of the beam,
i.e. from 1mm gap, it is being increased to 4mm gap.
But if we maintain the span (Y+430)mm, but increase the distance 46mm to 49mm, does this possible?

3). For the design of the X-rail and Y-rail, we stick to the your original plans.
However, after discussion with knife grinder and gear hobbing shops, this idea being put
forwards. Is this feasible?

[Gerald D]

"But if we maintain the span (Y+430)mm, but increase the distance 46mm to 49mm, does this possible?" Then your gantry will not fit over the rails - you will have to make the gantry longer.

That sketch is feasible.

[kkilst]

Hi Gerald,
I apologise of not posting any development of my project for quite sometimes, as we are looking for suitable location. We had just finalised a place of putting several units of Mechmate.
Lasercut parts had arrived quite sometimes.
Already purchased welding eguipments, magnetic portable drilling machine, precision square and tools.
Rails from knife grinder will be done this week.
Starting with the welding of Y-car and preparing to weld the gantry next.
We would be using DC servomotors and Rutex controller, as we are quite happy with our existing drilling machines using this controller. We can get the suitable gear reducer motor from used store, but mostly of
AC or stepper motors, brand Oriental Motors. So we will take only the gear reducer and the rotor, and try to connect it to our DC motor, still designing the connecting with timing belt and pulley.
As for the base table, most of the 150mm and 200mm hot-rolled U-channel in our domestic
market are not good in quality. They are either dented on the ends or visually can be seen "curve" for
the span of 3000mm.
So we are thingking of using 100x100mm hollow tube, and this is the preliminary construction.
My colleque is contemplating of using 50x100mm hollow tube as an alternative, similar design done by
(bradyaero-Greg Smiths Falls, Ontario, Canada).
Would appreciate any critique from the forum.
Thank you.

[Gerald D]

Our very first table, constructed in 2000, has 100X50 hollow tube longitudnals and it works fine.

[kkilst]

What is the thickness of 50x100mm hollow you are using for the longitudinal?
The available thickness of 50x100mm and 100x100mm is only 3mm,
therefore I am thinking of using 100x100mm.

[Gerald D]

If you weld it as shown in your sketch, 3mm is enough.

[kkilst]

Progress of my first Mechmate. Gantry seat perfectly on the rails.
Today we start painting, and install Z-assembly.

[hennie]

Mulyadi I had the same thing with the main c channel one was ok but the other one had a twist at the end and the supplier cut it to size and didn`t want to replace it but hey anything can be fixed with a grinder and a hammer