Project Description
“In theory there is no difference between theory and practice. In practice there is.” — Yogi Berra
The content of 2.72 has been scoped to include the majority of mechanical elements that are considered ubiquitous components of mechanical systems. All of these mechanical elements may be found in mechanical systems that could be the subject of a 2.72 design project. We have elected to use a desktop manual lathe as the 2.72 design project. This selection offers the unique opportunity to create a mechanical system that: (a) forms the basis of your assignments and laboratory activities (b) will be used to draw inter-related examples that demonstrate component/system design (c) you may keep as a “memento” of your mechanical design experience and accomplishment; and (d) you may use to create mechanical elements for future activities.
Lathe CAD (ZIP) (This ZIP file contains: 6 .stl files, 1 .dxf file, 7 .sldasm files, 5 .slddrw files, and 31 .sldprt files.)
Responsibility for Parts
| PART NAME | OUR RESPONSIBILITies | YOUR RESPONSIBILITies |
|---|---|---|
| Spindle |
Housing blank Shaft blank |
Housing Preload mechanisms End cap Shaft Bearings |
| Structure |
Headstock blank Tail stock blank Structure tube blank |
Rails Finished tube Finished tail stock Finished head stock |
| Lead screw drive |
Bearings Preload end cap Lead screw Preload washers Preload tube Lead screw bearing seat Bearing preload nut |
Drive nut Drive preload nut |
| Carriage |
Polymer bed blank* *May cast 3 pieces as one, stay tuned… |
Finished polymer bed* Drive flexure coupling Bushings Finished end skirts* Bushing flexure coupling |
| Cross feed |
Tool holder Lead screw |
Flexure bearing Front flexure mount Proper dial mount surfaces/flats on screw Rear flexure mount Thrust bearing |
| Miscellaneous |
Chuck > ¼ - 20 bolts – 0.50 in long |
Deliverable Schedule
“Let our advance worrying become advance thinking and planning” — Winston Churchill
All parts, models, measurements, document drafts/components, and presentation drafts/components must be started/finished no later than the following respective dates. You are responsible for (a) arranging all required meetings, (b) scheduling required resources, (c) placing timely orders for parts/materials, and (d) fabricating/calibrating the experimental setup. Don’t get frustrated if you get stuck. Ask for help so we can keep you moving. We reserve the right to (and we will!) ask you for proof of start/finishing at random intervals. If you are not on schedule, this will be reflected in your grade, no exceptions.
| ITEMS | START | FINISH |
|---|---|---|
| Fabrication task dates | ||
| Spindle shaft | Ses #3 | 1 day before Ses #6 |
| Housing | Ses #6 | 1 day after Ses #9 |
| Housing end caps | Ses #6 | 1 day after Ses #9 |
| Cross-feed flexure | Ses #8 | Ses #14 |
| Lead screw flexure | Ses #8 | Ses #14 |
| Error model task dates | ||
| List of spindle error sources | Ses #3 | Ses #7 |
| Model individual spindle errors | Ses #3 | Ses #10 |
| Finish full spindle error model | Ses #3 | Ses #11 |
| List of flexure error sources | Ses #8 | 1 day after Ses #13 |
| Model individual flexure errors | Ses #8 | 1 day after Ses #13 |
| Finish full flexure error model | Ses #8 | 1 day before Ses #16 |
| List of drive error sources | Ses #11 | 1 day before Ses #16 |
| Model individual drive error | Ses #11 | 2 day before Ses #20 |
| Finish full drive error model | Ses #11 | 2 day before Ses #20 |
| HTM-based lathe error model (in report) | Ses #5 | Ses #24 |
| Measurement task dates | ||
| CMM training | 1 day after Ses #9 | 1 day after Ses #13 |
| Spindle error motions | 1 day after Ses #9 | 1 day before Ses #12 |
| Cross slide error motions | Ses #13 | 1 day before Ses #16 |
| Carriage error motions | Ses #16 | 1 day before Ses #21 |
| Report results and conclusions | ||
| Outline (text, table & figure placeholders) | Ses #14 | 3 days before Ses #20 |
| Images | 1 day after Ses #3 | 1 day after Ses #21 |
| Tables | Ses #6 | 1 day after Ses #21 |
| 1st draft in separate modules | Ses #16 | 1 day after Ses #21 |
| Integrated, final draft | Ses #22 | Ses #24 |
| Design notebooks | 1 day after Ses #1 | Ses #24 |
Group Budgets
“It’s clearly a budget. It’s got a lot of numbers in it.” — George W. Bush
Each group will be allowed to spend up to $200 to purchase bearings, preload washers, rails, bushings, epoxy, etc. The TA will order them for you from McMaster. You must provide the (i) part number, (ii) name/description, (iii) quantity and (iv) cost. If you find that it is necessary to purchase items from another source, you must also provide the name, address, and phone number of the vendor. We encourage you to use McMaster. Other sources will only be allowed if there is a compelling reason. Materials will be shipped to the TA via 3-day ground and you may pick them up from the TA’s office.
Measurement Tools in Prof. Culpepper’s Lab
“It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.” — Abraham Maslow
You need to use capacitance probes and a data acquisition system to measure your spindle’s error motions. Given the delicacy of the probes, you must set up a meeting with the TA in order to run this experiment. You may arrange up to 2 hours per meeting per group. The TA will help you set up the probes and the data acquisition system. The TA will have a pre-arranged program that takes the measurements and exports data to a TXT file that can be imported to Excel or MathCAD.
Measurement Tools in the Shop
In addition to the stocked measurement tools in the shop, you will have access to special purpose tools that were purchased for this project that will make your job easier. See the Shop Manager to check them out. They must remain in the shop or adjoining computer room.
Two dial bore gages (for measuring the internal diameter of your spindle bearing bores)
Two digital micrometers (for measuring spindle shaft diameters)
Group Gurus
Your group needs to assign people to be responsible for the administration and conduct of certain tasks.
CAD Guru (SolidWorks)
FEA Guru (To be trained in structural, thermal, and vibration modeling in CosmosWorks)
Financial Guru (Budget and ordering)
Measurement Guru (CMM and various measurements)
MathCAD/Matlab Guru (Parametric modeling)
Documentation Guru (Pictures, video, etc…)
